Determination of γ‐aminobutyric acid in Chinese rice wines and its evolution during fermentation

γ‐Aminobutyric acid (GABA) is a functional amino acid that is widely present in Chinese rice wine. In this study, high‐performance liquid chromatography coupled with ultraviolet detection (HPLC‐UV) was established for the determination of γ‐aminobutyric acid in 22 Chinese rice wines collected from the Shaoxing region of China. Furthermore, the evolution of GABA was studied in Chinese rice wine during primary and post‐fermentation process. Results showed that the HPLC method was reliable with good linearity, accuracy, precision and stability. Additionally, the GABA content varied significantly in the 22 Chinese rice wines, and the content was much higher in wine samples with long aging periods. Regarding the evolution of GABA in Chinese rice wine during the brewing process, the level slowly increased during primary fermentation. A decrease in GABA was observed in the wine at the early stage of the post‐fermentation process. However, a marked increase on the GABA content occurred in wine at the late stage of post‐fermentation. The findings from this study are that HPLC can be successfully applied to determine GABA in Shaoxing brewed rice wines, and further provide useful information on quality control of such wines. Copyright © 2017 The Institute of Brewing & Distilling     

Effect of γ‐aminobutyric acid supplementation on the composition of Chinese rice wine

This study investigated the effect of γ‐aminobutyric acid (GABA) supplementation on the composition of Chinese rice wine. GABA was added at 188.5 and 377 mg/L at the beginning of primary fermentation or post‐fermentation. Addition of GABA during primary fermentation had no impact on alcohol and total acid formation or the utilisation of sugar. However, total free amino acids, total essential amino acids and GABA in rice wine supplemented with GABA were significantly lower than the control rice wine without supplementation. Alcohol formation, total acid, sugar content and total essential amino acids were similar compared with the control. However, the GABA post‐supplementation was significantly higher, suggesting that GABA supplementation post‐fermentation process could enhance the GABA content in rice wine. © 2018 The Institute of Brewing & Distilling     

Accumulating mechanism of γ‐aminobutyric acid in soybean (Glycine max L.) during germination

γ‐aminobutyric acid (GABA) has been found accumulating significantly in soybean seeds during germination. However, the mechanism of the accumulating process is not clear. Therefore, gene expression, enzyme activity and metabolites associated with GABA shunt in ZH 13 soybean during germination were analysed in this paper. GABA content in 5‐day germinated soybean was 0.26 ± 0.016 mg g^?1 DW, which was equivalent to six times concentration of original soybean. The GAD activity has a positive effect on the accumulation of GABA, as well as the GABA‐T activity was found to play a significant role in the degradation of GABA. The expression levels of GmGAD and GmGABA‐T may affect the GABA content by regulating the respective enzyme activities. In conclusion, upregulation of GAD and downregulation of GABA‐T may cause the accumulation of GABA.     

Determination of β‐Phenylethanol in Chinese Rice Wine by Reverse Phase High‐Performance Liquid Chromatography

The objective of this study was to develop a reverse phase HPLC method for determining the content of β‐phenylethanol in Chinese rice wine. The β‐phenylethanol was separated using a Synergi Hydro‐RP C18 (4.6 mm × 250 mm, 4 μm) column, CH₃OH:H₂O (50:50, v/v) as the mobile phase, and a diode array detector set at 210 nm. The results showed that when 5.00?30.00 mg/L of β‐phenylethanol was fortified, the average recoveries were between 99.5% and 99.8%, the RSD was 0.6% (n = 6), and the limit of determination was 0.05 mg/L. The calibration curve was linear over a range of 0.5 mg/L to 50 mg/L (R = 0.9999). The results of this method were almost the same as that of the gas chromatography method. The developed method is suitable to determine the β‐phenylethanol content in Chinese rice wine.     

Recent advances in γ‐aminobutyric acid (GABA) properties in pulses: an overview

Beans, peas, and lentils are all types of pulses that are extensively used as foods around the world due to their beneficial effects on human health including their low glycaemic index, cholesterol lowering effects, ability to decrease the risk of heart diseases and their protective effects against some cancers. These health benefits are a result of their components such as bioactive proteins, dietary fibre, slowly digested starches, minerals and vitamins, and bioactive compounds. Among these bioactive compounds, γ‐aminobutyric acid (GABA), a non‐proteinogenic amino acid with numerous reported health benefits (e.g. anti‐diabetic and hypotensive effects, depression and anxiety reduction) is of particular interest. GABA is primarily synthesised in plant tissues by the decarboxylation of l ‐glutamic acid in the presence of glutamate decarboxylase (GAD). It is widely reported that during various processes including enzymatic treatment, gaseous treatment (e.g. with carbon dioxide), and fermentation (with lactic acid bacteria), GABA content increases in the plant matrix. The objective of this review paper is to highlight the current state of knowledge on the occurrence of GABA in pulses with special focus on mechanisms by which GABA levels are increased and the analytical extraction and estimation methods for this bioactive phytochemical. © 2017 Society of Chemical Industry     

Effects of cultivar and culture conditions on γ‐aminobutyric acid accumulation in germinated fava beans (Vicia faba L.)

