Antibacterial food packaging capable of sustained and unidirectional release carvacrol/thymol nanoemulsions for pork preservation

Pork is highly susceptible to microbial spoilage and oxidative deterioration. In this work, an active packaging film capable of sustained and unidirectional release natural antimicrobials was developed to prolong the shelf life of chilled pork. Thymol&carvacrol nanoemulsions (TH&CA NEs) with two active constituents were prepared by low-energy spontaneous emulsification method and showed excellent antioxidant and antibacterial abilities. A trilayer film composed of loading, adhesive and barrier layers were fabricated using polyquaternium-10 (PQ-10)&carboxymethyl chitosan (CMC) microgels (denoted as PC), mixed solution of PQ-10 and zein (Z), and zein solution as raw material of each layer by layer-by-layer casting method. TH&CA@PC-PZ-Z packaging films were obtained by adding dropwise TH&CA NEs onto PC loading layer of PC-PZ-Z film and showed good interlaminar bonding strength, suitable water retention, satisfactory biological safety, as well as great antioxidant and antibacterial activities. In addition, most of TH&CA NEs in TH&CA@PC-PZ-Z films could be released from PC loading layer in a sustainable way for at least 7 days due to the block of Z barrier layer. The preservation effects of TH&CA@PC-PZ-Z films on chilled pork were further investigated in comparison with a plastic fresh-keeping film made by low-density polyethylene (LDPE). Results showed that TH&CA@PC-PZ-Z films could effectively retard lipid and protein oxidation and inhibit microbial growth during 11 days storage, thereby prolonged the shelf-life of chilled pork. We believe that the sustainable and unidirectional drug release film can be developed as a promising packaging film in preserving fresh meat products.