Development of polysaccharide based intelligent packaging system for visually monitoring of food freshness

With the increased awareness on food freshness and food quality among consumers, the intelligent packaging films that can visually monitor the freshness of packaged foods by observing the color changes of packaging materials are gradually drawing more and more attentions. In this paper, various colorimetric indicators, types of polysaccharides as film-forming materials, production methods, freshness monitoring application, along with the future development of different intelligent packaging films are illustrated detailedly and deeply. Natural pH sensitive indicators such as anthocyanin, alizarin, curcumin, betaines and chlorophylls, as well as the gases sensitive indicators (hydrogen sulfide sensitive indicators and ethylene sensitive indicators) are the most widely used indicators for monitoring of food freshness. By incorporating different colorimetric indicators into polysaccharides (starch, chitosan, gum and cellulose derivatives) based substrates, the intelligent packaging films can be fabricated by solvent casting method, extrusion-blow molding method and electrospinning technique for monitoring of meat products, fruits, vegetables, milk products and other food products. In conclusion, intelligent packaging films with colorimetric functions are promising and feasible methods for real-time monitoring of food freshness, while stable colorimetric indicators, new film-forming methods and cheaper polysaccharide materials are still needed to develop for further commercialization.