Download

ORIGINAL ARTICLE

Processing-induced modifications in bioactive compounds of black garlic: a comparative analysis with white garlic

Halil İbrahim Binici1*, Adem Savaş2, Burak Erim3

1Department of Food Technology, Vocational School, İstanbul Esenyurt University, İstanbul, Turkey;

2Hazelnut Specialisation Coordination Office, Giresun University, Prof. Ahmet Taner Kışlalı, Street, 28200 Giresun, Turkey;

3Faculty of Health Sciences, Department of Nutrition and Dietetics, Istanbul Esenyurt University, Adile Naşit Boulevard No. 1, 34510 Esenyurt, Istanbul, Turkey

Abstract

This study aimed to examine the differences in chemical and bioactive components between black garlic and white garlic under various processing conditions. The processing conditions significantly lowered the pH of black garlic while increasing its total acidity and organic acid levels, with citric acid being the dominant organic acid. Total phenolic compounds (TPC) and antioxidant activity in black garlic increased as a result of processing conditions. Notably, aging caused a significant increase in the levels of 5-hydroxymethylfurfural (HMF) and S-allyl-L-cysteine (SAC). Mineral analyses showed that magnesium and selenium levels in black garlic rose with extended aging. Correlation and Principal Component Analysis (PCA) revealed that the health-beneficial components of black garlic were significantly enhanced through processing, differentiating it from white garlic.

Key words: antioxidant, black garlic, S-allyl-L-cysteine, PCA, selenium

*Corresponding Author: Halil İbrahim Binici,, Department of Food Technology, Vocational School, İstanbul Esenyurt University, 34510 İstanbul, Turkey. Email: [email protected]

Academic Editor: Prof. Valeria Sileoni Universitas Mercatorum, Italy

Received: 3 November 2024; Accepted: 19 December 2024; Published: 15 January 2025

DOI: 10.15586/ijfs.v37i1.2877

© 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/)

Introductıon

Garlic (Allium sativum L.), a member of the Alliaceae family, is known for its shallow root system and various health benefits, and it is recognized as Generally Recognized as Safe (GRAS) (Stępień et al., 2024; Utama et al., 2024). It is widely used in traditional medicine due to its antioxidant, anti-inflammatory, anticancer, antibacterial, and blood lipid-regulating properties (Wu et al., 2024; Stępień et al., 2024). The bioactive components of garlic can vary depending on the preparation or processing method. Black garlic is produced by fermenting and aging fresh garlic for 10 to 80 days at controlled temperatures of 60–90°C and humidity levels of 60–80% (Stępień et al., 2024; Augustyńska-Prejsnar et al., 2023; Matsuse et al., 2024; Liu et al., 2024). During this process, white garlic loses its pungency due to the breakdown of the alliin compound, developing a sweet-sour taste and becoming odorless (Stępień et al., 2024). As black garlic forms, the allicin compound transforms into the water-soluble antioxidant S-allyl-L-cysteine, which is known for its antioxidant, anticarcinogenic, neuroprotective, anti-allergic, antidiabetic, and anti-inflammatory effects (Augustyńska-Prejsnar et al., 2023; Wu et al., 2024; Santos et al., 2024; Stępień et al., 2024). The fermentation and aging process also leads to the formation of 5-hydroxymethylfurfural (5-HMF), an intermediate of the Maillard reaction, which has been linked to various health concerns, including carcinogenicity, tumor formation, and liver and kidney toxicity, with an LD50 value reported as 871.12 mg kg−1 (Liu et al., 2024). Selenium, a crucial micronutrient obtained externally because the human body cannot synthesize it, plays significant roles in the immune system and body development. Selenium has been shown to have anti-aging properties (Bjørklund et al., 2022), enhance immune function (Avery and Hoffmann, 2018), prevent cardiovascular diseases (Jenkins et al., 2020), and exhibit anti-tumor effects (Ghose et al., 2001). Most research has focused on optimizing black garlic production by studying organosulfur compounds, polysaccharides, polyphenols, and other components. However, a comprehensive study using principal component analysis (PCA) to differentiate black garlic is still lacking.

This study aimed to investigate the chemical and bioactive changes in black garlic under varying processing conditions. Specifically, it analyzed changes in pH, total acidity, organic acids, total phenolic content (TPC), antioxidant activity (DPPH and ABTS), mineral content, hydroxymethylfurfural (HMF), and S-allyl-L-cysteine (SAC) levels in black garlic and compared these changes to those in white garlic. Additionally, the study assessed the chemical composition changes in black garlic during different aging periods using correlation analysis and principal component analysis (PCA). The goal was to explore the relationships between the chemical components of black garlic under various processing conditions and their differences from white garlic, thereby contributing to the evaluation of black garlic’s potential as a functional food by revealing how its biological and nutritional values change with processing.

