Bring some colour to your package: Freshness indicators based on anthocyanin extracts

Nowadays, consumers are more aware about what they eat and how it is packaged. Food quality is of paramount importance and consumers are eager to be constantly updated about the perishability and shelf-life of the food products they buy. This gave rise to intelligent packaging (IP) materials and devices that can communicate with all people throughout the entire food route. One of the main colour-based IP systems is based on the use of anthocyanin (ATH)-based natural dyes by exploiting their pH-dependent colour changes that can be easily readable by the naked eye. This review focuses on recent studies regarding ATH-based sensor packaging materials development for IP applications, offering valuable insights regarding the main factors that affect the efficacy of the developed IP, such as the material where the ATH is anchored, ATH type and concentration, the ingredients used in the formulation of the sensor and the storage conditions of the food product. Additionally, the last ATH-based IP developed are also summed and discussed in detail to identify the major bottlenecks that need to be overcome for accelerating the commercial application of ATH-based sensors in IP. Although ATH-based indicators are able to correctly indicate food shelf-life in several products at a laboratory scale, their industrial production is still impaired by the production methods used for this type of sensors. Furthermore, ATHs are labile compounds that require stabilization in the packaging material to yield stable, standardized and durable IP materials.