1Regional Center of Agricultural Research of Sidi Bouzid (CRRA), Sidi Bouzid, Tunisia;
2Department of Biosciences and Technology for Food Agriculture and Environment, University of Teramo, Campus Aurelio Saliceti, via Balzarini 1, Teramo, Italy;
3Department of Veterinary Sciences, University of Messina, Polo Universitario dell’Annunziata, Viale G. Palatucci, Messina, Italy
4Department of Agriculture, Food and Environment (Di3A), University of Catania, via S. Sofia 100, Catania, Italy
Prolonged drought poses a critical challenge for pistachio cultivation in Mediterranean regions. Water-saving strategies and selecting adapted cultivars can help maintain sustainable production. This study was conducted in the experimental orchard of the Regional Center of Agricultural Research of Sidi Bouzid, Tunisia. Four pistachio cultivars (Mateur, Elguetar, Kerman, and Ohadi) grafted on P. atlantica rootstock were used to investigate the impact of regulated deficit irrigation (RDI) on yield, nut composition, volatile compounds, phenolic compounds, fatty acid profile, and sensory analysis. Three irrigation treatments were applied: control (T0) received 100% crop evapotranspiration (ETc) during all stages of nut development; RDI treatment (T1) received 50% ETc during stages I and II of nut development, followed by 100% ETc during stage III; and stressed treatment (T2) received 50% ETc during two growing seasons (2017 and 2018). Pistachio nuts were immersed in a solution of NaCl (5% w/v) for 5 min and then introduced in an oven for 2 h at 120ºC to obtain ‘roasted’ pistachio for volatile and sensorial analysis. Results showed that RDI saved 20% of irrigation water during stages I and II of nut development while maintaining similar yield, nut composition, and fatty acid profile as that of control. Moreover, the volatile compounds content and oil yield were enhanced under drought stress. Roasting enhanced the perception of volatile compounds, especially nitrogenous ones. Cultivars Mateur and Ohadi showed high sensory quality, with Ohadi achieving the highest consumer satisfaction despite lower yield and dehiscence rate. Cultivar Mateur was suitable for high-density planting in semiarid environments. Overall, RDI proved effective for increasing water use efficiency without compromising pistachio quality, suggesting its suitability for arid and semiarid orchards.
Key words: nut quality, pistachio, regulated deficit irrigation, roasting, volatile compounds
*Corresponding Author: Valeria Rizzo, Department of Biosciences and Technology for Food, Agriculture and Environment, University of Teramo, Campus Aurelio Saliceti, via Balzarini 1, 64100 Teramo, Italy. Email: [email protected]
Academic Editor: Prof. Monica Rosa Loizzo -Università della Calabria, Italy
Received: 26 August 2024; Accepted: 13 October 2024; Published: 1 January 2025
© 2025 Codon Publications
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0). License (http://creativecommons.org/licenses/by-nc-sa/4.0/)
Pistachios are among the most nutritious nuts consumed as raw or roasted, with or without salt (Dini et al., 2019). The pistachio tree has the reputation of being drought-tolerant and saline-resistant species cultivated under rainfed conditions in its region of origin (Rieger, 1995). In Tunisia, pistachio production is around 3,190 tons with a cultivation area of 27,153 hectates (ha) (FAOSTAT, 2024). Recently, extension of pistachio cultivation has taken place in west-central Tunisia because of economic importance of pistachio nuts. New pistachio orchards are planted under high-density system, which increases water requirement. However, water availability for agriculture continues to decline due to changes in global climactic conditions. Therefore, great emphasis is placed on irrigation management in arid regions to increase water use efficiency (Abboud et al., 2019). Regulated deficit irrigation (RDI) is a system of managing water supply by imposing water deficits in specific phenological stages, which are found to be less sensitive, without loss of economic benefits (Carbonell-Barrachina et al., 2015). In pistachio production, development of nuts is characterized by three different periods (Goldhamer, 1995): stage I starts at the beginning of nut growth and ends when its maximum size is reached; during stage II, hardening of shells takes place; and finally, stage III is the period of kernel growth.
Pistachios are also considered functional food on account of their high contents of monounsaturated fatty acids, vitamins, minerals, sterols, polyphenols, and high antioxidant potential (Hojjati et al., 2013; Satil et al., 2003). Pistachio nuts contain about 50% of oil, with maximum of oleic acid (54.4–71.8%), linoleic acid (16.7–35.3%), palmitic acid (7.2–10.5%), stearic acid (0.9–10.5%), and linolenic acid (up to 2%) (Arena et al., 2007). These fatty acids have important therapeutic properties, such as reducing triacylglycerols, low-density cholesterol (LDL), total cholesterol, and glycemic index (Taghizadeh et al., 2018). Among different nuts, extraction of oil is an interesting alternative due to their high lipid content, such as almonds (53%), pistachios (50%), and walnuts (65%) (Sena-Moreno et al., 2015). Nutrient oil is used in the food and cosmetics industry, adding value to products.
Raw nuts, even if well appreciated, have a rather bland aroma, because of some compounds that are responsible for characteristic flavor generated during the roasting process (Aceña et al., 2010). Roasting is a key method in pistachio processing used to enhance sensory properties and aroma attributes of nuts influencing consumer’s acceptance (Aceña et al., 2011). It was reported that roasting of pistachio nuts increased free fatty acids, reduced total available carbohydrates, decreased moisture of nuts, produced a more crispy and fragile texture, enhanced Maillard reaction and degradation of lipids, and created desirable pigments and aroma compounds (Hojjati et al., 2013).
In this context, the present study was conducted to analyze the impact of RDI on pistachio nuts and oil bioactive compounds, volatile compounds, and sensorial analysis after the roasting process of cultivars Mateur, Elguetar, Kerman, and Ohadi grown under semiarid conditions.
The trial was carried out in the Regional Center of Agriculture Research (CRRA, Sidi Bouzid) in west-central Tunisia (9º43’ E, 35º01’ N; altitude 354 m) during the growing seasons of 2017 and 2018. Age-wise, 17-year-old pistachio trees of cultivars (cv.) Mateur, Elguetar, Kerman, and Ohadi grafted on P. atlantica rootstock were studied. Trees were trained to the standard open vase system planted at a spacing of 6 × 6 m, and grown under standard conditions of fertilization, pruning, pollination, pest, and disease control. The surveyed trees were selected for uniform trunk and canopy size.
The trial was set in a complete randomized block design arrangement. The area assigned for the experiment was divided into three main blocks corresponding to each irrigation treatment (T0 = 100% ETc: irrigation at full water requirements; treatment T1 = RDI: irrigation at 50% water requirements during stages I and II of nut development, and 100% ETc during stage III; and treatment T2 = 50% ETc: irrigation at 50% water requirements). Each main block was then divided into four experimental units, one for each cultivar. Each cultivar (experimental plot) had on nine trees (eight females and one male). Experimental area had semiarid Mediterranean climate with a low annual rainfall of 200 mm irregularly distributed over the growing season and a reference evapotranspiration (ETo) of 1,400 mm. The soil was aridisol, with a sandy-clay texture (clay = 13.69%, silt = 1.11%, and sand = 84.7%), 10% active CaCO3, basic pH of 8.6, and slightly saline concentration (3.6 dS/m). The irrigation water was slightly saline and had a high concentration of nitrate (EC = 1.5 dS/m; SAR = 2.4; NO3– = 50 ppm; pH = 7.9; and HCO3– = 16.0 meq-1) (Akrimi et al., 2020).
The treatments consisted of three different irrigation regimes (Table 1) during the two growing seasons. The phenological stages considered during RDI treatments were those suggested by Goldhamer and Beede (2004)—stage I: from sprouting until the end of rapid nut growth; stage II: from maximum nut size until the beginning of kernel growth; and stage III: from the beginning of kernel growth until harvest.
Table 1. Crop evapotranspiration rate (ETc) and irrigation regimes applied to the control (treatment T0), RDI (treatment T1), and stressed (treatment T2) during the growing season 2017–2018.
Water applied (mm) | |||||||
---|---|---|---|---|---|---|---|
Treatment | Year | ||||||
2017 | 2018 | ||||||
Stage I | Stage II | Stage III | Stage I | Stage II | Stage III | ||
ETc | T0 | 78.9 | 64.4 | 101.9 | 57.5 | 53.0 | 107.5 |
ETt1 | T1 | 39.4 | 32.2 | 101.9 | 28.7 | 26.5 | 107.5 |
ETt2 | T2 | 39.4 | 32.2 | 50.9 | 28.7 | 26.5 | 53.7 |
Rainfall (mm) | 112.9 | 9.4 | 16.6 | 58.6 | 3.6 | 48.6 | |
ET0 (mm) | 443.2 | 293.6 | 446.9 | 324.2 | 242.8 | 471.5 |
ETc: Crop evapotranspiration rate; ETt1: evapotranspiration rate under regulated deficit irrigation; ETt2: evapotranspiration rate under stressed treatments; ET0 : reference evapotranspiration of annual rainfall; Treatment: T0: well watered; T1: regulated deficit irrigation; T2: stressed; stage I: from sprouting until the end of rapid nut growth; stage II: from maximum nut size until the beginning of kernel growth; stage III: from the beginning of kernel growth up to harvest.
The applied treatments were as follows:
Treatment (T0): trees received water to cover estimated evapotranspiration losses (100% ETc), also referred to as ‘control’;
Treatment (T1): trees received 50% ETc during stages I and II, and 100% ETc during stage III, also referred to as ‘RDI’;
Treatment (T2): trees received 50% ETc during the growing season, also referred to as ‘stressed’.
Drip irrigation was applied for 3 days every week, and was controlled and adjusted weekly according to the potential of soil matrix measured by tensiometers located 0.5 m from the drip head at depths of 30 cm and 60 cm. A drip line was utilized in each tree row, with four self-compensating drippers (4 L/h) per tree, 0.5 m apart. The amount of provided water was calculated based on crop ETc and crop coefficient (Kc) according to the FAO method: ETc = ETo × Kc (Allen et al., 1998). The mean Kc values provided by Goldhamer (1995) were used: 0.39, 1.06, and 1.14 for stages I, II, and III, respectively.
After manual nut peeling, pistachio nuts were immersed in NaCl (5% w/v) solution for 5 min. Salted nuts were left to dry at room temperature for 30 min to release the excess of water and then kept in an oven for 2 h at 120ºC to obtain ‘roasted’ pistachio for volatile and sensorial analysis (Figure 1).
Figure 1. Outline of pistachio preparation phases for roasting and subsequent analyses.
Nuts were handpicked at commercial maturity and assessed by color of shells and dehiscence of nuts (Figure 2).
Figure 2. Pistachio nuts of the studied cultivars (M: Mateur, K: Kerman, E: Elguetar, and O: Ohadi).
Yield (in kg) was determined per tree. At harvest, a representative nut sample (100 nuts) was taken for pomological evaluations. Nut characteristics, such as mean nut weight (NW in g) and 100 kernel weight (g), were calculated using an electronic balance of 0.001-g sensitivity; split nuts (%), blank production (%), and infested nuts were evaluated. Nut dimensions and morphological and quality parameters of kernels were carried out at random on a sample of 100 nuts collected from trees. The color of crunched pistachios (Figure 3) was measured using a Konica Minolta CR-400 colorimeter (Tokio, Japan) to obtain CIE L*, a*, and b* chromatic coordinates.
Figure 3. Color determination of pistachio nuts collected from the studied cultivars.
The moisture content was determined with milled pistachio nuts at 105°C for 6 h in an oven (Memmert, Model UNE 400 PA; Scheabach, Germany) (Chahed et al., 2008). The ash content was determined by muffle furnace at 550°C. Concentration of proteins was determined according to the method from Bradford (1976) using bovine serum albumin (BSA) as a standard. Total protein content was expressed as mg g-1 of fresh weight (FW). The fiber content was determined according to Ashraf et al. (2011), and the fat content (FC) was determined using hexane as a solvent (Association of Official Analytical Chemists [AOAC], 1995). After calculating the moisture, ash, protein, fat, and crude fiber content in the form of a powder, the total carbohydrate content was determined using the following formula:
Total carbohydrates = 100 – (moisture [%] + ash [%] + protein [%] + fat [%] + crude fiber [%]).
Analyses were made in triplicate and the results were expressed as a percentage of grams of FW (% g-1). Oil yield is defined as the quotient of the weight of extracted oil and the weight of pistachio nut powder, and is expressed as percentage (%) (Uquiche et al., 2008). Oil extraction was accomplished by solvent extraction technique using n-hexane according to the method described previously (Damirchi et al., 2005). The prepared samples were kept at –20°C for further analysis.
Oil yield was determined using the weight of the oil extracted from 100-g pistachio samples. Free acidity was expressed as oleic acid (g 100 g-1 oil), and UV absorption characteristics (K232 and K270) were determined according to the International Olive Council (Conseil Oléicole International [IOC], 2015), while the refractive index (RI) was calculated according to the AOAC (2000) method. Carotenoid and chlorophyll from oil samples were extracted with cyclohexane, and their contents were determined according to the method described by Minguez-Mosquera et al. (1991). Pigments were measured at 470 nm and 670 nm, while the color of crunched pistachios was determined as described previously for nuts.
Samples were crunched to form powder in a mortar and pestle, separately. By weight, 20 g of pistachio kernel of each cultivar was extracted with 200 mL of 95% methanol for 48 h at room temperature. Then, the extracts were filtered and evaporated at low pressure; samples were stored at -20°C until analysis (Taghizadeh et al., 2018). Total anthocyanin content (TAC) was evaluated by measuring absorbance at 535 nm and 700 nm in hydroalcoholic extract (Fuleki and Francis, 1968). Concentration of anthocyanins was calculated using the molar extinction absorptivity coefficient Ɛ = 25,965/cm M and was expressed in mg of cyanidin 3-glucoside equivalents (C3Geq) per kilogram of dry weight (C3Geq/kg DW). Total flavonoid content (TFC) was measured as described by Huang et al. (2004). Briefly, 5 mL of 2% aluminum trichloride (AlCl3) in methanol was mixed with the same volume of extract. Absorbance was read at 367 nm and the TFC was determined by a standard curve plotted for catechin. Results were expressed as mg of catechin equivalents (mg CE/g). Total phenol content (TPC) was determined using the Folin–Ciocalteu method (Abidi et al., 2011). For this purpose, 100 μL of extract was mixed with 0.5-mL Folin–Ciocalteu reagent. Then, 7 mL of distilled water was added to the solution. After 5 min incubation at room temperature, 1.5 mL 10% sodium bicarbonate (Na2CO3) solution was added to the mixture and left in the dark for 2 h. Absorbance was read at 725 nm against blank and results were presented as mg gallic acid equivalence for 100 g of DW (mg GAE/100 g DW). Total phenols (TP) and antioxidant capacity (AC) of pistachio oil extracts were measured as described for pistachio nuts.