BACKGROUND: High levels of γ‐aminobutyric acid (GABA) accumulate in plant tissues under various stresses. GABA accumulation is also influenced by cultivar. This aim of this study was to select the most promising cultivar of fava bean for GABA accumulation and to optimise the culture conditions for GABA production in germinated fava beans by response surface methodology based on central composite design (CCD). RESULTS: GABA content and glutamate decarboxylase activity in germinated seeds of cultivar S2 were significantly higher than those in other cultivars (P < 0.05). A significant negative correlation (r = −0.765, P < 0.05) between germination percentage and 1000‐kernel weight was observed. There was a linear relationship between GABA content and sprout length (R² = 0.816). The regression model fitted to the experimental data of CCD was valid in predicting GABA production in germinated fava beans. Temperature and pH value of the culture solution had significant effects on GABA content in germinated fava beans. Under optimal culture conditions (33.6 °C, pH 3.19 and an air flow rate of 1.19 L min⁻¹), GABA content reached up to 2.41 g kg⁻¹ dry weight, about 48 times that in raw seeds. CONCLUSION: Germinated fava bean is a good resource of GABA‐rich food. Both cultivar and culture conditions have significant effects on GABA production. Copyright © 2009 Society of Chemical Industry     

Effect of γ‐aminobutyric acid on the physicochemical,rheological and sensory properties of yoghurt

This study aimed to investigate the impacts of dairy processing conditions on the γ‐aminobutyric acid (GABA) content and the effect of GABA on the quality of the resulting yoghurt. Serial concentrations of GABA (0.05–1.0%, w/w, milk basis) were designed during the preparation of yoghurt. Colour and physicochemical and rheological properties of yoghurt were also examined. The results indicated that the fermentation process had no significant influence on GABA content. The GABA level greatly improved the texture properties of the resulting product at a concentration of 0.5% (w/w), whereas higher GABA concentrations impaired the texture. The lightness (L) value of yoghurt also increased in line with the GABA concentration.     

高效液相色谱法测定黄酒中纽甜的不确定度评定

建立了高效液相色谱法测定黄酒中纽甜含量不确定度的分析方法。依据JJF 1059.1-2012《测量不确定度评定与表示》及CNAS-GL06：2006《化学分析中不确定度的评估指南》中不确定度评定的基本程序,建立数学模型,分析高效液相色谱法测定黄酒中纽甜含量过程中引入的各测量不确定度分量,计算得到测量结果的合成标准不确定度和扩展不确定度。结果表明：影响检测结果不确定度的因素主要是校准曲线拟合求浓度,其次是样品前处理及测定和标准工作溶液的配制,相对标准不确定度分别为0.016 13、0.011 27、0.007 90。其中样品前处理及测定因素中贡献大的分量是通过样品重复性引入的相对不确定度,相对标准不确定度为0.009 61。     

Selection of γ‐aminobutyric acid‐producing lactic acid bacteria and their potential as probiotics for use as starter cultures in Thai fermented sausages (Nham)

To produce a novel product of Thai fermented meats, such as healthy Nham, 602 lactic acid bacteria were isolated from fermented foods and fourteen isolates that produced high amounts of γ‐aminobutyric acid (GABA) were also tested for inhibiting the seven foodborne bacteria. Four selected isolates produced GABA in the range of 7339–9060 mg L^?1 (NH2 < NH102 < NH116 < HN8) and their culture filtrates with a pH of 3.8, except 4.2 for NH2 inhibited all target organisms. Selected strains were investigated for their physiological and functional properties of probiotics in vitro. Strain NH102 survived best in the gastrointestinal tract with only a one log cell decrease over 4 h, whereas strain NH116 was the best cholesterol removal (43%). None showed any haemolysis and all hydrolased bile salts. Strain NH2 was identified as Lactobacillus namurensis and all the others were Pediococcus pentosaceus. Strains HN8 and NH2 were potential starters for fermenting meats.     

Enzyme activity of α‐chymotrypsin after derivatization with phenolic compounds

α‐Chymotrypsin was allowed to react with selected phenolic and related compounds (chlorogenic acid, m‐, o‐, p‐dihydroxybenzene, p‐benzoquinone). The derivatized enzymes obtained were characterized in terms of their activity. In vitro experiments illustrated that the enzymatic activity of the derivatives was adversely affected. The kinetics of the enzymatic reactions showed that the hydrolysis of selected food proteins becomes slower and the affinity of the enzyme to these substrates declined as measured by Michaelis‐Menten constant and maximum velocity of the enzymatic reaction. This enzyme inhibition depended on the reactivity of the phenolic and related substances tested as well as on the degree of the derivatization. Further, influence of the enzyme‐substrate ratio was also demonstrated. The effects of the derivatization are more pronounced with increasing concentration of the substrates.     

