Lactic acid bacteria(LAB)fermentation is one of the important ways to improve the flavor profile of soymilks.In this study,the biotransformation of 4 important soymilk off-flavor components(ISOCs),including hexanal,(E...Lactic acid bacteria(LAB)fermentation is one of the important ways to improve the flavor profile of soymilks.In this study,the biotransformation of 4 important soymilk off-flavor components(ISOCs),including hexanal,(E)-2-heptenal,(E)-2-hexenal and 1-octen-3-ol during LAB fermentation was studied.A LAB fermentable simulated soymilk with low and stable levels of soymilk borne volatile compounds was prepared and used as fermentation bases.After the LAB fermentation of simulated soymilks with different levels of added ISOCs and the subsequent HS-SPME-GC-TOF-MS analysis,ISOCs derived biotransformation products were screened from the total volatile compounds using chemometric approaches,and the possible metabolic pathways were proposed.Subsequently,quantitative analysis of conversion rates and mass balances was conducted to study effects of ISOCs loads,variations in starter cultures and fermentation conditions on the LAB fermentationinduced biotransformation.Finally,the flavor intensity of different odor descriptors as affected by the biotransformation of ISOCs were evaluated based on the odor activity value calculation.This study provided technical methods for screening and quantitative analysis as well as experimental facts of the LAB fermentationinduced biotransformation of ISOCs.展开更多
While soy yogurts offer health benefits,their wide market acceptance is limited by the less desirable flavor.This study investigated the generation of yogurt flavor volatiles and the metabolic pathways in the soymilk ...While soy yogurts offer health benefits,their wide market acceptance is limited by the less desirable flavor.This study investigated the generation of yogurt flavor volatiles and the metabolic pathways in the soymilk lactic acid bacteria(LAB)fermentation system,using dairy milk as a reference,through comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry(GC×GC-TOFMS)and liquid chromatography-electrospray ionization-tandem mass spectrometry(LC-ESI-MS/MS)-based flavoromics and metabolomics.The results revealed that soy yogurts exhibited higher total volatile concentrations,but dairy yogurts demonstrated higher odor activity values(OAVs).Ten key metabolic pathways in soy-based fermentation,but 9 pathways in dairy-based system were identified.The pyruvate metabolism module served as a key node for the generation of yogurt flavor compounds in both systems;amino acid metabolic pathways were more active in soy than in dairy,while different carbohydrate metabolic pathways existed in soy-based and dairy-based systems.Expression levels of key enzymes for yogurt flavor formation were affected synergistically,antagonistically,or independently by the soy and dairy milk components.This work provides experimental evidence to solidify the theoretical framework of soymilk LAB fermentation.展开更多
基金supported by the National Natural Science Foundation of China(32272243 and 32072164)the Key Research and Development Program of Shandong Province(2022CXGC010603)the China Postdoctoral Science Foundation(2020M671342).
文摘Lactic acid bacteria(LAB)fermentation is one of the important ways to improve the flavor profile of soymilks.In this study,the biotransformation of 4 important soymilk off-flavor components(ISOCs),including hexanal,(E)-2-heptenal,(E)-2-hexenal and 1-octen-3-ol during LAB fermentation was studied.A LAB fermentable simulated soymilk with low and stable levels of soymilk borne volatile compounds was prepared and used as fermentation bases.After the LAB fermentation of simulated soymilks with different levels of added ISOCs and the subsequent HS-SPME-GC-TOF-MS analysis,ISOCs derived biotransformation products were screened from the total volatile compounds using chemometric approaches,and the possible metabolic pathways were proposed.Subsequently,quantitative analysis of conversion rates and mass balances was conducted to study effects of ISOCs loads,variations in starter cultures and fermentation conditions on the LAB fermentationinduced biotransformation.Finally,the flavor intensity of different odor descriptors as affected by the biotransformation of ISOCs were evaluated based on the odor activity value calculation.This study provided technical methods for screening and quantitative analysis as well as experimental facts of the LAB fermentationinduced biotransformation of ISOCs.
基金supported by the National Natural Science Foundation of China(32272243 and 32072164)the Key Research and Development Program of Shandong Province(2022CXGC010603)the China Postdoctoral Science Foundation(2020M671342).
文摘While soy yogurts offer health benefits,their wide market acceptance is limited by the less desirable flavor.This study investigated the generation of yogurt flavor volatiles and the metabolic pathways in the soymilk lactic acid bacteria(LAB)fermentation system,using dairy milk as a reference,through comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry(GC×GC-TOFMS)and liquid chromatography-electrospray ionization-tandem mass spectrometry(LC-ESI-MS/MS)-based flavoromics and metabolomics.The results revealed that soy yogurts exhibited higher total volatile concentrations,but dairy yogurts demonstrated higher odor activity values(OAVs).Ten key metabolic pathways in soy-based fermentation,but 9 pathways in dairy-based system were identified.The pyruvate metabolism module served as a key node for the generation of yogurt flavor compounds in both systems;amino acid metabolic pathways were more active in soy than in dairy,while different carbohydrate metabolic pathways existed in soy-based and dairy-based systems.Expression levels of key enzymes for yogurt flavor formation were affected synergistically,antagonistically,or independently by the soy and dairy milk components.This work provides experimental evidence to solidify the theoretical framework of soymilk LAB fermentation.
