Effect Of Heat-moisture Treatment On The Structure And Properties Of Starch

Heat-moisture treatment is a physical method to treat starch with a little moisture, which less than35%, at certain temperature. The starch only subject water and heat factors during heat-moisture treatment, without organic solvent or chemical agent, it is a pure physical modification. Although it is a simple treatment, researcher found it has significant impact on structure and properties of starch. Most of the works at home and abroad were focus on the effect of heat-moisture treatment on corn starch. The purpose of this paper was to study the effect of heat-moisture treatment on the structure and properties of cassava starch, wheat starch, sweet potato starch, potato starch, and the difference between variety starches. The results are as followed:1. The SEM photos showed that there were dents at granule appearance of cassava starch and wheat starch during the heat-moisture treatment. The amount of dent granule and area of dent increased with the initial moisture of starch before heat-moisture treatment. The higher the initial starch moisture the significantly the adherent between starch granule, the ratio of adherent starch granule increased with the rise of moisture.2. The heat-moisture treatment increased the gelatinization temperature and decreased the peak viscosity of cassava starch, wheat starch, sweet potato starch and potato starch. The higher initial moisture of heat-moisture treated starch the higher increased extent of gelatinization temperature. The changes of gelatinization temperature and peak viscosity were different of each starch variety.3. While at the same moisture, heat-moisture treatment increased the To、Tp、Tc of different starch and gelatinization temperature range, decreased gelatinization enthalpy.4.The results of acid hydrolysis indicated that the hydrolysis rate of heat-moisture treated starch were higher than that of native starch the day before7days but lower after7days. The hydrolyze rate grew gently after10days. Cassava starch, wheat starch, sweet potato starch and potato starch got the same variation law.5. The results of a-amylase hydrolysis showed that enzyme hydrolysis of heat-moisture treated cassava starch, wheat starch, sweet potato starch and potato starch increased obviously at earlier days, but grew unobvious later.