The Study Of Gelatin-based Antimicrobial Edible Coatings

Prepared chicken products, gaining popularity for their convenience, freshness, nutrition balance and low-fat properties, consists of fresh chicken and others added elements. Fresh chicken and products are highly perishable foods and susceptible to microbial spoilage which leads to short shelf-life, and while there also exists heavy drip loss during the refrigeration storage. Consequently, developing methods to extend the shelf-life and reduce the weight loss represents a major task for the poultry processing industry.In this study, the edible antibacterial gelatin based coatings added with several bacteriostatic agents was used for chicken products package. The following are the purpose of this research: (1) Studying the preservation of edible antibacterial gelatin based coatings added with Nisin and potassium sorbate during the storage of fresh chilled chicken breast, and selecting the best quantitative indicator used as the response value for the square response surface equation; (2) The optimization of the antimicrobial agents formula (Nisin, potassium sorbate and EDTA-2Na) in gelatin based coatings by establishing a square response surface equation; (3) The application of the edible antibacterial gelatin coatings on prepared chicken products(Chuanxiang chicken fillet), and developing a proper method of active edible package for fresh chicken products.The results of the experiments were as follows:(1) The preservation effect of gelatin based edible coatings added with Nisin on chilled fresh chicken breast was evaluated. The result showed that the Nisin-gelatin based edible coatings had a significant inhibitory action on the total number of visible colonies(TVC) of chicken breast, and the inhibitory effect increased with the strengthen of Nisin's concentration (p<0.05); The addition of Nisin to the gelatin based edible coatings showed no significant effect on the center pH of chicken breast during refrigeration (p>0.05), but significantly improved the color of chicken breast in the beginning period of storage (p<0.05); The drip loss of chicken breast was significantly reduced during storage by the treatment of gelatin based edible coatings (p<0.01). It was indicated that the TVC of the chicken breast treated by edible fresh-keeping coatings was proper for the indicator used for the square response surface equation which could optimize the formula of antimicrobial agents in edible gelatin coatings.(2) The preservation effect of gelatin based edible coatings added with potassium sorbate on chilled fresh chicken breast was evaluated. The results showed that the potassium sorbate-gelatin edible coatings had a significant inhibitory action on the TVC of chicken breast, and the inhibitory effect increased with the strengthen of potassium sorbate's concentration (p<0.05); The total volatile basic nitrogen(TVB-N) had no significant difference between the coatings groups treated by potassium sorbate-gelatin edible coatings and the control group (p>0.05); The edible gelatin coatings added with potassium sorbate had no influence on both chroma and central pH of the chicken breast. It illustrated that the socalled TVB-N was not proper used as a quantitative indicator for chicken products of freshness.(3) The square response surface equation which response value was the TVC of chicken breast in the 4th day of storage and the independent variable was the addition value of the three antimicrobial agents (Nisin, potassium sorbate and EDTA-2Na) was set up. It showed that there existed a stable point where the TVC of the coated chicken was in the lowest level, in other means that the three antimicrobial agents had a optional regrouping which had the best inhibit action of the three antimicrobial agents added into gelatin coatings; According to the optimization formula attained by the square response equation the addition of the thee antimicrobial agents was fixed. (Nisin:936 mg/L, potassium sorbate:23 g/L, EDTA-2Na:7.99g/ L).(4) The preservation effect of edible gelatin antimicrobial coatings on the chilled fresh chicken breast and Chuanxiang chicken fillet stored under refrigeration (0-4℃) was analyzed. The result showed that the coatings treatment had separately extended the shelf-life of the fresh chilled chicken breast and Chuanxiang chicken fillet by approximately 100% and 75% compared to the control groups in the way of significantly inhibition of the TVC (p<0.01); The drip loss of the fresh chicken products had been reduce from 7.5% to 0.8% by the edible gelatin coatings(p<0.01); Compared with the control group the edible gelatin coatings had the ability to improve the colour quality of chicken products. The edible gelatin based coatings added with antibacterial agents was proved to be fit as an active anti-microbial package which could maintain a long shelf-life by controlling the growth of the microorganism and reducing the drip loss in the chilled chicken prepared products.