Using Human Whole Saliva to Better Understand the Influences of Yogurt Rheological and Tribological Behaviors on Their Sensory Texture

Abstract

Saliva plays a critical role in texture perception of semisolid foods. Therefore, human whole saliva (HWS) application during rheometry and tribometry may help determine how texture attributes are perceived during oral processing. The formulation of these products can significantly impact their textural properties as well as their extent of breakdown after incorporation with HWS. Hydrocolloids are used in reduced or non-fat semisolid foods, e.g. yogurts, as texture enhancers. Understanding the effect of HWS and hydrocolloids on texture perception of yogurts can help manufacturers design reduced- or non-fat products with similar texture to their full-fat counterparts. Thus, the objective of this study was to determine the effects of HWS on yogurt microstructure, rheological, tribological, and texture relationships. Twelve formulations of yogurts were prepared using hydrocolloids (carboxymethyl cellulose, locust bean gum, potato starch, corn starch, whey protein isolate, and skim milk powder), skim milk, and cream. Viscosity, viscoelastic behaviors, and confocal microscopy evaluations were performed with and without HWS. Descriptive sensory analysis was also performed to evaluate yogurt textural attributes. Overall, microstructural images showed that hydrocolloids and HWS addition resulted in a denser protein network with thicker chains and fat coalescence for the formulations with milkfat compared to the control. Viscosity flow curves were fit to four shear-thinning models: Cross-Williams (R2 > 0.998), Cross (R2 > 0.961), Herschel-Bulkley (R2 > 0.74), and power law (R2 > 0.985). In general, yogurt viscosity, viscoelastic behaviors, and Stribeck curve profiles were significantly affected by formulation and addition of HWS. Additionally, yogurt formulation significantly impacted sensory texture attributes. Texture attributes were significantly correlated to both rheological and tribological behaviors, and these correlations were affected by HWS application during instrumental testing. The results of this study not only showed that rheology and tribology can be useful for indicating sensory texture but also that addition of HWS during instrumental testing provided a better approximation of how semisolid food texture is perceived during oral processing. This information can be used in optimizing fat-free or reduced-fat semisolid products when hydrocolloids are used as fat replacers or texture enhancers.