Materials and Methods

Araban garlic, which is cultivated in Turkey and has received geographical indication, was used as the material in this study. Araban garlic was collected from a local seller during the June harvest period.

Production of black garlic

Araban garlic was weighed at 250 g. The weighed fresh garlic was then placed in a climate conditioning device (Nüve, TK600) at Atatürk University Food Engineering Laboratories and subjected to an aging process for 10, 20, and 30 days at 60°C and 80% relative humidity to obtain 10-day (BG10), 20-day (BG20), and 30-day (BG30) samples (Zhang et al., 2015).

Method

pH analysis

The pH was determined according to Kang (2016).

Total acidity analysis

Total acidity was measured using acid-base titration as described by Leng et al. (2020). In summary, five grams of garlic samples were weighed, crushed, and then diluted to 100 mL with distilled water. A few drops of phenolphthalein indicator were added, and the mixture was titrated with 0.1 mol L−1 NaOH solution until a pink color appeared, at which point the volume of NaOH used was recorded.

Extraction method

Phenolic contents are extracted using either organic or inorganic solvents, with the efficiency of the extraction being influenced by the choice of solvent (Takım, 2020). Ağbaş et al. (2013) found that ethanol extraction demonstrated superior activity in terms of both phenolic and antioxidant components. The extraction procedure was adapted from the methods described by Choi et al. (2014) and Takım (2020). To prepare the garlic samples, they were peeled, chopped into small pieces, and then crushed using a mortar and pestle. The crushed garlic was subsequently lyophilized. The lyophilized garlic was mixed with 50% methanol-water at a garlic-to-solvent ratio of 1:10, subjected to ultrasonic treatment in a water bath for 15 min, and then centrifuged at 6000 rpm for 10 min. The resulting extract was filtered through Whatman No. 1 filter paper and used for the analysis of total phenolic content, DPPH radical scavenging activity, and ABTS assays.

For the extraction process used in organic acid and HMF analyses, 5 g of the sample was soaked in 15 mL of distilled water at +4°C for 24 h. The sample was then homogenized using an Ultraturrax for 3 min. From this homogenized mixture, 5 g was transferred to a 50 mL volumetric flask, treated in an ultrasonic water bath for 30 min, and then centrifuged at 2000 g for 15 min. Subsequently, 10 mL of the supernatant was collected, to which 0.5 mL of Carez 1 (potassium hexacyanoferrate (II)) and Carez 2 (zinc sulfate heptahydrate) solutions were added sequentially. The mixture was then filtered through a 0.45 µm filter paper and analyzed using an HPLC device. Results are presented on a dry weight basis.

Organic acid analysis

The analysis of organic acids was performed with modifications based on the method described by Castellari et al. (2000). Organic acid analyses were conducted using an HPLC RID system (Agilent 1260 Infinity Series, Agilent Technologies, Waldbronn, Germany) equipped with a MetaCarb H Plus column. The mobile phase consisted of 0.045 N sulfuric acid and water in a 99:1 ratio, under isocratic conditions. The flow rate was set at 0.6 mL min−1, with a column temperature of 30°C, a detection wavelength of 210 nm, an injection volume of 10 µL, and a total run time of 40 min. The analysis allowed for the quantification of citric acid, lactic acid, and propionic acid.

Total phenolic content

The TPC of the samples was determined according to Binici et al. (2021). Briefly, 0.100 mL of the white garlic and black garlic extracts were taken and sequentially mixed with 0.800 mL of 0.2 N Folin-Ciocalteu reagent (FCR), 0.800 mL of 10% sodium carbonate (Na2CO3), and 0.800 mL of distilled water. The final volume was adjusted to 2.5 mL. Total phenolic content was determined using a spectrophotometer (PG Instrument TV-60) at 760 nm, with gallic acid (GA) as the standard. The samples were kept in the dark for 30 min before measurement at 760 nm.

DPPH assay

The DPPH assay was carried out with modifications based on the method described by Binici et al. (2021). In this procedure, 0.02 mM DPPH was weighed and dissolved in 100 mL of ethanol. The prepared extracts were adjusted to various concentrations, with the final volume set to 2.5 mL. The mixture was then incubated in the dark for 30 min and measured at a wavelength of 517 nm using a spectrophotometer.

