Comparative study of plant protein extracts as wall materials for the improvement of the oxidative stability of sunflower oil by microencapsulation

This study investigated the potential of five commercially available plant protein extracts (pea protein isolate, soybean protein isolate, brown rice protein, hemp protein and sunflower protein) as wall materials for the microencapsulation of sunflower oil by spray drying. Emulsions were prepared with 10% w/v of protein extracts and 10% w/v of sunflower oil (core/wall materials ratio 1:1). No organic solvent or surfactant were used in the preparation process. The main objective of this microencapsulation was to improve the oxidative stability of sunflower oil. This parameter was evaluated by accelerated oxidative tests with the Rancimat method. Based on this technique, the induction period (IP) was calculated, corresponding to the stability time of the sample while heated at a certain temperature, and compared to the IP of non-encapsulated oil (9.50 h). Additional analyses for the characterization of the oil in water emulsions and dried microparticles were also performed. Results showed that sunflower oil encapsulated in pea protein isolate had the best oxidative stability (21.26 h), followed by microparticles made of soybean protein isolate (12.49 h). The formulation with hemp protein extract had no significant effect on the oxidative stability of sunflower oil (9.72 h) and the use of sunflower and brown rice protein extracts decreased the induction time of sunflower oil (7.20 and 6.97 h, respectively). These results were related to the protein fractions compositions and their influences on the diffusivity and film forming properties of the plant protein extracts.