Elucidation of temporal relationships between bolus structure, physical properties, and sensory changes during mastication of rice crackers

高橋 孝太朗*; 村上 里佳*; 伊藤 克祥*; 平田 芳信; 今泉 鉄平*; 西津 貴久*

Takahashi, Kotaro*; Murakami, Rika*; Ito, Katsuyoshi*; Hirata, Yoshinobu; Imaizumi, Teppei*; Nishizu, Takahisa*

This study investigated the structural and physicochemical changes in bolus properties underlying the perception of melt-in-the-mouth sensation during the mastication of rice crackers. Oral processing was reproduced under controlled conditions using an artificial mastication device, and boluses prepared from four rice crackers with different melt-in-the-mouth characteristics were collected at 5, 10, 15, and 20 s of artificial mastication. Temporal changes in the median particle size, starch hydrolysis, bolus hardness, and bolus adhesiveness were analyzed. Dynamic sensory perception was evaluated using the Temporal Dominance of Sensations method. Principal Component Analysis (PCA) was performed to compare the temporal changes in bolus structure, physicochemical properties, and sensory perception among samples during mastication. Samples with a stronger melt-in-the-mouth sensation exhibited a more rapid reduction in particle size, reaching approximately 710-825 m after 20 s of mastication, whereas samples with a weaker melt-in-the-mouth sensation retained larger particle sizes and remained above 1300 m even after 20 s. Starch hydrolysis and the associated changes in bolus hardness and adhesiveness occurred at earlier stages of mastication in rice crackers with a stronger melt-in-the-mouth sensation. PCA analysis demonstrated that rice crackers with a stronger melt-in-the-mouth sensation exhibited larger trajectory shifts during mastication, reflecting faster structural breakdown and physicochemical changes of the bolus, ultimately reaching a dispersed state. In contrast, samples with a weaker melt-in-the-mouth sensation showed limited trajectory changes and retained a more cohesive bolus structure, corresponding to slower structural transformation.