ABTS assay

The ABTS+ assay for garlic samples was conducted with modifications based on the methods outlined by Tahir (2022). To prepare the ABTS+ solution, 7 mM ABTS+ was combined with 5 mL of 2.45 mM potassium persulfate, resulting in a total volume of 10 mL. This mixture was placed in a foil-wrapped bottle and left in a dark environment for 16 h to allow stabilization. The stabilized solution was then diluted with ethanol to achieve an absorbance of 0.700 at 734 nm. For the assay, 10 µL of garlic extract was added to 1.990 mL of the ABTS+ solution, mixed thoroughly, and after a 6-min incubation period, the absorbance was measured at 734 nm using a spectrophotometer. The concentration of the extracts that achieved 50% ABTS+ radical scavenging activity (IC50) was determined from the graph plotting extract concentration against radical scavenging activity (%) and was expressed in mg mL−1.

Mineral content

Mineral content was determined according to Zor et al. (2024). Briefly, approximately 0.5 g of the sample was subjected to digestion using a mixture of 6 mL of 65% HNO3 and 2 mL of 30% H2O2, making a total of 8 mL of acid. Following the digestion process, the sample volume was adjusted to 14 mL. From the diluted sample, 1 mL was taken and further diluted to 16 mL, resulting in a 16-fold dilution. These dilutions were incorporated into the final calculations. The results are expressed in ppm for Mg, Ca, and Fe, and in ppb for Cu and Se.

5-HMF analysis

A novel method for HMF analysis was established using HPLC, featuring an Ace C18 column (5 μm, 250 × 4.6 mm). The analysis was performed with a mobile phase composed of methanol and water (80:20, v/v), a flow rate of 1 mL min−1, an injection volume of 5 μL, and detection at a wavelength of 284 nm. The identification of HMF was accomplished using an HMF standard. A calibration curve was generated by plotting the peak areas against the concentrations of HMF solutions prepared at various concentrations.

SAC analysis

The extraction process was conducted by combining and modifying the methods described by Chen et al. (2020) and Bae et al. (2012). In this procedure, 1 g of garlic samples was dissolved in 10 mL of distilled water (1:10 w/v) and subjected to ultrasonic treatment in a water bath for 30 min. The mixture was then filtered through Whatman No. 2 filter paper, and the resulting filtrate was further filtered using a 0.45 µm syringe filter. Subsequently, 20 µL of the filtrate was injected into an HPLC-UV-DAD system. For the analysis of S-allyl-L-cysteine, standard solutions were derivatized with dansyl chloride in a basic borate buffer. A 100 µg mL−1 S-allyl-L-cysteine stock solution was initially prepared in methanol, and standard solutions ranging from 0.1 to 50 µg mL−1 were prepared from this stock. To each standard solution, 0.1 mL was taken, followed by the addition of 0.25 mL dansyl chloride and 0.65 mL borate buffer (pH 9.2). The mixture was vortexed for 30 s and left to react at room temperature for 15 min. The resulting turbid solutions were filtered through a 0.22 μm filter, producing final standard concentrations ranging from 0.01 to 5 µg mL−1 after dilution. A new HPLC method was developed for the analysis of S-allyl-L-cysteine, utilizing an Ace C18 column (5 μm, 150 x 4.6 mm) with a mobile phase consisting of 50 mM sodium acetate buffer (pH 5) and methanol (35:65, v/v). The analysis was performed at a flow rate of 1 mL min−1, with an injection volume of 10 μL and detection at 250 nm.

Statistical analysis

The data collected in the study were analyzed using correlation and variance analyses with IBM SPSS Statistics 25.0 software (IBM, Armonk, New York). Duncan’s multiple comparison tests were performed to identify significant differences between the groups at the p = 0.01 and 0.05 levels. To identify groupings among the black garlic samples, principal component analysis (PCA) was conducted using SIMCA 14.1 software (MKS UMETRICS, Umea, Sweden).

Results

The pH, total acidity, and organic acid content of black garlic (BG) processed under various conditions are presented in Table 1. Compared to white garlic (WG), the total acidity of BG increased significantly, while its pH decreased markedly from 4.64 to 3.86, compared to 6.53 in WG (p < 0.01). Analysis of the organic acids in BG revealed an increase in their levels due to different processing conditions, compared to WG (Table 1, p < 0.01). Citric acid emerged as the most abundant organic acid, with levels ranging from 246.83 to 425.13 g kg−1 in BG, compared to 283.02 g kg−1 in WG.

