Water Vapour Permeability and Light-Barrier Properties of Starch Films Incorporated with Amaranthus dubius Extract for Potential Fruit Preservation

Abstract

Commercial fruit coatings such as beeswax and paraffin often cause problems such as poor gas exchange, blushing during storage, and skin whitening, limiting their effectiveness in maintaining fruit quality. Thus Amaranthus dubius (red spinach) having antioxidant and antimicrobial properties offers a promising solution. This study evaluated the effect of red spinach extract concentrations (40%, 60%, and 80% w/w polymer) on the light barrier and water vapor permeability (WVP) of starch films potential for fruit coating applications. Light barrier properties were evaluated by measuring film transmission at 200–800 nm using a UV–Vis spectrophotometer, while water vapour permeability was determined by the gravimetric cup method under controlled temperature and relative humidity. Light barrier analysis revealed a significant reduction in film transmission with 80% extract concentration, particularly at shorter wavelengths (200 nm), due to the high betacyanin content which absorbs and scatters light in the UV-visible spectrum. This suggests the films’ potential as UV-blocking agents. Meanwhile, the WVP of all films decreased over a 7-day period. On day 1, the 60% extract film exhibited the highest WVP (1.88×10⁻⁶ g/d·m·Pa), attributed to hydrophilic compounds like betacyanin and polyphenols that enhance water vapor diffusion. However, as films dried, permeability decreased significantly, with the 40% extract film achieving the lowest value by day 7 (6.39×10⁻⁷ g/d·m·Pa), indicating greater structural compactness and barrier efficiency. Notably, the WVP values observed in this study were lower than the standard range for food packaging films, confirming the red spinach extract’s contribution to improve moisture and UV barrier properties. These findings highlight the multifunctional potential of red spinach extract in edible coatings for extending shelf life and preserving the quality of fresh produce.