Food spoilage, bioactive food fresh-keeping films and functional edible coatings: Research status, existing problems and development trend

Microbial contamination and oxidation of nutrients are two main reasons for food spoilage. Bioactive food fresh-keeping films (FFKFs) or functional edible coatings (FECs), which refer to a class of nature polymer-based preservation materials with advantages of green, nontoxic, edible and degradable characteristics, can effectively maintain the freshness of food stuffs and have gained considerable attentions. Two major factors in food spoilage, microbial contamination and nutrient oxidation, are described. Besides, the compositions, preparation technologies, and application range of functional FFKFs and FECs are introduced. This review also emphasizes the classification, preparation methods, modification approaches and application objects of FFKFs, as well as the development bottlenecks of FFKFs and FECs, and elaborating their development trends. Bioactive FFKFs and FECs play vital roles in inhibiting microbial contamination and oxidative deterioration of food products for extending their shelf lives. However, poor mechanical properties, gas barrier properties and heat resistance are the main problems of multifunctional FFKFs. Besides, poor hydrophobicity and bad water resistance of FFKFs make them easy to break when exposed to water, which limit their applications in preservation of some food products with high surface water content or easy to leak water. For FECs, the main problem is that the formulation and application of FECs should be properly performed based on different food stuffs to avoid their unnecessary removal. Future research should focus on designing suitable preservation strategies for different food stuffs according to their own different spoilage reasons. Importantly, it is necessary to track and deepen the researchers in order to optimize the properties of FFKFs and FECs and understand their action mechanisms, which will be very meaningful to allow these materials for specific applications in food industry.