摘要：
For 12 kinds of brewing vinegar in four brands and different years which were purchased from market, the analysis of the changes in their six indexes were performed, which include total polyphenols, flavonoids, total oxidation value, 1,1-diphenyl-2-picrylhydrazyl free radical(DPPH·), hydroxyl free radical (·OH) and superoxide anion (O2-·) clearance. And by analyzing correlation, doing principal component analysis,their antioxidant properties were evaluated. The results showed that with the aging time increasing, the clearance rate of three free radicals of Zhenjiang vinegar increased, Z10>Z6>Z3, whereas the content of total flavonoids, total polyphenols and total antioxidant capacity were Z10>Z3>Z6. Six indexes of Sichuan bran vinegar showed that 5 year old vinegar was better than 3 year old vinegar. The content of total flavonoids, total polyphenols and total antioxidant capacity in Shanxi aged vinegar were positively correlated with the aging time, O2-· and DPPH radical clearance showed S3>S10>S5, and ·OH clearance trend was S10>S3>S5. There was no obvious rule between the changes of 6 indexes and the aging time of single aged vinegar products. The content of total flavonoids, total polyphenols and total antioxidant capacity all presented D4>D8>D3>D5, O2-· and ·OH scavenging rates were D5>D4>D8>D3,and DPPH radical scavenging rates were D5>D8>D4>D3.Correlation analysis showed that the total polyphenols and total flavonoids in all products tested were significantly correlated. Principal component analysis showed that O2-· clearance and DPPH radical clearance had a highly positive correlation with component 2, ·OH clearance, total polyphenols and total flavonoids had a highly negative correlation with PC2, and all the above variables had a good positive correlation with PC1. This paper can provide theoretical basis and technical support for the study of antioxidant properties of brewing vinegar.
关键词：
Douchi fermentation;GC-TOF/MS;metabolic characterization;orthogonal partial least squares-discriminant analysis;principal components analysis
摘要：
Intensive study of the metabolome during the Douchi fermentation can provide new knowledge for optimizing the fermentation process. In this work, the metabolic characterization throughout the fermentation of Mucor racemosus Douchi was investigated using gas chromatography with time-of-flight mass spectrometry. A total of 511 peaks were found, and 114 metabolites were identified. The fermentation process was clearly distinguished into two main phases by principal components analysis and orthogonal partial least squares-discriminant analysis. All the samples in the score plots were within the 95% Hotelling T (2) ellipse. Two separated clusters can be seen clearly in the score plot, which represents the two stages of fermentation: koji-making (within 48 hr) and postfermentation (after 48 hr). Besides, clear separation and discrimination by both methods were found among different fermentation time within 15 days, while the discrimination cannot be found with more than 15 days of fermentation, indicating that the fermentation of Douchi was finished in 15 days. Due to the synergistic effect of protease and hydrolase accumulated in the early stage, proteins and other big molecular substances are rapidly hydrolyzed into a large number of small molecule components. However, the activity of enzymes decreased with the further fermentation, and some free amino acids were consumed in Maillard reaction. Therefore, there was no significant change in the content of small molecular substances after 15 days of fermentation. Furthermore, the levels of some metabolites such as alanine and lysine involved in the fermentation varied significantly throughout the processes. This study provides new insights for the metabolomics characteristics of Douchi fermentation.
摘要：
以10年老酸水泡制酸笋样品(B SFA F)、发酵6个月块状酸笋(M B SF)和丝状酸笋样品(FB SF)为研究对象,应用Illum ina M iSeq高通量测序技术并通过生物信息统计与分析,探索广西无盐发酵酸笋样品中细菌菌群结构及多样性.结果表明:3组酸笋样品共得到148656个有效的序列数(Tags),聚类后总共得到1116个分类操作单元(O TU s).根据物种注释结果,在3组酸笋样品中共注释到12个门、23个纲、37个目、98个科和190个属.在门分类水平上,3组样品中厚壁菌门(Firm icutes)占绝对优势,其次是变形杆菌门(Proteobacteria)和放线菌门(A ctinobacteria);在属分类水平上,乳杆菌属(Lactobacillus)、乳球菌属(Lactococcus)和魏斯氏菌属(W eis-sella)是3组样品中的优势菌属.其中,丝状酸笋(FB SF)组的香农(Shannon)、辛普森(Sim pson)及A C E指数均显著高于其他两组,且乳杆菌属(Lactobacillus)、乳球菌属(Lactococcus)和魏斯氏菌属(W eissella)的平均相对丰度总和最高,可达99.8％.因此,以泉水泡制发酵丝状竹笋生产酸笋可能更佳.
摘要：
It is difficult to produce southern stinky tofu, a famous traditional Chinese snack, at industry scale due to the complex composition of its brine. In this study, the fingerprints of organic volatile flavor compounds in the southern stinky tofu brine samples from five manufacturers were studied using headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) with the aid of chemometric methods. The fingerprints were obtained by HS-SPME/GC-MS and analyzed with the time shift alignment method, Shannon entropy, correlation coefficient, and principal component analysis. The results show that the time shifts in the samples can be accurately corrected by the time shift alignment method despite unexpected interferences. The fingerprint information was evaluated by Shannon entropy, while the similarities and differences in the fingerprints were investigated by correlation coefficient. Moreover, the identification of stinky tofu manufacturers can be achieved by principal component analysis. The predominant volatile compounds in southern stinky tofu brines were indole, 3-methylindole, phenol, and 4-methylphenol. Therefore, the established fingerprinting of volatile compounds for the brines by combining HS-SPME/GC-MS with chemometric methods was a simple and reliable method.
