Whey protein fibrils enhance fat-related texture of emulsion systems: Translating structural changes to textural perception

Abstract

Thickeners display great potential for fat substitution in emulsion systems. The underlying mechanisms remain understudied because of the difficulty of defining the structure of thickeners (e.g., compositional and structural complexity). Herein, we designed a thickened emulsion with precise structure and high kinetic stability by blending whey protein fibril dispersions and fragmented freeze-dried whey protein fibril (FWPF)-stabilized emulsions. The structural changes of the blends regarding to microstructure, rheology, and tribology that were determined by confocal laser scanning microscopy, transmission electron microscopy, the shear flow test, the oscillatory shear test, the coefficient of friction test, etc. were achieved by: 1) increasing fibril concentration; 2) reducing electrostatic repulsion among fibrils, aiming to decipher how the structural changes induced by thickening effect were translated into textural perception. We demonstrated that the perceived thickness of the blends had a positive linear correlation with their bulk rheology regardless of the way inducing structural changes, which was mainly determined by the magnitude of interactions between structural units and their collective macroscale response. The perceived grittiness was detrimental to the perceived smoothness and creaminess due to the formation of large irregular protein aggregates with increasing fibril concentration even though irregular protein aggregates enhanced lubricity of the blends in the tribological test. However, the similar irregular protein aggregates induced by the reduction of electrostatic repulsion among fibrils did not change the perceived grittiness/smoothness, demonstrating the combined role of thickener concentration and microstructure in the perception of grittiness and smoothness. Moreover, we found that the perceived creaminess was enhanced by the reduction of electrostatic repulsion, indicating that it reflected the combined textural aspects of the oil-in-water emulsion. Our findings would provide a structural design strategy for developing reduced-fat foods with desired sensory properties.