Abstract: The microstructure, particle size, molecular structure and crystalline structure of tapioca starch (from the cultivars SC9, SC205 and LMC), sweet potato starch (from the cultivar XSSP) and yam starch (from the cultivars GY2, SFY and MPY) were studied, and the correlation between starch structural properties and vermicelli quality was analyzed. The results showed that the root crops significantly differed in the microstructure, granule size, molecular structure and crystalline structure of starch. The granule size, 1 045 cm-1/1 022 cm-1 peak intensity ratio and crystallinity of yam starch were larger than those of tapioca starch and sweet potato starch. Starch structural properties had significant effects on the quality of vermicelli. Starch granule size was positively correlated (P < 0.05) with swelling index of vermicelli. Root-mean-square rotation radius (Rg) was significantly positively correlation with breaking rate (P < 0.01) and swelling index (P < 0.05) of vermicelli, but negatively correlated with comprehensive evaluation score (P < 0.05). Polydispersity coefficient was significantly negatively correlated with hardness (P < 0.05), but positively correlated with tensile work of vermicelli (P < 0.05). There was a significant negative correlation between 1 045 cm-1/1 022 cm-1 peak intensity ratio and cohesiveness of vermicelli (P < 0.01). Starch granule size, Rg, polydispersity coefficient, and 1 045 cm-1/1 022 cm-1 peak intensity ratio had a significant impact on the quality of vermicelli. This study provides theoretical reference for the selection of raw materials for vermicelli and quality improvement.

Key words: yam starch; crystalline structure; molecular structure; vermicelli quality