The antioxidant capacity of pistachio methanolic extracts was evaluated using modified 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), ferric reducing/antioxidant power (FRAP), and β-carotene bleaching (β-carot) activity assays. The DPPH assay was performed using the method adapted from Brand-Williams et al. (1995). In brief, 0.1-mM solution of DPPH in methanol was prepared and 2.9 mL of the solution was added to 0.1 mL of extract. The mixture was shaken vigorously for about 10 s and incubated in the dark at room temperature for 10 min; the absorbance was recorded at 515 nm against a blank (50 μL of sample with 950 μL of ethanol 80%). The control was a mixture of DPPH (950 μL) plus ethanol 80% (50 μL). A standard curve was drawn with Trolox (0.5–10 ppm). Results were expressed as µg of Trolox equivalence (TE) per gram of DW.
The FRAP assay was performed using 2,4,6-tripyridylS-triazine (TPTZ) solution according to the method described by Fu et al. (2020). In brief, 4.9 mL of FRAP solution (2.5 mL of 0.1-M acetate buffer [pH = 3.6], 250 µL of 10-mM TPTZ, and 250 µL of 20-mM FeCl3) was mixed with 0.1 mL of sample extract. Thereafter, the obtained mixture was shaken vigorously and incubated in the dark for 10 min at room temperature. Finally, the absorbance was measured at 593 nm. Results were calculated using a Trolox standard curve and expressed as µg of TE per gram of DW.
β-carot activity was determined using the method described by Kim et al. (2019). A mixture of 20-μL linoleic acid and 100-μL Tween 20 was dissolved in 10-mL chloroform. After removing chloroform, 10 mL of distilled water was added and stirred vigorously. Then, 240 μL of emulsion was mixed with 10 μL of extracts at various concentrations (1, 2, 3, 4, and 5 mg/mL) or butylated hydroxytoluene (BHT) as a positive control. The absorbance was measured every 15 min for 120 min at 470 nm. The antioxidant activity of extracts in terms of β-carot was calculated using the following formula:
The volatile aroma compounds of raw and roasted pistachio nuts from each cultivar were extracted and analyzed by Head Space–Solid Phase Micro-Extraction–Gas Chromatography–Mass Spectrometry (HS-SPME-GC-MS) using the method suggested by Aceña et al. (2010) with slight modifications. Briefly, 1 g of finely crunched pistachio samples was placed into a 40-mL glass vial with 18 mL of NaCl saturated aqueous solution and sealed with a ‘mininert’ valve (Supelco; Bellefonte, PA, USA). Each sample was equilibrated for 30 min at 50°C with continuous stirring (700 rpm) in a thermostatic bath. Then, a divinylbenzene–carboxen-polydimethylsiloxane (DVB/CAR/PDMS) 2-cm fiber with 50/30-µm thickness, purchased from Supelco (Bellfonte, USA), was exposed for 1 h at 50°C in a vial headspace for the extraction of volatile compounds. After extraction, the fiber was inserted into the injection port of GC for the thermal desorption of analyte at 260°C for 3 min. The fiber was conditioned before use and thermally cleaned after each analysis at 250°C in the injector port of GC. A Shimadzu GC 2010 Plus gas chromatograph directly interfaced with a TQMS 8040 triple quadrupole mass spectrometer (Shimadzu; Milan, Italy) was used for GC-MS analysis. Two capillary columns of different polarity were used: (1) VF-WAXms, 60 m, 0.25-mm i.d., 0.25-μm film thickness polar column (Agilent Technologies Italia S.p.A., Milan, Italy) and (2) DB-5 ms, 30 m, 0.25-mm i.d., 0.25-μm film thickness polar column (Agilent Technologies).
The GC conditions were as follows—injector temperature, 260°C; injection mode, splitless: (1) oven temperature VF-WAXms, 45°C held for 5 min, then increased from 80°C at a rate of 10°C/min to 210°C at a rate of 2°C/min and 240°C at 20°C/min; (2) oven temperature SLB-5ms, 60°C to 110°C at a rate of 2°C/min, from 110°C to 160°C at a rate of 3°C/min, and from 160°C to 260°C at a rate of 10°C/min; carrier gas, helium at a constant flow of 1 mL/min; transfer line temperature, 250°C; acquisition range, 40–400 mz-1; and scan speed, 1,250 amu/s. Each compound was identified using mass spectral data, NIST’ 20 (NIST/EPA/NIH Mass Spectra Library, version 2.0, NanoTech Analysis, Turin; Italy) and FFNSC 3.0 database, linear retention indices (LRI) according to the equation of Van Den Dool and Kratz (1963), literature data, and the injection of available standards, as reported previously (Cincotta et al., 2018). The samples were analyzed in duplicate. The compounds were quantified using peak area, and average value was calculated.
The fatty acid composition of oils was analyzed using GC to determine fatty acid methyl esters (FAMEs), following the method outlined in Ghrab et al. (2010). FAMEs were prepared by saponification/methylation with sodium methylate according to the European Union Commission modified Regulation EEC 2568/91. A capillary column (30-m length and 0.32-mm i.d.; Stabilwax; Restek, Bellefonte, PA, USA) coated with a stationary phase formed by carbowax (0.25-mm thickness) in GC (Shimadzu GC-17A; Japan) was used. The analytical conditions were as follows: flame ionization detector (FID), nitrogen as vector gas at a flow rate of 1 mL/min. The column temperature was isothermal at 180°C and the injector and detector were at 230°C and 250°C, respectively. In all, ten fatty acids were identified by comparing retention times with standard compounds: palmitic acid (C16:0), palmitoleic acid (C16:1), margaric acid (C17:0), heptadecenoic acid (C17:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), linolenic acid (C18:3), arachidic acid (C20:0), and gadoleic acid (C20:1).
This analysis was performed with salted and roasted pistachio nuts of the four studied varieties grafted on P. atlantica rootstock and conducted with three irrigation treatments of RDI. The sensory study was performed as suggested previously (Carbonell-Barrachina et al., 2015; Noguera-Artiaga et al., 2020). A consumer panel was carried out with 60 consumers selected from personal staff and students of the Faculty of Science of Sidi Bouzid (Tunisia) to study the sensory properties of pistachios. Consumers were aged 20–60 years and had no diet restrictions or allergies for any type of nut. In all, 74% of panelists were women, and 65% were aged between 20 and 35 years, 20% between 35 and 50 years, and 15% were aged between 50 and 65 years. Ten pistachio nuts were served at room temperature to each panelist in an odor-free disposable 60-mL covered plastic cups coded using two-digit numbers. Unsalted crackers and drinking water were used between samples to clean panelists’ palate. Natural illumination was used during the test, and the temperature of the testing room was 20ºC ± 2°C. Panelists responded using a 9-point hedonic scale, where 9 = like extremely and 1 = dislike extremely; they were asked to indicate their order of preference for samples and mark reasons for their preferences regarding the attributes under study (color, hardness, size, roasted and sweet/almond odor, sweet and sour taste, and global satisfaction).
All traits were measured or scored for each treatment separately during the two growing seasons. Mean values and mean standard error (SE) were calculated for each studied trait using SPSS 20.0 (SPSS Inc., Chicago, IL). Analysis of variance (ANOVA) was used to test the effects of water treatments and roasting on the studied parameters, and the significance was expressed as p < 0.05. The test Scheffe one ANOVA factor was used to compare means values. Pearson’s correlation at 5% level of significance was performed between antioxidants and antioxidant capacity using the software SPSS 20. Principal components analysis (PCA) of all studied traits was carried out using SPSS 20.0. Component matrix was evaluated and orthogonal factors were rotated using variance maximization (Varimax).
During the 2-year experimental period, results showed significant differences (p < 0.05) between cultivars concerning yield (Table 2). Low yield was observed in treatment T2 whereas treatments T0 and T1 presented the same behavior. The highest yield (7.5 kg/tree) with control treatment was observed for cv. Mateur, followed by cv. Kerman (6.4 kg/tree) and Elguetar (5.1 kg/tree) whereas cv. Ohadi showed the lowest yield (3.8 kg/tree). Results showed that the RDI treatment presented a similar yield as that observed with control treatment when 20% of water was saved during stages I and II of fruit development that increased water productivity. In this sense, Galindo et al. (2018) reported that RDI could benefit water productivity by increasing irrigation water savings, minimizing or eliminating negative impacts on yield and crop revenue, and even improving harvest quality. Findings of the present study agreed with the study conducted by Memmi et al. (2015), reporting that the water restriction applied to pistachio trees at stages I and II of nut development did not affect the final yield. Nut’s FW showed different patterns depending on the genotype. Hence, cv. Ohadi with full irrigated regime (T0) showed the highest nut FW (0.77 g) whereas the lowest value (0.44 g) was shown in cv. Elguetar. Nut weight was not affected by irrigation strategy. These findings were in accordance with the study conducted by Carbonell-Barrachina et al. (2015), reporting that the RDI treatment did not significantly affect the weight of whole pistachio, its edible portion, and its shell.
Table 2. Agronomical and pomological traits of four pistachio cultivars grown under RDI treatments.
Traits | Mateur | Kerman | Elguetar | Ohadi | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | |
Yield | 7.1 ± 1a,A | 6.4 ± 2a,A | 5.1 ± 1b,A | 6.4 ± 2a,A | 5.4 ± 2b,B | 4.8 ± 1b,A | 5.1 ± 1a,B | 4.7 ± 3a,B | 4.0 ± 2b,B | 3.8 ± 1a,C | 3.1 ± 1b,C | 2.1 ± 3c,C |
WP | 0.6 ± 0.1a,A | 0.8 ± 0.2a,A | 0.5 ± 0.1b,A | 0.6 ± 0.1a,A | 0.7 ± 0.2a,A | 0.5 ± 0.1a,A | 0.7 ± 0.2a,A | 0.6 ± 0.2a,A | 0.5 ± 0.1b,A | 0.4 ± 0.2a,B | 0.3 ± 0.2a,B | 0.2 ± 0.1b,B |
NFW | 0.6 ± 0.1a,A | 0.6 ± 0.5a,A | 0.6 ± 0.4a,B | 0.4 ± 0.4a,A | 0.5 ± 0.5a,A | 0.4 ± 0.5a,C | 0.6 ± 0.1a,A | 0.6 ± 0.6a,A | 0.5 ± 0.1a,C | 0.8 ± 0.1a,A | 0.8 ± 0.1a,A | 0.8 ± 0.4a,A |
NDW | 0.5 ± 0.1a,A | 0.5 ± 0.5a,A | 0.5 ± 0.4a,B | 0.3 ± 0.4a,A | 0.3 ± 0.7a,B | 0.3 ± 0.4a,C | 0.5 ± 0.1a,A | 0.4 ± 0.7a,A | 0.3 ± 0.1a,C | 0.6 ± 0.1a,A | 0.6 ± 0.1a,A | 0.7 ± 0.4a,A |
L | 17.8 ± 2a,A | 17.4 ± 1a,A | 17.1 ± 1a,A | 18.2 ± 1a,A | 18.1 ± 1a,A | 17.9 ± 1a,A | 14.8 ± 2a,B | 14.4 ± 1a,B | 14.1 ± 1a,B | 18.2 ± 1a,A | 18.1 ± 1a,A | 17.9 ± 1a,A |
l | 9.1 ± 1a,A | 9.1 ± 1a,A | 9.0 ± 1a,A | 10.6 ± 1a,A | 10.4 ± 1a,A | 10.1 ± 1a,A | 8.1 ± 1a,B | 8.1 ± 1a,B | 8.0 ± 1a,B | 11.6 ± 1a,A | 11.4 ± 1a,A | 11.1 ± 1a,A |
H | 7.9 ± 1a,A | 7.7 ± 1a,A | 7.5 ± 1a,B | 8.9 ± 1a,A | 8.8 ± 1a,A | 8.7 ± 1a,A | 6.8 ± 1a,B | 6.7 ± 1a,B | 6.5 ± 1a,B | 10.9 ± 1a,A | 10.8 ± 1a,A | 10.7 ± 1a,A |
Split nut | 76 ± 5a,A | 70 ± 3a,A | 68 ± 4b,A | 70 ± 3a,A | 65 ± 2a,A | 72 ± 3a,A | 71 ± 5b,A | 75 ± 2a,A | 70 ± 3b,A | 55 ± 6a,B | 48 ± 4b,B | 46 ± 2b,B |
Blanks | 7 ± 2c,B | 12 ± 2b,B | 19 ± 1a,B | 10 ± 3b,B | 12 ± 3b,B | 18 ± 2a,B | 9 ± 3c,B | 13 ± 3b,B | 16 ± 2a,B | 25 ± 5c,A | 29 ± 2b,A | 35 ± 2a,A |
Infested | 6 ± 1b,A | 7 ± 2b,A | 10 ± 1a,A | 5 ± 2b,A | 4 ± 2b,A | 7 ± 1a,A | 6 ± 2b,A | 7 ± 2b,A | 11 ± 3a,A | 5 ± 2a,A | 4 ± 1b,A | 7 ± 2a,A |
Notes. Values are means (n = 3) ± SE (mean standard error). Different superscripted lowercase letters a, b, and c indicate difference (p < 0.05) among three irrigations treatments (T0: control; T1: regulated deficit irrigation; T2: stressed) in the same cultivar. Superscripted uppercase letters A, B, and C indicate differences (p < 0.05) among cultivars in the same treatment.
Yield: kg/tree; WP = water productivity (kg /m3); NDW = nut dry weight (g); NFW = nut fresh weight (g); L = length (mm); l = width (mm); and H = thickness (mm).
Pomological parameters showed statistically significant differences (p < 0.05) between stated cultivars (Table 2). The physical properties of nuts revealed that cv. Ohadi had the highest dimensions of length, L (18.2 mm) and width, l (11.6 mm). Ohadi nuts were thicker, larger, and longer than three other cultivars whereas the kernel of cv. Elguetar had the lowest dimensions (L = 14.8 mm, and l = 8.1 mm). In an experiment conducted in Tunisia, Ghrab et al. (2004) reported that cv. Ohadi produced nuts with a higher weight and a larger size. Nut dimensions presented significant differences between cultivars, mainly explained by the genotype. Carbonell-Barrachina et al. (2015) reported that the size of pistachio nuts was not affected by the RDI irrigation treatment. Cv. Mateur, Kerman, and Elguetar recorded the highest split nut rate of fruit dehiscence (76%, 70%, and 71%, respectively, with control treatment; Table 2). Cv. Ohadi showed the lowest split nut rate (55% with treatment T0, 48% with treatment T1, and 46% with treatment T2) and the highest rate (25%) of blanks. The split and blank proportions of nuts were also affected by the genotype. Present results were in accordance with Zribi et al. (2006), showing that cv. Ohadi presented a low split proportion of 49% whereas cv. Mateur had the higher split proportion (67%). Ghrab et al. (2004) reported that the high proportion of non-split nuts observed between cv. Ohadi and other varieties could be due to the cultivar and the season. The proportion of blanks was higher under stressed treatment (T2). These results were in accordance with the findings of Galindo et al. (2018), reporting that irrigation increased yield, nut size, and splitting, and reduced alternate bearing pattern and incidence of blank nuts. An explanation of blanks proportion in pistachio nuts could be attributed to lack of pollination, poor nutrition, rainfall during anthesis, and water deficit during seed development (Crane and Iwakiri, 1981). Present results showed lower proportions of infested nuts under different irrigation regimes. The observed fungal decay and insect infestation of the kernel was generally low in the present conditions.
