发酵处理对小米粉物化特性的影响

Effect of fermentation treatment on physical and chemical characteristics of millet flour

目的探讨自然发酵筛选的优势菌种对小米粉物化特性的影响,为分析自然发酵小米粉的品质及开发小米发酵新途径提供参考。方法按照小米与水1∶1.2 g/ml的比例加入蒸馏水,30℃下自然发酵96 h后,从发酵液中筛选出优势菌种(乳酸菌和酵母菌),扩大培养后,分别在最适温度(乳酸菌37℃,酵母菌28℃)下培养96 h进行发酵,并制备发酵小米粉。扫描电镜观察不同发酵小米粉的颗粒特性;X-射线粉末衍射仪测定其结晶度;RVA4500型快速黏度分析仪测定其黏度;TA.XT Express质构仪测定其淀粉凝胶的质构特性;并利用DSC1型差示扫描量热仪分析其热特性。结果 3种发酵所得小米粉均有明显的淀粉颗粒,而小米原粉则无,且乳酸菌、酵母菌发酵小米淀粉的受损程度高于自然发酵;发酵未使小米淀粉的晶型改变,依然为A型,但乳酸菌、酵母菌发酵小米粉的结晶度较自然发酵增加了3.04%和1.58%;发酵96 h时,乳酸菌、酵母菌发酵的热焓值分别较自然发酵上升2.32和1.27 J/g,峰值黏度降低179和180 m Pa·s,衰减值下降102和349 mPa·s,回生值下降229和50 mPa·s;乳酸菌、酵母菌发酵小米粉的凝胶硬度较自然发酵分别降低34.95和28.45 g,胶着性分别下降25.75和33.203 g。结论自然发酵中乳酸菌、酵母菌对小米粉品质起主要作用。

Objective To investigate the effect of prominent bacteria screened by natural fermentation on the physical and chemical characteristics of millet flour,and provide a reference for analysis of quality of naturally fermented millet flour and development of a novel route for fermentation of millet flour. Methods Millet was added with sterilized water at a ratio of 1 ∶ 1. 2 mg/ml for natural fermentation at 30 ℃ for 96 h. Prominent bacteria（lactobacillus and yeast） were screened from the fermentation liquid and subjected to amplification culture,then cultured at optimal temperatures（37 ℃for lactobacillus and 28 ℃ for yeast） for 96 h for fermentation,and prepared into flour. The millet four was observed for characteristics of granules by scanning electron microscopy, determined for crystallization degree by X-ray powder diffractometer,for viscosity by RVA4500 rapid viscosity analyzer,for texture by TA. XT Express texture analyzer,and analyzed for thermal performance by DSC1 diffential scanning calorimeter. Results Obvious starch granules were observed in the millet flours obtained by fermentations with lactobacillus and with yeast as well as natural fermentation but not in the original millet flour. However,the damage extents of millet flours fermented with lactobacillus and with yeast were severer than that fermented naturally. The crystal form of millet flour showed no change after fermentation,which was still form A. However,the crystallization degrees of millet flours fermented with lactobacillus and with yeast increased by 3. 04% and 1. 58% respectively as compared with that fermented naturally. As compared with those after natural fermentation,the enthalpies of millet flours 96 h after fermentation with lactobacillus and with yeast increased by 2. 32 and 1. 27 J/g,while the peak viscosities decreased by 179 and 180 m Pa·s,the pad values decreased by 102 and349 m Pa·s,the revives values decreased by 229 and 50 m Pa·s,the gel hardness decreased by 34. 95 and 28. 45 g,and the gumminess decreased by 25. 75 and 33. 203 g,respectively. Conclusion The lactobacillus and yeast played major roles in the quality of millet flour during natural fermentation.