Effect of lactobacteria fermentation on structure and physicochemical properties of Chinese yam starch (Dioscorea opposita Thunb.)

Biotransformation is an effective technique to modify the structure and physicochemical properties of carbohydrates. In this work, Chinese yam (Dioscorea opposita Thunb.) starch was fermented by lactobacteria. The effect of fermentation time (6, 12, 30, 42 and 72 h) on structure and physicochemical properties of Chinese yam starch were investigated. The microstructure was destroyed after lactobacteria fermentation for 42 and 72 h. The X-ray diffraction pattern of Chinese yam starch indicated a transformed A to A + V crystalline type. -> 4)-alpha-D-glucose-(1 -> from backbone and unreduced terminal alpha-D-glucose-(1 -> 4 from branch were identified by NMR spectra, and free glucose was only detected in fermented starch at 72 h. With the extension of fermentation time, the crystallinity and thermal parameters increased within 42 h and thereafter decreased. M-w, M-w/M-n, long chains of DP25-36 and DP >= 37, peak viscosity, trough viscosity, finally viscosity and setback presented a reverse trend.