Table 1. pH, total acidity and organic acid content of garlic according to different processing conditions.

Samples/analyses pH Total acidity (g 100−1) Organic acids
Citric acid (g kg−1) Lactic acid (g kg−1) Propionic acid (g kg−1)
WG 6.53±0.01a 0.43±0.04d 283.02±3.09c 11.02±0.27b 16.42±0.40d
BG10 4.64±0.01b 1.24±0.01c 246.83±0.15d 7.23±0.03d 61.27±0.25c
BG20 4.25±0.01c 1.33±0.01b 314.88±0.04b 8.44±0.23c 124.64±0.64b
BG30 3.86±0.02d 1.42±0.01a 425.13±3.91a 17.20±0.33a 138.09±0.15a
Sig. ** ** ** ** **

n:3, Data shown as mean ± standart deviation. Values on the same column with different superscript letters are statistically different. **: p<0.01. Results are given on dry weight basis. WG: white garlic, BG10: aged black garlic 10 days, BG20: aged black garlic 10 days, BG30: aged black garlic 30 days.

The total phenolic content (TPC) and antioxidant levels of BG under different processing conditions are provided in Table 2. The TPC in WG was 16.88 mg GAE g−1, while in BG, it ranged from 25.44 to 46.27 mg g−1. The DPPH IC50 values varied between 4.67 and 23.88 mg mL−1. In WG, the DPPH IC50 was 23.88 mg mL−1, which decreased in BG due to different processing conditions, indicating enhanced antioxidant activity (Table 2). There is an inverse relationship between IC50 values and antioxidant activity, with higher IC50 values indicating lower antioxidant activity (Binici et al., 2024). In our samples, BG aged for thirty days exhibited higher antioxidant activity than WG, with a DPPH IC50 value of 4.67 mg mL−1. The ABTS IC50 value was 5.02 mg mL−1 in WG, while in BG, it ranged from 2.64 to 3.57 mg mL−1 (Table 2). As the aging time increased, the ABTS IC50 value decreased, indicating a rise in antioxidant activity.

Table 2. TPC and antioxidant content of garlic according to different processing conditions.

Samples/analyses TPC (mg GAE g−1) DPPH IC50 (mg mL−1) ABTS IC50 (mg mL−1)
WG 16.88±0.37d 23.88±0.15a 5.02±0.03a
BG10 25.44±0.73c 20.92±0.17b 3.57±0.01b
BG20 39.86±0.29b 9.44±0.20c 2.99±0.05c
BG30 46.27±0.19a 4.67±0.36d 2.64±0.02d
Sig. ** ** **

n:3, Data shown as mean ± standart deviation. Values on the same column with different superscript letters are statistically different. **: p<0.01. Results are given on dry weight basis. WG: White Garlic, BG10: aged black garlic 10 days, BG20: aged black garlic 10 days, BG30: aged black garlic 30 days.

The mineral content of BG under different processing conditions is shown in Table 3. Magnesium was the most abundant mineral, while selenium was the least, as presented in Table 3. Generally, the mineral content of BG increases with aging. The magnesium content in WG was 27.10 ppm, while in BG, it ranged from 27.56 to 31.16 ppm, increasing with longer maturation times.

Table 3. The mineral content of garlic according to different processing conditions.

Samples/analyses Mg (ppm) Cu (ppb) Se (ppb) Ca (ppm) Fe (ppm)
WG 27.10±0.62b 632.10±70.17b 100.32±25.23b 2.10±0.03a 0.64±0.07a
BG10 27.56±2.51b 646.20±61.56b 142.65±51.02ab 1.73±0.03b 0.66±0.05a
BG20 27.58±0.36b 859.23±20.39a 203.13±30.94a 1.71±0.02b 0.78±0.03a
BG30 31.16±0.42a 889.23±22.05a 207.63±28.95a 1.71±0.02b 0.74±0.07a
Sig. * ** * ** ns

n:3, Data shown as mean ± standart deviation. Values on the same column with different superscript letters are statistically different. **: p<0.01, ppm: mg kg−1, ppb: µg kg−1. Results are given on dry weight basis. WG: White Garlic, BG10: aged black garlic 10 days, BG20: aged black garlic 10 days, BG30: aged black garlic 30 days.

