Effect of acid modification of soy glycinin on its interfacial and emulsifying properties

ABIRACHED, C; MEDRANO A; AÑON, MARÍA CRISTINA; PANIZZOLO, L.A

JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY (JAOCS)

SPRINGER

Lugar: Berlin; Año: 2018

0003-021X

Soybean glycinin (11S) was modified by an acidic pH treatment to improve its emulsifying properties.Glycinin was obtained by isoelectric precipitation (11Sn) and then treated with acid (11St). Oil-water interfacial tension and rheology were measured. The rate constants of adsorption (ka) and rearrangement (kr) of proteins at the interface and the dilational (E), elastic (Ed) and viscous modulus (Ev) of the proteininterfacial film were determined. Particle size distribution (PSD),interfacial protein concentration (Γ) and the creaming destabilization rate constants ks (for the smaller droplets) and kl (for the larger droplets) were analyzed in oil-in-water emulsions (25% v/v of oil and 75% v/v of 1 mg/ml protein solution in 10 mM sodium phosphate buffers, pH 7.0 and 2.5, respectively).Compared to the native protein, the acid treatment caused irreversible denaturation of 11S and significantly increased Г, ka, E, Ed and Ev (p ≤ 0.05), resulting in a greater rate of protein adsorption to the interface and a stronger interfacial film. The PSD exhibited a bimodal distribution with peaks above and below 4 μm. Smaller droplets moved towards smaller diameters for 11St. The 11St showed lower values of creaming destabilization constants, ks (d ≤ 4 μm) and kl (d ≥ 4 μm) than 11Sn. In conclusion, acid treatment of 11S enhanced the creaming stability of its emulsions by improving the interfacial propertiesand reducing the droplet size.