Quinoa protein-chitosan-sunflower oil edible film: Mechanical, barrier and structural properties

Quinoa protein extracts (Q) were prepared and alkalised at pH 8 and 12 (Q-8 and Q-12). Qs were mixed with chitosan (CH) to form Q/CH mixtures. The optimal proportion of the mixtures was determined by the formation of coacervates. All the films were obtained by solution casting. From the optimal Q/CH mixture and the addition of three different concentrations of sunflower oil (SO) 2.9, 3.8 and 4.7 g/100 mL, and the optimal proportion of SO g/100 mL was selected based on the mechanical and barrier properties of the films. The CH, Q/CH and Q/CH/SO optimal blend films were characterised by FTIR, X-ray diffraction, and SEM. The physicochemical properties of the films were also evaluated. The 0.1 Q-8/CH blend was selected due to its high degree of interaction between the quinoa proteins and CH. The optimum concentration of SO used in the Q-8/CH/SO film was 2.9 g/100 mL. The addition of SO to the film improved the water-vapour permeability (WVP) as a result of hydrophobic interactions and the presence of clusters of hydrophobic masses on the surfaces of these films but reduced the film's tensile strength and oxygen permeability due to the formation of micropores and microfractures detected by SEM.

► Alkaline extracts of quinoa protein Q were mixed with chitosan CH. ► Sunflower oil SO was added to Q/CH and it was formed edible films. ► Structural, mechanical, and barrier properties of Q/CH/SO films were evaluated.