后发酵温度对不同大豆品种细菌型豆豉氨基酸态氮生成动力学及理化性质的影响

Effects of Post-Fermentation Temperature on Amino Nitrogen Formation Kinetics and Physicochemical Properties of Bacterial-type Douchi from Different Soybean Varieties

为提高细菌型豆豉在工业生产上的品质稳定性,以4种不同品种的市售大豆(LS、DBL、DBS、BS)为原料,使用修正后的Gompertz方程拟合3种不同后发酵温度(15、25℃和40℃)下细菌型豆豉的氨基酸态氮含量变化,并测定发酵终点时其游离氨基酸含量。结果表明,Gompertz方程可以很好地拟合氨基酸态氮生成动力学(判定系数>0.96),3种不同后发酵温度下(25、15℃和40℃)拟合的预测发酵终点分别为发酵9、10 d和4 d左右;4种细菌型豆豉在15℃后发酵温度下的氨基酸态氮生成最大值为DBL>LS>DBS>BS,在25℃和40℃后发酵温度下的氨基酸态氮生成最大值为LS>DBL>DBS>BS;其中黑豆型豆豉的氨基酸态氮含量和游离氨基酸含量明显低于黄豆型豆豉,而黄豆型豆豉间无明显差异。相比于发酵前,4种细菌型豆豉发酵后的鲜味氨基酸比例增加、苦味氨基酸比例减少。但相比于15℃后发酵温度,后发酵温度为40℃时所得的4种细菌型豆豉均出现鲜味氨基酸比例降低,而苦味氨基酸比例增加,这可能与高温促进美拉德反应从而消耗鲜味氨基酸有关。品质指标的相关性分析表明,4种细菌型豆豉的趋势相似。本研究可为细菌型豆豉的工业生产提供一定理论指导。

In order to improve the quality stability of bacterial-type douchi during industrial production,four different varieties of soybean(LS,DBL,DBS and BS)were used to make bacterial-type douchi,and the modified Gompertz equation was used to fit the changes in the amino nitrogen content of bacterial-type douchi at three different post-fermentation temperatures(15,25 and 40℃).Also,the free amino acid content was determined at the end of fermentation.The results showed that the Gompertz equation could well fit the kinetics of amino nitrogen formation(coefficient of determination>0.96).The predicted fermentation endpoints at post-fermentation temperatures of 25,15 and 40℃were approximately 9,10,and 4 days,respectively.The maximum production of amino acid nitrogen in the four bacterial-type douchi at post-fermentation temperature of 15℃decreased in the following order:DBL>LS>DBS>BS,while the maximum production of amino nitrogen at 25 and 40℃decreased in the following order:LS>DBL>DBS>BS.The contents of amino nitrogen and free amino acids in black soybean douchi were significantly lower than those in yellow soybean douchi,but there was no significant difference among douchi from different yellow soybean varieties.After post-fermentation,the proportion of umami amino acids in the four bacterial-type douchi increased,and the proportion of bitter amino acids decreased.The proportion of umami amino acids in the four bacterial-type douchi at post-fermentation temperature of 40℃decreased and the proportion of bitter amino acids increased compared with that at 15℃.This may be related to consumption of umami amino acids by the Maillard reaction at high temperatures.The correlation analysis of quality indexes shows that the trend of four bacterial-type douchi was similar.The results of this study can provide theoretical guidance for the industrial production of bacterial-type douchi.