Characterization of soy-protein based SO<SUB>2</SUB>-releasing pads for browning prevention in fresh-cut apples

Abstract

The use of polymeric matrices releasing active principles is a promising strategy to circumvent dipping treatments and reduce additive usage. Herein, we developed soy protein-based films containing 0, 10, 25 or 50% sodium sulfite on protein isolate basis (SPI), and determined the influence of the antioxidant on the color, thickness, opacity, solubility, moisture, water permeability and mechanical properties of the resulting materials. Raising sulfite concentration reduced the tensile strength, without affecting the Young´s modulus of the films. The formulation containing 50% sodium sulfite on SPI basis was selected based on the lighter color, lowest moisture and higher permeability of the resulting films to evaluate the efficacy of the materials to prevent apple browning. The incorporation of SO2-releasers in packages containing fresh-cut apples delayed fruit yellowing (increase of b*values) by 40%. This shows that sodium sulfite soy protein based films may be useful to extend the postharvest life of fresh-cut apple.