Study On Preparation Of Edible Films Containing Lactic Acid Bacteria And Application On Fresh-keeping Of Fresh-cut Cantaloupe

Due to poor bacteriostasis and biodegradability.,traditional packaging materials have caused serious public health and environmental problems.Therefore,the edible film with biological activity and biodegradability has become a new development direction of food packaging.Lactic acid bacteria have good antibacterial and fresh-keeping effects.But because they can use carbohydrates for growth and reproduction,the direct use of lactic acid bacteria in fresh food is likely to cause the total number of bacterial colonies to exceed the standard,which could cause food safety hazards.In this paper,gelatin and sodium alginate are used as film-forming base materials,glycerin is used as a plasticizer,inulin is used as a protective agent for lactic acid bacteria,and Lactococcus lactis is used as an antibacterial agent to prepare edible films.First,the single-factor experiment was used to determine the protective agent of lactic acid bacteria with the best performance.Subsequently,on this basis,a gradient concentration of Lactococcus lactis was added to discuss its effect on the physical,optical,mechanical and antibacterial properties of edible film to optimize Lactococcus lactis add amount.Finally,the lactic acid bacteria-containing edible film was prepared under the optimal lactic acid bacteria protective agent and Lactococcus lactis concentration for fresh-keeping of fresh-cut cantaloupe,and its effect on the quality of fresh-cut cantaloupe during storage was studied.The main research findings are as follows.(1)The gelatin-sodium alginate edible film was prepared by casting method.Inulin and so on were added as the protective agent of lactic acid bacteria,determines the optimal type of protective agent of lactic acid bacteria through the change of performance index..The experimental results show that the edible film with inulin as the protective agent of lactic acid bacteria has the best comprehensive performance.The survival rate of Lactococcus lactis during the baking process is 6.00%.After 22 days of storage,it can maintain 5.08 log CFU/g of the viable bacterial count,and the film thickness is 0.26 mm,the water vapor transmission coefficient is 2.69×10^-12g·m/m²·s·Pa,the tensile strength is24.74 MPa,and the elongation at break is 17.13%.(2)Adding Lactococcus lactis as an antibacterial agent,and exploring the effect of Lactococcus lactis concentration on the number of viable bacteria,color of edible film,microstructure,mechanical properties and antibacterial activity.The results show that the edible film has a strong intermolecular force and a mysterious microstructure when the amount of Lactococcus lactis added is 1.5%.After the 7 days antibacterial experiment,the number of viable bacteria of Staphylococcus aureus and Escherichia coli can be reduced by 4 and 3 log units.(3)Inulin was selected as the protective agent of lactic acid bacteria,and the lactic acid bacteria-containing edible film prepared under the optimal concentration of Lactococcus lactis(1.5%w/w)was used in fresh cut cantaloupe storage and freshness.The sensory quality,hardness,weight loss rate,decay rate,soluble solids content,Vc content,titratable acid content and total number of colonies were measured in the blank group and the experimental group of fresh-cut cantaloupe within 5 days at different temperatures.The experimental results show that the index of fresh-cut cantaloupe at 4?is better than that at 25?which under the same packaging conditions,and the edible film packaging film containing Lactococcus lactis has the best preservation effect than the edible film without Lactococcus lactis and the traditional PE packaging film.