Sensory Texture of Model Foods Based on Oral Processing and Food Material Properties Considerations

Food structure design, for specific textural properties, can only be achieved by understanding how food structure is transformed into the cognitive representation of food texture by oral processing. Different structural properties in biopolymer gels can be obtained by changing polymer concentration, solution conditions (i.e., pH, salt), and process conditions (time, temperature, shear). Another way to alter structure is by forming multicomponent gels. To understand transformation of food structure in texture perception by oral processing, polysaccharide based soft solid gels were used as model foods. The response of human senses to food structure was investigated via assessments of material properties (rheological/fracture characteristics), sensory perception and oral processing.;Initially, fundamental mechanical properties (fracture stress and fracture strain) of agar and kappa-carrageenan-locust bean gum gels varied by changing polymer concentrations. When model foods became stronger and more deformable, more chewing cycles and relatively greater muscle activity were required to prepare samples for swallowing. Chewing frequency remained the same, indicating a consistent rhythmic jaw movement. Model foods showed differences in sensory perception of hardness, deformability, size of breakdown particles, rate of breakdown, particle mouthcoating and number of chews. Hardness, fracture stress, stress intensity factor, and muscle activities are closely associated and are the best indicators of number of chews. Moreover, fracture strain, fracture surface energy, deformability and occlusal durations exhibited strong correlations. Fracture modulus was closely associated with jaw vertical movements. Relations among sensory attributes, material properties and oral processing were established by model foods with well defined physical properties.;In the next phase of study, emulsion filled gels were used as model foods to understand textural changes in foods by fat reduction. Agar gels had a brittle fracture pattern while kappa-carrageenan-locust bean gum gels displayed elasto-plastic (ductile) fracture based on fracture mechanics considerations. Agar gels and kappa-carrageenan-locust bean gum gels, at similar strengths but different deformability, were filled with various phase volumes of corn oil. Corn oil droplets (approximately 1 microm) were stabilized by surfactants that had no charge (Tween 20), negative (beta-lactoglobulin) or positive (lactoferrin) charge at neutral pH. Increasing the phase volume of oil droplets decreased fracture stress and stress intensity factor of both filled gels, while the main effect on fracture strain was observed for the highly deformable kappa-carrageenan gels. The key factor determining physical properties of filled gels were filler-network interactions and relative mechanical properties of filler droplets compared to the gel network. Oil droplets stabilized with beta-lactoglobulin reduced sensory springiness, increased adhesiveness and cohesiveness of agar gels but not kappa-carrageenan-locust bean gum gels. Increased adhesiveness and cohesiveness coincided with a greater degree of coalescence of oil droplets during compression. Sensory hardness of both networks was significantly reduced by oil droplets, while deformability decreased only for the kappa-carrageenan-locust bean gum gels. The number of chews and muscle activities were mastication parameters affected by textural changes caused by oil droplets, while jaw movements mainly reflected the type of gel. Sensory adhesiveness and particle mouthcoating were related to digastrics activity and anterior posterior jaw movements. Inactive oil droplets significantly affected sensory properties and oral processing of polysaccharide gels and that this may be related to the fracture pattern of the networks and combined effect of mechanical properties.;Sensory textures of model foods are adequately reconciled taking into consideration food mechanical properties and alterations in oral processing. Investigations of model foods with different material properties demonstrated that the key element controlling the oral breakdown of structure and sensory perception is the properties of the continuous gel network. Moreover, oral processing adaptation to different structures is controlled by sensory input and is related to a combination of food material properties.