Optimization of the conditions for producing soy protein isolate films

Abstract

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.

Production and characterization of thin films based on soy protein isolate with kraft lignin and tannins obtained by casting

“…After this step, the solution was cooled in an ice bath to ~ 25 °C. Later, pH was adjusted to 8.5, 9.5 and 10.5 with 0.1 Mol L -1 NaOH solution, distant from the SPI isoelectric point, identified as 1, 2 and 3, respectively (PAGLIONE et al, 2019). Then, the solutions were poured onto Petri dishes (290 mm × 280 mm × 50 mm) and dried at 25 °C room temperature for 12 hours.…”

“…The DSC curves show information about miscibility of the mixture components through the analysis of changes in melting temperature (Tm) and glass transition temperature (Tg) due to its composition (Blanco et al, 2017;De Souza et al, 2019;Boubekeur et al, 2020;Kiruthika et al, 2020), as seen in (Table 1).…”

Recent Advances in the Development of Smart and Active Biodegradable Packaging Materials

“…Previously, zein has been used as a constituent of packaging materials for various foods [66,67]. The proteins isolated from soybeans have also been shown to be suitable for forming edible films [68], which is often carried out using film casting or baking methods [69]. Smooth and stretchable edible films can be formed from soy proteins that have good mechanical properties, but again their water barrier properties tend to be poor [70].…”

Soy Protein Isolate Films Incorporated with Pinhão (Araucaria angustifolia (Bertol.) Kuntze) Extract for Potential Use as Edible Oil Active Packaging

“…The SPI films were prepared by the casting method according Paglione et al (2019). The formulations consisted of 7.56% (wt/wt) of SPI in relation to the film-forming solution and 25% (wt/wt) of glycerol in relation to SPI.…”