In-mouth mechanisms leading to physicochemical changes and textural perception of cooked rice prepared with different heating rates

Abstract

Oral textural perception is a complex process that involves tooth fragmentation and salivary lubrication. To reveal the associated in-mouth mechanisms, three stages of testing were conducted in this study, including the initial cooked rice stage (0%), the deformation stage (50%), and the swallowing stage (100%). The total chewing time of high/low heating rate rice (HHRR/LHRR) was 25.46 ± 6.22 s and 22.11 ± 5.02 s, respectively. However, no significant difference in the chewing frequency. The salivary flow rate in LHRR (28.18 mg/s) was higher than in HHRR (22.57 mg/s). At the 0% stage, LHRR had a higher moisture content and expansion rate. At the 50% stage, rice boluses exhibited a significant difference in texture properties measured by instrumental analysis. At the 100% stage, two rice boluses reached similar hardness and chewiness, with smaller particles for swallowing. These results indicated that the deformation stage (50%) played a critical role in differentiating the textural perception. The initial properties of cooked rice influenced chewing manner and salivary secretion, contributing to differences in the reduction of particle size, water migration, and the inner microstructure evolution of corresponding rice boluses. These differences will feed back as different texture perceptions during oral processing.