Influence of Thermal Processing on the Bioactive, Antioxidant, and Physicochemical Properties of Conventional and Organic Agriculture Black Garlic (Allium sativum L.)

Production monitoring and quality characterization of black garlic using Vis-NIR hyperspectral imaging integrated with chemometrics strategies

As a new deep-processing garlic product with notable health benefits, the accurate discrimination of processing stages and prediction of key physicochemical constituents in black garlic are vital for maintaining product quality. This study proposed a novel method utilizing hyperspectral imaging technology to both rapidly monitor the processing stages and quantitatively predict changes in the key physicochemical constituents during black garlic processing. Multiple methods of noise reduction and feature screening were used to process the acquired hyperspectral information. To differentiate processing stages, pattern recognition methods including linear discriminant analysis (LDA), K-nearest neighbor (KNN), support vector machine classification (SVC) analysis were utilized, achieving a discriminant accuracy of up to 98.46 %. Furthermore, partial least squares regression (PLSR) and support vector machine regression (SVR) analysis were performed to achieve quantitative prediction of the key physicochemical constituents including moisture and 5-HMF. PLSR models outperformed SVR models, with correlation coefficient of prediction of 0.9762 and 0.9744 for moisture and 5-HMF content, respectively. The current study can not only offer an effective approach for quality detection and assessment during black garlic processing, but also have a positive significance for the advancement of black garlic related industries.

Changes in Garlic Quality during Fermentation under Different Conditions

One of the garlic processing methods is fermentation, which produces black garlic with completely different chemical, physical, sensory, culinary, and health-enhancing properties. Our study aimed to compare the influence of various processing conditions on the quality indicators of black garlic (BG). Samples of white garlic (WG) were placed in laboratory climatic chambers. BG1 samples were packed in plastic bags and vacuumed, BG2 and BG3 samples were packed in textile mesh bags. BG1 samples were fermented in 70% humidity at 50 °C for 28 days, BG2 samples in 85% humidity at 60 °C for 99 days, and BG3 samples in 80% humidity at 80 °C for 14 days. The dependence of changes in chemical composition, color, and texture of garlic on fermentation conditions was analyzed. Proximate composition analyses and antioxidant activity of WG and BG were performed using standard methods. It was established that regardless of the fermentation conditions, BG's chemical composition became richer than WG's. They significantly increased vitamin C content (1.5-5.8 fold), titratable acidity (14.7-21.0 fold), protein (1.4-3.2 fold), fiber (4.6-7.0 fold), and ash (1.2-3.9 fold) content, amount of total phenolic compounds (6.6-9.6 fold) and antioxidant activity (5.3-9.9 fold). Fermented garlic turned dark in color and soft and sticky in texture. The higher fermentation temperature (80 °C) but the shorter time (14 days) had the greatest positive effect on the quality of black garlic.

Changes in the aroma and key odorants from white garlic to black garlic using approaches of molecular sensory science: A review

Black garlic is a relatively new product that has become very popular in recent years. It is obtained by fermenting raw (white) garlic by the application of heat treatment. The undesirable pungent odor of the white garlic disappears and the black garlic product with a sweet-sour flavor is formed after various reactions during the applied heat process. As a result, black garlic is more preferred and easily consumed by the consumers compared to white garlic. This review aims to summarize the studies on the changes in the odorants during the heat treatment employed in the production of black garlic as well as the factors affecting the changes in the aroma and aroma-active compounds and the use of molecular sensory science (MSS) approach, which has been applied in recent years as a new method for the determination of the aroma compounds. This work revealed that the use of the MSS on the aroma changes in black garlic is quite limited in the literature. Thus, more studies are needed to understand the aroma changes that occur during the formation of black garlic from white garlic in more detail.