The HMF and SAC content of BG under different processing conditions are presented in Table 4. While HMF was not detected in WG, it was found in BG in amounts ranging from 57.63 to 70.86 mg kg−1, with levels increasing as aging time extended.

Table 4. 5-HMF and SAC amounts of garlic according to different processing conditions.

Samples/analyses 5-HMF (mg kg−1) SAC (ug g−1)
WG nd 11.98±0.24d
BG10 57.63±0.02c 31.90±0.15c
BG20 63.86±0.16b 35.13±0.03b
BG30 70.86±0.15a 43.96±0.09a
Sig. ** **

n:3, Data shown as mean ± standart deviation. Values on the same column with different superscript letters are statistically different. **: p<0.01, nd: not determined. Results are given on dry weight basis. WG: White Garlic, BG10: aged black garlic 10 days, BG20: aged black garlic 10 days, BG30: aged black garlic 30 days.

Separation of garlic samples using correlation and principal component analysis (PCA)

The correlation matrix for black garlic under different processing conditions is presented in Table 5. A strong negative correlation exists between pH and total acidity (–0.992) as well as pH and TPC (–0.902). This suggests that as pH values increase, total acidity and TPC decrease. Additionally, pH values are significantly correlated with antioxidant activity, mineral content, HMF, and SAC levels. A strong positive correlation is observed between selenium content and HMF (0.747), SAC (0.770), and propionic acid (0.838), indicating that an increase in selenium levels is associated with an increase in HMF, SAC, and propionic acid concentrations. Figure 1–1C display the PCA plots for black garlic processed under different conditions. The combined contribution of PC1 and PC2 accounted for 94.7% of the total variance, indicating that the results obtained in this study are well-suited for PCA, making the method effective and useful for analysis. White garlic samples were more distinctly separated compared to black garlic (Figure 1A). TPC, Fe, Cu, Mg, and citric acid clustered on the left side of the plot (Figure 1B). Furthermore, it was observed that black garlic aged for thirty days had higher levels of HMF, Se, SAC, TPC, Fe, Mg, Cu, total acidity, propionic acid, and citric acid compared to white garlic (Figure 1C).

Table 5. Correlation table of garlic according to different processing conditions.

Figure 1. PCA values of garlic according to different processing conditions.

Discussion

This finding aligns with the study by Choi et al. (2014), which reported a pH reduction in BG from 6.33 to 3.74 after 35 days of aging. Similarly, Shin et al. (2008) found that the pH of BG decreased from 6.40 to 5.29. Sasmaz et al. (2022) identified various organic acids in both WG and BG, including lactic, citric, pyruvic, malic, succinic, oxalic, fumaric, pyroglutamic, acetic, and ascorbic acids. Previous studies have shown that citric, formic, malic, lactic, and fumaric acids are more prevalent in WG (Bonasia et al., 2020; Liang et al., 2015; Petropoulos et al., 2018). The increase in organic acids in BG relative to WG is likely attributed to the formation of short-chain carboxylic acids through alkali group breakdown and the Maillard reaction during processing (Ahmed and Wang, 2021). Due to limited studies on organic acids in BG, comprehensive data is scarce. The TPC increased as the aging process progressed, consistent with findings by Choi et al. (2014), who observed an increase from 25.81 mg GAE g−1 to 58.25 mg GAE g−1 after 35 days of aging. Wu et al. (2007) also reported that heat treatment increased free phenolic acids and compounds while decreasing ester, glycoside, and ester-bound fractions, leading to a rise in free phenolic forms. Chua et al. (2022) reported DPPH IC50 values for BG aged 12 days ranging from 3.91 to 16.31 µg mL−1, compared to 24.12 µg mL−1 in fresh garlic. Our DPPH IC50 values were higher than those found in other studies, possibly due to differences in extraction methods and garlic varieties. Choi et al. (2014) reported ABTS values in BG ranging from 92.43 to 245.45 mM TE g−1 after 35 days of aging, with an increase observed on days other than the 35th day. Kim et al. (2012) found the ABTS IC50 value in BG to be 6.5 mg mL−1. Various methods are used to assess the antioxidant activity of naturally occurring bioactive substances in foods, with DPPH and ABTS assays being widely employed for this purpose due to their simplicity and ease of application (Choi et al., 2014; Kim et al., 2012). Šnirc et al. (2023) reported magnesium levels in fresh garlic samples from different cultures between 453.70 and 520.10 mg kg−1. Chua et al. (2022) found magnesium content in BG aged 12 days to range from 202 to 385.1 µg mL−1. The increase in mineral content is likely due to weight loss in BG caused by the evaporation of water and volatile compounds during maturation. Kang (2016) suggested that the increase in minerals during BG fermentation was due to variations in temperature and humidity. Selenium, although once considered toxic in the 1950s, is now recognized as vital for preventing diseases like coronary heart disease, Type 2 diabetes, and liver disorders (Genchi et al., 2023). Selenium’s presence in BG is particularly noteworthy, as it plays an important role in human health and, given BG’s lack of odor, suggests it may be suitable for consumption. HMF is a five-carbon aromatic aldehyde with antioxidant properties formed during Maillard reactions, which are accelerated by high temperatures and acidic conditions. This likely explains the observed increase in HMF levels (Chua et al., 2022). The SAC content in WG was 11.98 µg g−1, while in BG, it ranged from 31.90 to 43.96 µg g−1, increasing with longer aging times. Saputra et al. (2024) found SAC, a bioactive compound, to be present at 122 µg g−1 in fresh garlic and 335.46 µg g−1 in BG. In our study, SAC levels in BG were approximately 3.7 times higher than in WG. Bae et al. (2014) reported a 5.78-fold increase in SAC content in BG compared to fresh garlic. The increase in SAC content is likely influenced by various factors, including processing temperature, humidity, duration, variety, and garlic species used in BG production (Manoonphol et al., 2023).

