Preparation Of Active Edible Membrane And The Effects On Preservation Of Jujube With Different Maturities

The golden silk jujube has a wealth of nutritional and medicinal value, which hasa broad market prospect. However, the fresh dates are difficult to store due to its ownphysiological characteristics, which can only be kept fresh for a few days, then theflesh softens and becomes brown, and the Vc is almost entirely oxidized. Thetraditional storage methods include dring and processing. After the harvest season, itis hard to see the fresh dates in the market, the preservation of fresh dates becomes thebottleneck of the development of the jujube industry.In this study, sodium alginate and carrageenan are chosen as the film-formingmaterial, and glycerol is as plasticizer, the formation process conditions of sodiumalginate-carrageenan composite film were optimized by orthogonal experiments,salicylic acid was added to prepare an active coating liquid, and the properties ofactive composite film and its factory application to the coating preservation of lelingjujube were studied in order to provide a more convenient, safe and efficient methodfor the preservation of leling jujube. The main research results are as follows:(1) The determination of film-forming formula and improvement of coating processof the composite membrane. Sodium alginate and carrageenan were blended, andsalicylic acid was added as ethylene inhibitors and antibacterial agents to prepare anactive coating liquid. The optimum blend ratio of sodium alginate and carrageenan,chlorine calcium concentration, glycerol concentration and crosslinking time weredetermined through the indexes of tensile strength, elongation, water vaportransmission rate and transparency, the formulation of the composite membrane wasoptimized through the four factors and three-level orthogonal experiment. The bestfilm-forming process conditions are as follows: the blend ratio6:4, calcium chlorideconcentration4%, glycerol concentration0.3%, crosslinking time2min. Crosslinkingtreatment right after the surface coating of leling jujube solved the problem that themembrane liquid was dissolved in condensed water and that affected the appearance. （2）Through the determination of DSC, FT-IR, X-RD, SEM and transparency, stronginteraction and good compatibility between the two polysaccharides sodium andcarrageenan were proved from their micro structure.（3）Using golden silk jujube at full-white, half-red, full-red storage as materials, theeffects of different preservation treatments(60Co-γ irradiation, coating with sodiumalginate and carrageenan, and60Co-γ irradiation+coating with sodium alginate andcarrageenan, calcium chloride, respectively) on the postharvest fruit quality duringcold storage were investigated, preservation results are as follows:（a） Under lowtemperature conditions, irradiation, irradiation+coating, coating and calcium chloridetreatments can reduce the corruption rate of golden silk jujube, the corruption rate ofirradiation+coating was the lowest, irradiation reduced the corruption ratesignificantly, and the decay rate increased with the higher maturity.（b）The impactsof different treatments on the quality of the leling jujube in different maturity are asfollows: All the treatments can reduce the weight loss rate of leling jujube duringstorage, irradiation+coating and coating group showed the lowest weight loss rate,while Vc, titratable acidity, total sugar and soluble solids, etc. maintained a highercontent and lower consumption rate, keeping good storage quality. The quality ofjujube at half-red and full-red storage was better than which at full-white storage.（c）Through the comparative analysis of corruption rate、weight loss rate,nutrient qualityand sensory quality, coating and calcium chloride treatment groups have the betterstorage quality, and the jujube at half-red storage has the best storage quality.（4）Through the research of the fresh-keeping mechanism of the different treatments,the effects of different treatments on the postharvest physiology of the leling jujube indifferent maturity showed that: Respiratory intensity of each treatment group can beinhibited effectively and respiration consumption reduced; irradiation may accelerateethylene generation and increase the MDA content; coating and calcium chloridetreatment can effectively inhibit ethylene production and maintain a higher SOD andPOD, CAT activity, while inhibit the formation of MDA, delay the ripening andsenescing process of the jujube, and improve the fruit storage quality.