Properties of soy protein isolate films fortified with underutilized quinoa stalks and leaves

Abstract

Quinoa (Chenopodium Quinoa Wild) stalk and leaf are abundant and underutilized materials. Quinoa stalk and leaf extracts were used to modify properties of soy protein isolate films thus extending the application of films. Quinoa stalk cellulose (QSC) was extracted by NaOH and HCl. QSC was added in film forming solution then the solution was casted into film. QSC can be incorporated into soy protein isolate (SPI) films to improve their tensile strength. This was because of the possible interaction of hydrogen bonding between QSC and SPI macromolecules. However, the color of soy protein isolate films was affected by QSC. Quinoa leaf extract (QLE) was rich in phenolic compounds. QLE and gallic acid were used as fillers to modify edible SPI films. Ethanol/water extracted QLE, contributed to the improved mechanical, antioxidant, and antimicrobial properties of SPI films. Hydrogen bonding was the major interaction between phenolic compounds and SPI macromolecules. This contributed to reinforcing the mechanical properties. The antioxidant and antimicrobial properties of SPI films were significantly improved by adding QLE. QSC and QLE both can increase the mechanical properties of SPI films, and QLE added films had also showed improved antioxidant and antimicrobial capacities.