Nut color parameters (L*, a*, b*, and C*) presented statistically significant differences (p < 0.05) among genotypes (Figure 4). L* varied from 40.7 in cv. Ohadi to 43.5 in cv. Kerman with control treatment. The a* value ranged from 22.9 in cv. Elguetar to 28.4 in cv. Mateur. The b* value ranged from 16.9 in cv. Mateur to 21.5 in cv. Elguetar. Similar results were reported by Carbonell-Barrachina et al. (2015) and Galindo et al. (2015), stating that the RDI treatments applied did not significantly affect pistachio nut color.
Figure 4. Variation in nut color from the pistachio cultivars (C) under irrigation treatments (T). L* means the brightness of the sample while a* and b* represent color directions, and C* = chroma. Values are mean values of three measurements (n = 3) ± SE. Different letters a, b, and c indicate significant differences between the storage periods of each cultivar (NS: not significant; *p < 0.05, **p < 0.01) according to Duncan’s multiple range test.
Regarding the effect of water regimes on pistachio nut color, results of the present study were in accordance with Guerrero et al. (2005), showing that irrigation increased kernel weight but did not show significant impact on shell and kernel colors. The obtained values in the present study were consistent with those observed by Dini et al. (2019), studying the kinetics of color degradation, chlorophylls, and xanthophylls loss in pistachio nuts during roasting.
Nut composition (moisture, carbohydrates, ash, protein, fiber, and oil yield) varied between cultivars, depending on RDI treatments (Table 3). Hence, treatment T2 presented significant (p < 0.05) lower values of carbohydrates, compared to the control and RDI treatments. Ash content also decreased under stressed treatment (T2), showing a statistically significant (p < 0.05) difference between cv. Mateur, Kerman, and Ohadi. The protein content ranged from 18.6% in cv. Mateur to 25.1% in cv. Ohadi. This trait was also affected by water restriction, showing significant (p < 0.05) lower values with treatment T2. The fiber content presented a similar trend showing significantly lower values with treatmentr T2 whereas treatments T0 and T1 presented the same content. Moisture in nuts decreased with decrease in water supply, showing significant (p < 0.05) lower values under stressed treatment T2.
Table 3. Nut composition (%) for the studied pistachio cultivars grown under RDI treatments.
Traits | Mateur | Elguetar | Kerman | Ohadi | |
---|---|---|---|---|---|
Carbohydrates | T0 | 9.20 ± 2a,A | 8.70 ± 1a,B | 7.80 ± 2a,B | 10.20 ± 1a,A |
T1 | 8.10 ± 2a,A | 8.10 ± 1a,A | 7.23 ± 2a,B | 9.83 ± 1a,A | |
T2 | 7.85 ± 2b,B | 7.73 ± 1b,B | 7.00 ± 2b,B | 9.35 ± 1b,A | |
Ash | T0 | 0.50 ± 0.2a,A | 0.43 ± 0.1a,B | 0.46 ± 0.1a,B | 0.52 ± 0.1a,A |
T1 | 0.45 ± 0.2a,A | 0.37 ± 0.1b,B | 0.45 ± 0.1a,A | 0.48 ± 0.1a,A | |
T2 | 0.36 ± 0.2b,B | 0.40 ± 0.1a,A | 0.38 ± 0.1b,B | 0.42 ± 0.1b,A | |
Proteins | T0 | 20.5 ± 0.1a,B | 22.5 ± 0.1a,A | 21.4 ± 0.1a,B | 25.1 ± 0.2a,A |
T1 | 19.3 ± 0.1a,B | 20.1 ± 0.1a,B | 20.4 ± 0.1a,B | 23.1 ± 0.2a,A | |
T2 | 18.6 ± 0.1b,B | 19.5 ± 0.1b,B | 19.1 ± 0.1b,B | 22.3 ± 0.2b,A | |
Fiber | T0 | 1.23 ± 0.5a,B | 1.35 ± 0.2a,B | 1.52 ± 0.5a,A | 1.60 ± 0.2a,A |
T1 | 1.20 ± 0.5a,B | 1.15 ± 0.2b,B | 1.34 ± 0.5a,A | 1.56 ± 0.2a,A | |
T2 | 1.13 ± 0.5b,B | 1.05 ± 0.2b,B | 1.12 ± 0.5b,B | 1.21 ± 0.2b,A | |
Moisture | T0 | 28.26 ± 0.6a,B | 29.94 ± 0.5a,A | 30.07 ± 0.6a,A | 35.61 ± 0.1a,A |
T1 | 24.52 ± 0.4b,B | 30.16 ± 0.4a,A | 29.47 ± 1.0a,A | 33.54 ± 0.6a,A | |
T2 | 22.92 ± 0.5b,B | 24.66 ± 0.7b,B | 26.41 ± 0.9b,B | 32.1 ± 0.6b,A | |
Oil yield (%) | T0 | 54.45 ± 0.3a,A | 53.62 ± 0.2a,A | 56.63 ± 0.1a,A | 46.84 ± 0.3b,B |
T1 | 54.07 ± 0.9a,A | 52.77 ± 0.2a,A | 55.76 ± 0.3a,A | 54.45 ± 0.3a,A | |
T2 | 54.38 ± 0.3a,A | 53.24 ± 0.1a,A | 57.11 ± 0.3a,A | 47.57 ± 0.2b,B |
FW: fresh weight; DW: dry weight, FC: fat content.
Data are presented as mean ± SE (n = 3). Different superscripted lowercase letters a, b, and c indicate difference (p < 0.05) among three irrigation treatments (T0: control; T1: regulated deficit irrigation; and T2: stressed) in the same cultivar. Uppercase superscripted letters A and B indicate differences (p < 0.05) among cultivars in the same treatment. Mean separation within columns by Scheffe´s test (p ≤ 0.05). In each column, values with the same letter are not significantly different.
Regarding oil yield, cv. Mateur, Elguetar, and Kerman presented similar values under three water regimes. Cv. Ohadi presented higher oil content under RDI treatment, showing a significant difference between treatments T0 and T2. These results were in accordance with those reported by Carbonell-Barrachina et al. (2015), stating that the nuts from treatment T1 showed the highest oil content, followed by control and treatment T2. Yahyavi et al. (2020) reported that differences in oil contents of pistachio cultivars could be due to differences in factors, such as growing conditions, harvesting, and climate.
As expected, irrigation regimes significantly affected nut composition, except for oil yield, which was consistent with water treatments. Nut composition identified cv. Ohadi with high carbohydrates, ash, protein, fiber, and moisture contents. In the present study, nut composition was affected by drought stress, showing lower contents in treatment T2. Kola et al. (2018) reported that irrigation increased crude fiber, ash, and oil contents of pistachio nuts, but decreased protein content. Oil yield showed the same pattern under three water regimes, showing that water restriction did not affect oil content.
Contents of anthocyanins, flavonoids, and total phenolics and the antioxidant capacity of pistachio nuts are shown in Table 4. Treatments T0 and T1 presented the same values of anthocyanins, flavonoids, total phenols, and RAC, showing statistically significant differences (p < 0.05) with treatment T2. Cv. Elguetar showed low flavonoid content, compared to other three cultivars. Cv. Mateur presented high TPC (410.5 mg GAE/100 g of DW), followed by cv. Kerman (365.38 mg GAE/100 g of DW). Changes in the antioxidant capacity of pistachio nuts were consistent with changes in flavonoid and TPC. The observed values of RAC with DPPH, FRAP, and β-carotene assays showed that DPPH scavenging ability was stronger, which could be due to specific antioxidant compounds discovered in pistachio nuts. In the present study, TPC in pistachio nuts presented high variability between cultivars under three water regimes. It was observed that treatments T0 and T1 presented high values of bioactive compounds whereas treatment T2 presented lower values. As stated by Ojeda-Amador et al. (2019), the observed variability in phenolic compounds was explained by different factors, such as cultivar, geographical origin, ripening stage, and industrial processing. Our findings were in line with the results of Noguera-Artiaga et al. (2020a), reporting that moderate RDI (T1 treatment) produced nuts with good functional quality (high values of TPC and antioxidant capacity), without affecting their sensory quality.
Table 4. Phenolic compounds in pistachio nuts under RDI.
Traits | Mateur | Elguetar | Kerman | Ohadi | |
---|---|---|---|---|---|
Pistachio fresh nuts | |||||
Anthocyanins | T0 | 7.72 ± 2a,A | 6.63 ± 1a,B | 6.38 ± 2a,B | 8.25 ± 1a,A |
T1 | 6.78 ± 2a,A | 5.98 ± 1a,B | 5.82 ± 2a,B | 7.51 ± 1a,A | |
T2 | 4.85 ± 2b,A | 4.38 ± 1b,A | 3.40 ± 2b,B | 4.33 ± 1b,A | |
Flavonoids | T0 | 12.18 ± 0.2a,B | 10.63 ± 0.1a,B | 15.38 ± 0.1a,A | 14.25 ± 0.1a,A |
T1 | 13.28 ± 0.2a,A | 8.68 ± 0.1a,B | 12.82 ± 0.1a,A | 13.51 ± 0.1a,A | |
T2 | 8.75 ± 0.2b,B | 7.38 ± 0.1b,B | 9.40 ± 0.1b,A | 10.33 ± 0.1b,A | |
Total phenols | T0 | 410.50 ± 0.1a,A | 323.63 ± 0.1a,B | 365.38 ± 0.1a,B | 334.25 ± 0.2a,B |
T1 | 385.50 ± 0.1a,A | 300.20 ± 0.1a,B | 305.58 ± 0.1b,B | 344.51 ± 0.2a,A | |
T2 | 311.50 ± 0.1b,A | 207.38 ± 0.1b,C | 257.40 ± 0.1c,B | 237.33 ± 0.2b,A | |
RAC | T0 | 121.90 ± 0.5a,B | 131.20 ± 0.2a,B | 162.43 ± 0.5a,A | 153.00 ± 0.2a,A |
T1 | 112.40 ± 0.5a,C | 123.08 ± 0.2a,B | 142.99 ± 0.5a,A | 132.69 ± 0.2a,B | |
T2 | 84.31 ± 0.5c,B | 92.75 ± 0.2b,A | 73.46 ± 0.5b,C | 102.47 ± 0.2b,A | |
FRAP | T0 | 125.00 ± 1.5a,B | 123.00 ± 0.5a,B | 150.00 ± 1.5a,A | 140.00 ± 0.5a,A |
T1 | 110.00 ± 1.0b,C | 120.00 ± 2.0a,B | 140.00 ± 1.5a,A | 143.00 ± 1.0a,A | |
T2 | 100.50 ± 0.5b,B | 123.00 ± 1.0a,A | 115.00 ± 1.0b,A | 98.00 ± 2.0b,B | |
β-carot (%) | T0 | 60.50 ± 2.0ª,A | 56.50 ± 1.0ª,A | 40.00 ± 2.0ª,A | 42.50 ± 2.0b,B |
T1 | 55.0 ± 3.0a,A | 52.0 ± 2.0a,A | 45.50 ± 2.0a,A | 57.10 ± 3.0a,A | |
T2 | 40.60 ± 2.0b,B | 43.60 ± 3.0b,B | 37.20 ± 1.0b,B | 52.20 ± 2.0a,A | |
ANOVA | C | * | * | * | * |
T | ** | ** | ** | ** | |
C*T | * | * | * | * |
Anthocyanin: mg C3Geq kg-1 of DW; flavonoids: mg CE/100 g of DW; total phenols: mg GAE/100 g of DW; RAC: relative antioxidant capacity (μg TE/g of DW). C3Geq: Cyanidin-3-glucoside equivalents; CE: catechin equivalents; GAE: gallic acid equivalence; β-carot: β-carotene bleaching activity; DW: dry weight.
Values are means (n = 3) ± SE. Different superscripted lowercase letters a, b, and c indicate difference (p < 0.05) among the irrigation treatments in the same cultivar. Superscripted uppercase letters A, B, and C indicate differences (p < 0.05) among cultivars (C) in the same treatment (T) (T0: control [100% ETc]; T1: treatment RDI [50% ETc during stage I and stage of nut development and 100% ETc during the stage III]; T2: stressed treatment (50% ETc).
Pistachio oil samples were investigated for acidity, chlorophyll, carotenoid pigments, and specific extinction coefficient (K232, and K270) as shown in Table 5. Physicochemical parameters varied between cultivars whereas water regimes did not show significant differences. Acidity showed a statistically significant difference (p < 0.05) between the studied cultivars. Cv. Ohadi showed the highest value (0.55 g/100 g) of acidity with treatment T2 whereas the lowest value (0.32 g/100 g) was observed in cv. Mateur with treatment T1. The lower values of acidity in oil samples of raw kernels indicated that hydrolytic rancidity had not occurred. Oil acidity observed in the present study was in the range of 0.37–0.62 meq O2/kg of oil, as also reported by Daneshmandi et al. (2014).
Table 5. Physicochemical and biochemical parameters of pistachio oil of the four studied cultivars grown with RDI treatments.
