Influence of rice protein hydrolysate on lipid oxidation stability and physico-chemical properties of linseed oil microparticles obtained through spray-drying

Abstract

In recent years, the use of plant protein in various food applications is an increasing trend in the food industry. The present study aimed to evaluate the effect of rice protein hydrolysate as an encapsulating material on lipid oxidation stability and the physico-chemical properties of linseed oil microparticles obtained through spray-drying. Rice protein isolate was hydrolyzed to an 8% degree of hydrolysis by the proteases Alcalase and Flavourzyme. Linseed oil was microencapsulated using protein hydrolysate or intact protein combined with maltodextrin. Sorption isotherms and glass transition temperature of microparticles were determined by the static gravimetric method and differential scanning calorimetry. Lipid oxidation stability of microparticles, evaluated by peroxide value, was carried out at 45 °C for 55 days. The sorption isotherms corresponded to the characteristics of BET II type isotherm and the GAB model was used to calculate thermodynamic properties of water adsorption. The monolayer moisture content values were between 3.76 and 4.96 g/100 g dry matter. Protein hydrolysates obtained by Alcalase and Flavourzyme did not significantly depress the glass transition temperature of microparticles (~98 °C and 103 °C, respectively) and did not change the structure of microparticles. On the contrary, the Alcalase protein hydrolysate improved the protection of the microparticles against lipid oxidation in approximately 95% when compared to the intact protein. This result can be due to the higher antioxidant capacity of Alcalase protein hydrolysate (3239 μmol TE/g protein) when compared to the intact protein (352 μmol TE/g protein).