Multivalent cations modulating microstructure and interactions of potato protein and fungal hyphae in a functional meat analogue

Concentrated Fusarium venenatum biomass commonly known as mycoprotein (MYC) naturally rich in high quality proteins has been commercially used to fabricate vegan meat analogues by incorporating potato protein (PoP). In this work, we studied the effect of multivalent cations, focusing particularly on essential micronutrients such as calcium (0–100 mM) and ferric ions (0–1.0 mM), on the microstructure of the fungal hyphae (MYC)-PoP composites, as characterized via rheology and microscopic techniques as a function of pH (3.0–7.0), Na+ (0–200 mM) with and without added PoP. A clear dependency of storage modulus (G′) on pH, ionic strength and specific concentrations of Ca2+ and Fe3+ was observed, with Fe3+, PoP concentration and acidic pH having the largest impact. Microscopy across various length scales revealed that PoP coats the hyphae's rough surface and dominates the interactions between the hyphae. G′ responsiveness to NaCl and CaCl2 concentrations indicated that electrostatic interactions between the fungal hyphae and PoP coverage mainly govern texture properties. Interestingly, Fe3+ induced protein-protein aggregation which led to a reduction in G′ of MYC without PoP. However, the effect of Fe3+ was modulated by Ca2+, where increasing concentration of both salts seemed to narrow the rheological (G′) differences between MYC with and without PoP at higher pH. Fe3+ alone significantly increased the G′ of MYC-PoP except at pH 5.0. Thus, a subtle balancing of pH and added levels of calcium is needed to enable iron supplementation with minimal textural effects when formulating mycoprotein-based meat analogues with PoP as protein binding agent.