Cultivar | Treatment | Acidity | Chlorophyll | Carotenoids | K232(1%) | K270(1%) | Total phenols | RAC | FRAP | β-carot |
---|---|---|---|---|---|---|---|---|---|---|
Mateur | T0 | 0.35 ± 0.1a,B | 3.89 ± 0.05a,C | 27.38 ± 2.0a,C | 1.85 ± 0.14a,B | 0.17 ± 0.04a,A | 128.26 ± 0.1a,B | 48.80 ± 0.5a,B | 52.50 ± 1.0a,B | 47.20 ± 2.0a,B |
T1 | 0.32 ± 0.2b,B | 4.20 ± 0.01a,B | 26.59 ± 1.6a,B | 1.88 ± 0.25a,B | 0.15 ± 0.05a,A | 127.21 ± 0.1a,B | 42.40 ± 0.5b,A | 40.10 ± 0.5b,B | 35.70 ± 1.5b,B | |
T2 | 0.40 ± 0.1a,B | 3.93 ± 0.27a,C | 27.27 ± 0.7a,B | 1.84 ± 0.11a,B | 0.17 ± 0.01a,A | 113.79 ± 0.1b,B | 30.20 ± 0.5c,A | 50.50 ± 1.0a,A | 45.30 ± 2.0a,A | |
Elguetar | T0 | 0.44 ± 0.1a,A | 4.91 ± 0.96a,B | 31.61 ± 2.1a,B | 1.98 ± 0.19a,A | 0.14 ± 0.03a,A | 109.58 ± 0.1a,C | 53.63 ± 0.2a,A | 62.20 ± 0.5a,A | 57.10 ± 1.5a,A |
T1 | 0.37 ± 0.2a,B | 4.71 ± 0.40a,B | 34.74 ± 1.4a,A | 2.12 ± 0.11a,A | 0.15 ± 0.04a,A | 113.36 ± 0.1a,B | 40.98 ± 0.2b,A | 53.50 ± 1.0b,A | 48.20 ± 1.0b,A | |
T2 | 0.40 ± 0.1a,B | 4.63 ± 0.64a,B | 32.43 ± 0.3a,A | 2.01 ± 0.41a,A | 0.14 ± 0.07a,A | 101.55 ± 0.1b,B | 27.38 ± 0.2c,B | 45.50 ± 0.5c,B | 40.30 ± 1.5c,B | |
Ohadi | T0 | 0.49 ± 0.1a,A | 7.35 ± 0.05b,A | 38.04 ± 2.0a,A | 2.17 ± 0.10a,A | 0.18 ± 0.04a,A | 138.85 ± 0.2a,A | 47.25 ± 0.2a,B | 45.55 ± 0.5a,C | 40.25 ± 1.5a,C |
T1 | 0.42 ± 0.1b,A | 8.11 ± 0.05a,A | 38.66 ± 2.0a,A | 2.31 ± 0.11a,A | 0.19 ± 0.01a,A | 137.25 ± 0.2a,A | 37.51 ± 0.2b,B | 47.20 ± 1.5a,B | 42.70 ± 2.5a,B | |
T2 | 0.55 ± 0.1a,A | 7.80 ± 0.95a,A | 36.37 ± 2.0b,A | 2.05 ± 0.10b,A | 0.17 ± 0.01a,A | 125.41 ± 0.2b,A | 27.33 ± 0.2c,B | 47.15 ± 2.0a,B | 44.55 ± 1.0a,A | |
Kerman | T0 | 0.43 ± 0.1b,A | 5.07 ± 0.31a,B | 29.28 ± 4.2a,C | 1.67 ± 0.06b,C | 0.15 ± 0.03b,A | 73.25 ± 0.1b,C | 40.80 ± 0.5a,C | 50.20 ± 1.5a,C | 45.50 ± 2.5a,C |
T1 | 0.43 ± 0.1b,A | 5.35 ± 0.09a,B | 29.21 ± 6.4a,B | 1.86 ± 0.05a,B | 0.18 ± 0.03a,A | 76.67 ± 0.1a,C | 32.82 ± 0.5b,C | 30.10 ± 1.0b,C | 25.50 ± 2.0b,C | |
T2 | 0.54 ± 0.1a,A | 5.34 ± 0.42a,B | 29.39 ± 1.2a,B | 1.71 ± 0.04a,B | 0.16 ± 0.04a,A | 68.29 ± 0.1c,C | 22.40 ± 0.5c,C | 32.20 ± 0.5b,C | 27.50 ± 1.5b,C | |
ANOVA | C | * | * | * | * | NS | * | * | * | * |
T | * | * | * | * | NS | * | * | * | * | |
C*T | * | NS | NS | NS | NS | ** | ** | ** | ** |
Acidity: g 100 g-1; chlorophyll: mg kg-1; carotenoids: mg kg-1; K232 = absorbance at a wavelength of 232 nm; K270 = absorbance at a wavelength of 270 nm; total phenols: mg kg-1; RAC: relative antioxidant capacity (μg TEg-1 of DW). T0: control (100% ETc); T1: regulated deficit irrigation (RDI; 50% ETc during stage I and stage of nut development and 100% ETc during stage III); T2: stressed treatments (50% ETc).
Values are means (n = 3) ± SE. Different superscripted lowercase letters a, b, and c indicate difference (p < 0.05) among three irrigation treatments (T0, T1, and T2) in the same cultivar. Different superscripted uppercase letters A, B, and C indicate differences (p < 0.05) among cultivars in the same treatment.
Arena et al. (2007) found 6.8 meq O2/kg of oil as peroxide number in Iranian pistachio oil. Yahyavi et al (2020) reported that the peroxide number was the main indicator of fat oxidation, measuring the concentration of hydroperoxide formed during lipid oxidation. The specific extinction index is often used to evaluate the presence of primary (K232) or secondary (K270) oxidation products. The K232 values in pistachio oil were higher in cv. Ohadi (2.17, 2.31, and 2.05 for treatments T0, T1, and T2, respectively) followed by cv. Elguetar. Interestingly, no significant variation of RI, even at 270 nm, was observed in pistachio oil of the studied cultivars. RI of pistachio oil samples was the same between cultivars (1.47) and years of study. These results were consistent with the results of the previous studies, reporting that the RI of pistachio oil was around 1.4 for different varieties and regions without any significant changes (Yahyavi et al., 2020; Yildiz et al., 1998). Results further showed that cv. Ohadi showed the most considerable content of chlorophyll for three irrigation regimes (7.35, 8.11, and 7.8 mg/kg for treatments T0, T1, and T2, respectively). However, carotenoids content showed a significant difference (p < 0.05) between cultivars. Hence, carotenoid dominated in cv. Ohadi (38.04, 38.66, and 36.37 mg/kg for treatments T0, T1, and T2, respectively), followed by cv. Elguetar. Analysis revealed that the oil extracted from cv. Mateur had the lowest content of carotenoids (25.38 mg/kg) for treatment T0. Treatment T0 showed lower values of carotenoids, compared to treatments T1 and T2. Bellomo and Fallico (2007) reported that the content of pigments in pistachio oils was in the range of 18–52 mg/kg of DW. These values were linked to genotype, degree of ripeness, environmental conditions, and geographical origin (Giuffrida et al., 2006).
The TPC of the extracted pistachio oil in control and treatment T1 was the same, showing a statistically significant difference (p < 0.05) with the treatment T2 (Table 5). Among cultivars studied, TPC of pistachio oil samples showed statistically significant differences (p < 0.05). Cv. Ohadi had the highest values of TPC, followed by cv. Mateur and Elguetar, while cv. Kerman presented the lowest values of TPC for three irrigation treatments. Irrigation treatments significantly affected the TPC, with treatment T2 presenting lower values for the four studied cultivars. These results were in line with the study done by Miraliakbari and Shahidi (2008), showing a TPC of 158 mg/kg oil for commercial pistachio. Irrigation treatments affected significantly the TPC, with treatment T2 presenting the lowest values in the four studied cultivars.
The RAC values conducted with DPPH assay showed values of DPPH ranging from 22.40 µg TE/g to 53.63 µg TE/g of oil. Pistachio oil from treatment T2 always presented lower values of RAC, compared to treatment T0 and RDI (treatment T1). Extracted oil from cv. Kerman showed lower values for AC and presented statistically significant difference (p < 0.05) compared to cv. Mateur, Ohadi, and Elguetar. The AC values were consistent within the range of 20.7–87.4 µg TE/g of oil as reported in a previous paper on fatty acid composition, antioxidant, and antibacterial activities of Pistacia fruit oils (Mezni et al., 2020).
Pearson’s correlation between antioxidants showed a strong positive association between total phenols and DPPH (r = 0.45), flavonoids and anthocyanin (r = 0.56), flavonoids and FRAP (r = 0.52), and flavonoids and β-carot (r = 0.40) (Table 6). A low positive correlation was observed between anthocyanin and β-carot (r = 0.32). Negative correlations were observed between total phenols and flavonoids (r = -0.50), total phenols and anthocyanin (r = -0.62), total phenols and FRAP (r = -0.68), and anthocyanin and β-carot (r = -0.70). Moreover, a positive relationship (r = 0.45) that manifested between total phenols and DPPH implied the contribution of phenols in DPPH capacity. However, total phenols showed a negative correlation with FRAP and β-carot. Meanwhile, flavonoids and anthocyanin had a positive correlation with FRAP and β-carot but a negative association with DPPH. These demonstrated their contributions to radical scavenging in pistachio nuts, but they were not key components of DPPH activity.
Table 6. Correlation between antioxidants and antioxidant activity in pistachio nuts.
TP | Flav | Anth | FRAP | DPPH | β-carot | |
---|---|---|---|---|---|---|
TP | 1 | –0.50** | –0.62** | –0.68** | 0.45** | –0.70** |
Flav | 1 | 0.56** | 0.52** | –0.32* | 0.40* | |
Anth | 1 | 0.60** | –0.42** | 0.32** | ||
FRAP | 1 | –0.10NS | 0.60** | |||
DPPH | 1 | –0.37** | ||||
β-carot | 1 |
*, **, and *** indicate significance at p < 0.05, 0.01, and 0.001, respectively.
NS = not significant; TP: total phenols; Flav: flavonoids; Anth: anthocyanin; FRAP: ferric-reducing antioxidant power; DPPH: 1,1-diphenyl-2-picrylhydrazyl capacity; β-carot: β-carotene bleaching activity assay.
The analysis of volatile compounds in raw pistachio nuts identified 76 volatiles belonging to the chemical classes of acids, aldehydes, alcohols, terpenes, ketones, esters, aromatics, and nitrogen compounds as shown in Table 7. Water regime affected the volatile content of the studied cultivars, showing high values in treatment T2 whereas treatments T0 and T1 presented similar volatile compounds content. The most abundant compounds were terpenes, such as α-pinene, terpinolene, and limonene, followed by 1-methyl-pyrrole. Terpenes and 1-methyl-pyrrole (nutty and sweet) constituted 80% of volatile compounds. The results revealed statistically significant differences (p < 0.05) in the contents of volatile compounds of the studied cultivars under three water regimes. The amount of terpenes and 1-methyl-pyrrole in raw pistachio nuts was higher with T2 stressed treatment in all studied cultivars. In the same manner, aliphatic alcohols, aldehydes, and 1-methyl-pyrrole also increased with decrease in water regime. Hence, the amount of 1-methyl-pyrrole increased by about 50% in cv. Mateur and Ohadi with stressed treatment T2. Alcohols were the second most represented class consisting mainly of 1-hexanol, 1-nonanol, and 1-dodecanol. Among the aldehydes, nonanal (nonanaldehyde) had the highest content, especially in cv. Ohadi and Elguetar.
Table 7. Amount* of volatile aroma compounds for classes of substances in raw pistachio samples of the four studied pistachio cultivars subjected to different irrigation treatments.
