Bolus formation of cooked rice: Methodology development and optimization of in vitro texture evaluation

Quantifying rice texture in vitro persists as a challenge in quality assessment. The middle chewing phase is critical for detecting textural variations in cooked rice. In this study, an in vitro multiple extrusion system was developed to quantify texture formation in diverse rice varieties, using in vivo evaluation as the control. Correlations between the properties of cooked rice and in vitro chewing cycles and conditions were explored. A higher number of chewing cycles enhanced bolus chewing efficiency, particle count, solid leakage, and iodine blue value while reducing residual work and adhesiveness. Elevated saliva and enzyme levels significantly increased, reducing sugar release, while decreasing hardness and initial and residual work. The optimal in vitro conditions were saliva amount (0.6 g/g), chewing cycles (10), and enzyme activity (5 U/mL). The in vitro–chewed bolus was similar to orally chewed rice bolus in terms of total particle number (99 %), water content (95 %), reducing-sugar content (96 %), and microstructure. Thus, in vitro oral simulation enables quantification of rice texture and facilitates efficient quality evaluation.