Preparation Of Nanoemulsion-based Edible Coating And Its Effect On The Shelf Life Of Carbonado Chicken

Sauce and halogen meat products are the representative traditional meat products in China,favored by consumers due to its good flavor and tastes,forming the regional characteristics of "sweet south and salty north" in China.Carbonado chicken is one of the typical sauce and halogen meat products and welcomed by consumers due to its unique shape,flavor,tastes and a good source of protein,minerals,vitamins and essential polyunsaturated fatty acids(PUFAs).However,such products are susceptible to external influences and easy to deteriorate during sale,thus affecting the quality,leading to spoilage.Edible coatings refer to thin layers of material coated on various foods,functioning as good carriers of food additives,which can prolong its shelf life by isolating external microorganisms and oxygen,delaying lipid oxidation,preventing the degradation of protein,and reducing off-odors,discoloration and moisture loss.With green,safe,low-cost,and edible properties of edible coatings,however,few studies were reported of its preservation on cooked meat products.The aim of the study is to develop edible coatings for the preservation of carbonado chicken,thereby further improving its quality and shelf life.In this research,gelatin and chitosan were selected as the coating matrix,and rosemary extract and ?-poly-L-lysine(?-PL)selected as the active compounds.The coating coarse emulsion and nanoemulsion were prepared by high-shear homogenization and high-pressure homogenization,respectively.The physicochemical properties of the two coating emulsion were characterized about their particle size distribution,stability,and microstructure.On this basis,the barrier properties,oxidation resistance and bacteriostatic properties of the coating were explored.Finally,the effect of nanoemulsion-based coating on the preservation of carbonado chicken were studied.At the same time,it provided theoretical basis and support for improving the edible quality of sauce and halogen meat products and further developing edible coatings.The main findings are ranked as follows:1.Preparation of nanoemulsion-based edible coating and study on its physicochemical propertiesWith gelatin and chitosan as the coating matrix,rosemary extract and ?-PL as the active substances,the nanoemulsion edible coating liquid was prepared by high-pressure homogenization.The objective of this study was to investigate the effect of the addition(0.5%,1.0%,2.0%)of fat-soluble phase rosemary extract(REO)and high-pressure homogenization processing on the particle size,zeta-potential,microstructure,stability,rheological properties and semi-solid properties of edible coatings.Results showed that the particle size of the coarse emulsion increased with the addition of the REO and the particle size distribution was uneven,indicating the emulsion system is unstable.High pressure homogenization can effectively fabricate the nano-size droplet emulsion(253?258 nm),and improve the stability of the coating emulsion liquid.Rheological results showed that the emulsion coating liquids of all groups exhibited shear thinning fluid behavior,and the coatings had an ordered and elastic strong gel structures.SEM images of nanoemulsion-based coating displayed smooth and homogeneous surfaces without pores and with excellent structural integrity.FT-IR showed that no new chemical bonds were introduced when REO added or treated by high-pressure homogenization.In all,the high-pressure homogenization technology can effectively prepare the nanoemulsion coating liquid,causing oil droplets to a homogeneous nanosize,making a smooth,homogeneous coating surface.2.Study on the functional characteristics of nanoemulsion-based coatingThis chapter studied the effects of different REO addition(0.5%,1.0%,2.0%)and high-pressure homogenization on the functional characteristics of edible coatings,including barrier properties,antioxidant properties,and antibacterial properties.Results showed the oxygen permeability of the edible coating gradually decreased with the addition of REO.Moreover,the decrease of emulsion droplet size of the coating liquid could significantly reduce the oxygen permeability of edible coating(P<0.05).The free radical scavenging rate of the coating increased with the addition of rosemary extract.However,there was no significant difference in the free radical scavenging capacity of the coating emulsion before and after homogenization.Inhibition zone method and viable counting method were used to test the antibacterial performance of the coating emulsion before and after homogenization.Compared with the coarse coating emulsion,nanoemulsion has higher antibacterial properties.Meanwhile,as the content of REO increased,the antibacterial ability of the coating emulsion gradually increased.These results indicated that nanoemulsion-based coating prepared by high pressure homogenization had good functional characteristics.Based on the above results,the group of 2.0%rosemary extract was selected for subsequent storage experiments.3.Effects of nanoemulsion-based coating on the shelf life of carbonado chickenBased on the above results,this study investigated the effect of different coatings on the shelf life of carbonado chicken.Four treatments were prepared:samples coated with nanoemulsion(E2);samples coated with coarse emulsion(E1);samples coated with gelatin-chitosan(G+C),and the uncoated samples(CK).The samples of each group were packed in trays and stored at 4±1?.The TVC,enterobacteriaceae,molds and yeasts,pH value,lipid oxidation,protein degradation and color were analyzed every 2 days.Results showed that nanoemulsion-based coating could significantly reduce the total aerobic bacteria,enterobacteriaceae,molds and yeasts counts of chicken(P<0.05),delay the lipid oxidation and protein degradation,and maintain the pH and good color of chicken during refrigeration.Compared with uncoated chicken,the nanoemulsion-based coating could effcetively extend the shelf life of carbonado chicken from 8 days to 14 days.