Compounds | LRI | Mateur | Kerman | Ohadi | Elguetar | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
VF-Vax | SLB-5 | T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | |
Acids | ||||||||||||||
Acetic | 1,448 | 596 | 195b | 201b | 176a | 273b | 284b | 142a | 174a | 172a | 314b | 157a | 143a | 296b |
Isobutyric | 1,566 | 742 | 54b | 60b | 0a | 10a | 15a | 18a | 103b | 111b | 88a | 46b | 50b | 35a |
Pentanoic | 1,740 | 894 | 101b | 105b | 36a | 40a | 38a | 43a | 161b | 180b | 70a | 35a | 36a | 53b |
Hexanoic | 1,849 | 983 | 200a | 206a | 225b | 372b | 315a | 325a | 342a | 349a | 387a | 361a | 386a | 526b |
2-Ethyl-hexanoic | 1,952 | 1,123 | 32a | 33a | 38a | 75b | 79b | 25a | 53a | 52a | 47a | 20a | 29a | 48b |
Octanoic | 2,062 | 1,180 | 173b | 159b | 84a | 79a | 96b | 77a | 150a | 172a | 163a | 214b | 244b | 136a |
Nonanoic | 2,149 | 1,280 | 119a | 125a | 208b | 162b | 120a | 135a | 389b | 355b | 319a | 172a | 170a | 230b |
All | 874b | 889b | 767a | 1011c | 947b | 765a | 1,372a | 1,391a | 1,388a | 1,005a | 1,058a | 1,324b | ||
Aldehydes | ||||||||||||||
2-Methyl-butanal | 915 | 646 | 55a | 53a | 78b | 71a | 71a | 96b | 33a | 25a | 87b | 23a | 29a | 48b |
3-Methyl-butanal | 919 | 652 | 20a | 17a | 44b | 28a | 22a | 39b | 12a | 19a | 30b | 13a | 19a | 38b |
Hexanal | 1,076 | 810 | 850a | 871a | 1218b | 356a | 359a | 579b | 165a | 166a | 374b | 504a | 578a | 842b |
Heptanal | 1,175 | 912 | 410a | 428a | 531b | 180a | 235a | 295b | 121a | 133a | 289b | 146a | 143a | 267b |
Octanal | 1,279 | 1,006 | 120a | 132a | 245b | 30a | 26a | 56b | 60a | 58a | 254b | 235a | 241a | 320b |
(Z)-2-Heptenal | 1,316 | 964 | 129a | 144a | 172b | 29a | 35a | 50b | 95a | 93a | 184b | 79a | 84a | 188b |
Nonanal | 1,377 | 1,107 | 410a | 432a | 552b | 495a | 545a | 968b | 1,732a | 1,681a | 3,819b | 2,491a | 2,556b | 3,344c |
(E)-2-Octenal | 1,419 | 1,057 | 33a | 34a | 40a | 80a | 79a | 203b | 63a | 66a | 124b | 24a | 27a | 31a |
Decanal | 1,491 | 1,209 | 168a | 177a | 264b | 175a | 157a | 246b | 216a | 230a | 351b | 128a | 155a | 258b |
Benzaldehyde | 1,520 | 953 | 166a | 167a | 189b | 133a | 131a | 238b | 132a | 133a | 281b | 75a | 84a | 186b |
(E)-2-Nonenal | 1,530 | 1,161 | 144a | 136a | 240b | 160a | 122a | 273b | 180a | 226a | 337b | 145a | 104a | 270b |
1-Methyl-pyrrole-2-carboxaldehyde | 1,621 | 993 | 39a | 41a | 84b | 27a | 21a | 47b | 26a | 21a | 102b | 26a | 24a | 72b |
All | 2,544a | 2,632a | 3,657b | 1,764a | 1,803a | 3,090b | 2,835a | 2,851a | 6,232b | 3,889a | 4,044b | 5,864c | ||
Alcohols | ||||||||||||||
2-Methyl-1-butanol | 1,201 | 730 | 289a | 275a | 394b | 97a | 107a | 209b | 88a | 99a | 150b | 99a | 100a | 143b |
1-Pentanol | 1,240 | 768 | 92a | 90a | 254b | 168a | 199b | 618c | 603a | 622a | 859b | 323a | 360a | 786b |
Heptan-2-ol | 1,307 | 900 | 125a | 129a | 266b | 80a | 76a | 120b | 112a | 116a | 380b | 81a | 111a | 144b |
Hexanol | 1,340 | 871 | 364a | 344a | 750b | 1,574a | 1,523a | 2,683b | 2,202a | 2,209a | 2,861b | 3,064a | 3,066a | 4,025b |
2-Butoxy-ethanol | 1,393 | 910 | 160a | 175a | 219b | 330a | 344a | 578b | 308a | 302a | 411b | 253a | 279a | 324b |
2-Octanol | 1,406 | 997 | 77a | 89a | 132b | 32a | 47a | 68b | 53a | 86a | 124b | 58a | 55a | 137b |
1-Octen-3-ol | 1,437 | 985 | 240a | 220a | 331b | 177a | 156a | 321b | 174a | 163a | 240b | 223a | 236a | 290b |
1-Heptanol | 1,443 | 972 | 270b | 201a | 633c | 275a | 284a | 511b | 350a | 363a | 383a | 337a | 339a | 778b |
6-Methyl-hept-5-en-2-ol | 1,451 | 994 | 87a | 90a | 161b | 105a | 120a | 277b | 105a | 101a | 154b | 79a | 106a | 183b |
2-Ethyl-1-hexanol | 1,477 | 1,038 | 271a | 293a | 335b | 449a | 474a | 597b | 510a | 501a | 584b | 340a | 376a | 476b |
Nonan-2-ol | 1,507 | 1,088 | 53a | 41a | 90b | 45a | 53a | 87b | 60a | 62a | 118b | 52a | 67a | 139b |
1-Octanol | 1,548 | 1,075 | 328a | 377a | 643b | 1,311a | 1,297a | 2,773b | 631a | 637a | 950b | 851a | 868a | 938b |
1-Nonanol | 1,653 | 1,172 | 387a | 417a | 532b | 727a | 785a | 899b | 955a | 958a | 1,112b | 1,039a | 1,047a | 1,494b |
(Z)-3-Nonen-1-ol | 1,680 | 1,160 | 43a | 40a | 124b | 56a | 53a | 151b | 46a | 42a | 92b | 46a | 56a | 79a |
1-Decanol | 1,760 | 1,267 | 102a | 99a | 216b | 72a | 85a | 167b | 81a | 87a | 101a | 109a | 138a | 222b |
Benzylalchohol | 1,879 | 1,029 | 176a | 173a | 240b | 175a | 173a | 241b | 216a | 213a | 245b | 361a | 343a | 480b |
Phenylethylalchohol | 1,913 | 1,112 | 80a | 92a | 190b | 165a | 135a | 294b | 132a | 184a | 257b | 313a | 317a | 397b |
1-Dodecanol | 1,967 | 1,475 | 317a | 378a | 991b | 205a | 184a | 292b | 148a | 114a | 765b | 112a | 139a | 472b |
All | 3,461a | 3,523a | 6,501b | 6,043a | 6,095a | 10,886b | 6,774a | 6,859b | 9,786c | 7,740a | 8,003b | 11,507c | ||
Terpenes | ||||||||||||||
Tricyclene | 1,005 | 922 | 129a | 119a | 246b | 76a | 78a | 180b | 112a | 102a | 200b | 131a | 140a | 268b |
α-Pinene | 1,019 | 940 | 1,6103b | 15,895a | 17,433c | 11,018a | 12,897b | 15,450c | 13,458a | 13,357a | 16,501b | 15,071a | 15,602b | 16,309c |
α-Thujene | 1,023 | 932 | 76a | 83a | 96a | 222a | 201a | 390b | 224a | 217a | 402b | 81a | 100a | 123a |
α-Fenchene | 1,052 | 953 | 53a | 43a | 79a | 59a | 54a | 70a | 38a | 37a | 47a | 59a | 61a | 74a |
Camphene | 1,058 | 955 | 473a | 502a | 654b | 393a | 362a | 1034b | 500a | 529a | 661b | 522b | 474a | 637c |
β-Pinene | 1,094 | 980 | 808a | 807a | 934b | 399a | 530b | 1483c | 1780a | 1774a | 1851b | 663a | 639a | 750b |
Sabinene | 1,107 | 978 | 40a | 38a | 57a | 138a | 134a | 202b | 91a | 91a | 111a | 42a | 30a | 61a |
2-Carene | 1,119 | 1006 | 80a | 82a | 113a | 108a | 114a | 137b | 87a | 104a | 245b | 46a | 42a | 149b |
3-Carene | 1,128 | 1,012 | 445a | 456a | 483a | 215a | 234a | 340b | 514a | 487a | 670b | 138a | 173b | 571c |
Myrcene | 1,138 | 991 | 809a | 806a | 1420b | 818a | 849a | 2,575b | 1,113a | 1,114a | 1,325b | 1,954a | 2,232b | 3,817c |
α-Phellandrene | 1,141 | 1,005 | 106a | 117a | 320b | 217a | 255a | 278a | 192a | 183a | 282b | 138a | 146a | 274b |
α-Terpinene | 1,153 | 1,018 | 158a | 144a | 250b | 212a | 192a | 600b | 250a | 288a | 356b | 284a | 258a | 860b |
Limonene | 1,183 | 1,032 | 2,215a | 2,243a | 4,088b | 12,618a | 13,499b | 16,691c | 11,528a | 11,842b | 17,707c | 10,768a | 10,943b | 12,120c |
β-Phellandrene | 1,194 | 1,030 | 210a | 261a | 356b | 369a | 318a | 553b | 423a | 429a | 385b | 132a | 187a | 328b |
γ-Terpinene | 1,231 | 1,064 | 335a | 327a | 456b | 1351b | 1292a | 1516c | 632a | 640a | 1211b | 742a | 754a | 938b |
β-Ocimene | 1,236 | 1,050 | 50a | 43a | 73a | 208a | 183a | 326b | 49a | 37a | 82b | 489a | 532a | 937b |
p-Cymene | 1,246 | 1,022 | 1,778a | 1,786a | 1,813b | 2,365a | 2,500b | 3,202c | 1,448a | 1,997b | 3,029c | 2,206a | 2,292b | 2,957c |
o-Cymene | 1,250 | 1,021 | 47a | 50a | 105b | 344a | 360a | 429b | 207a | 209a | 316b | 15a | 37a | 79b |
Terpinolene | 1256 | 1088 | 9421a | 9394a | 10058b | 2119a | 2159a | 5743b | 2612a | 2789b | 3664c | 6958b | 6875a | 7794c |
p-Mentha-1,5,8-triene | 1,410 | 1,113 | 180a | 197a | 330b | 61a | 52a | 80a | 69a | 76a | 80a | 101a | 128a | 282b |
p-Cymenene | 1,423 | 1,091 | 1,078a | 1,016a | 1,498b | 512a | 503a | 614b | 599a | 580a | 966b | 1,404a | 1,438a | 2,669b |
m-Cymenene | 1,431 | 1,085 | 68a | 79a | 139b | 352a | 314a | 402b | 243a | 255a | 412b | 152a | 134a | 233b |
Camphor | 1,509 | 1,143 | 78a | 95a | 154b | 137a | 124a | 255b | 99a | 118a | 271b | 128a | 127a | 310b |
Linalool | 1,536 | 1,098 | 117a | 111a | 285b | 242a | 283a | 363b | 129a | 109a | 227b | 173a | 158a | 314b |
α-Terpineol | 1,694 | 1,191 | 38a | 30a | 89b | 105a | 109a | 242b | 38a | 37a | 62b | 26a | 39a | 86b |
m-Cymen-8-ol | 1,850 | 1,185 | 179a | 187a | 389b | 161a | 168a | 208b | 162a | 187a | 206b | 294a | 287a | 423b |
Nerylacetone | 1,855 | 1,435 | 90a | 87a | 219b | 23a | 29a | 50b | 19a | 25a | 53b | 80a | 62a | 142b |
Eucalyptol | 1,190 | 1,032 | 44a | 35a | 75b | 870a | 872a | 902b | 113a | 106a | 143b | 38a | 53a | 114b |
Bornylacetate | 1,575 | 1,280 | 20a | 25a | 58b | 38a | 37a | 51b | 35a | 32a | 48a | 18a | 16a | 112b |
All | 35,228a | 35,058a | 42,270b | 35,750a | 38,702b | 54,366c | 36,764a | 37,751b | 51,513c | 42,853a | 43,959b | 53,731c | ||
Ketones | ||||||||||||||
6-Methyl-5-hepten-2-one | 1,326 | 986 | 113a | 156b | 220c | 208a | 235a | 391b | 136a | 151a | 321b | 320a | 305a | 691b |
Oct-3-en-2-one | 1,399 | 1,040 | 34a | 46a | 176b | 89a | 83a | 177b | 55a | 60a | 134b | 119a | 141a | 235a |
Acetophenone | 1,651 | 1,068 | 43a | 37a | 131b | 32a | 54a | 137b | 41a | 62a | 152b | 48a | 39a | 138b |
All | 190a | 239a | 527b | 329a | 372a | 705b | 232a | 273a | 607b | 487a | 485a | 1,064b | ||
Others | ||||||||||||||
Toluene | 1,038 | 761 | 83a | 94a | 79a | 148b | 100a | 84a | 183a | 163a | 155a | 145b | 99a | 121b |
1-Methyl-pyrrole | 1,133 | 750 | 3,917a | 3,952a | 6,925b | 5,462a | 5,612b | 7,415c | 2,648a | 2,700b | 5,901c | 2,790a | 2,863a | 5,374b |
Styrene | 1,242 | 889 | 35a | 28a | 25a | 22a | 20a | 55b | 36a | 18a | 32a | 41a | 31a | 49a |
Octylacetate | 1,465 | 1,213 | 15a | 24a | 48b | 105b | 105b | 67a | 44a | 40a | 55a | 36a | 35a | 71b |
Benzothiazole | 1,956 | 1,224 | 351a | 347a | 428b | 279a | 270a | 432b | 361a | 388a | 410b | 340a | 355a | 417b |
Phenol | 2,011 | 992 | 212a | 204a | 354b | 270a | 263a | 320b | 244a | 276a | 348b | 250a | 230a | 355b |
γ-Nonalactone | 2,032 | 1,344 | 36a | 20a | 124b | 13a | 20a | 52b | 35a | 42a | 143b | 35a | 45a | 85b |
All | 4,649c | 4,677c | 8,031a | 6,301b | 6,390b | 8,425a | 3,551c | 3,627c | 7,044b | 3,637c | 3,658c | 64,72b |
Peak area, arbitrary scale; T0: control; T1: regulated deficit irrigation (RDI); T2: stressed; different lowercase superscripted letters in the same row indicate difference (p < 0.05) among three irrigation treatments (T0, T1, and T2) and cultivars by Scheffe´s test.
Seventy volatiles were identified in pistacho nuts after the roasting process, including acids, aldehydes, alcohols, terpenes, ketones, esters, aromatic compounds, pyridine, pyrazines, pyrimidines, and furan derivatives (Table 8). The predominant volatile compounds were α-pinene and limonene, which are terpenes. Terpenes constituted the primary class of substances, comprising 50% of all volatile compounds, followed by aldehydes and nitrogenous compounds. The roasted pistachio showed an evident increase in pyridine, pyrazines, pyrimidines, furan derivatives, and aldehydes arising from Maillard reaction during roasting (Table 8).
Table 8. Amount* of volatile compounds and classes of substances in roasted pistachio samples of the four studied pistachio cultivars subjected to different irrigation treatments.
