Preparation Of Antimicrobial Film Based On Sorbic Acid-loaded Chitosan Microcapsules And Its Application In Snakehead Preservation

With the improvement of social progress and economic level, consumption patterns and consumer attitudes of people people are undergoing great changes. People have paid more attention to nutrition and safety of food. With the rise of fresh food e-commerce company, how to extend the shelf life of fresh food become the key point to solve the Fresh Food Distribution "last kilometer". By inhibiting the growth of microorganisms, antimicrobial packaging food can ensure the quality of fresh food and extend its shelf life.In this paper, With sorbic acid(S), chitosan(CS) and sodium triphosphateas as materials, chitosan microcapsules(MP), sorbic acid loaded chitosan microcapsules(S-MP) were prepared by ionic crosslinking method and spray drying method. With 3%(w:w) sorbic acid, CS, MP, S-MP as antibacterial ingredients, antibacterial films that low density polyethylene(LDPE)and ethylene/vinyl alcohol copolymer(EVOH) were selected as membrane material, were prepared by Blending granulation extrusion blow molding. the basic properties of the films were investigated and the effect of the antibacterial films on preservation properties of snakehead under the condition of cold storage(4 + 1) ℃.⑴ Under the same conditions of spray-drying, S-MP and MP had a diameter of 1 ~ 4μm. With the addition of 3%(w:w) sorbic acid, CS, S-MP and MP, decreased the tensile strength(Ts), water vapor barrier and transmittance of films, improved oxygen barrier, had no significant effect on the elongation at break(ε) of films. With respect to PE film, S-PE, CS-PE, S-MP-PE, MP-PE film all had strong inhibitory effect for Staphylococcus aureus and Escherichia coli. S-PE film had the best inhibitory effect against Staphylococcus aureus and Escherichia coli, followed by S-MP-PE film.⑵ Sorbic acid had good compatibility with EVOH. S-MP, MP could be uniformly distributed to the EVOH film, and the content of 3% chitosan was too high to occur agglomeration in the EVOH film. With the addition of 3% sorbic acid, S-MP and MP the tensile strength of films enhanced, and 3% CS added leaded tensile strength of film decreased. Compared with EVOH film, the ε of S-EVOH film increased, that of S-MP-EVOH, MP-EVOH, CS-EVOH occurred varying degrees of decline. The addition of sorbic acid, S-MP, MP, chitosan decreased the transmittance of EVOH films and rised the haze. Since chitosan appears agglomeration in EVOH film, CS-EVOH film had the highest haze and lowest transmittance. Comoared with blank EVOH film, the oxygen permeability(OP) of CS-EVOH was highest, and OP of S-MP-EVOH, MP-EVOH films decreased. There was not significant difference between OP of EVOH and S-EVOH film. Antibacterial test showed inhibitory effect of S-MP- EVOH, MPEVOH, CS- EVOH films against gram-negative bacteria(S. enterica and E. coli) was better than that against gram-positive bacteria(L. monocytogenes). The inhibitory effect of S-MP- EVOH film against S. enterica, E. coli and L. monocytogenes are second only to S- EVOH film.⑶ S-PE、S-MP-PE、MP-PE、CS-PE antibacterial films were applied to keep the quality of snakehead during cold storage. The total volatile basic nitrogen(TVB-N), total viable counts(TVC), pH, TBA, Drop loss were analyzed periodically as freshness indicators in snakehead. All the freshness indicators reflected S-PE, S-MP-PE films had better preservation effect on snakehead than other films. In terms of TVC less than 6 lg(CFU/g) for the edible standards, At 4 ℃, the shelf life of snakehead treated by PE film was 6 days, S-PE, S-MP-PE, MP-PE, CS-PE film could extend the shelf life of snakehead to 8 days. On day 8, S-PE, the TVC of snakehead samples treated by S-MP-PE and S-PE film was significantly lower than that of snakehead samples treated by MP-PE, CS-PE film. S-PE, S-MP-PE, MP-PE, CS-PE antimicrobial films can effectively extend the shelf life of snakehead by 2 days. If S-PE film was placed a long time under atmosphere, sorbic acid may be oxidized and turned pink,which made the antibacterial effect of film weakened. Sorbic acid was embedded into microcapsules, avoiding the oxidation of sorbic acid. So S-MP-PE film in food antimicrobial preservation had broad application prospect.⑷Total viable counts(TVC), total volatile basic nitrogen(TVB-N), pH, TBA value, drip loss, K value as freshness indicators,antibacterial films were applied to keep the quality of snakehead during cold storage.All freshness indicators and sensory evaluation reflected the effects of S-EVOH / PET, S-MP-EVOH / PET film for snakehead preservation were better than other films. In terms of TVC less than 6lg(CFU/g) as the edible standard, at 4 ℃,the shelf-life of snakehead treated by MP-EVOH / PET, CS-EVOH / PET film could extend to 8 days. S-EVOH / PET, S-MP-EVOH / PET film could extend the shelf-life of snakehead to 10 days. Compared to EVOH / PET film, S-EVOH / PET, S-MP-EVOH / PET antibacterial films all could effectively extend the shelf life of snakehead for 4days. S-EVOH / PET and S-MP-EVOH / PET films had good antibacterial effect, and broad application prospects in fresh food preservation.