One of the traditional residues obtained from pinhão seeds (Araucaria angustifolia (Bertol.) Kuntze) consists of an aqueous extract produced from the cooking process, which presents a significant concentration of phenolic compounds with antioxidant properties. In this work, soy protein isolate (SPI) films with different concentrations of pinhão cooking water extract (EP, 0.5, 1, and 2% wt/wt) were produced and physical properties, microstructure, and antioxidant capacity were investigated. The films were applied as packaging (as sachet-type) for linseed oil, and the oil oxidative stability was evaluated during 10 days under accelerated storage condition (60°C) by conventional procedures (peroxide index, specific extinction coefficient, and UV-Vis spectrophotometry) and by multivariate curve resolution with alternating least squares (MCR-ALS) chemometric method. The film with EP contributed to the oxidative stability of linseed oil being an interesting alternative of active biodegradable packaging for edible oils.

The soy protein isolate (SPI) is a biopolymer highlighted as a raw material for producing films and demands the investigation of the processing conditions that make it possible to obtain a film with adequate functional properties. The objective of this work was to evaluate the effect of the pH and concentration of SPI on the mechanical properties, water vapor permeability, solubility, and color of the SPI films produced by casting using a central composite rotational design (CCRD). In general, the films presented a yellow coloration with a continuous aspect, good handling, and no apparent glycerol migration. The linear effect of pH positively influenced the tensile strength (TS) and elongation at break (ELO) of the film (p <0.05) but negatively influence the solubility (SOL) and color parameter L* for which we obtained lower values ​​of SOL and L* at a high pH. This possibly occurred because of the denaturation of the soy proteins at an alkaline pH, far from the isoelectric point, resulting in their unfolding and solubilization which facilitated the interaction between the chains, forming a more compact structure. Considering the optimization by the desirability function, to obtain a film with high TS and ELO and low SOL, it is necessary to use 7.56 g/100 g of SPI film-forming solution and to adjust the film-producing solution to pH 10.54.

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