The Impact of Formulation on the Rheological, Tribological, and Microstructural Properties of Acid Milk Gels

Abstract

Reduction or removal of fat in semisolid foods can negatively affect their textural properties. Also, incorporation of human whole saliva (HWS) with food in the mouth can alter the texture characteristics of foods. Hydrocolloids can be used to improve the texture of reduced or non-fat semisolid foods through different mechanisms, including altering the interaction of food components with saliva compounds. Thus, the objective of this study was to determine the effects of HWS and hydrocolloids on rheological, tribological and microstructural behaviors of acid milk gels, a model system for yogurts. 24 acid milk gels were prepared using skim milk, cream, and hydrocolloids (locust bean gum, cellulose gum, corn starch, potato starch, whey protein isolate, and skim milk powder). Standard rheological analyses were carried out for all samples with or without HWS at 8 °C and 25 °C. Tribometry was done at only 25 °C with and without HWS. Samples were also imaged by confocal laser scanning microscopy. Overall, viscosity and viscoelastic moduli (G′ and G′′) decreased when samples were mixed with HWS and tested at 25 °C, but the specific effects were dependent on the type of hydrocolloids used. Friction coefficient decreased with addition of HWS. Addition of hydrocolloids resulted in protein aggregates with thicker chains and clusters, particularly when starch with larger granules was combined with an anionic hydrocolloid. More aggregation and open pores in the acid milk gel protein matrix microstructures were linked to higher viscosity and higher friction. These results improve the understanding of how hydrocolloid selection and HWS impact acid milk gel microstructures, rheological behaviors, and textures; they can be used to design palatable reduced-fat semisolid products.