Effect of pre‐germination time of brown rice on serum cholesterol levels of hypercholesterolaemic rats

BACKGROUND: Brown rice is unpolished rice with immeasurable benefits for human health. Brown rice (BR) and pre‐germinated brown rice (PGBR) are known to contain various functional compounds such as γ‐oryzanol, dietary fibre and γ‐aminobutyric acid (GABA). In the present study, the experimental diets containing BR and PGBR (24, 48 h pre‐germination) were used to investigate the influence of pre‐germination time of brown rice on blood cholesterol in Sprague–Dawley male rats. RESULTS: Hypercholesterolaemia and elevation of LDL‐cholesterol were successfully ameliorated by the experimental diets containing BR and PGBR (24 and 48 h pre‐germination). As compared to the control sample, the pre‐germination time had a significant (P < 0.05) effect on blood cholesterol of Sprague–Dawley male rats. It was also found that the significantly (P < 0.05) better effect on lipid profile of hypercholesterolaemic rats was observed by prolonging the pre‐germination time. As compared to non‐germinated brown rice, the germinated brown rice showed the higher cardio‐protective effect on hypercholesterolaemic Sprague–Dawley male rats. CONCLUSION: The present study suggests that the changes of blood cholesterol can be mainly modulated by using the PGBR rather than BR. The prolonging of pre‐germination time led to an increase in the bioactive components, thereby providing a more efficient functional diet affecting the high blood cholesterol. This study suggests that PGBR can be used instead of BR and polished rice in the human diet. Copyright © 2009 Society of Chemical Industry     

Mango wine aroma enhancement by pulp contact and β‐glucosidase

This study determined the influence of pulp maceration and β‐glucosidase on mango wine physico‐chemical properties and volatile profiles. The distinction in pH, sugars and organic acids among different treatments was not statistically significant. All wine samples reached around 8% (v/v) ethanol from about 16% (w/v) of sugars. The wine with pulp contact contained about ten times higher α‐terpinolene and up to three times higher acetate esters than the wine without pulp contact, but mitigated the production of medium‐chain fatty acids and relative ethyl esters by up to six times. β‐glucosidase enhanced terpenols by up to ten times and acetate esters by up to three times. Furthermore, enzyme treatment mitigated, by up to five times, the formation of medium‐chain fatty acids and ethyl esters to moderate levels. Sensory evaluation showed pulp contact, and β‐glucosidase not only improved the intensity and complexity of wine aroma but balanced odour attributes.     

Preferential extractability of γ‐oryzanol from dried soapstock using different solvents

BACKGROUND: γ‐Oryzanol from rice bran has lately gained potential importance because of its proven health benefits. Thus the extractability of γ‐oryzanol from the soapstock of crude rice bran oil is important from the perspective of future large‐scale production, which would give value addition to this by‐product obtained from the rice bran oil industry. The aim of the present study was to investigate the extraction of γ‐oryzanol from the drum‐dried soapstock of rice bran oil using various solvents. RESULTS: It was found that γ‐oryzanol could be extracted most effectively using ethyl acetate, followed by dichloromethane and ethyl methyl ketone. All components of γ‐oryzanol have an alcohol group in the ferulate portion giving rise to relatively high polarity, thereby increasing the extraction in more polar solvents efficiently. Ethyl acetate showed maximum extractability of γ‐oryzanol by the Soxhlet method. To quantify γ‐oryzanol, reverse phase high‐performance liquid chromatography (RP‐HPLC) was used for fingerprinting the γ‐oryzanol analogues with respect to standard γ‐oryzanol. CONCLUSION: A new RP‐HPLC method for determining the individual components of γ‐oryzanol has been reported that can be used for performing an online characterisation of γ‐oryzanol analogues by liquid chromatography/mass spectrometry. Copyright © 2008 Society of Chemical Industry     

Structural characterisation of β‐cyclodextrin crosslinked by adipic acid

This study was conducted to investigate the structural characterisation of β‐cyclodextrin (β‐CD) crosslinked by adipic acid. β‐CD was treated with different concentrations (0%, 5%, 10% and 15%, w/v) of adipic acid. Different instruments, such as scanning electron microsope (SEM), Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were used to find out chemical structure in the crosslinked β‐CD. SEM analysis suggested that crosslinking β‐CD with 15% adipic acid changed the original morphology and considerably increased the particle size of the raw material. FT‐IR spectroscopy data showed that an intensive absorption band at 1706 cm^?1 was present in the β‐CD samples treated with 10% and 15% adipic acid, indicating a crosslinking between hydroxyl groups of β‐CD and carboxyl groups of adipic acid. NMR spectra revealed that the ester linkages between hydroxyl groups of β‐CD and carboxyl groups of adipic acid were formed after crosslinking of β‐CD with adipic acid.