纯种发酵对小米淀粉分子结构及老化特性的影响

利用自然发酵液中对淀粉老化特性起主要作用的菌种发酵,研究发酵对小米淀粉分子结构及老化特性的影响。采用0.2 g/100 m L的NaOH溶液提取发酵后的小米淀粉,研究不同菌种发酵后对小米淀粉颗粒特性、官能团、分子质量、糊化及老化特性的影响。结果表明:发酵未改变淀粉的偏光十字;植物乳杆菌、戊糖片球菌和屎肠球菌发酵后小米淀粉表面被侵蚀,酿酒酵母及芽孢菌发酵后淀粉颗粒表面侵蚀迹象变重,孔道加深且数量增多;酿酒酵母及芽孢菌发酵后小米淀粉官能团区的峰位未变,但特征峰强度减弱,植物乳杆菌、戊糖片球菌及屎肠球菌发酵后小米淀粉指纹区图谱部分消失;植物乳杆菌发酵后Ⅰ区、Ⅱ区的重均、数均分子质量较小米淀粉降低。戊糖片球菌、屎肠球菌、酿酒酵母发酵后Ⅰ区的重均分子质量升高,数均分子质量降低,Ⅱ区重均、数均分子质量降低。芽孢菌发酵后Ⅰ区的数均分子质量略有升高,Ⅱ区重均、数均分子质量降低。植物乳杆菌、戊糖片球菌及屎肠球菌发酵后淀粉的糊化温度、回生值及最终黏度降低,热焓值升高。酿酒酵母发酵后糊化温度及回生值降低,最终黏度及热焓值升高。发酵使淀粉的分子结构、支链淀粉及直链淀粉分子发生改变,短期抗老化性能提高。

Effects of Pure Culture Fermentation on Molecular Structure and Retrogradation Characteristics of Millet Starch

In this study, we examined the effects of fermentation by pure cultures of Lactobacillus plantarum, Pediococcus pentosaceus, Enterococcus faecium, Saccharomyces cerevisiae and Bacillus, which play an important role in affecting the retrogradation properties of naturally fermented starch, on the molecular structure and retrogradation characteristics of millet starch with the aim of providing a theoretical basis and data support for elucidating the mechanism by which natural fermentation and pure culture fermentation improve the retrogradation properties of millet starch, and new ways of developing fermented millet products. Millet starch was extracted from fermented millet with 0.2 g/100 mL NaOH and evaluated for granular characteristics, functional groups, molecular mass and, pasting and retrogradation properties. The results obtained were as follows. Fermentation did not changed the cross polarization characteristics of starch. The surface of millet starch granules fermented by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium was eroded, but the surface of starch granules after fermentation by Saccharomyces cerevisiae and Bacillus was eroded more seriously, with more deeper channels. The fermentation by Saccharomyces cerevisiae and Bacillus did not change the peak positions in the functional region, but reduced the intensity of the characteristic peaks. The fingerprint region of millet starch fermented by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium partially disappeared, The weight average and number average molecular masses in regions Ⅰ and Ⅱ were decreased after fermentation by Lactobacillus plantarum. In region Ⅰ, the weight average molecular mass after fermentation by Pediococcus pentosaceus, Enterococcus faecium and Saccharomyces cerevisiae was increased, and the average molecular weight was decreased, while in region Ⅱ, the weight average and number average molecular masses were both decreased. After fermentation by Bacillus, the number average molecular mass in region Ⅰ was slightly increased, but the weight average molecular weight was slightly decreased; both the weight average and number average molecular weight in region Ⅱ were decreased. The gelatinization temperature, final viscosity and retrogradation value were decreased, but the enthalpy was increased after fermentation by Lactobacillus plantarum, Pediococcus pentosaceus and Enterococcus faecium. The gelatinization temperature and retrogradation value were decreased, the final viscosity and enthalpy were increased after fermentation by Saccharomyces cerevisiae. In conclusion, fermentation could change the molecular structure of starch, branched chain starch and amylose, and improve the short-term anti-retrogradation performance.