Multivariate analysis of the mechanical properties of boluses during mastication with the normal dentitions.

The aim of this study was to investigate changing mechanical properties of the bolus during mastication and to quantify mechanical properties of the final bolus at swallowing. Changing mechanical properties of the bolus of three different types of foods (rice cracker, cheese and peanuts) by twelve normal dentitions were investigated by principal component analysis (PCA) on six mechanical properties (rupture energy, elasticity, viscosity, hardness, cohesiveness and adhesiveness). The raw data of cohesiveness immediately before swallowing was always constant. In all three food samples, the results by PCA on six parameters indicated that cohesiveness was independent from the remaining five parameters, and two factors were extracted on these five parameters by PCA. Furthermore, factor structure of bolus at swallowing showed no difference between the three food samples in spite of the variations in the raw data. The mechanical properties of swallowable bolus were clarified for the first time.