Recent developments in the application of natural pigments as pH-sensitive food freshness indicators in biopolymer-based smart packaging: challenges and opportunities

Recently, the assimilation of pH-sensitive natural pigments into biopolymers has shown promising prospects for pH-reactive based smart packaging material. Unlike synthetic pigments, which have potential safety problems due to migration, natural pigments have negligible toxicity levels both to humans and the environment and some even possess nutritional and pharmacological properties. To complement the advantages of natural pigments, natural biopolymers have proven to be ideal candidates for the development of smart packaging because of their biocompatibility, availability, biodegradability, stability, minimum toxicity and good film-forming capability. Smart packaging gives consumers real-time signals on the quality of packaged food via food deterioration indicators like pH alteration. This review will consider the recent progress in the development of pH-responsive smart packaging based on natural pH-sensitive pigments and natural biopolymers from 2013 to the present. It will further discuss the challenges and opportunities of colorimetric smart packaging.