Destructuration mechanisms of bread enriched with fibers during mastication

• The decrease of the median size of bread bolus particles depends only on chewing time.
• Bolus hydration by saliva governs consistency decrease through starch plasticization.
• Bolus moisture can be predicted by salivary flow, chewing time and particle size.
• Amylase activity does not contribute directly to bread oral destructuration.
• A simple model could predict bread destructuration defined by bolus consistency.

Three breads of different densities and salt contents were chewed by 16 healthy subjects, with controlled physiological characteristics, for three different stages of mastication until swallowing. The distribution of chewed bread particle size was determined by imaging of the boluses at each stage, for the 3 breads and all subjects. Bread piece was reduced into an increasing number of small particles with a median size, function of mastication time, taking an average value of 1.9 mm at swallowing. Bolus moisture content could be predicted from theoretical salivary flow and particle median size. Bolus consistency was derived from the apparent viscosity measured by capillary rheometry. It decreased with chewing time, and this decrease was linked to bolus moisture by a plasticization coefficient, which varied with the individual (12 < α < 30). A basic model involving hydration and fragmentation could be suggested to predict bread destructuration, defined by the ratio of consistency of the bolus on that of initial bread.