Onion peel extract as milk freshness indicator in biopolymer-based intelligent packaging films

Abstract

Intelligent food packaging is used to monitor quality / freshness of packaged food product, and to communicate them to consumers. Natural color-based pH indicators can be effective agents in biopolymer-based intelligent packaging systems. In this study, gelatin and sodium alginate-based sustainable intelligent packaging films incorporated with onion peel extract (OPE) as the pH indicator were fabricated for monitoring and indicating milk freshness. Effects of incorporation of OPE on moisture content, solubility, swelling, transparency, antioxidant activity, and total phenolic contents of the fabricated films were also evaluated. The developed films were characterized using Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and their color changes due to pH sensitivity were measured. The fabricated intelligent films / labels were tested against milk at different pH of 6.5, 6, 5.5, 5, 4.5, 4, and 3.5, and the discernible color changes were measured. The developed intelligent films / labels showed significant change in their color with change in pH of the milk samples. Thus, the films can be used as sustainable alternative, as freshness indicator for packaged milk.