pH-sensitive (halochromic) smart packaging films based on natural food colorants for the monitoring of food quality and safety

The recent rise in awareness of safe food and changing consumer attitudes have brought many innovations in packaging technology. Consumers are increasingly demanding natural food colorants such as carotenoids, betaines, anthocyanins and chlorophylls rather than synthetic dyes for food applications. As a result, smart packaging based on natural colorants and biopolymers has been introduced as the latest technology in the food packaging field. Smart products not only protect food from environmental hazards, but also send real-time signals (colorimetric, chemical, or electrical) to consumers for changes in the packaging environment and food quality. This paper reviewed the pH-sensitive smart packaging films based on natural food colorants and biopolymers and key applications in the food industry. Technological aspects associated with the natural colorant-based pH-responsive packaging films, biopolymer-based smart packaging, and the importance of natural colorants compared with synthetic dyes are discussed. The most commonly used colorimetric indicators indicating changes in pH, the application of smart food packaging films in real food systems, and the trend of future research were investigated. Based on natural food colorants, smart packaging monitors the qualitative properties of foods in real-time, including freshness, microbial growth, and chemical changes in the product, through visual changes and quantification of pH changes in the food. It provides a fast and reliable inline assessment of food quality and safety. Nevertheless, future studies should consider commercially sustainable key points such as consumer acceptance and trust, cost, regulatory considerations (i.e. labeling) and multifunctional performance of smart films.