Partial replacement of β-casein by napin, a rapeseed protein, as ingredient for processed foods: Thermoreversible aggregation

- Napin induces aggregation of β-casein.
- Mass ratio, pH, salt concentration and temperature affect aggregation.
- Calcium is strongly assumed to promote reversible aggregation at a given temperature.
- The aggregation is thermoreversible.

Environmental, demographic and economic motives draw a worldwide tendency to introduce plant proteins into processed foods. However the total replacement of animal proteins by plant proteins is not easy to perform due to the specific physicochemical properties (aggregation, solubility, interactions …) and taste of these proteins. In a first step, combined plant/animal assemblies could be an attractive approach. Consequently, to drive this trend towards practical applications, deeper investigations must be performed to control the properties of such mixed assemblies. In the current study, the interactions of β-casein with napin, a rapeseed protein poorly valorized in human nutrition, was investigated in various physico-chemical conditions (pH, sodium chloride concentration, mass ratio). The properties of the mix were followed by turbidimetry, and microscopy. The statistical analysis of the whole set of data indicated that the effects of the three factors were significant (p < 0.05) without significant cross effects. Furthermore, the aggregation is enhanced by temperature with a reversible effect. The aggregation is also suppressed by adding salt or divalent cation chelating agents (ethylene diamine tetracetic acid, EDTA). The functional combination of β-casein with napin can thus be controlled by modulating the salinity of the media and/or by introducing a complexing agent.