Understanding the effect of aggregation temperature on molecular interactions in zein gels to tailor the matrix for plant-based cheese alternatives

Abstract

A common disadvantage of plant protein gels is their lack of techno-functional properties that are needed to mimic plant-based cheese alternatives (especially melting). This study explores the aggregation temperature (=ϑ_Aggregation) of zein in an aqueous system to target the characteristics of traditional semi-hard or hard cheese. Zein gels were prepared at ϑ_Aggregation = 20, 40, 60, and 90 °C and analyzed for dry matter, syneresis, uniaxial compression response, melting properties, and microstructure, comparing them with Emmental cheese, tofu, and α-casein gels. A modified Schreiber-test (180 °C, 10 min) was conducted and oscillatory rheology methods as well as confocal laser scanning microscopy (=CLSM) images were used. Our findings reveal that zein gels prepared at ϑ_Aggregation = 20 °C were cohesive and firm, whereas gels prepared at ϑ_Aggregation ≥ 40 °C (above glass transition temperature) exhibited increased syneresis, reduced firmness, and less cohesiveness due to enhanced hydrophobic interactions and disulfide bond formation. Additionally, temperature and frequency sweep data indicated that higher ϑ_Aggregation (≥80 °C) strengthen hydrophobic interactions and impact melting behavior negatively. As application for plant-based cheese alternatives zein gels show a high protein content with 32 % (w/w) and thermo-reversibility was observed, but further research must be conducted to optimize firmness, cohesiveness, and melting behavior. The findings of this work recommend a ϑ_Aggregation between 40 °C and 60 °C to overcome the glass transition temperature but to avoid highly cross-linked matrices that are not thermo-reversible.