Variable Contact Area-Based Compressive Properties of Orally Self-Disintegrating Puffs

Milk protein-rich, orally self-disintegrating puffs were designed utilizing supercritical fluid extrusion (SCFX) to address the needs of both infants and the elderly who require high protein foods and suffer from swallowing difficulties. The physio-mechanical properties of the puffs need to be accurately evaluated as the physiological processes occurring in the mouth are quite complex. Generally, mastication is simulated through a compressive test that utilizes a constant contact area which does not well simulate the oral environment. Most snacks do not have a uniform shape and undergo a change in contact area during compressing leading to inaccurate predictions of the sample's response in the mouth. The objective of this study was to quantify the change in the contact area and its effect on compressive properties. Variable contact area was experimentally measured to provide an accurate estimation of the sample stress during testing. The sample's mean variable yield contact area was 43.1 mm² while the constant yield contact area was significantly higher at 100.5 mm² (p < 0.05). The relationship between the variable contact area and deformation was determined by fitting the data to a polynomial model (R² = 0.99). From this relationship, Young's modulus and Poisson's ratio were evaluated. The Young's modulus values determined with variable contact area correlate well with each puff's corresponding disintegration time. The puffs have soaked Poisson's ratio values close to 1.00 indicating that these sample are deforming more like a liquid than a solid. Overall, the results showed that the variable contact area should be utilized when analyzing compressive properties to form accurate predictions of oral disintegration for extruded puffs to meet the needs of those who have difficulty swallowing.