乳酸菌混合发酵对脱脂麦胚的理化性质及抗氧化活性的影响

Effect of mixed fermentation of lactic acid bacteria on physicochemical properties and antioxidant activity of defatted wheat germ

为探究植物乳杆菌及戊糖乳杆菌发酵对脱脂麦胚发酵过程中理化性质的影响,将2种乳酸菌单独发酵及以1∶1体积比混合发酵,测定发酵过程中酸面团pH及可滴定酸度、植酸含量和膳食纤维含量的变化。分析发酵对脱脂麦胚游离氨基酸及蛋白质结构的影响,并对发酵条件进行优化。结果表明:在发酵过程中(20~28 h),混合发酵脱脂麦胚中的菌体数量高于单独菌株发酵。当脱脂麦胚发酵24 h时,混合发酵组与单独发酵组相比具有更低的pH、植酸含量及更高的可滴定酸度;可溶性膳食纤维含量为(4.43±0.01)g/100 g,较单独发酵组分别提高21%、11%;混合发酵的脱脂麦胚中游离氨基酸含量最高,达到(16.25±0.23) mg/g,是未发酵组的1.85倍。傅里叶红外光谱表明,发酵能降低脱脂麦胚中蛋白质的α-螺旋和β-折叠总含量,增加β-转角和无规则卷曲总含量。最佳发酵条件为发酵时间35 h、发酵剂量2.8×10^(8) CFU/mL(以质量分数为0.85%无菌生理盐水体积计)、发酵温度37℃。在此条件下脱脂麦胚总酚含量达到(5.27±0.23) mg/g, DPPH·清除率达到44.61%±0.37%,ABTS+·清除率达到46.83%±0.17%。

In order to explore the effects of Lactobacillus plantarum and Lactobacillus pentosus fermenta-tion on physicochemical properties of defatted wheat germ fermentation process,two kinds of lactic acid bacteria were fermented separately and mixed fermentation with 1:1 volume ratio.The changes of sour dough pH and titratable acid,phytic acid content and dietary fiber content during fermentation were de-termined.The effects of fermentation on the free amino acid and protein structure of defatted wheat germ were analyzed,and the fermentation conditions were optimized.The results showed that during the fer-mentation process(20-28 h),the number of bacteria in the mixed fermentation defatted wheat germ was higher than that in the single strain fermentation.When the defatted wheat germ was fermented 24 h,the mixed fermentation group had lower pH,phytic acid content and higher titratable acid than that in single fermentation group.The content of soluble dietary fiber was(4.43±0.01)g/100 g,which was 21%and 11%higher than that of single fermentation group,respectively.The content of free amino acids in defatted wheat germ fermented by mixed fermentation was the highest,reaching(16.25±0.23)mg/g,which was 1.85 times that of the unfermented group.Fourier transform infrared spectrosco-py showed that fermentation could reduce the total content ofα-helix andβ-sheet of protein in defatted wheat germ,and increase the total content ofβ-turn and random coil.The optimal fermentation condi-tions were fermentation time 35 h,fermentation dose 2.8×10^(8) CFU/mL(caculated based on the volume mass of fraction 0.85%physiological saline),and fermentation temperature 37℃.Underthecondi-tions,the total phenolic content of defatted wheat germ reached(5.27±0.23)mg/g,the DPPH·scav-enging rate reached 44.61%±0.37%,and the ABTS*.scavenging rate reached 46.83%±0.17%.