草莓酵素发酵过程中代谢产物及抗氧化性的变化研究

以草莓为原材料,发酵制备酵素,探究发酵过程中总糖、总多酚、总酸及特征性有机酸等功能成分的变化,研究各功能成分与4种抗氧化参数(DPPH、羟基、ABTS等三种自由基清除率及还原力)的相关性,并基于主成分分析降维思想,建立有关草莓酵素的综合评价系统。结果表明:草莓酵素在发酵前期(20 d前)总糖含量下降不多,总酚、总酸、柠檬酸、L-苹果酸等含量略微上升,DPPH自由基、ABTS自由基清除率相对较低,且还原力始终低于0.5,不仅对羟基自由基无清除能力,而且起促氧化作用;在发酵中期(20~30 d),草莓酵素中的总糖含量迅速下降,总酸、4种有机酸及总酚等代谢产物含量大大提高,各抗氧化指标均快速提升;发酵后期(30~75 d),草莓酵素的各种代谢产物积累量呈现稳定的趋势,其中柠檬酸和L-苹果酸积累量降低不明显。草莓酵素的还原力呈增加的趋势,发酵后期还原力增加速率变缓。经过30 d发酵,草莓酵素总糖、总酸、有机酸、总酚以及抗氧化活性趋于稳定。草莓酵素综合评价指标(CEI)在第75天综合得分最高,可作为前发酵参考终点或添补糖液、酵液的依据。建立一种草莓酵素发酵过程中综合性指标评价方法,可为草莓酵素的精准发酵奠定理论基础。

Studies on the Changes of Metabolites and Antioxidant Activity during the Fermentation Process of Strawberry Jiaosu

In this study,strawberry was used as raw material to ferment into jiaosu.The total sugar,total titratable acidity,citric acid,L-malic acid,acetic acid,lactic acid,total phenols and antioxidant properties(scavenging activities against DPPH radical,hydroxyl radical,ABTS radical and reducing power)were investigated.The relationship between metabolites and the antioxidant indicators was studied.Besides,principal component analysis was used to establish the change of comprehensive index in the fermentation process of strawberry jiaosu.The results showed that during the initial fermentation time(the first 20 days),the content of total sugar decreased little,and the content of total phenolic,total titratable acidity,citric acid and L-malic acid decreased.The scavenging ability of strawberry jiaosu against DPPH free radical and ABTS free radical was low,and the reducing power was less than 0.5.Meanwhile,the promoting effects against the hydroxyl radical was observed.In the mid-fermentation(20 d to 30 d),the content of total sugar decreased obviously,and the content of total titratable acidity,citric acid,L-malic acid,acetic acid and lactic acid and total phenols increased obviously,with scavenging activities against DPPH radical,hydroxyl radical,ABTS radical and reducing power increasing significantly.During the later phase of fermentation(30 d to 75 d),the content of each metabolites tended to be stable,and the content of citric acid and L-malic acid decreased slightly.The reducing power of strawberry jiaosu increased in the entire fermentation process,and the reduction rate against reducing power slowed down.After fermentation of 30 d,the total sugar,total titratable acidity,organic acids,total phenolic and antioxidant activity tends to be stable.The comprehensive evaluation index(CEI)of strawberry jiasu has the highest comprehensive score at 75 d,which can be used as the reference end point of fermentation or the basis of adding syrup or yeast.The establishment of comprehensive indexes in the fermentation process of strawberry jiaosu provides a theoretical basis for the precise fermentation of strawberry jiaosu.