Conclusions

This study demonstrated that black garlic exhibited significant differences in chemical and bioactive components compared to white garlic, which were influenced by processing conditions. The pH of black garlic decreased markedly, while total acidity and organic acid levels, particularly citric acid, increased significantly. Aging enhanced the levels of total phenolic compounds (TPC), antioxidant activity, 5-hydroxymethylfurfural (HMF), and S-allyl-L-cysteine (SAC) in black garlic. Mineral analysis revealed that magnesium and selenium contents increased with aging. Correlation and Principal Component Analysis effectively identified relationships between pH, total acidity, TPC, antioxidant activity, and mineral content, highlighting the differentiation of black garlic from white garlic. In conclusion, black garlic can be considered a functional food due to its enriched phenolic content and antioxidant activity. These findings support the health benefits of black garlic and suggest the need for further in-depth research in this area.

Author Contributions

Halil İbrahim Binici: Conceptualization, Investigation, Methodology, Writing - original draft, Project administration. Adem Savaş Conceptualization, Writing - original draft, Methodology, Validation, Visualization. Burak Erim Methodology, Conceptualization, Supervision.

Conflict of Interest

The author’s declare no conflicts of interest.

Funding

None.

REFERENCES

Ağbaş, B., Karakuş, D., Adigüzel, R., Keser, S., & Demir, E. (2013). Comparison of total antioxidant properties and dry matter content of Tunceli Garlic (Allium tuncelianum) and Normal Garlic (Allium sativum). Bilim ve Gençlik Dergisi, 2, 50–62. 10.1234/abc123

Ahmed, T., and C. K. Wang. 2021. Black garlic and its bioactive compounds on human health diseases: A review. Molecules, 26(16), 5028. 10.3390/molecules26165028

Augustyńska-Prejsnar A., M. Kačániová, M. Ormian, J. Topczewska, Z. Sokołowicz, and P. Hanus. 2023. Quality Assessment of Minced Poultry Products Including Black Fermented Garlic. Foods, 13(1), 70. 10.3390/foods13010070

Avery, J. C., & Hoffmann, P. R. (2018). Selenium, selenoproteins, and immunity. Nutrients, 10(9), 1203. 10.3390/nu10091203

Bae, S. E., Cho, S. Y., Won, Y. D., Lee, S. H., & Park, H. J. (2012). A comparative study of the different analytical methods for analysis of S-allyl cysteine in black garlic by HPLC. LWT–Food Science and Technology, 46(2), 532–535. 10.1016/j.lwt.2012.01.014

Bae, S. E., Cho, S. Y., Won, Y. D., Lee, S. H., & Park, H. J. (2014). Changes in S-allyl cysteine contents and physicochemical properties of black garlic during heat treatment. LWT–Food Science and Technology, 55(1), 397–402. 10.1016/j.lwt.2013.05.006

Binici, H. I., Şat, İ. G., & Aoudeh, E. (2021). The effect of different drying methods on nutritional composition and antioxidantactivity of purslane (Portulaca oleracea). Turkish Journal of Agriculture and Forestry, 45(5), 680–689. 10.3906/tar-2105-47

