Smart monitoring of gas/temperature changes within food packaging based on natural colorants

The development of smart packaging and innovation in common food packaging technology will greatly help to meet market needs, including consumer preference for "safe" foods, high-quality products and mitigate the negative environmental impacts of food packaging. In addition, consumers' tendency to use natural ingredients such as pigments and biopolymers has provided the basis for their application in the food industry, including smart food packaging. Hence, smart packaging in addition to protecting food products against environmental damage can also reveal a sign (colorimetric, chemical, electric, etc.) in real time in response to any changes in the packaging conditions and food quality. This comprehensive review emphasizes on the gas/temperature-sensitive smart films based on natural colorants and their key applications in the food packaging systems. Technological considerations associated with the natural colorant-responsive films, smart packaging, biopolymers, and importance of natural colorants versus synthetic dyes are investigated. In practice, the most common designed colorimetric indicators for monitoring gas and temperature changes and application of relevant smart films in real food models have also been discussed. Gas and time-temperature indicators provide a rapid, reliable, and online assessment and a visual indication of the food product quality level, usually through a color change, which is directly related to gas and temperature conditions during distribution and storage of relevant food products. However, future studies need to consider main points such as cost, consumers' acceptance, and confidence, regulatory aspects (i.e., labeling) and multifunctionality of smart packaging to be commercially sustainable.