Structural Changes Within a Biscuit Bolus During Mastication

Solid food undergoes drastic structural changes during its transformation into a cohesive bolus, which play a key role in the perception of different textures during mastication. This article describes the structural changes in biscuits during mastication through particle agglomeration. Apparent particle size and bolus moisture content were measured at different chewing stages by image and gravimetric analyses. The microstructure of the ready-to-swallow bolus was also examined with light microscopy and cryo-scanning electron microscopy (cryo-SEM). The results reveal that moisture content increased at a parabolic rate during mastication, and the absorbed saliva increased apparent particle size and decreased particle number through agglomeration. Furthermore, both cryo-SEM and light microscopy indicate that a majority of the solid particles in the ready-to-swallow bolus were individual starch granules. The results from cryo-SEM also suggest that saliva composition varied locally within the final bolus, thereby implying that laminar mixing governs bolus formation during mastication. Practical ApplicationsIn materials science it is well-known that the properties of a material are related to its structure. This concept can also be applied to the food bolus: the structure of a bolus determines its mechanical and rheological properties. These properties are perceived by senses within our mouths during mastication and translate to the perception of food texture. Hence, texture perception cannot be fully understood without analyzing bolus structure. This article also suggests that bolus structure is related to the type of mixing that operates within the mouth. Identifying the mechanisms involved in mastication will contribute towards a better understanding of texture perception, and can be applied in computational models of food breakdown and flavor release. This knowledge will allow solid food structures to be designed to enhance sensory appeal or follow a particular breakdown path in health food applications.