Impact of Oral Mastication on the in vitro Digestibility of Pigmented and Non-Pigmented Rice Varieties

Abstract

The extent of starch hydrolysis and glycemic index (GI) of foods depends on how it is orally processed, but many in vitro digestion studies failed to consider the oral phase of digestion. This research aimed to understand the relationship between oral mastication and GI of rice. For this study, different rice varieties (pigmented and non-pigmented) were selected and analyzed for their physicochemical properties. The amylose content for all rice varieties was higher than 25%, with the starch content of 68.68 ± 0.70% - 81.60 ± 1.78%. Temporal dominance of sensation was determined for rice samples to understand the consumers' sensory preferences towards the pigmented rice varieties. In vivo oral mastication studies were also performed for the rice varieties, in which significant differences were observed amongst pigmented and non-pigmented rice samples. The particle size for pigmented rice varieties after in vivo oral mastication was significantly larger (50% particles greater than 2 mm; due to its intact morphology) than non-pigmented rice. The significant impact of oral processing on the GI of rice irrespective of the varieties was also observed in this study. Thus, this research sheds light on the need for oral processing for in vitro digestion studies.