A DSC Study of Gelatinisation of Rice
Understanding the behaviour of starch upon heating is important to optimise processing and texture of grain-based foods. Differential scanning calorimetry (DSC) is a very useful tool for studying thermal characteristics of starches including their melting, gelatinisation and glass transition (peak) temperatures and degree of crystallinity (peak area). Previous studies have been particularly focussed on wheat and corn with relatively little published on rice flour and even less on whole grain (brown) rice. Most reports pertain to flour samples in the presence of large amounts of water with limited information available on partially hydrated samples. In addition, there have been few systematic studies on the impact of DSC test variables on starch properties.
This paper describes a DSC study of Australian "Amaroo" rice supplied by SunRice. It reports on test method development and the effect of test variables on the rice's measured thermal properties. Equipment variables include the type of vessel and heating rate. Sample variables were rice age, rice preparation (whole grain or flour), sample size, steeping time, and moisture level. The results show that many variables affect both the peak temperatures and areas. The peak temperatures depend on heating rate, rice age, sample size, steeping time and moisture level and whether pans are sealed and rice is whole grain or flour. Peak areas depend on heating rate, steeping time and moisture level. Hence an understanding of the effects of test method variables is crucial in measuring properties and relating the data to the processing and texture of rice.