Effects of gradient milling on textural perception, swallowing threshold, and starch hydrolysis of cooked black rice: Implications for human mastication

Abstract

This study endeavored to examine the impact of gradient milling on the oral processing of black rice through an oral chewing and texture perception test conducted on healthy adult volunteers. Utilizing standard white rice samples as a reference, subjective texture perception tests employing a visual analogue scale (VAS) showed that participants subjectively perceived a notable reduction in perceived hardness, chewing difficulty, and swallowing difficulty of black rice as the milling degree increased. Compared to refined black rice, whole grain and lightly milled black rice substantially prolonged chewing time at the first swallowing, chewing time at the swallowing threshold, and significantly increased glucose content released during oral processing. Correlation analysis unveiled significant positive associations between the chewing time at the swallowing threshold and the chewing time at the first swallowing (R² = 0.7661, p < 0.001), as well as the subjective hardness perception of the subjects and the chewing time at the swallowing threshold (R² = 0.0600, p < 0.001). Furthermore, the chewing time at the first swallowing displayed a significant positive correlation with the amount of released glucose in the oral digestion (R² = 0.1255, p < 0.001), while the amount of saliva impregnation exhibited a significant positive correlation with the glucose amount released in the oral digestion (R² = 0.3666, p < 0.001).