Research Of Natural Preservatives On Fresh-Keeping Of Malu Grape

In this study, Malu grapes, local varieties of fruit in Shanghai, were used as material, the postharvest physiological characteristics and the effects of chitosan,alginate,nisin and lysozyme on preservation and fresh-keeping of Malu grapes were compared by determining their sensory quality, weight loss,hardness, respiration rate, VC content, soluble solids content and SOD activity during the storage, the formulation of the preservative was optimized by the orthogonal experimental design and response surface methods, and thus we determined the best preservative formula of Malu grapes, from which we could solve the problem of storage and preservation that restricted the industrial development of Malu grapes, while provide theoretical and practical basis of the application of natural preservative to the storage and preservation of fruit and vegetables. The results showed that:1. Chitosan, alginate, nisin and lysozyme had some effect on preservation and fresh-keeping of Malu grapes, all could effectively reduce the transpiration, resist pathogen infection, enhance disease resistance, significantly inhibit the recession of physiological and biochemical functions of Malu grapes, and prolong the shelf life of the fruit.2. In comparison, of the four treatments,chitosan coating gave the best effect, determined25days after coating and storaged at4±1℃, the weight loss rate was9.34%, VC content was2.3mg/100g, soluble solids content was up to12.1%, hardness was1027.59kg/cm2, SOD activity was87.3U/g, respiration was significantly lower than other groups.3. The formulation of the preservative were optimized by the orthogonal experimental design, the results showed that the best coating ratio was1.0%chitosan,1.5%citric acid and0.15%lysozyme.4. The formulation of the preservative were optimized by the response surface method, with the sensory score of Malu grapes as the response value, and three concentration of preservative as factors, a multiple quadratic equation was established, the best coating concentration was obtained by calculating the extremes, the results showed that the best coating ratio was0.88%chitosan,1.58%citric acid and0.15%lysozyme. Both the validation test results and theoretical studies showed that natural preservatives coated on the surface of Malu grapes could not only play a good preservation effect, but also improve the chemical preservative residues which had lots of negative impact on human health and environment, and with a more simple method, lower equipment requirements, much more significant results than other preservation methods.