酵母菌发酵对小米淀粉分子结构及糊化特性的影响

Effects of yeast fermentation on molecular structure and pasting properties of millet starch

研究自然发酵及其优势菌(酵母菌)对小米淀粉分子结构及糊化特性的影响,为剖析不同菌属在小米自然发酵中的改性机理及发酵对小米淀粉性质的影响奠定理论基础。采用0.2 g/100 m L的Na OH提取发酵后的小米淀粉,研究自然发酵及优势菌发酵后对小米淀粉颗粒特性、结晶度、官能团、分子量、糊化及老化特性的影响。结果如下:酵母菌发酵后,淀粉颗粒表面有明显的侵蚀迹象,而自然发酵淀粉颗粒表面侵蚀迹象较轻;酵母菌发酵后小米淀粉的结晶度较自然发酵减少0.33%;发酵并未改变小米淀粉官能团区的峰位,但特征峰强度减弱,酵母菌发酵后小米淀粉指纹区图谱消失;未发酵小米淀粉重均分子量为1.5×10~4~5.9×10~5g/mol^(-1),自然发酵分子量在2.1×10~4~5.4×10~5 g/mol^(-1)间,酵母菌发酵后支链淀粉长链及直链淀粉比例减少而中间及短支链淀粉的比例相对增加;酵母菌发酵96 h糊化温度较自然发酵下降1.07℃,热焓值较上升0.78J·g^(-1);回生值较自然发酵下降471 m Pa·s。自然发酵的优势菌(酵母菌)使小米淀粉的分子结构、糊化及老化特性发生明显变化,并在小米自然发酵过程中起主导作用。

This paper studied natural fermentation and the effect of dominant bacteria（yeast）on millet starch molecular structure and pasting properties,which lay the theoretical foundation for the analysis of millet natural fermentation and the effect of different kinds of bacteria on modification mechanism.The experiment extracted the starch from fermented millet by 0.2 g/100 m L Na OH,then the effects of natural fermentation and the dominant bacteria on millet starch＇s particle characteristics,crystallinity,functional groups,molecular weight,pasting and aging properties were studied.Results were as follows：after yeast fermented,the surface of starch granules had obvious signs of erosion,while the erosion signs with natural fermentation were lighter;compared to natural fermentation,the yeast fermentation resulted in 0.33% reduction of millet starch crystallinity;fermentation did not change the peaks of millet starch＇s functional group area,but the intensity of characteristic peak was weakened,and the fingerprint region of millet starch was disappeared with yeast fermentation;the average molecular weight of unfermented millet starch was between 1.5×10^4 ~ 5.9×10^5 g/mol^-1,of natural fermented was between 2.1×10^4 ~ 5.4×10^5 g/mol^-1,and of yeast fermented was between 1.6×10^4 ~ 4.7×10^5 g/mol^-1,after fermentation,the proportion of long chain starch and straight starch decreased,the proportion of short chain starch increased.Compared to natural fermentation,with 96 h yeast fermentation,the gelatinization temperature decreased 1.07 ℃,the enthalpy rose 0.78 J · g^-1 and the retrogradation value decreased 471 m Pa · s.The dominant bacteria（yeast）in natural fermentation plays a major role in changing the molecular structure,pasting and aging characteristics of millet starch.