Assessment of standardization of domestic commercial black garlic extract for S-allyl-l-cysteine and S-1-propenyl-l-cysteine.

Aged garlic extract (AGE) contains a significant amount of bioactive compounds, including S-allyl-l-cysteine (SAC), which is associated with various health benefits. Among different AGE products, black garlic extract (BGE) is widely consumed and a common product in the Korean market. BGE products do however contain different levels of SAC and S1PC. Here, the SAC contents in commercial BGE products were found to be in the range of 0.31-27.22 mg/100 mL, while the SAC contents of commercial black garlic (BG) cloves were in the range of 22.28-63.71 mg/100 g. Recently, S-1-propenyl-l-cysteine (S1PC) has emerged as a new bioactive compound of interest in AGE products. Analysis of BG and BGE indicated that their S1PC contents were 2.24-16.58 mg/100 g and ND-3.68 mg/100 mL, respectively. Based on the significance of these compounds, standardization of the SAC and S1PC content in commercial BGE products is required.

Microbial ecology of watery kimchi.

The biochemistry and microbial ecology of 2 similar types of watery (mul) kimchi, containing sliced and unsliced radish and vegetables (nabak and dongchimi, respectively), were investigated. Samples from kimchi were fermented at 4, 10, and 20 °C were analyzed by plating on differential and selective media, high-performance liquid chromatography, and high-throughput DNA sequencing of 16S rDNA. Nabak kimchi showed similar trends as dongchimi, with increasing lactic and acetic acids and decreasing pH for each temperature, but differences in microbiota were apparent. Interestingly, bacteria from the Proteobacterium phylum, including Enterobacteriaceae, decreased more rapidly during fermentation at 4 °C in nabak cabbage fermentations compared with dongchimi. Although changes for Proteobacterium and Enterobacteriaceae populations were similar during fermentation at 10 and 20 °C, the homolactic stage of fermentation did not develop for the 4 and 10 °C samples of both nabak and dongchimi during the experiment. These data show the differences in biochemistry and microbial ecology that can result from preparation method and fermentation conditions of the kimchi, which may impact safety (Enterobacteriaceae populations may include pathogenic bacteria) and quality (homolactic fermentation can be undesirable, if too much acid is produced) of the product. In addition, the data also illustrate the need for improved methods for identifying and differentiating closely related lactic acid bacteria species using high-throughput sequencing methods.

Cysteine reacts to form blue-green pigments with thiosulfinates obtained from garlic (Allium sativum L.).

Cysteine was found to form pigments with garlic thiosulfinates in this investigation, in contrast to previous reports. Pigments were formed only when the molar concentration ratios of cysteine to total thiosulfinates were smaller than 2:1. Cysteine does not form pigments with thiosulfinates in the same manner as other pigment-forming amino compounds because it has a sulfhydryl (SH) group. A colour reaction of cysteine with thiosulfinates is proposed where colourless disulphide-type S-alk(en)yl mercaptocysteines (SAMCs) are formed first by the SH-involved reaction between cysteine and thiosulfinates, and then SAMCs react with residual thiosulfinates to form pigments. When the cysteine to total thiosulfinate molar concentration ratio was 2:1 or greater, total thiosulfinates were consumed to form SAMCs without leaving any thiosulfinates remaining available for the following colour reactions.

Antimicrobial properties of allium species.

The antimicrobial activity of Allium species has long been recognized, with allicin, other thiosulfinates, and their transformation products having antimicrobial activity. Alliums are inhibitory against all tested microorganisms such as bacteria, fungi, viruses, and parasites. Alliums inhibit multi-drug-resistant microorganisms and often work synergistically with common antimicrobials. Allium-derived antimicrobial compounds inhibit microorganisms by reacting with the sulfhydryl (SH) groups of cellular proteins. It used to be thought that allicin reacts only with cysteine and not with non-SH amino acids, but evidence has accumulated that allicin and other thiosulfinates also react with non-SH amino acids.

3-(allyltrisulfanyl)-2-aminopropanoic acid, a novel nonvolatile water-soluble antimicrobial sulfur compound in heated garlic.

A nonvolatile and slightly water-soluble antimicrobial sulfur compound newly isolated from heated garlic extract was characterized. The compound was generated most when heated at 120°C for 30 minutes and completely disappeared after 90 minutes of heating. It has a molecular mass of 225 daltons with an elemental ratio of C6H11N1O2S3, and the interpretation of ¹H- and ¹³C-nuclear magnetic resonance and Fourier transform-infrared data showed that the compound was CH2=CH-CH2-S-S-S-CH2-CH(NH2)COOH, 3-(allyltrisulfanyl)-2-aminopropanoic acid, a derivative of cysteine, presumably derived from alliin (S-allyl-L-cysteine sulfoxide). This novel compound has comparatively potent anti-yeast activity and rather weak antibacterial activity, similar to other antimicrobial compounds in garlic.