Compounds | LRI | Mateur | Kerman | Ohadi | Elguetar | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
VF-Vax | SLB-5 | T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | T0 | T1 | T2 | |
Acids | ||||||||||||||
Acetic | 1,448 | 596 | 584a | 591a | 649b | 514b | 548b | 437a | 261a | 395b | 372b | 220a | 252a | 339b |
Pentanoic | 1,740 | 894 | 55a | 50a | 55a | 49a | 57a | 71b | 41a | 43a | 48a | 73a | 89a | 135b |
Hexanoic | 1,849 | 983 | 755b | 784b | 703a | 328b | 273a | 305b | 547a | 564a | 559a | 1,309a | 1,399b | 1,322a |
Heptanoic | 1,956 | 1,083 | 336a | 363b | 316a | 219a | 210a | 238a | 204a | 235b | 238b | 442a | 410a | 580b |
Octanoic | 2,062 | 1,180 | 286a | 269a | 332b | 89a | 76a | 85a | 117a | 126a | 144b | 378a | 357a | 395b |
Nonanoic | 2,149 | 1,280 | 351b | 327a | 320a | 119a | 118a | 165b | 217a | 249b | 213a | 221a | 220a | 225a |
All | 2,367a | 2,384a | 2,375a | 1,318b | 1,282a | 1,301b | 1,387a | 1,612c | 1,574b | 2,643a | 2,727b | 2,996c | ||
Aldehydes | ||||||||||||||
2-Methyl-butanal | 915 | 646 | 2,148a | 2,604b | 2,847c | 1,674a | 1,975b | 3,412c | 1,858a | 1,856a | 5,229b | 4,733a | 4,733a | 6,105b |
3-Methyl-butanal | 918 | 652 | 972a | 977a | 1083b | 684a | 688a | 890b | 449a | 495a | 631b | 155a | 180a | 348b |
Pentanal | 919 | 715 | 307a | 316a | 445b | 248a | 273a | 478b | 170a | 147a | 509b | 129a | 126a | 345b |
Hexanal | 1,076 | 810 | 1,658a | 1,617a | 2,404b | 1,073a | 1,016a | 2,436b | 1,388a | 1,381a | 1,783b | 1,300a | 1,356a | 2,675b |
Heptanal | 1,175 | 912 | 378a | 373a | 423b | 113a | 92a | 501b | 746a | 791a | 948b | 584a | 589a | 813b |
Octanal | 1,279 | 1,006 | 748a | 725a | 1514b | 742a | 699a | 822b | 919a | 918a | 2,705b | 1,444a | 1,440a | 2,189b |
Nonanal | 1,377 | 1,107 | 5,250a | 5,166a | 8,844b | 2,580a | 2,573a | 4,084b | 2,81a | 2,70a | 398b | 56a | 64a | 780b |
(E)-2-Octenal | 1,419 | 1,057 | 19a | 65b | 91c | 32a | 24a | 76b | 55a | 91a | 276b | 272a | 261a | 315b |
Decanal | 1,491 | 1,209 | 45a | 56a | 98b | 12a | 18a | 54b | 154a | 172a | 360b | 60a | 76a | 122b |
Benzaldehyde | 1,520 | 953 | 467a | 418a | 611b | 609a | 655a | 758b | 890a | 848a | 1,082b | 769a | 761a | 1,494b |
(E)-2-Nonenal | 1,530 | 1,161 | 292a | 350b | 540c | 11a | 16a | 23b | 69a | 70a | 199b | 39a | 44a | 77b |
1-Methy-pyrrole-2-carboxaldehyde | 1,621 | 993 | 154a | 146a | 385b | 112a | 122a | 295b | 129a | 139a | 424b | 322a | 307a | 465b |
Benzeneacetaldehyde | 1,644 | 1,043 | 74a | 78a | 199b | 156a | 167a | 300b | 232a | 231a | 430b | 54a | 67a | 154b |
Pyrrole-2-carboxaldehyde | 2,028 | 1,015 | 45a | 56a | 123b | 51a | 75b | 90c | 59a | 82a | 134b | 78a | 99a | 236b |
All | 12,557a | 12,947a | 19,607b | 8,097a | 8,393a | 14,219b | 7,399a | 7,491a | 15,108b | 9,995a | 10,103b | 16,118c | ||
Alcohols | ||||||||||||||
2-Methyl-1-butanol | 1,201 | 730 | 178a | 201b | 369c | 312a | 325a | 426b | 163a | 165a | 542b | 160a | 187a | 255b |
Hexanol | 1,340 | 871 | 1,435a | 1,433a | 2,395b | 1,066a | 1,087a | 1,941b | 1,739a | 1,762a | 2,380b | 963a | 1,116a | 2,451b |
2-Octanol | 1,406 | 997 | 71a | 82a | 124b | 61a | 40a | 120b | 103a | 110a | 261b | 398a | 421a | 564b |
1-Heptanol | 1,443 | 972 | 487a | 481a | 710b | 251a | 221a | 599b | 341a | 447a | 644b | 165a | 184a | 295b |
2-Ethyl-1-hexanol | 1,478 | 1,038 | 165a | 219b | 375c | 330a | 302a | 473b | 257a | 276a | 894b | 357a | 365a | 723b |
1-Octanol | 1,548 | 1,548 | 1,114a | 1,180a | 1,575b | 1,156a | 1,178a | 2,106b | 1,073a | 1,072a | 2,111b | 87a | 85a | 180b |
1-Nonanol | 1,653 | 1,653 | 539a | 615b | 824c | 534a | 554a | 680b | 599a | 601a | 791b | 419a | 467a | 606b |
Benzylalchohol | 1,879 | 1,029 | 56a | 59a | 143b | 179a | 144a | 214b | 176a | 168a | 602b | 420a | 452a | 676b |
Phenylethylalchohol | 1,913 | 1,112 | 167a | 162a | 209b | 300a | 335a | 410b | 516a | 547a | 702b | 170a | 179a | 739b |
1-Dodecanol | 1,967 | 1,475 | 1,193a | 1,200b | 1,738c | 70a | 132b | 274c | 94a | 90a | 163b | 61a | 67a | 99b |
Pentadecanol | 2,151 | 1,778 | 352a | 298a | 451b | 69a | 64a | 80b | 42a | 41a | 100b | 29a | 32a | 75b |
All | 5,757a | 5,930a | 8,913b | 4,328a | 4,382a | 7,323c | 5,103a | 5,279a | 9,190b | 3,229a | 3,582a | 6,663b | ||
Terpenes | ||||||||||||||
Tricyclene | 1,005 | 922 | 127a | 132a | 303b | 124a | 100a | 208b | 154a | 161a | 268b | 105a | 108a | 129b |
α-Pinene | 1,019 | 940 | 14,739a | 1,5114b | 16,556c | 10,193a | 10,997b | 13,215c | 14,984a | 15,700b | 16,259c | 13,722a | 14,159b | 16,063c |
α-Thujene | 1,023 | 932 | 111a | 103a | 228b | 198a | 192a | 303b | 161a | 167a | 346b | 309a | 370a | 910b |
Camphene | 1,058 | 955 | 669a | 613a | 768b | 851a | 857a | 1043b | 693a | 695a | 757b | 659a | 652a | 789b |
β-Pinene | 1,094 | 980 | 859a | 870a | 1020b | 1015a | 1020a | 1240b | 980a | 1074b | 2079c | 491a | 538a | 679b |
Sabinene | 1,107 | 978 | 24a | 30a | 44a | 35a | 55a | 105b | 130a | 123a | 168b | 109a | 118a | 236b |
Myrcene | 1,138 | 991 | 1,296a | 1,323a | 1,582b | 1,077a | 1,080a | 1,406b | 1,281a | 1,465b | 3,278c | 2,328a | 2,883b | 4,570c |
α-Terpinene | 1,153 | 1,018 | 291a | 297a | 378b | 424a | 444a | 792b | 251a | 283a | 366b | 1,729a | 1,770a | 2,917b |
Limonene | 1,183 | 1,032 | 6,313a | 6,867b | 9,348c | 9,266a | 9,366b | 10,613c | 10,855a | 10,852a | 15,004b | 1,4888a | 15,821b | 17,002c |
β-Phellandrene | 1,194 | 1,030 | 201a | 170a | 309b | 388a | 420a | 540b | 381a | 417a | 638b | 359a | 439b | 664c |
γ-Terpinene | 1,231 | 1,064 | 612a | 669a | 909b | 613a | 627a | 836b | 846a | 870a | 1123b | 626a | 666a | 860b |
p-Cymene | 1,260 | 1,022 | 1,610a | 1,632a | 2,541b | 2,455a | 2,480a | 2,728b | 3,158b | 2,907a | 7,239c | 9,618a | 9,784b | 11,656c |
Terpinolene | 1,273 | 1,088 | 5,063a | 5,101b | 6,664c | 1,365a | 2,155b | 3,659c | 2,406a | 2,420a | 3,641b | 1,709a | 1,720a | 3,275b |
p-Mentha-1,5,8-triene | 1,410 | 1,113 | 128a | 169a | 212b | 33a | 35a | 89b | 76a | 70a | 138b | 105a | 148a | 229b |
p-Cymenene | 1,423 | 1,019 | 185a | 170a | 282b | 204a | 201a | 291b | 366a | 336a | 432b | 319a | 320a | 665b |
Linalool | 1,537 | 1,191 | 71a | 80a | 142b | 129a | 191a | 295b | 93a | 131a | 732b | 222a | 227a | 412b |
Bornylacetate | 1,575 | 1,280 | 34a | 39a | 80b | 59a | 67a | 132b | 37a | 27a | 91b | 52a | 60a | 179b |
m-Cymen-8-ol | 1,850 | 1,185 | 521a | 521a | 722b | 273a | 276a | 400b | 357a | 443b | 553c | 447a | 477a | 770b |
All | 32,854a | 33,900b | 42,088c | 28,702a | 30,563b | 37,895c | 37,259a | 38,141b | 53,112c | 47,797a | 50,260b | 62,005c | ||
Nitrogenous | ||||||||||||||
2,6-Diethyl-pyrazine | 1,426 | 1,093 | 87a | 90a | 199b | 78a | 95a | 132b | 82a | 107a | 261b | 32a | 36a | 68b |
3,5-Diethyl-2-methyl-pyrazine | 1,486 | 1,166 | 543a | 571a | 763b | 430a | 441a | 540b | 162a | 230b | 348c | 45a | 47a | 173b |
(E)-2-Methyl-5-(1-propenyl)-pyrazine | 1,712 | 1,133 | 81a | 82a | 127b | 58a | 62a | 83b | 103a | 144a | 258b | 124a | 129a | 332b |
2-Ethyl-5-methyl-pyrazine | 1,378 | 998 | 359a | 360a | 514b | 202a | 259a | 374b | 335a | 354a | 615b | 283a | 311a | 536b |
Trimethyl-pyrazine | 1,398 | 1005 | 393a | 411a | 618b | 244a | 317b | 496c | 444a | 467a | 687b | 760a | 769a | 913b |
2,5-Dimethyl-pyrazine | 1,318 | 927 | 1,369a | 1,395a | 1,662b | 1,060a | 1,130b | 1,525c | 1,099a | 1,339b | 2,741c | 1,169a | 1,180a | 2,648b |
4,6-Dimethyl-pyrimidine | 1,323 | 928 | 71a | 80a | 179b | 45a | 57a | 87b | 162a | 175a | 471b | 149a | 197a | 424b |
2-Ethyl-3,5-dimethyl-pyrazine | 1,437 | 1,082 | 1,542a | 1,557a | 2,011b | 1,067a | 1,072a | 1,662b | 1,901a | 1,966a | 2,725b | 4,987a | 4,990a | 6,164b |
N-acetyl-4(H)-pyridine | 1,721 | 1,038 | 184a | 185a | 270b | 84a | 102a | 137b | 156a | 217b | 282c | 101a | 120a | 206b |
All | 4,629a | 4,731b | 6,343c | 3,268a | 3,535b | 5,036c | 4,444a | 4,999b | 8,388c | 7,650a | 7,779b | 11,464c | ||
Furans | ||||||||||||||
2-Pentyl-furan | 1,220 | 992 | 56a | 61a | 78a | 29a | 30a | 82b | 75a | 77a | 183b | 66a | 69a | 166b |
Furfural | 1,460 | 836 | 628a | 669a | 890b | 479a | 515b | 742c | 600a | 614a | 800b | 89a | 94a | 145b |
5-Methyl-furfural | 1,572 | 964 | 73a | 75a | 86b | 39a | 49a | 154b | 55a | 71a | 684b | 533a | 537a | 757b |
2-Furanmethanol | 1,659 | 864 | 90a | 91a | 200b | 120a | 126a | 244b | 59a | 79a | 111b | 58a | 76a | 189b |
All | 847a | 896a | 1254b | 667a | 720b | 1222c | 789a | 841b | 1778c | 746a | 776a | 1257b | ||
Ketones | ||||||||||||||
2,3-Pentanedione | 1,055 | 702 | 123a | 131a | 166b | 103a | 135a | 324b | 139a | 142a | 248b | 113a | 148a | 194b |
2-Heptanone | 1,174 | 889 | 538a | 552a | 700b | 217a | 266a | 455b | 409a | 420a | 647b | 237a | 264a | 338b |
2-Octanone | 1,276 | 986 | 803a | 816a | 1077b | 580a | 589a | 830b | 1037a | 1041a | 1934b | 395a | 433a | 780b |
2-Nonanone | 1,380 | 1,093 | 99a | 120a | 184b | 64a | 68a | 112b | 78a | 98a | 187b | 70a | 78a | 135b |
Oct-3-en-2-one | 1,401 | 1,040 | 318a | 319a | 240b | 137a | 139a | 272b | 116a | 155a | 289b | 238a | 241a | 309b |
Acetophenone | 1,650 | 1,068 | 34a | 43a | 97b | 86a | 94a | 180b | 68a | 78a | 92b | 12a | 24a | 113b |
All | 1,915a | 1,981a | 2,464b | 1,187a | 1,291b | 2,173c | 1,847a | 1,934b | 3,397c | 1,065a | 1,188b | 1,869c | ||
Pyrroles | ||||||||||||||
1-methyl-pyrrole | 1,133 | 750 | 3,098a | 3,173b | 5,064c | 8,174a | 8,260b | 10,632c | 4,067a | 4,099a | 4,725b | 4,187a | 4,190a | 5,164b |
Others | ||||||||||||||
Phenol | 2,011 | 992 | 234a | 268a | 432b | 15a | 35a | 86b | 249a | 267a | 374b | 143a | 154a | 327b |
*Peak area, arbitrary scale; T0: control; T1: regulated deficit irrigation (RDI); T2: stressed; different lowercase superscripted letters in the same row indicate difference (p < 0.05) among three irrigation treatments (T0, T1, and T2) and different cultivars by Scheffe’s test. Each compound was identified using mass spectral data, NIST’ 20 and FFNSC 3.0 database, linear retention indices (LRI) according to the Van Den Dool and Kratz equation, calculated on VF-Wax 60 m and SLB-5ms 30-m capillary columns.
Irrigation treatments have similar effects on the content of volatile compounds of raw and roasted pistachio nuts. Results showed that terpenes were the most abundant compounds. Kendirci and Onoğur (2011), studying raw pistachio nuts of different cultivars in Turkey, observed that terpenes and mainly α-pinene (pine-like, resinous) were the major volatile compounds contributing to flavor. These authors suggested that terpenes and 1-methyl-pyrrole were the key odorants found in the highest amount in all cultivars grown under the T2 stressed treatment. Key aroma compounds, such as terpenes, aldehydes, and nitrogenous compounds, were improved in raw and roasted nuts grown under the T2 irrigation treatment. Galindo et al. (2018) reported that severe RDI during stage II increased the contents of aldehydes and reduced those of pyrazines and terpenes. These findings were in accordance with the results shown by Şahan and Bozkurt (2020), reporting that flavoring compounds were higher in rain-fed pistachios than irrigated trees and the concentration of terpenes, the most abundant volatile compounds in dried pistachio nuts, decreased with irrigation. Increase in pyridines, pyrazines, pyrimidines, and furan derivatives as well as aldehydes in roasted pistachio was evident. This behavior is related to the roasting process, as these volatiles arise from Maillard reactions as well as from the Strecker degradation of α-amino acids, producing aldehydes and α-aminoketones, as reported by Rodríguez-Bencomo et al. (2015).
In the present study, the RDI irrigation treatments did not affect the fatty acid profile, and the fatty acid composition didn’t show a consistent behavior with irrigation treatments (Table 9). Moreover, Noguera-Artiaga et al. (2020b) showed that pistachios obtained under moderate RDI (treatment T1) had the highest content of oleic acid and the lowest content of α-linolenic, compared to those of control (T0) and treatment T2. In the same manner, Carbonell-Barrachina et al. (2015) reported that moderate RDI increased the content of linoleic acid. Moreover, 50% ETc water regime (treatment T2) contributed to higher fatty acid content for all cultivars in both years, compared to control (100% ETc) and RDI (T1) treatments. It was clear from the results of this investigation that the fatty acid content appeared to be insensitive to water deficit. This finding confirmed the results of previous investigations under deficit irrigation, showing that deficit irrigation allowed the maintenance of higher fatty acids, compared to full irrigation (Ahumada-Orellana et al., 2018; Motilva et al., 2000). This contrasting behavior could be attributed to the higher influence of varietal factors and climatic conditions on the composition of fatty acids than to water status (Fernandes-Silva et al., 2021).
Table 9. Fatty acids profile of four pistachio nuts grown under RDI treatments.
