Mixing whey and soy proteins: Consequences for the gel mechanical response and water holding

• Mixtures of whey and soy proteins gelled simultaneously upon heating resulting in the formation of one network.
• Major changes in gel properties occurred at small amounts (1–3%) of soy protein.
• Gel stiffness decreased and water holding increased with increase in soy protein concentration.
• Gel microstructure showed a decrease in coarseness with increase in soy protein concentration both at 0.1 and 0.3 M NaCl.

To design food products based on mixtures of proteins from animal and plant sources, understanding of how the structural and mechanical properties of mixed protein systems can benefit from selectively mixing is essential. Heat-induced gels were prepared from mixtures of whey proteins (WP) and soy proteins (SP) at different ratios and constant total protein concentration (10 w/w %). The effect of mixing on the aggregation phenomena (light scattering), mechanical response, and microstructure (CLSM, SEM) was investigated at ionic strengths of 0.1 and 0.3 M. Having similar gelation mechanisms, whey and soy proteins formed one network with both proteins contributing to the gel properties. With an increasing fraction of SP in the mixed protein gel, gel strength and stiffness decreased and water holding increased. In addition, a decrease in gel coarseness was observed, which was most significant for 0–3 w/w % SP fraction. A similar transition was also observed in the aggregation kinetics and aggregate size in dilute solutions.

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