Stability enhancement methods for natural pigments in intelligent packaging: a review

Intelligent packaging (also called smart packaging) has garnered significant attention for its ability to monitor food quality and spoilage during storage, without compromising packaging integrity. Natural pigments are being explored as sensors of food properties in these applications, but they are often chemically unstable, which limits their widespread utilization for this purpose. Therefore, enhancing pigment stability is imperative. This review article discusses the different types of natural pigments used in intelligent packaging applications. It then highlights the origin of their chemical instability and the factors that impact it, before outlining potential strategies to improve their stability. Natural pigments used in intelligent packaging include phenolic-, quinone-, pyrrole-, polyene- and betalain-based molecules, which are characterized by their unique chemical structures, especially the presence of conjugated structures that selectively absorb visible light. The environmental conditions that trigger a color-change in each pigment are highlighted. Pigment stability can be enhanced through a variety of approaches, including molecular modifications, pigment encapsulation, and label matrix design. These approaches modify the microenvironment of the pigments, thereby increasing their stability. These pigment enhancement methods hold promise for the development of intelligent packaging materials that can be used in the food and other industries.