Effect of whey protein isolate films incorporated with montmorillonite and citric acid on the preservation of fresh-cut apples

The objective of this paper was to evaluate the effect of bioactive whey protein isolate/montmorillonite films containing citric acid on the inhibition of enzymatic browning and physicochemical properties in minimally processed apples. Whey protein isolate films incorporated with montmorillonite (3 g,/100 g) and citric acid (5 and 10 g/100 g) were applied to the apples slices. All samples were packaged in polypropylene trays (14.6 cm x 11.4 cm x 6.5 cm) and stored at 5 +/- 2 degrees C and 85 +/- 3% RH for eight days. Every two days, the apples samples were evaluated for color, acidity, pH, soluble solids, water activity and polyphenol oxidase and peroxidase enzyme activity. The enzymatic browning of the apples slices was reduced for all films during storage. However, the films containing citric acid maintained the color characteristics, reducing the loss of quality associated the maintenance of acidity, soluble solids, water activity, reduction of polyphenol oxidase and peroxidase activity, thus prolonging the shelf life of the apples.