Emulsifying ability of soy protein isolates obtained at pilot plant under simultaneous heat and reducing treatments / Capacidad emulsionante de aislados proteicos de soja obtenidos en planta piloto con tratamientos térmicos y reductores simultáneos

Abstract

The emulsifying abilities of 12 soy protein isolate samples were studied in relation to their solubilities (Sol) in different solvents and their sulfhydryl contents (SH_L). Samples were obtained at pilot plant under different heat and reducing treatments, according to a central composite design 2² + star with a triplicate central point, resulting in 11 samples. An untreated sample (standard) was also included. The independent variables were heat treatment temperature (T) and sulfite concentration (C _Na2SO3) while the responses were Sol in water (Sol_w), Sol in phosphate buffer (Sol_buf), Sol in 2-mercaptoethanol (Sol_2-Mer), Sol in SDS (Sol_SDS) and SH_I. The results indicated a good fit to a second order polynomial equation for Sol_w, Sol_buf' Sol_2-Mer and SH_L, while in the case of Sol_SDS the only significant term was the linear one for T. The dependence of emulsion ability (A ₅₀₀ as a measure of interfacial area) with time (t) and protein dispersion concentration (C) was evaluated using response surface methodology (RSM). The A ₅₀₀ showed a very good fit to a second order polynomial equation with R ² higher than 89%. The structural differences among samples caused by different treatments were well explained by the A ₅₀₀. Simultaneous heat and reducing treatment under mild conditions (T = 60-65 °C and C _Na2SO3 = 0.2- 0.4%) were able to open the protein structure, increasing SH_L. Samples highly soluble in every sol vent (without aggregation effects) showed the highest emulsion ability.

Keywords

soy proteins emulsions solubility heating reduction

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