Interfacial and emulsifying behaviour of rice protein concentrate

Interfacial and emulsifying properties of rice protein concentrate (RPC) have been studied in order to evaluate its potential application to stabilize O–W emulsions. The interfacial behaviour of adsorbed proteins films constituted with RPC has been studied at the air–water and oil–water interfaces at two pH values (2 and 8). The type and the amount of soluble proteins have been determined in aqueous dispersions and results put forward the presence of most frequent rice protein profile and a significant degree of protein denaturation with a very low solubility. Air–water and oil–water interfacial properties have been determined as a function of time, concentration and pH: air–water by surface pressure under compression–expansion cycles and oil–water by interfacial tension. Interfacial rheology has been studied under dilatational deformations, either at the initial step of film formation or once the interfacial tension was at equilibrium (the film was completely formed). RPC-stabilised O–W emulsions has been also analysed by Droplet Size Distribution (DSD) measurements and interfacial protein concentration. Both interfacial and bulk emulsion properties reveal that RPC showed an enhanced potential as emulsifier at low pH. Globally; results indicate clearly important differences in the structural characteristics of rice protein films between pH 2 and 8 that impact on emulsifying properties.