Effect of Thermal Processes on S-Allyl Cysteine Content in Black Garlic

As a key component of black garlic (BG) products, S-allyl cysteine (SAC) is useful in reducing oxidative stress and inflammation. Several BG products with a high SAC content have been developed by thermal processing; however, the optimum conditions for thermal treatment for producing Thai garlic (multicloves) with a high SAC content compared to Chinese garlic (single clove) are still unknown. Moreover, the mechanism underlying the increase in SAC content in BG is unclear. Thus, this study aimed to investigate the optimum thermal condition for developing Thai BG with high SAC content base on methods A (70 °C and 80% RH) and B (60–75 °C and 80–85% RH). The total phenolic contents and antioxidant activities of Thai fresh garlic, Thai BG, and their powder forms were also compared. Method A worked the best for both types of garlic. The results indicated that the SAC content increased significantly after 7 days of fermentation and decreased drastically afterward with prolonged heat treatment. The optimum thermal condition for producing Thai fresh garlic and Chinese fresh garlic with high SAC content was 70 °C and a relative humidity of 80% for 12 days in an industrial fermentation chamber. The SAC content of Thai BG and Chinese BG increased approximately 139- and 122-fold, respectively. Furthermore, significant antioxidant capabilities determined by ferric ion-reducing antioxidant power, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, and oxygen radical absorbance capacity assays were 34-, 6-, and 3-fold higher, respectively, than those of fresh garlic.

Changes in the Physicochemical Properties, Antioxidant Activity and Metabolite Analysis of Black Elephant Garlic (Allium ampeloprasum L.) during Aging Period

This study investigated the effects of the aging period on the black elephant garlic (Allium ampeloprasum L.) manufacturing process. Black elephant garlic is a processed elephant garlic product prepared by high-temperature and high-humidity treatment for 40 days. The proximate composition (moisture, crude lipid, crude protein, carbohydrate, and ash), minerals, color values, reducing sugars, pH, total polyphenol contents, total flavonoid contents and antioxidant activities of elephant garlic and black elephant garlic were evaluated. The browning intensity of elephant garlic increased with the aging period, but the browning reaction terminated after aging for 30 days, exhibiting the same browning level. Reducing sugars increased over the aging period until 20 days, and then decreased with the aging period, in contrast to the pH, which decreased from 6.47 to 3.68 over the aging period. Antioxidant components, including the total polyphenol and total flavonoid contents of black elephant garlic, increased significantly until day 30 of aging. From the metabolite profiles determined through GC/MS analysis, it was confirmed that primary metabolites related to antioxidant components, such as lactic acid and 5-hydroxymethyl-2-furoic acid, were generated during the aging process of elephant garlic.

Black garlic: A review of its biological significance

Garlic has been used as a vegetable since ancient times, and it has proved versatility in preventative and therapeutic approaches. The use of garlic in the food business was restricted because of its strong flavor and harsh odor. Fermentation and different chemical processes, such as the Millard reaction and microbial fermentation, produce black garlic. Thermal processing at precise temperatures and relative humidity enhanced flavor and prolonged shelf life. This article holds the most up-to-date information about the resourcefulness and complexity of garlic processing and its biological implications. Recent findings have shown proof of the superior qualitative features and physical activities of black garlic. Before introducing this to the food market, researchers must conduct high-quality research to evaluate the changes of metabolites to achieve largest antioxidant, anticancer, anti-obesity, anti-inflammatory, immune, hepatoprotective, cardioprotective, neuroprotective, and anti-allergenic performance. Researchers should evaluate the quality, marketing, post-harvest handling, and consumption practices of black garlic.

Phenolic Compound in Garlic (Allium sativum) and Black Garlic Potency as Antigout Using Molecular Docking Approach

Phenolics, including flavonoids, are bioactive components in garlic in relatively abundant amounts and are present 2–4 times more in black garlic. Both of these compounds are reported to have biological activity, with one of them acting as an antioxidant. However, its ability as an antigout is still not widely reported. Xanthine oxidase, adenine deaminase, guanine deaminase, purine nucleoside phosphorylase, and 5-Nucleotidase II are involved during the production of uric acid and causes gout. This study predicted the potential of the phenolic and flavonoid compounds in garlic and black garlic as antigout in inhibiting five target receptors through a molecular docking approach. Utilizing AutoDock Tools v.1.5.7 for receptor and ligand preparation, AutoDock Vina and AutoDock4 for molecular docking, and LigPlot+ and PyMOL for visualization. About 21 compounds from the phenolic and flavonoid groups were used as test ligands and 16 reference ligands (substrate and commercial). SwissADME predicted the pharmacokinetic parameters. The results showed that apigenin, morin, resveratrol, kaempferol, (+)-catechin, isorhamnetin, and (-)-epicatechin were predicted to have good interactions at each target receptor and had the potential to be developed as candidates for multi-target antigout. Based on the pharmacokinetic parameters, all these compounds had good scores in each, making them feasible to continue in vitro or in vivo trials.