Binici, H. İ., Şat, İ. G., & Yilmaz, B. (2024). Comparison of antioxidant, phenolic profile, melatonin, and volatile compounds of some selected plant samples. Food Science & Nutrition, 12(10), 7158–7165. 10.1002/fsn3.4334

Bjørklund, G., Shanaida, M., Lysiuk, R., Antonyak, H., Klishch, I., Shanaida, V., & Peana, M. (2022). Selenium: an antioxidant with a critical role in anti-aging. Molecules, 27(19), 6613. 10.3390/molecules27196613

Bonasia, A., Conversa, G., Lazzizera, C., Loizzo, P., Gambacorta, G., & Elia, A. (2020). Evaluation of garlic landraces from Foggia province (Puglia region; Italy). Foods, 9(7), 850. 10.3390/foods9070850

Castellari, M., Versari, A., Spinabelli, U., Galassi, S., & Amati, A. (2000). An improved HPLC method for the analysis of organic acids, carbohydrates, and alcohols in grape musts and wines. Journal of liquid chromatography & related technologies, 23(13), 2047–2056. 10.1081/JLC-100101670

Chen, Y. T., Chen, Y. A., Lee, C. H., Wu, J. T., Cheng, K. C., & Hsieh, C. W. (2020). A strategy for promoting γ-glutamyltransferase activity and enzymatic synthesis of S-allyl-(L)-cysteine in aged garlic via high hydrostatic pressure pretreatments. Food Chemistry, 316, 126347. 10.1016/j.foodchem.2020.126347

Choi, I. S., Cha, H. S., & Lee, Y. S. (2014). Physicochemical and antioxidant properties of black garlic. Molecules, 19(10), 16811–16823. 10.3390/molecules191016811

Chua, L. S., Abdullah, F. I., & Lim, S. H. (2022). Physiochemical changes and nutritional content of black garlic during fermentation. Applied Food Research, 2(2), 100216. 10.1016/j.afres.2022.100216

Genchi, G., Lauria, G., Catalano, A., Sinicropi, M. S., & Carocci, A. (2023). Biological activity of selenium and its impact on human health. International journal of molecular sciences, 24(3), 2633. 10.3390/ijms24032633

Ghose, A., Fleming, J., & Harrison, P. R. (2001). Selenium and signal transduction: roads to cell death and anti-tumour activity. Biofactors, 14(1–4), 127–133. 10.1002/biof.5520140114

Jenkins, D. J., Kitts, D., Giovannucci, E. L., Sahye-Pudaruth, S., Paquette, M., Mejia, S. B., et al. (2020). Selenium, antioxidants, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition, 112(6), 1642–1652. 10.1093/ajcn/nqaa191

Kang, O. J. (2016). Physicochemical characteristics of black garlic after different thermal processing steps. Preventive Nutrition and Food Science, 21(4), 348. 10.3746/pnf.2016.21.4.348

Kim, J. H., Nam, S. H., Rico, C. W., & Kang, M. Y. (2012). A comparative study on the antioxidative and anti-allergic activities of fresh and aged black garlic extracts. International Journal of Food Science & Technology, 47(6), 1176–1182. 10.1111/j.1365-2621.2012.03093.x

Leng, Y., Huang, S., & Chen, B. (2020). Improvement of the key flavour compounds of fermented garlic by fermentation process optimization. African Journal of Biotechnology, 19(10), 789–798. 10.5897/AJB2020.17056

Liang T, Wei F, Lu Y, Kodani Y, Nakada M, Miyakawa T. (2015). Isıl işlemi sırasında siyah sarımsağın bileşimsel değişimlerinin kapsamlı NMR analizi. Journal of Agricultural and Food Chemistry, 63(2), 683–691. 10.1021/jf5054574

Liu, J., Li, J., Ge, S., Fu, X., Zhu, J., Wang, M., ... & Liu, Y. G. (2024). Characterization of a Short-term Processing Technology of Black Garlic with Low 5-HMF Content. Food Control, 110650. 10.1016/j.foodcont.2020.110650

Manoonphol, K., Suttisansanee, U., Promkum, C., & Butryee, C. (2023). Effect of Thermal Processes on S-Allyl Cysteine Content in Black Garlic. Foods, 12(6), 1227. 10.3390/foods12061227

Matsuse, K., Hirata, S., Abdelrahman, M., Nakajima, T., Iuchi, Y., Kambayashi, S., et al. (2024). Comparative Studies of Bioactivities and Chemical Components in Fresh and Black Garlics. Molecules, 29(10), 2258. 10.3390/molecules29102258