Cultivar | Trt | C16:0 | C16:1 | C17:0 | C17:1 | C18:0 | C18:1 | C18:2 | C18:3 | C20:0 | C20:1 |
---|---|---|---|---|---|---|---|---|---|---|---|
Mateur | T0 | 9.25±0.17aA | 0.55±0.01aA | 0.02±0.0aA | 0.05±0.01aA | 1.45±0.04aA | 68.23±1.03aA | 19.88±1.22aA | 0.24±0.01aA | 0.07±0.01aA | 0.27±0.04aA |
T1 | 9.48±0.16aA | 0.61±0.06aA | 0.02±0.0aA | 0.04±0.01aA | 1.47±0.12aA | 68.13±1.29aA | 19.70±1.56aA | 0.24±0.01aA | 0.07±0.01aA | 0.26±0.04aA | |
T2 | 9.42±0.31Aa | 0.62±0.03aA | 0.02±0.0aA | 0.04±0.01aA | 1.45±0.04aA | 68.3 ±0.87aA | 19.53±1.24aA | 0.24±0.02aA | 0.07±0.01aA | 0.29±0.02aA | |
Elguetar | T0 | 8.47±0.53aB | 0.68±0.14aA | 0.02±0.0aA | 0.05±0.01aA | 1.52±0.01aA | 68.7 ±0.66aA | 19.84±0.01aA | 0.30±0.08aA | 0.08±0.01aA | 0.32±0.06aA |
T1 | 8.85±0.91aB | 0.74±0.09aA | 0.02±0.0aA | 0.05±0.01aA | 1.40±0.02aA | 68.7 ±0.89aA | 19.63±0.01aA | 0.29±0.01aA | 0.07±0.01aA | 0.21±0.08aA | |
T2 | 8.86±0.69aB | 0.71±0.19aA | 0.02±0.0aA | 0.05±0.01aA | 1.51±0.16aA | 68.7 ±0.73aA | 19.49±0.14aA | 0.3±0.02aA | 0.06±0.03aA | 0.24±0.13aA | |
Ohadi | T0 | 9.92±0.15aA | 0.81±0.01aA | 0.02±0.0aA | 0.04±0.01aA | 0.95±0.04aB | 59.0 ±1.00aB | 28.62±1.20aB | 0.34±0.00aA | 0.05±0.00aA | 0.22±0.01aA |
T1 | 10.13±0.15aA | 0.97±0.01aA | 0.02±0.0aA | 0.05±0.01aA | 0.8±0.01aB | 58.7 ±1.00aB | 28.75±1.02aB | 0.28±0.01aA | 0.05±0.01aA | 0.20±0.01aA | |
T2 | 9.67±0.75aA | 0.72±0.18aA | 0.02±0.0aA | 0.05±0.01aA | 0.93±0.06aB | 59.4 ±0.37aB | 28.52±0.41aB | 0.31±0.01aA | 0.07±0.01aA | 0.27±0.04aA | |
Kerman | T0 | 9.35±0.12aA | 0.68±0.06aA | 0.02±0.0aA | 0.05±0.01aA | 1.44±0.11aA | 68.7 ±0.05aA | 19.88±0.22aA | 0.26±0.01aA | 0.06±0.01aA | 0.27±0.01aA |
T1 | 9.72±0.55aA | 0.69±0.01aA | 0.02±0.0aA | 0.05±0.01aA | 1.44±0.01aA | 68.35±0.1aA | 19.24±0.64aA | 0.24±0.01aA | 0.06±0.02aA | 0.21±0.01aA | |
T2 | 9.51±0.4aA | 0.62±0.13aA | 0.02±0.0aA | 0.05±0.01aA | 1.44±0.04aA | 68.23± 1.0aA | 19.88 ± 1.2aA | 0.24±0.01aA | 0.07±0.01aA | 0.27±0.04aA | |
ANOVA | C | * | ns | ns | ns | * | * | * | ns | ns | ns |
T | ns | ns | ns | ns | ns | ns | ns | ns | ns | ns | |
C*T | ns | ns | ns | ns | ns | ns | ns | ns | ns | ns |
palmitic acid (C16:0); palmitoleic acid (C16:1); margaric acid (C17:0); Heptadecenoic acid (C17:1); stearic acid (C18:0); oleic acid (C18:1); linoleic acid (C18:2); linolenic acid (C18:3); arachidic acid (C20:0) and gadoleic acid (C20:1)
Analysis of the fatty acid profile revealed four main fatty acids: oleic acid (C18:1), linoleic acid (C18:2), palmitic acid (C16:0), and stearic acid (C18:0) (Table 8). Oleic acid was dominant (68% of the total content), followed by linoleic (19% of the total content), palmitic (9% of the total content), and steric acids (1% of the total content). Our findings matched with Acar et al. (2017), reporting that main fatty acids found in pistachio were oleic, linoleic, and palmitic acids. Oleic acid ranged from 58.75% in cv. Ohadi to 68.70% in cv. Elguetar. Our results for the oleic acid content (58–68%) in pistachio samples were confirmed by previous studies (Arena et al., 2007; Noguera-Artiaga et al., 2020a). In the same line, Ghrab et al. (2010) reported that oleic acid was the main monounsaturated fatty acid, the total contents of saturated and unsaturated fatty acids being constant at 10% and 89%, respectively, and other fatty acids were determined in traces. Cv. Ohadi showed the lowest value of oleic acid (59.0; 58.7, and 59.4 with treatments T0, T1, and T2, respectively). Linoleic acid was the dominant polyunsaturated fatty acid, varying from 19.49% in cv. Elguetar to 28.75% in cv. Ohadi. Hence, the extracted oil from cv. Ohadi had higher content of linoleic acid (28.62%, 28.75%, and 28.52% with treatment T0, T1, and T2, respectively). Palmitic acid was the main saturated fatty acid ranging from 8.85% in cv. Elguetar to 10.13% in cv. Ohadi. Regarding stearic acid, it was found as a minor saturated fatty acid in pistachio kernels, ranging from 0.8% in cv. Ohadi to 1.52% in cv. Elguetar. Our results revealed that both cv. Ohadi and Elguetar had the most interesting fatty acid compositions among the studied cultivars. Statistically, neither of the treatments nor the ‘cultivar × treatment’ interaction (C × T) showed significant results; the only significant differences (p < 0.05) observed among cultivars were for four main FAMEs (oleic acid, linoleic acid, palmitic acid, and stearic acid).
Sensory attributes of nuts, such as color, odor, size, sweetness, acidity, and hardness, were studied to assess their organoleptic quality and meet consumer preferences (Figure 5). These attributes influence the consumer’s sensory experiences, contributing to the overall perception of product. As expected, irrigation treatments significantly (p < 0.05) affected the sensory features and consumer’s global preferences. Pistachios grown with treatments T0 and T1 gained higher values of the most studied attributes, showing statistically significant differences (p < 0.05) with treatment T2. Our findings matched with those of Noguera-Artiaga et al. (2020a), studying sensorial properties of pistachios under RDI and reporting that pistachios under treatment T1 were the most appreciated ones. In addition, an international consumer study on the same topic indicated that the kernels resulting from moderate RDI applied during stage II had a higher intensity of sensory attributes and a greater level of satisfaction among consumers than the kernels obtained from well-watered trees or from those exposed to severe RDI during stage II (Noguera-Artiaga et al., 2016).
Figure 5. Sensorial analysis of salted and roasted (SRP) nuts of four pistachio cultiars grown under RDI treatments. Abbreviations: M = Mateur, E = Elguetar, K = Kerman, O = Ohadi. T0 = well watered, T1 = regulated deficit irrigation treatment, and T2 = stressed treatment.
Regarding nut color (Figure 5A), cv. Ohadi showed the highest values with irrigation treatments T2 and T0. Cv. Mateur with treatment T0 (7.5) had the highest value of sweet taste (Figure 5B). In the present study, sour taste (Figure 5C) showed a different trend, with treatments T0 and T1 having less sour taste than treatment T2 samples. The highest value of sour taste (6.5) was observed in cv. Mateur for treatment T2.
The nut size was cultivar-dependent, with cv. Ohadi demonstrated the highest value for treatment T0 (Figure 5D). Cv. Ohadi showed the highest value of nut hardness (Figure 5e) for treatment T0, with no significant difference compared to treatment T1.
The highest score for the roasted odor resulted in cv. Mateur grown for two water regimes of T0 and T1 (Figure 5f). The sweet/almond odor was also noted in cv. Mateur for two water regimes of T0 and T1 (Figure 5g). Considering global satisfaction (Figure 5h), which defines the final opinion of consumers about the overall quality of samples, all the studied cultivars grown under treatment T0 obtained the highest score, followed by treatment T1, which received water restriction during stages I and II of nut development, whereas treatment T2 was statistically different from both treatments T0 and T1.
The sensorial analysis performed in this study showed that cv. Mateur and Ohadi grown with treatments T0 and T1 were the most appreciated varieties among consumers. The roasting process had a significant impact on the sensorial quality of pistachio nuts. Roasted nuts from cv. Ohadi and Mateur grown under 100% ETc water regime were the most appreciated nuts, followed by treatment T1 nuts. Rodríguez-Bencomo et al. (2015) reported that the roasting process makes the pistachio commercially viable and valuable as it improved nut’s hallmark sensory characteristics, such as flavor, color, odor, and texture.
Nuts of local cv. Mateur were highly appreciated by consumers. Ojeda-Amador et al. (2018) reported that cv. Mateur presented a marked green appearance and higher intensity of the roasted nuts attribute and were appreciated for their flavor, intensity, and the persistence of pistachio aroma in the mouth. Regarding the roasted and sweet/almond odor, the resulting acceptability was confirmed by Noguera-Artiaga et al. (2016) and Ojeda-Amador et al. (2018).
The multivariate analysis of data permitted the reduction of variables to two principal components, PC1 and PC2, revealing an interesting grouping of the studied cultivars under RDI strategy (Figure 6a). Depending on the water regime, the studied cultivars were distributed into four groups. Cv. Mateur, Elguetar, and Ohadi, grown with treatments T0 and T1, occupied the positive side of PC1 and PC2. These cultivars occupied the negative side of PC2 if subjected to severe drought stress (treatment T2). Cv. Kerman subjected to treatments T0 and T1 occupied the positive side of PC2 and the negative side of PC1. Cv. Kerman under severe drought stress (treatment T2) occupied the negative side of both PC1 and PC2.
Figure 6. Principal component analysis of main agronomical and biochemical pistachio nuts and oil quality of the four studied cultivars under RDI treatments: (treatment T0) control (100% ETc); (treatment T1) regulated deficit irrigation RDI (50% ETc during stage I and stage of nut development and 100% ETc during stage III); (T2) stressed treatment (50% ETc). Values are means (n = 3) ± SE. Abbreviations: TCSA = trunk cross-sectional area; FW = fresh weight; DW = dry weight.
The two principal components presented 61.0% of total variability. The first principal component PC1 showed 35.52% of the observed variability and separated the cultivars based on biochemical traits, fatty acid profile, composition, and size of nuts.
According to a PCA biplot, size, fat content (FC), C18:1 content, total phenols in oil, and carbohydrates of nuts were positively correlated to PC1 whereas absorbance at a wavelength of 270 nm (K270), chlorophylls, and C18:2 content were negatively correlated to PC1. Parameters such as biochemical traits, oil quality, and composition of nuts explained PC1 separation in a better way (Figure 6b). Principal component PC2, explaining 25.57% of total variability, was able to separate cultivars depending on water regime. Hence, treatment T2 occupied the negative side of PC2 whereas treatments T0 and T1 occupied its positive side. Among all the traits that contributed mostly to PC2 separation were phenolic compounds and the nutritional components of pistachios, with split nut and C18:1 being the only two parameters showing a negative correlation (Figure 6B).
The moderate water stress generated by RDI (treatment T1; 50% ETc during fruit development stages I and II, followed by full irrigation at 100% ETc during stage III) maintained nut organoleptic quality as compared to control trees. Water restriction applied in treatment T2 (50% ETc) during all growing seasons decreased nut composition and biochemical compounds. Cv. Ohadi presented nuts with higher dimensions and higher content of carbohydrates, ash, fiber, and proteins under three water regimes. Cv. Mateur and Ohadi presented high sensorial quality and were more accepted by consumers. Cv. Mateur appeared suitable for high-density planting under semiarid conditions. In the present study, the RDI irrigation treatments did not affect fatty acid profile. Oleic, linoleic, palmitic, and steric acids were the main components. Higher contents of volatile compounds were observed in pistachios roasted under stressed treatment T2 (50% ETc); hence, terpenes were abundantly found in non-irrigated pistachios. Oil yield of pistachio nuts was improved under treatment T2. Treatment T1 (RDI) reduced water supply by 20% during stages I and II of nut development, thus increasing water use efficiency without compromising yield and nut quality. Our results suggested that the RDI water management strategy could be applied in pistachio orchards grown under arid and semiarid conditions.
The authors thanked Boutheina Fridhi, Chaima Maamri, Boutheina Hajlaoui, and Dhiaa Miri for technical assistance and support, and Prof. Antonella Verzera for her helpful advice. Authors also thanked the staff of Aroma and Sensory Laboratory (ASLab) of the University of Messina for the analysis of volatile compounds.
Walid Abidi and Rawaa Akrimi: conceptualization, data curation, formal analysis, and writing of original draft and review & editing. Valeria Rizzo: formal analysis, and writing of original draft and review & editing. Fabrizio Cincotta: data curation, formal analysis, and writing of original draft. Antonella Verzera: resources, supervision and writing and review & editing. Giuseppe Muratore: resources, supervision, and writing and review & editing. All authors read and approved the final manuscript.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Panellists were informed about the conducted study and they agreed to the publication of the results of their sensorial modules. They were fully aware of the implications of publication and accepted any associated risk. All collected forms were anonymous. None of the participants was identified based on the details or images contained in the paper.
The authors declared that they had no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Data are available on request.
Abboud S., Dbara S., Abidi W., and Braham, M., 2019. Differential agro-physiological responses induced by partial root-zone drying irrigation in olive cultivars grown in semi-arid conditions. Environ Exp Bot. 167: 103863. 10.1016/j.envexpbot.2019.103863
Abidi W., Jimenez S., Moreno M.Á., and Gogorcena Y., 2011. Evaluation of antioxidant compounds and total sugar content in a nectarine [Prunus persica (L.) Batsch] progeny. Int J Mol Sci. 12(10): 6919–6935. 10.3390/ijms12106919
Acar I., Kafkas S., Kapchina-Toteva V., and Ercisli S., 2017. Effect of rootstock on fat content and fatty acid composition of immature pistachio kernels. Comptes Rendus l’Acad Bulg Sci. 70: 1049–1056.
Aceña L., Vera L., Guasch J., Busto O., and Mestres M., 2010. Comparative study of two extraction techniques to obtain representative aroma extracts for being analysed by gas chromatography–olfactometry: application to roasted pistachio aroma. J Chromatogr A. 1217: 7781–7787. 10.1016/j.chroma.2010.10.030
Aceña L., Vera L., Guasch J., Busto O., and Mestres M., 2011. Determination of roasted pistachio (Pista ciavera L.) key odorants by headspace solid-phase microextraction and gas chromatography−olfactometry. J Agric Food Chem. 59(6): 2518–2523. 10.1021/jf104496u
Ahumada-Orellana L.E., Ortega-Farías S., and Searles P.S., 2018. Olive oil quality response to irrigation cut-off strategies in a super-high density orchard. Agric Water Manag. 202: 81–88.
