Effects Of Heat Treatment On The Emulsifying Property And Interfacial Adsorption Behavior Of Pea Proteins

Pea proteins, whose amino acid profiles were relatively well-balanced, have advantages of wide sources, low prices, no cholesterol and few allergens when compared with animal proteins. As an indispensable operation unit in food industrial production, heat treatment has important influences on the functional properties of proteins. Compared with soy proteins, the current studies on pea proteins were relatively few, especially the understanding of effects of heat treatment on the emulsifying and interfacial properties of pea proteins was still insufficient. This paper studied the influences of heat treatment on the adsorption kinetics of pea proteins at the oil/water interface, and investigated the effects of heating temperature, protein aggregation degree, emulsification protein concentrations and ionic strengths on the properties of oil-in-water emulsions which were prepared by unheated and heat-treated pea proteins.The particle size of unheated pea proteins was 65.27 nm, and the particle size increased in a small extent when the heating temperature was less than 70?C, and the particle size had a substantial increase when the heating temperature was more than 70?C. The emulsifying activity and emulsifying stability also increased with heating temperature(50~100?C), when the heating temperature was 100?C, the emulsifying activity increased from 11.26 m2/g to 17.88 m2/g, the emulsifying stability increased form 14.28 min to 32.90 min. According to the electrophoresis analysis, heat-induced protein aggregates could adsorb at the oil/water interface during emulsification, and the subunits in unheated and heat-treated pea proteins adsorbed at the oil/water interface without selectivity.The aggregation extent(the particle size and proportion of aggregates) of pea proteins increased with heating protein concentration(1.0~5.0%, w/v). Compared with unheated pea proteins, the heat-treated pea proteins showed higher diffusion rate at the oil/water interface and larger interfacial elasticity modulus, and the diffusion rate and interfacial elasticity modulus decreased with protein aggregation extent. With the increase of heating protein concentration(1.0~5.0%, w/v), the droplet size of emulsions decreased, the percentage of adsorbed proteins, flocculation index, viscosity and creaming stability of emulsions increased. With the increase of emulsification protein concentration(0.1~0.5%, w/v), when the oil volume fraction was 0.1, the droplet size of emulsion decreased from 9.88 ?m to 1.29 ?m, the flocculation index decreased from 2.35 to 0.11, and the interfacial protein concentration increased from 2.41 mg/m2 to 3.10 mg/m2.With the increase of ionic strengths(0~0.5 M), the emulsifying activity and the emulsifying stability of pea proteins decreased. When the ionic strength increased to 0.5 M, the emulsifying activity of unheated pea proteins decreased from 11.26 m2/g to 9.45 m2/g, and the emulsifying activity of heated pea proteins(95?C, 30 min) decreased from 17.5 m2/g to 13.2 m2/g. Compared with emulsions with no NaCl, the addition of NaCl increased the droplet size, the flocculation extent of droplets and viscosity in emulsions, and decreased the creaming stability apparently. At the same ionic strength, the heat treatment(95?C, 30 min) of pea proteins decreased the droplet size of emulsions and increased the creaming stability. Different ionic strengths had no significant effects on the components of adsorbed proteins in emulsions.This study could provide theoretical basis for the deep processing of pea proteins and furtherly broaden its application area, which has important theoretical and practical significance.