The Effects of Processing Time on the Total Phenolic, Flavonoid Content, and Antioxidant Activity of Multi Bulb and Single Bulb Black Garlic

Black garlic is produced by processing multi-bulb garlic (Allium sativum) or single-bulb garlic in high temperature and high humidity for several days. Black garlic has many health benefits, such as an antioxidant activity resulting from its compound, including groups of flavonoid and phenolic compounds. This study aimed to analyze the effect of aging time on multi-bulb and single-bulb black garlic on the content of total phenolic, flavonoid, and antioxidant activity. Black garlic was processed at a 60-70°C heating temperature and 70-80% relative humidity for 25 days. Determination of total phenol and flavonoid contents was conducted using spectrophotometric methods with gallic acid as a standard of total phenolic and quercetin as a standard of flavonoid, while the antioxidant activity was determined by DPPH radical reduction. The results showed that total phenolic contents (% w/w GAE), flavonoids contents (% w/w QE), and EC50 values at 0 until day 25 increased on a particular day in multi-bulb and single-bulb black garlic. The optimal total phenolic content of both black garlic was obtained by heating for 20 days, flavonoid content of multi-bulb garlic for 10 days, and single-bulb black garlic for 15 days. Highest antioxidant activity was obtained on days 20 and 25 for single-bulb black garlic and multi-bulb black garlic, respectively. The aging time of black garlic affects total phenolic, flavonoid content, and antioxidant activity. In general, longer processing time caused an increase in the total phenolic content, flavonoid content, and antioxidant activity of both black garlics. Multi-bulb black garlic showed higher phenolic or flavonoid content and antioxidant activity than single-bulb black garlic.

The Physicochemical Properties, Volatile Compounds and Taste Profile of Black Garlic (Allium sativum L.) Cloves, Paste and Powder

Black garlic is produced as a result of the so-called “fermentation processes” of whole heads or cloves kept under controlled conditions of temperature and humidity for several weeks. During this long-term heat treatment, garlic undergoes enzymatic and non-enzymatic browning reactions, which greatly change its taste, aroma, physicochemical, organoleptic and bioactive properties. Black garlic is most often produced in the form of cloves, and recently also in the form of paste and powder. This work focused on the comparison of functional properties of black garlic, such as volatile compounds, taste profile, total polyphenols content, antioxidant activity, color (CIE L*, a*, b*), water activity (aw), pH, soluble solids content (°Brix) and moisture content, depending on the form of its occurrence: cloves, spreading paste and powder. After long-term heat treatment, garlic was characterized by a higher content of dry matter and water-soluble solids, respectively at about 22% and 24% for spreading paste and 166% and 44% for powder. The conducted research showed significant differences in the bioactive properties of the tested garlic samples, with the lowest content of polyphenols and antioxidant properties in fresh, unprocessed garlic (6.05 ± 0.07 mg GAE/1 g d.m. and 232.95 ± 4.06 µM TEAC/1 g d.m., respectively), while in garlic subjected to long-term heat treatment, the total polyphenols content and antioxidant potential were two times higher than in the unprocessed garlic. The polyphenol content and antioxidant properties were the highest in the spread garlic (respectively, 15.16 ± 0.08 mg GAE/1 g d.m. and 638.46 ± 3.37 µM TEAC/1 g d.m.) and the lowest in the powdered samples (respectively, 11.02 ± 0.51 mg GAE/1 g d.m. and 541.71 ± 5.22 µM TEAC/1 g d.m.). Obtained black garlic samples gain completely different sensory characteristics determined using instrumental methods. In black garlic and its preparations, the intensity of unpleasant taste and aroma is reduced as a result of the appearance of metabolites during the long-term heat treatment, which in turn determined the specific, delicate sweet–sour taste and pleasant aroma, completely unrelated to the aroma of the unprocessed product. Taking into account the obtained results, it can be stated that black garlic, in the form of cloves, paste and powder, exhibits completely different properties than white garlic.

