Mixing commercial plant proteins compromises the mechanical properties of heat-set gels

Mixing plant proteins can be a strategy to improve the nutritional value, availability, costs, flavour and functionality of plant proteins in food products. However, a challenge is that the properties of mixed gels cannot yet be predicted by the characteristics of the protein sources alone. To address this challenge, we here systematically study mixed heat-set gels for two commercial plant protein isolates. Separate stock dispersions of two commercial plant protein isolates (pea (PPI) and fava bean (FBPI)) that differ in gelling properties, were created under various conditions: 10–15 % w/w protein, pH 6 and 7, with or without homogenization (500 bar_2cycles) and mixed at different ratios (4:0, 3:1, 2:2, 1:3 and 0:4). We observed mainly anti-synergistic mixing behaviour: shear moduli and fracture stress were lower for mixed gels than for the pure counterparts. Microstructural analysis did not reveal any phase separation, suggesting the proteins were not incompatible. Lowering the pH from pH 7 to pH 6 led to less anti-synergistic mixing behaviour, but overall, large deformation properties decreased. Our results demonstrate that the possible benefits of mixing must be balanced with the impact of mixing on functionality.