Functional properties and starch digestibility of instant Jasmine rice porridges

Abstract

Ten instant rice porridges made from Jasmine rice mixed with other ingredients purchased from commercial outlets in Thailand were studied for their functional properties and starch digestibility. The starch contents of the samples varied from 59–84 g/100 g dry solids. Differential scanning calorimetry showed a single endothermic peak located around 56–82 °C for most samples, indicating that starch was partially gelatinized during processing. However, two samples did not show any transition enthalpy to suggest that they were completely gelatinized during processing. Rice porridge samples with similar ingredients exhibited different pasting properties because of significant effects of processing and possibly the type of ingredients, and differences in their hydration/swelling behaviours. From in vitro starch digestion, the rice porridge samples were high glycaemic index (GI) foods with calculated GIs ranging from 68 to 97. Generally, rice porridges that were completely gelatinized gave the highest GI values because gelatinization, in the absence of pronounced retrogradation and molecular reorganization, enhances digestibility. The present study demonstrated the importance of non-rice ingredients in the functional and digestion properties of rice porridge samples, and the need to understand how spices, animal and plant proteins, flavour enhancers (e.g. monosodium glutamate), and flavourings influence GI of rice porridges so as to guide processing and selection of ingredients.