Modified Chitosan And Irradiation Treatment On Preservation Of New Pears

The structure and function of homemade carboxymethyl chitosan (CMCS) and the effect of CMCS coating and irradiation technology on prolonging postharvest life of Niitaka pear were investigated by measuring the fruit quality and physiological and biochemical parameter during the storage period. The results were showed as follow:1. The procedure of CMCS production and featuresThe degree of substitution in chitosan reach over90%after carboxymethylation, and its solubility is5.034g/100mL.The viscosity-average molecular weight of CMCS which were irradiated by different radiation doses was declined again with the increasing radiation doses, and their substitution reaction was mainly found on Nitrogen atom of amino acid with infrared spectrum detection. Only the glycosidic bond of CMCS were interrupted by irradiation, and resulted in smaller molecular weight, and the C2-N-carboxymethyl and C6-O-carboxymethyl weren’t damaged or interrupted. The results suggest that irradiation didn’t destroy the original function of the chitosan.By carrying out the preliminary preservation experiments,21#and22#is better among CMCS of different molecular weight and selected for use in subsequent experiment.2. The effect of two treatments on the quality of Niitaka pearThe effects of CMCS coating and irradiation on extending postharvest life of pear were investigated through healthy ratio, hardness, browning degree, TA, TSS and VC. Research shows that the healthy ratio of Niitaka pear declined slower because of CMCS coating and faster because of irradiation. The hardness of Niitaka pear was maintained by CMCS coating and1kGy. The browning degree of Niitaka pear was restrained only by21CMCS coating and1kGy, but aggravated by3kGy later. And there were no significant differences between all treatment groups in the TA content of Niitaka pear. The TSS of Niitaka pear was reduced by CMCS coating and irradiation treatment, especially22. The VC content was slowly degraded by CMCS coating and1kGy.3. The effect of two treatments on the physiological and biochemical characteristics of Niitaka pearThe effect of CMCS coating and irradiation treatment on preservation of Niitaka pear were evaluated through the determination of weight loss ratio, respiratory rate, cell membrane permeability, polyphenol oxidase (PPO) activity and MDA content in the storage period. The weight loss ratio was postponed by CMCS coating opposite to irradiation. The respiratory rate of Niitaka pear effectively inhibited by CMCS coating, which reduced the consumption of nutrients, but accelerated by irradiation. The damage of cell structure of Niitaka pear was reduced by CMCS coating, and had not too many differences between irradiation and control. The browning of pulp was inhibited because its PPO peak was delayed by CMCS coating and irradiation. It showed a trend of decrease after a first rise in the basic between all treatment on the change of MDA content, but it decreased in chitosan treatment group slower, and it was under control first and higher than the control later by1kGy treatment opposite to3kGy.