Keywords: Anthocyanin; Roselle; plasticizer; film; sensor; food spoilage

Abstract

Food packaging featuring colorimetric pH indicators is among the most reliable and intelligent packaging system. In the present study, the pH indicator film was made up of corn starch and glycerol, with the addition of a natural dye extracted from Roselle calyxes, Hibiscus sabdariffa. This work emphasized on the development of a pH indicator film made of corn starch-glycerol and anthocyanin to detect food spoilage. Corn starch and glycerol acted as polymer and plasticizer, respectively, thus creating a solid matrix to immobilize anthocyanin within the film. Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectra confirmed the effective incorporation of anthocyanin in the corn starch-glycerol mixture. The film color variation was measured using a chromameter after immersing the film in acidic and basic solutions of different pH values. In order to evaluate the applicability and reliability of the proposed pH indicator film, a test on real samples, i.e. milk and meat, was conducted. The indicator film turned pink and green when in contact with spoiled milk and meat, respectively, which proved the acidic and basic features of spoiled food. Therefore, it shows that this pH indicator film can be used as a sensor in order to notify the quality of food.