Study On The Preparation Of Edible Fresh-keeping Composite Film And Its Fresh-keeping Effect On Chilled Chicken

The traditional meat preservation methods,such as low temperature cold storage,freezing,vacuum packaging and so on,have some problems,such as poor fresh-keeping effect,short shelf life,affecting meat quality and so on.Edible film as a new type of packaging material has the characteristics of safety and environmental protection.Adding natural ingredients with bacteriostatic effect can effectively improve the above problems.As a natural preservative,spices have the advantages of safety,non-toxicity and good bacteriostatic effect.the edible film with spice essential oil is widely used in meat preservation because of its good mechanical properties and bacteriostatic properties.In this experiment,sodium carboxymethyl cellulose（CMC）and sodium alginate（SA）were used as raw materials to develop the basic membrane formula.Six kinds of spices commonly used in meat processing were used to test the bacteriostasis of two typical representative bacteria Escherichia coli and Staphylococcus aureus.Two kinds of spice essential oils with the best antibacterial effect were added to the base membrane to obtain spice essential oil composite membrane.The composite film was wrapped on the surface of chicken,and its fresh-keeping effect on chicken under cold storage（4℃）and room temperature（24℃）was studied.The main conclusions are as follows:1.Using CMC and SA as film-forming materials and glycerol as plasticizer,through single factor test and orthogonal test,the formula of base membrane was determined as follows:CMC/SA is 3:7,glycerol content is 0.8g·100m L^-1,drying temperature is 55℃.The base membrane prepared with this formula has good mechanical properties,low solubility and water vapor permeability and high light transmittance.2.Six kinds of spice essential oils were extracted and tested against Escherichia coli and Staphylococcus aureus respectively.The spices with the best bacteriostatic effect were screened and the minimum inhibitory concentration（MIC）was determined.The results showed that the spices with good bacteriostatic effect on the two kinds of bacteria were clove and alpinia officinalis,and the MIC was 0.25%and 0.5%,respectively.3.The combined bacteriostatic effect of clove essential oil and alpinia ginger essential oil was investigated by chessboard dilution method.The results showed that the graded inhibitory concentration index（FICI）of Escherichia coli and FICI of Staphylococcus aureus were 0.75and 1,respectively.The optimum volume ratio of clove essential oil to alpinia ginger essential oil was 1:2.4.The compound essential oil was added to the base membrane at different concentrations,and the effect of the concentration of essential oil on the composite membrane was investigated.The optimum formula of the composite membrane was determined as follows:CMC/SA is 3:7,glycerol 0.8g·100m L^-1,drying temperature 55℃,clove essential oil/ginger essential oil 1%,compound essential oil 0.6%.The composite membrane prepared by this formula had good bacteriostatic effect on Escherichia coli and Staphylococcus aureus.The diameter of bacteriostatic zone was 16.40mm and 15.52mm respectively.5.The composite film was covered on the surface of chicken by wrapping,and the untreated chicken was used as the control group to study the fresh-keeping effect of the composite film on chicken under cold storage and room temperature conditions.the chicken in the treatment group still reached the sales standard on the 10th day,while the chicken in the control group was seriously rotten on the 4th day,and the composite film could prolong the shelf life of chicken under cold storage for 6 days.Under the condition of storage at room temperature,the chicken in the treatment group could still reach the standard of sub-fresh meat at 60 hours,while the chicken in the control group was rotten at 36 hours,and the composite film could prolong the shelf life of chicken at room temperature for 24 hours.