Akrimi R., Hajlaoui H., Rizzo V., Muratore G., and Mhamdi M., 2020. Agronomical traits, phenolic compounds and antioxidant activity in raw and cooked potato tubers growing under saline conditions. J Sci Food Agric. 100(9): 3719–3728. 10.1002/jsfa.10411
Allen R.G., Pereira L.S., Raes D., and Smith M., 1998. Crop Evapotranspiration-Guidelines for Computing Crop Water Requirements, Irrigation and Drain, Paper No. 56. FAO, Rome, Italy, 300 p.
Arena, E., Campisi, S., Fallico B., and Maccarone E., 2007. Distribution of fatty acids and phytosterols as a criterion to discriminate geographic origin of pistachio seeds. Food Chem. 104: 403–408. 10.1016/j.foodchem.2006.09.029
Ashraf C.M., Iqbal S., and Ahmed D., 2011. Nutritional and physicochemical studies on fruit pulp, seed and shell of indigenous Prunuspersica. J Med Plants Res. 5(16): 3917–3921. 10.5897/JMPR.9000941
Association of Official Analytical Chemists (AOAC), 1995. Official Methods of Analysis. AOAC, Washington, DC.
Association of Official Analytical Chemists (AOAC), 2000. Official Methods of Analysis, 17th edn. AOAC, Washington, DC.
Bellomo M.G., and Fallico B., 2007. Anthocyanins, chlorophylls and xanthophylls in pistachio nuts (Pistacia vera) of different geographic origin. J Food Comp Anal. 20(3–4): 352–359. 10.1016/j.jfca.2006.04.002
Bradford M.M., 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 72: 248–254. 10.1016/0003-2697(76)90527-3
Brand-Williams W., Cuvelier M.E., and Berset C., 1995. Use of a free-radical method to evaluate antioxidant activity. Food Sci Technol (LWT). 28:, 25–30. 10.1016/S0023-6438(95)80008-5
Carbonell-Barrachina A.A., Memmi H., Noguera-Artiaga L., Gijon-Lopez Mdel C., Ciapa R., and Perez-Lopez D., 2015. Quality attributes of pistachio nuts as affected by rootstock and deficit irrigation. J Sci Food Agric. 95: 2866–2873. 10.1002/jsfa.7027
Chahed T., Bellila A., Dhifi W., Hamrouni I., M’hamdi B., Kchouk M.E., and Marzouk B., 2008. Pistachio (Pistacia vera) seed oil composition: geographic situation and variety effects. Grasas Aceites. 59(1): 51–56. 10.3989/GYA.2008.V59.I1.490
Cincotta F., Verzera A., Tripodi G., and Condurso C., 2018. Non-intentionally added substances in PET bottled mineral water during the shelf-life. Eur Food Res Technol. 244(3): 433–439. 10.1007/s00217-017-2971-6
Commission Regulation (EEC) No 2568/91 of 11 July 1991 on the characteristics of olive oil and olive-residue oil and on the relevant methods of analysis. Available at: https://eur-lex.europa.eu/legal-content/en/ALL/?uri=CELEX%3A31991R2568
Conseil Oléicole International (IOC), 2015. COI/T.15/NC no 3/Rév. 8 février 2015. FRANÇAIS Original: FRANÇAIS.
Crane J.C., and Iwakiri B.T., 1981. Morphology and reproduction of pistachio. Hortic Rev. 3: 376–393. 10.1002/9781118060766.ch8
Damirchi S.A., Savage G.P., and Dutta P.C., 2005. Sterol fractions in hazelnut and virgin olive oils and 4,4´-dimethylsterols as possible markers for detection of adulteration of virgin olive oil. J Am Oil Chem Soc. 82: 717–725. 10.1007/s11746-005-1133-y
Daneshmandi M.S., Azizi M., and Farhoosh R., 2014. The study on physical, chemical and biochemical characteristics of pistachio (Pistacia vera L. Cv. Daneshmandi) and its comparison to some commercial cultivars from Iran. J Hortic Sci. 28(1): 10–17. 10.22067/jhorts4.v0i0.34996
Dini A., Falahati-pour S.K., Behmaram K., and Sedaghat N., 2019.The kinetics of colour degradation, chlorophylls and xanthophylls loss in pistachio nuts during roasting process. Food Qual Saf. 3: 251–263. 10.1093/fqsafe/fyz020
FAOSTAT, 2024. Food and Agriculture Organization statistics. Available at: https://www.fao.org/faostat/en/#search/Pistachios%2C%20in%20shell (Accessed on: 14 March 2024).
Fernandes-Silva A., Marques P., Brito T., Canas L., Cruz R., and Casal S., 2021. Olive oil composition of Cv. Cobrançosa is affected by regulated and sustained deficit irrigation. Biol Life Sci Forum. 3: 63. 10.3390/IECAG2021-09735
Fu H., Mu X., Wang P., Zhang J., Fu B., and Du J., 2020. Fruit quality and antioxidant potential of Prunus humilis Bunge accessions. PLoS ONE. 15(12): e0244445. 10.1371/journal.pone.0244445
Fuleki T., and Francis F.J., 1968. Quantitative methods for anthocyanins. 2. Determination of total anthocyanin and degradation index for cranberry juice. Food Sci. 33: 78–83. 10.1111/j.1365-2621.1968.tb00888.x
Galindo A., Collado-González J., Griñán I., Corell M., Centeno A., Martín-Palomo M. J., and Carbonell-Barrachina A.A., 2018. Deficit irrigation and emerging fruit crops as a strategy to save water in Mediterranean semiarid agrosystems. Agric Water Manag. 202: 311–324. 10.1016/j.agwat.2017.08.015
Galindo A., Noguera-Artiaga L., Cruz Z.N., Burló F., Hernández F., Torrecillas A., and Carbonell-Barrachina, Á.A., 2015. Sensory and physico-chemical quality attributes of jujube fruits as affected by crop load. Food Sci Technol (LWT). 63: 899–905. 10.1016/j.lwt.2015.04.055
Ghrab M., Ben Mimoun M., and Gouta H., 2004. Pistachio production in Tunisia. FAO-CIHEAM-Nucis-Newslett. 12: 19–21. Available at: https://www.cabidigitallibrary.org/doi/full/10.5555/20053007093
Ghrab, M., Zribi F., Ayadi M., Elloumi O., Mnafki N., and Ben Mimoun M., 2010. Lipid characterization of local pistachio germoplasm in central and southern Tunisia. J Food Composit Anal. 23: 605–612. 10.1016/j.jfca.2009.08.016
Giuffrida D., Saitta M., La Torre L., Bombaci L., and Dugo G., 2006. Carotenoid, chlorophyll and chlorophyll-derived compounds in pistachio kernels (Pistacia vera L.) from Sicily. Italian J Food Sci. 18: 309–316.
Goldhamer D.A., 1995. Irrigation management. In: Ferguson, L. (ed.) Pistachio Production. Center for Fruit and Nut Research and Information, Davis, CA, pp. 71–81.
Goldhamer D.A., and Beede B.H., 2004. Regulated deficit irrigation effects on yield, nut quality and water-use efficiency of mature pistachio trees. J Hortic Sci Biotechnol. 79(4): 538–545. 10.1080/14620316.2004.11511802
Guerrero J., Moriana A., Pérez-López D., Couceiro J.F., Olmedilla N., and Gijón M.C., 2005. Regulated deficit irrigation and the recovery of water relations in pistachio trees. Tree Physiol. 26: 87–92. 10.1093/treephys/26.1.87
Hojjati M., Calín-Sánchez, Á., Razavi S.H., and Carbonell-Barrachina, Á.A., 2013. Effect of roasting on colour and volatile composition of pistachios (Pistacia vera L.). Inter J Food Sci Technol. 48(2): 437–443. 10.1111/j.1365-2621.2012.03206.x
Huang D.-J., Lin C.-D., Chen H.-J., and Lin Y.-H., 2004. Antioxidant and antiproliferative activities of sweet potato (Ipomoea batatas [L.] Lam Tainong 57’) constituents. Bot Bull Acad Sin. 45: 179–186. https://ejournal.sinica.edu.tw/bbas/content/2004/3/Bot453-01.pdf
Kendirci P., and Onoğur T.A., 2011. Investigation of volatile compounds and characterization of flavor profiles of fresh pistachio nuts (Pistacia vera L.). Int J Food Prop. 14(2): 319–330. 10.1080/10942910903177830
Kim J., YilSoh S., Bae H., and Nam S.Y., 2019. Antioxidant and phenolic contents in potatoes (Solanum tuberosum L.) and micropropagated potatoes. Appl Biol Chem. 62: 17. 10.1186/s13765-019-0422-8
Kola O., Hayoğlu İ., Türkoğlu H., Parıldı E., Ak B.E., and Akkaya, M.R., 2018. Physical and chemical properties of some pistachio varieties (Pistacia vera L.) and oils grown under irrigated and non-irrigated conditions in Turkey. Qual Assu Safety Crops Foods, 10(4): 383–388. 10.3920/QAS2017.1152
Memmi H., Gijón M.C., Couceiro J.F., and Pérez-López D., 2015. Water stress thresholds for regulated deficit irrigation in pistachio trees: rootstock influence and effects on yield quality. Agric Water Manage. 164(P 1): 58–72. 10.1016/j.agwat.2015.08006
Mezni F., Martine L., Khouja M.L., Berdeaux O., and Khaldi A., 2020. Identification and quantitation of tocopherols, carotenoids and triglycerides in edible Pistacialentiscus oil from Tunisia. J Mater Environ Sci. 11(1): pp. 79–84.
Minguez-Mosquera M.I., Rejano-Navarro L., Gandul-Rojas B., SanchezGomez A.H., and Garrido-Fernandez J., 1991. Color-pigment correlation in virgin olive oil. J Am Oil Chem Soc. 68: 322–336. 10.1007/BF02657688
Miraliakbari H., and Shahidi F., 2008. Antioxidant activity of minor components of tree nut oils. Food Chem. 111(2): 421–427. 10.1016/j.foodchem.2008.04.008
Motilva M.J., Tovar M.J., Romero M.P., Alegre S., and Girona J., 2000. Influence of regulated deficit irrigation strategies applied to olive trees (Arbequina cultivar) on oil yield and oil composition during the fruit ripening period. J Sci Food Agric. 80: 2037–2043. 10.1002/1097-0010(200011)80:14<2037::AID-JSFA733>3.0.CO;2-0
Noguera-Artiaga L., Lipan L., Vázquez-Araújo L., Barber X., Pérez-López D., and Carbonell-Barrachina Á.A., 2016. Opinion of Spanish consumers on hydrosustainable pistachios. J Food Sci. 81(10): S2559–S2565. 10.1111/1750-3841.13501
Noguera-Artiaga L., Sánchez-Bravo P., Hernández F., Burgos-Hernández A., Pérez-López D., and Carbonell-Barrachina Á.A., 2020a. Influence of regulated deficit irrigation and rootstock on the functional, nutritional and sensory quality of pistachio nuts. Sci Hortic. 261: 108994. 10.1016/j.scienta.2019.108994
Noguera-Artiaga L., Sánchez-Bravo P., Pérez-López D., Szumny A., Calin-Sánchez A., Burgos-Hernández A., and Carbonell-Barrachina Á.A., 2020b. Volatile, sensory and functional properties of Hydro SOS Pistachios. Foods. 9(2): 158. 10.3390/foods9020158
Ojeda-Amador R.M., Salvador Moya M.D., Fregapane G., and Gómez Alonso S., 2019. Comprehensive study of phenolic compounds profile and antioxidant activity of eight pistachio cultivars, their residual cakes and virgin oils. J Agric Food Chem. 67(13): 3583–3594. 10.1021/acs.jafc.8b06509
Ojeda-Amador R.M., Trapani S., Fregapane G., and Salvador M.D., 2018. Phenolics, tocopherols, and volatiles changes during virgin pistachio oil processing under different technological conditions. Eur J Lipid Sci Technol. 120: 1800221. 10.1002/ejlt.201800221.
Rieger M., 1995. Offsetting effects of reduced root hydraulic conductivity and osmotic adjustment following drought. Tree Physiol. 15(6): 379–385. 10.1093/treephys/15.6.379
Rodríguez-Bencomo J.J., Kelebek H., Sonmezdag A.S., Rodríguez-Alcalá L.M., Fontecha J., and Selli S., 2015. Characterization of the aroma-active, phenolic, and lipid profiles of the pistachio (Pistacia vera L.) nut as affected by the single and double roasting process. J Agric Food Chem. 63(35): 7830–7839. 10.1021/acs.jafc.5b02576
Şahan A., and Bozkurt H. (2020). Effects of harvesting time and irrigation on aroma active compounds and quality parameters of pistachio. Sci Hortic. 261: 108905. 10.1016/j.scienta.2019.108905
Satil F., Azcan N., and Baser K.H.C., 2003. Fatty acid composition of pistachio nuts in Turkey. Chem Nat Compd. 39(4): 322–324. https://link.springer.com/content/pdf/10.1023/b:conc.0000003408.63300.b5.pdf
Sena-Moreno E., Pardo J.E., Catalán L., Gómez R., Pardo-Giménez A., and Alvarez-Ortí M., 2015. Drying temperature and extraction method influence physicochemical and sensory characteristics of pistachio oils. Eur J Lipid Sci Technol. 117: 684–691.
Taghizadeh S.F., Rezaee R., Davarynejad G., Karimi G., Nemati S.H., and Asili J., 2018. Phenolic profile and antioxidant activity of Pistaciavera var. Sarakhs hull and kernel extracts: the influence of different solvents. J Food Meas Charact. 12: 2138–2144. 10.1007/s11694-018-9829-x
Uquiche E., Jerez M., and Ortiz J., 2008. Effect of pretreatment with microwaves on mechanical extraction yield and quality of vegetable oil from Chilean hazelnuts (Gevuina avellane Mol). Innov Food Sci Emerg Technol. 9(4): 495–500. 10.1016/j.ifset.2008.05.004
Van Den Dool, H. A. N. D., and Kratz, P. D. 1963. A generalization of the retention index system including linear temperature programmed gas-liquid partition chromatography. J Chromatogr. A, 11: 463–471. 10.1016/S0021-9673(01)80947-X
Yahyavi F., Alizadeh-Khaledabada M., and Azadmard-Damirchib S., 2020. Oil quality of pistachios (Pistacia vera L.) grown in East Azerbaijan, Iran. NFS J. 18: 12–18. 10.1016/j.nfs.2019.11.001
Yildiz M., Turcan G.S., and Ozdemir M., 1998. Oil composition of pistachio nuts (Pistacia vera L.) from Turkey. Fett/Lipid. 100(3): 84–86. 10.1002/(SICI)1521-4133(199803)100:3<84::AID-LIPI84>3.0.CO;2-6
Zribi F., Ben Mimoun M., Ghrab M., Ayadi M., and Salah M.B., 2006. Split rate and nuts oil composition of pistachio during maturity process. In: Javanshah A. et al. (Eds.), Proceedings of the IV International Symposium on Pistachios and Almonds. ISHS Acta Hort. 726: 533–53. 10.17660/ActaHortic.2006.726.89