Effect of vacuum combined ultrasound treatment on the fine structure and physiochemical properties of rice starch

This study aimed to investigate the effect of vacuum combined ultrasound treatment on the fine structure and the physicochemical properties of rice starch. Rice starch was treated with vacuum (0.09 MPa) and ultrasound (300 W) in different ways, separately or jointly. The granular morphology, particle size distribution, lamellar architecture, chain length distribution, crystal structure, thermal property and gelatinization property of starch were analyzed. The results showed that vacuum combined ultrasound treatment could result in severe shrinkage and damage of starch granules. Examination of starch structure revealed a reduced average particle size with narrowed distribution range, decreased ordering degree of lamellar architecture and shortened chain length of rice starch after vacuum combined ultrasound treatment. Although vacuum combined ultrasound treatment had no effects on crystal type and functional chemical groups of rice starch, it reduced the relative crystallinity. Physiochemical investigation suggested that vacuum combined ultrasound treatment altered the thermal and gelatinization properties of rice flour by reducing the gelatinization enthalpy and gelatinization temperature. Our results suggested that vacuum combined ultrasound treatment affected the fine structure of rice starch and subsequently altered the physiochemical properties of rice flour.