Petropoulos SA, Fernandes Â, Ntatsi G, Petrotos K, Barros L, Ferreira ICFR. (2018). Yunan sarılarının yerel ırklarının besin değeri, kimyasal karakterizasyonu ve soğan morfolojisi. Moleküller. 23, 1–14. 10.3390/molecules23010014

Santos, L. C. R., Santos, E. N. F., Oliveira, C. C., Nascentes, G. A. N., Saldaña, E., Bastos, L. M., et al. (2024). Black garlic extract: Phytochemical characterisation and application as natural antioxidant in burgers. International Food Research Journal, 31(3). 10.1111/j.1365-2621.2024.03978.x

Saputra, F. A., Khayrani, A. C., Fauzantoro, R. A., Marwanta, E., Mahsunah, A. H., Marasabessy, A., et al. (2024). Optimizing s-allyl-cysteine (SAC) content in extract black garlic (Stamilic) for health supplement. In AIP Conference Proceedings (Vol. 3080, No. 1). AIP Publishing.

Sasmaz, H. K., Sevindik, O., Kadiroglu, P., Adal, E., Erkin, Ö. C., Selli, S., & Kelebek, H. (2022). Comparative assessment of quality parameters and bioactive compounds of white and black garlic. European Food Research and Technology, 248(9), 2393–2407. 10.1007/s11483-022-

Shin, J. H., Choi, D. J., Chung, M. J., Kang, M. J., & Sung, N. J. (2008). Changes of physicochemical components and antioxidant activity of aged garlic at different temperatures. Journal of the Korean Society of Food Science and Nutrition, 37(9), 1174–1181. 10.3746/jkfn.2008.37.9.1174

Šnirc, M., Lidiková, J., Čeryová, N., Pintér, E., Ivanišová, E., Musilová, J., et al. (2023). Mineral and phytochemical profiles of selected garlic (Allium sativum L.) cultivars. South African Journal of Botany, 158, 319–325. 10.1016/j.sajb.2023.01.016

Stępień, A. E., Trojniak, J., & Tabarkiewicz, J. (2024). Anti-Cancer and Anti-Inflammatory Properties of Black Garlic. International Journal of Molecular Sciences, 25(3), 1801. 10.3390/ijms25031801

Tahir, Z., Saeed, F., Nosheen, F., Ahmed, A., & Anjum, F. M. (2022). Comparative study of nutritional properties and antioxidant activity of raw and fermented (black) garlic. International Journal of Food Properties, 25(1), 116–127. 10.1080/10942912.2022.2032783

Takım, K. (2020). Comparison of amount of phenolic compounds by using LC-MS/MS in Tunceli mountain garlic (Allium tuncelianum) different extracts. 10.29050/harranziraat.591171

Utama, G. L., Rahmi, Z., Sari, M. P., & Hanidah, I. I. (2024). Psychochemical changes and functional properties of organosulfur and polysaccharide compounds of black garlic (Allium sativum L.). Current Research in Food Science, 100717. 10.1016/j.crfs.2023.100717

Wu, W. M., Lu, L., Long, Y., Wang, T., Liu, L., Chen, Q., & Wang, R. (2007). Free radical scavenging and antioxidative activities of caffeic acid phenethyl ester (CAPE) and its related compounds in solution and membranes: a structure–activity insight. Food Chemistry, 105(1), 107–115. 10.1016/j.foodchem.2007.02.043

Wu, Z. G., Jin, N., Deng, Y. F., Shen, X. F., Liu, C. Y., Ding, B. Y., et al. (2024). Protective action of selenium-enriched black garlic extract in rats with lipopolysaccharide/D-galactosamine-induced acute liver failure. Journal of Functional Foods, 115, 106123. 10.1016/j.jff.2024.106123

Zhang, Z., Lei, M., Liu, R., Gao, Y., Xu, M., & Zhang, M. (2015). Evaluation of alliin, saccharide contents and antioxidant activities of black garlic during thermal processing. Journal of Food Biochemistry, 39(1), 39–47. 10.1111/jfbc.12110

Zor, M., Bulut, M., Karagöz, S. G., Çetintaş, Y., & Alwazeer, D. (2024). Use of Hydrogen-Rich water in rice milk preparation improves the nutritional and sensory properties of product. Food Chemistry, 437, 137821. 10.1016/j.foodchem.2023.137821