Development of cassava starch/soy protein blends incorporated with active agents by extrusion

Abstract

Lipid oxidation causes the deterioration of foods with high oil and fat content. Active packaging is a promising alternative for the preservation of these foods because, besides the protection to external factors such as oxygen, light and humidity that conventional packaging presents, antioxidant agents are added. Given the above, the study aimed to develop and characterize biopolymer blends of thermoplastic starch from cassava (STP) and soy protein isolate (PIS) by the extrusion method and subsequently incorporate tomato peel and seeds (TPS) and microparticles of camu-camu extract (MC) for the development of active packaging. First, STP and PIS blends were developed and characterized. Subsequently, TPS were added to the STP polymer matrix at STP: TPS ratios of 100:0; 96:4 and 92:8 (STP100-TPS0, STP96-TPS4 and STP92-TPS8) for the development of active films. The films were characterized and applied to Brazil nuts, in the form of sealed packages, to evaluate the ability to reduce the oxidative process. Brazil nuts were also stored without packaging and in a commercial polypropylene (PP) packaging for comparison with the developed ones. In addition, MCs were incorporated into blends containing 60 % soy protein at blend (SP): MC ratios of 100:0, 90:10 and 80:20 (SP100-MC0, SP90-MC10 and SP80-MC20) for the development and characterization of antioxidant films. The addition of protein at higher concentrations increased the stiffness and decreased the water vapor permeability (WVP) of the blends, probably due to the interaction of the STP and PIS polymer chains when at higher SIP concentrations (45 and 60%). Therefore, the blend with 60% SIP was selected for the incorporation of TPS and MC. However, when incorporating TPS into the selected blends, film formation was not possible by the extrusion and thermo-compression method. Therefore, the addition of TPS was performed in the STP matrix. The incorporation of TPS reduced the WVP of the films. The transparency was not altered by the addition of TPS, but the films became darker (higher L*) and with reddish yellow coloration (higher a* and b*). The treatments STP96-TP4, STP92-TP8 and PP packaging had the same efficiency for reducing the oxidative process, being potential substitutes for these packages. It was also observed that the incorporation of MC in the blend caused a decrease in the moisture content of the monolayer by water sorption isotherm analysis at 25°C, consequently, a decrease in WVP values was also observed for SP90-MC10 and SP80-MC20 films. Furthermore, the films presented low equilibrium moisture at water activities below 0.75, showing good stability up to this relative humidity. The films showed low transparency, showing good light barrier, and the incorporation of microparticles resulted in brownish films. Furthermore, antioxidant activity of 59.7 % and 79.4 % was observed for SP90-MC10 and SP80- MC20 films while SP100-MC0 film showed only 3.81 %. The results show that SP90-MC10 and SP80-MC20 films have potential to be used in food packaging that has water activity below 0.75 and is susceptible to lipid oxidation.