Design Of Edible Coating Containing Microcapsules And Its Study In Preserving Fresh-cut Purple Yam

Fresh-cut fruits and vegetables are a kind of convenient and fresh food that is widely loved by the public.However,fresh-cut fruits and vegetables are highly susceptible to damage and microbial infection during processing and transportation,and the loss of nutrients caused by their own metabolism will affect the quality of fresh-cut fruits and vegetables and shorten their shelf life.Essential oil is used as a natural preservative and is of good antioxidant and antibacterial properties,while its volatility and poor stability limit its application.Microcapsule technology can well embed essential oils and increase their stability,what's more,it can extend the life cycle of essential oils.Coating technology is a convenient and safe technology used to preserve fresh-cut fruits and vegetables and it can extend the shelf life of fresh-cut fruits and vegetables to some extent.In this paper,using ?-cyclodextrin as the core material,the oregano essential oil as the core material,and the sugar ester as the emulsifier.The ?-cyclodextrin-oregano essential oil microcapsules were prepared by molecular entrapment method,and the optimal preparation was explored.The process is:stirring time was 3 h,the volume ratio of oregano essential oil to absolute ethanol is 1:5,the mass of cyclodextrin is 6 g,and the stirring temperature is 50 ?.The embedding rate of microcapsule prepared under the optimal preparation conditions was 55.14%.Fourier transform infrared spectroscopy,XRD analysis and thermogravimetric analysis indicated that the P-cyclodextrin-oregano essential oil microcapsules were successfully prepared by molecular embedding method,and the thermal stability of the microcapsules was improved.By surface morphology analysis,the surface of?-cyclodextrin-oregano essential oil microcapsules was wrinkled and stacked,and the microcapsules were full and uniform in size,and the particle size was about 40-50 ?m.?-cyclodextrin-oregano essential oil microcapsules have significant inhibitory effects on the growth of Escherichia coli and Listeria monocytogenes.In order to characterize its antibacterial properties,Optical density method was used to test its antibacterial effect.And the results showed that the minimum inhibitory concentration of P-cyclodextrin-oregano essential oil microcapsules against Escherichia coli and Listeria monocytogenes was 1250?g/mL and 312.5 ?g/mL,respectively.The edible coating containing microcapsules consists of sodium alginate,citric acid and microcapsules.According to the antibacterial effect of the microcapsules,The amount of microcapsules added to the edible film was 1250 ?g/mL.The browning degree of fresh-cut purple yam was used as the evaluation index,and the concentrations of citric acid and sodium alginate in the edible coating were determined by experiments to be 0.8%and 1.5%,respectively.After determining the amount of each component of the edible coating,a coating layer of edible coating containing microcapsules(Coating B)was constructed on the surface of fresh-cut purple yam,what's more,edible coating without microcapsules(Coating A)and blank control(citric acid solution)were prepared at the same time.And the effects of preserving fresh-cut purple yam were studied.It was observed by SEM that the edible coating has been successfully adhered to the surface of fresh-cut purple yam,and the edible coating was relatively flat.Through the detection and analysis of the browning degree,hardness,aerobic plate count,soluble solids content,ascorbic acid content and anthocyanidin content of fresh-cut purple yam treated with different coatings,the results showed that the fresh-cut purple yam treated with Coating B can maintain a high nutrient level during the storage for 24 hours.