The Influence of Plants from the Alliaceae Family on Morphological Parameters of the Intestine in Atherogenic Rats

Bulbs from the Alliaceae family have been well-known and valued spices for thousands of years, not only for their unique flavor and aroma features, but also for their high nutritional and health-promoting values. Long-term or excessive consumption of these vegetables, especially raw garlic, can have side effects in the body (including in the digestive tract), causing a number of pathological changes in the intestinal wall; these changes lead, in turn, to its damage, dysfunction, and disorder development. Therefore, the aim of this study was to investigate the effect of the addition of freeze-dried vegetables from the Alliaceae family, i.e., garlic (Allium sativum L.), white onion, and red onion (Allium cepa L.) on the morphometric parameters (intestinal villi length, crypt depth, thickness of tunica mucosa, and the thickness of tunica muscle) of the jejunum of rats fed a semi-synthetic atherogenic diet (1% dietary cholesterol). In freeze-dried vegetables administered to rats, the contents of selected bioactive ingredients and their antioxidant potentials were determined. The effect of the onion vegetable supplements on growth parameters, serum lipid profile, plasma antioxidant potential, and the intestinal morphological parameters of rats loaded with cholesterol was determined. In an animal experiment, 30 male Wistar rats were divided into 5 diet groups, diet consumption and FER were studied. Supplementation of the atherogenic diet with vegetables improved the blood plasma lipid profiles and atherogenic indices, in a manner that was dependent on the type of supplementation used, with the best hypolipidemic and anti-atherosclerotic effects found in garlic use. The atherogenic diet, as well as the supplementation of this diet with the tested vegetables from the Alliaceae family, influenced the histological changes in the epithelium of the jejunum of rats. The damage to the intestinal mucosa was the greatest in animals fed an atherogenic diet supplemented with garlic. Bearing in mind that the desired beneficial therapeutic or prophylactic effects of onion vegetables (in particular garlic) in the course of various metabolic ailments (including atherosclerosis) are achieved during long-term supplementation, it is important to remember their possible cytotoxic effects (e.g., on the digestive tract) in order to achieve real benefits related to the supplementation with vegetables from the Alliaceae family.

The content of bioactive compounds and antioxidant activity of garlic (Allium sativum L.)

Garlic (Allium sativum L.) is one of the most commonly grown vegetables and thanks to its sensory properties, it has an important place in numerous world cuisines. Garlic is also known for its health-promoting properties, which are attributed to its chemical composition. The health benefits of garlic depending on the content of biologically active compounds, which vary between cultivars and geographical areas. Seven cultivars of garlic, namely Sukoradsky, Zahorsky, Germidour, Mojmir, Karel IV., Arkus, Makoi, were analyzed in this study. This study aimed to determine the total polyphenol content, total flavonoid content, and antioxidant activity of garlic. Studied characteristics were analyzed by the UV-VIS spectrometry method. Total polyphenol content ranged from 430.26 to 640.04 mg GAE.kg-1 FW. Total flavonoid content ranged from 10.29 to 60.49 mg CE.kg-1 FW. Antioxidant activity measured by ABTS assay ranged from 1.098 to 1.955 mmol TE.kg-1 FW. Antioxidant activity measured by FRAP assay ranged from 0.63 to 1.467 mmol.kg-1 FW. Highest TPC, TFC, and AA were determined in the cultivar Mojmir. The lowest TPC and TFC were determined in the cultivar Zahorsky. The lowest AA was determined in the cultivar Sukoradsky. High positive correlations were determined between individual parameters.

Evaluation of Bioactive and Physicochemical Properties of White and Black Garlic (Allium sativum L.) from Conventional and Organic Cultivation

The aim of this study was to evaluate the bioactive and physicochemical properties of white and black garlic (Allium sativum L.) from conventional and organic cultivation. Both white conventional (G) and organic (EG) garlic were processed during 45 days heat treatment at 70 °C temperature and 80% relative humidity. In black garlic (BG) samples the content of soluble solids, total reducing sugars, total polyphenol as well as antioxidant activity significantly (p < 0.05) increased (by about 33.5%, 60.5%, 118.4%, 125.8%, respectively), while a pH significantly (p < 0.05) decreased (by about 41.1%) as compared to white garlic samples. The study showed significant differences between colour of white and black garlic, both in the L*a*b* and RGB colour space, especially in the case of the L* parameter, indicating that the colour of garlic changed from white to dark brown or black during the thermal processing. All organic garlic samples had improved bioactive ingredients and antioxidant activity compared to conventional garlic for both fresh (unprocessed) and heat-treated black garlic. The production of black garlic, especially organic (EBG), allows one to obtain a product with higher amount of bioactive compounds, which can be widely used in the design of health-promoting functional food.