乳酸菌强化发酵对小米淀粉分子结构及糊化特性的影响

Effect of lactobacillus fermentation on molecular structure and pasting properties of millet starch

目的研究自然发酵的优势菌-乳酸菌对小米淀粉分子结构及糊化特性的影响,为分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基础。方法采用0.2 g/100 ml的Na OH提取发酵后的小米淀粉,检测乳酸菌发酵后对小米淀粉颗粒结构、结晶度、官能团、分子量、糊化及老化特性的影响。结果乳酸菌发酵后,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。乳酸菌发酵后小米淀粉的结晶度较自然发酵增加1.49%。发酵未改变小米淀粉官能团区的峰位,但特征峰强度减弱,乳酸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(Mw)在1.5×10~4~5.9×10~5 g/mol之间,自然发酵小米淀粉Mw在2.1×10~4~5.4×10~5g/mol之间,乳酸菌发酵小米淀粉Mw在1.6×10~4~5.3×10~5 g/mol之间,乳酸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。乳酸菌发酵96 h,与自然发酵相比,糊化温度下降0.84℃,热焓值增加1.00 J/g,回生值下降743 m Pa·s。结论自然发酵的优势菌-乳酸菌可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。

Objective To investigate the effect of lactobacillus, a prominent bacterium for natural fermentation, on the molecular structure and pasting properties of millet starch, and lay a foundation of analyzing the mechanism of optimization of various bacteria in natural fermentation as well as the effect on the properties of millet starch. Methods The millet starch after fermentation was extracted with 0. 2 g/100 ml sodium hydroxide, and analyzed for the effect on particle structure, erystallinity, molecular weight as well as pasting and aging properties. Results Obvious signs of erosion appeared on the surface of starch granules after lactobacillns fermentation, while light erosion on those after natural fermentation. The crystallinity of millet starch after lactobacillus fermentation increased by 1.49% as compared with that after natural fermentation. The functional area of peaks of millet starch after fermentation showed no change, while the intensity of characteristic peak decreased, and the fingerprint region of millet starch after lactobacillus disappeared. The average molecular weight （Mw） of millet starch was 1.5 × 10^4 - 5.9×105 g/mol before fermentation, 2. 1 ×10^4 ~ 5.4 × 10^5 g/mol after natural fermentation, and 1.6 × 10^4 ~ 5. 3 × 10^5 g/tool after lactobacillus fermentation. The proportions of long chain of pullulan and amylocellulose decreased, while those of moderate and short chains of pullulan increased. The gelatinization temperature 96 h after lactobacillus fermentation decreased by 0. 84℃ compared with that after natural fermentation, while the enthalpy increased by 1. 00 J/g, and the setback decreased by 743 mPa·s. Conclusion Lactobacillus, a prominent bacterium for natural fermentation, changed the molecular structure as well as pasting and aging properties of millet starch, which played an important role in the natural fermentation of millet.