Microbiomics and metabolomics insights into the microbial regulation on the formation of flavor components in the traditional fermentation process of Chinese Hongqu aged vinegar

This study aimed to investigate microbial succession and metabolic dynamics during the traditional fermentation of Hongqu aged vinegar,and explore the core functional microbes closely related to the formation of flavor components.Microbiome analysis demonstrated that Lactobacillus,Acetobacter,Bacillus,Enterobacter,Lactococcus,Leuconostoc and Weissella were the predominant bacterial genera,while Aspergillus piperis,Aspergillus oryzae,Monascus purpureus,Candida athensensis,C.xylopsoci,Penicillium ochrosalmoneum and Simplicillium aogashimaense were the predominant fungal species.Correlation analysis revealed that Acetobacter was positively correlated with the production of tetramethylpyrazine,acetoin and acetic acid,Lactococcus showed positive correlation with the production of 2-nonanone,2-heptanone,ethyl caprylate,ethyl caprate,1-hexanol,1-octanol and 1-octen-3-ol,C.xylopsoci and C.rugosa were positively associated with the production of diethyl malonate,2,3-butanediyl diacetate,acetoin,benzaldehyde and tetramethylpyrazine.Correspondingly,non-volatile metabolites were also detected through ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry.A variety of amino acids and functional dipeptides were identified during the traditional brewing of Hongqu aged vinegar.Correlation analysis revealed that Lactobacillus was significantly associated with DL-lactate,indolelactic acid,D-(+)-3-phenyllactic acid,pimelic acid,pregabalin and 3-aminobutanoic acid.This study is useful for understanding flavor formation mechanism and developing effective strategies for the suitable strains selection to improve the flavor quality of Hongqu aged vinegar.

卷烟加工关键工序烟草碱、中性香味成分变化研究

卷烟在制丝过程中,烟叶原料要经过加温、加湿和干燥等处理,温度、湿度等外界条件在不断地发生变化,必然会引起烟草内部化学成分的一系列变化[1].本文采用同时蒸馏萃取的前处理方法,对卷烟加工过程中松片回潮、润叶加料、烘丝3个关键生产工序前后的碱、中性香味成分进行了GC-MS法定性定量分析[2].为卷烟加工工艺技术参数的优化、工艺控制的改进提供理论依据.……

Impact of Low-temperature Storage on Volatile Flavor Compounds in Prepared Pork Products

[Objectives]This study was conducted to explore the dynamic changes of volatile flavor compounds in prepared pork during storage at different low-temperature conditions.[Methods]Prepared pork was stored at 4,-4 and-18℃.The volatile flavor compounds of prepared pork were determined by solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS)at days 0,7,14,21 and 28,and relative odor activity value(OAV),principal component analysis(PCA)and cluster analysis(CA)were combined to analyze changes in volatile flavor compounds of prepared pork during storage.[Results]The total number of volatile flavor compounds gradually decreased with the prolongation of the storage period,and OAV analysis identified 22 key flavor compounds(OAV≥1).The results of PCA and CA showed that 2-methyl-1-butanol,1-octen-3-ol,linalool,cineole,hexanal and nonanal were the main key flavor components,and the degree of flavor degradation was low under both superchilling and freezing conditions.After 28 days of storage,the alcohol content in the chilling group was significantly higher than other two groups,and the overall content of volatile flavor compounds was also significantly higher than other two groups,indicating that the-4℃chilling storage was more favorable for maintaining the overall flavor of prepared pork.[Conclusions]This study provides a theoretical basis for finding a better storage method for prepared meat products.

Physicochemical properties and volatile components of pea flour fermented by Lactobacillus rhamnosus L08

Pea(Pisum sativum L.)is an important source of plant proteins.However,the use of pea flour as a food ingredient is greatly limited due to its strong beany flavor.In this work,we investigated the effects of Lactobacillus rhamnosus L08(L.rhamnosus L08)fermentation on the physicochemical characteristics,amino acids composition and volatile flavor compounds of pea flour.We found that L.rhamnosus L08 had the probiotic potential of utilizing pea flour as fermentation substrate.L.rhamnosus L08 fermentation significantly increased the content of most amino acids,and total amino acid content increased from 222.18 mg/g at 0 h to 262.35 mg/g at 6 h.A total of 44 volatile compounds were identified in pea flour.L.rhamnosus L08 fermentation increased the variety of acids and esters,while reduced the unpleasant flavor such as nonanal,decanal,octanal,1-hexanol and 2-ethyl-1-hexanol.The emulsifying stability and foam stability of pea flour were slightly enhanced during fermentation.Our results illustrate that lactic acid bacteria fermentation is a promising approach to eliminate undesirable aroma of pea flour.Moreover,this study provides theoretical support for the application of peas as high-quality protein source.