Emulsion Gels Based on Quinoa Protein Hydrolysates, Alginate, and High-Oleic Sunflower Oil: Evaluation of Their Physicochemical and Textural Properties

Abstract

This study aims to assess the physicochemical and mechanical properties of O/W emulsion gels formulated with quinoa protein partial hydrolysates (QPH). The effect of varying QPH concentrations (0.5%, 1%, and 2%) on these attributes was also investigated. The QPH were obtained from quinoa protein concentrate (QPC) after treatment with alcalase. Surface hydrophobicity (S0) and emulsifying properties of QPH suspensions were determined. Microstructure, color, water holding capacity (WHC), thermal stability, as well as textural properties of the formulated emulsion gels, were also evaluated. After the hydrolysis treatment, S0 exhibited a significant increase (p = 0.006). The emulsifying activity of QPH also increased (p = 0.002), while the emulsion stability decreased (p < 0.000) as QPH concentrations increased. Confocal laser scanning microscopy images showed that in QPH-based emulsion gels, oil droplets seemed to be more associated with each other forming a three-dimensional network that was less bound to the matrix, in comparison with QPC-based emulsion gels. In addition, hydrolysis produced a significant reduction in WHC of emulsion gels (p = 0.000); however, in all samples evaluated the WHC was around 70%. Furthermore, after heat treatment, there was a decrease in this parameter (p < 0.000). The evaluation of textural properties showed that hardness was significantly lower for emulsion gels formulated with QPH (p < 0.000); whereas no differences between emulsion gels with 0.5% QPC and those with 0.5, 1, and 2% QPH were obtained. Therefore, hydrolysates have the potential to be used in emulsion gel formulation and could be applied to the development of soft-solid food products.