Changes in interfacial properties of legumin from faba beans (Vicia faba I.) by tryptic hydrolysis

Changes of the surface tension at a planar interface and of the emulsifying properties of tryptically digested legumin from faba beans (enzyme/substrate ratio = 1/40) were studied in terms of time of hydrolysis (0 – 48 h). Simultaneously, molecular changes of legumin were studied by determination of liberated amino groups, RP‐HPLC, and SDS‐PAGE analysis. While the surface tension continuously decreases with increasing amount of liberated amino groups, improved emulsion properties, i.e. decreasing droplet size and increasing coalescence as well as creaming stability, were only observed during the first 240 min of hydrolysis, where increase in the content of free amino groups amounted to 18 – 24 free amino groups per protein subunit. The surface tension during the diffusion‐controlled phase reached the lowest value after a hydrolysis time of 24 h which corresponds to an increase of 44 – 50 free amino groups per protein subunit. Additionally, the results support the view that the interfacial adsorption at quiet interfaces and during emulsion formation are governed by different transport mechanisms.