Study On The Preservation And Alleviating Chilling Injury Of Summer Squash And Cucumber By Chitosan Film

The effects of different concentrations of chitosan coating films on storage quality, cellmetabolic anenzymes and other main physiological and biochemical characteristics of summersquash and cucumber were studied. And the influence of chitosan coating on chilling injuryresistance of two vegetables which stored under low temperature condition was alsodiscussed. At the same time, the effect of chitosan coating on antioxidant system of cucumberunder room temperature was further studied. The mechanism of chitosan treatment to extend thestorage period of cucumber in room temperature was discussed too. The main results wereshowed as following:(1) Under20℃, the influence of chitosan coating with different concentration(0.25%,0.5%,0.75%and1.0%) on physiological and biochemical characteristics of summer squash wasstudied. The results showed that: the appearance quality of summer squash could bemaintained, respiration intensity could be inhibited and the emergence of the respiratorypeak was delayed, the degradation of soluble solids and chlorophyll were postponed, theincrease of cell membrane permeability and the accumulation of malondialdehyde wereinhibited, the activity of catalase and peroxidase was increased. chitosan coating of0.75%concentration showed the best effect.(2) Under5℃, the influence of chitosan coating with different concentration on the chillingtolerance and physiological and biochemical indexes of summer squash was studied. Theresults showed that: The emergence of summer squash chilling injury could be effectivelydelayed, the respiration intensity could be inhibited, the degradation of peel chlorophyllcuold be slowed down, the rise of cell membrane permeability and the accumulation ofMDA were inhibited, the activity of catalase (CAT) and peroxidase (POD) were increased.The chitosan coating of1%concentration showed the best effect.(3) Under3℃, the influence of chitosan coating with different concentration on the chillinginjury and physiological and biochemical indicators of cucumber was studied.The resultsshowed that:The appearance of chilling injury of cucumber could be effectively delayedand the chilling injury symptoms could be reduced, respiration rate was inhibited, thedegradation of chlorophyl was delayed,and the rise of cell membrane permeability wasinhibited, the accumulation malondialdehyde (MDA) was postponed, the activity of CAT and POD was improved. Chitosan coating of1%Concentration showed the optimisticeffect.(4) Under20℃, The following results came out with the study of cucumber weight loss rate,respiration rate, chlorophyll, ascorbic acid (Vc), the membrane relative conductivity,content of malondialdehyde (MDA) and catalase (CAT), polyphenol oxidase (PPO),peroxidase (POD), glutathione reductase (APX) and ascorbate peroxidase (GR) activity.Theweight loss of cucumber could be effectively reduced, the respiration intensity wasinhibited,the degradation of chlorophyll and ascorbic acid in peel were delayed, and the riseof cell membrane permeability and the accumulation of MDA and CAT were inhibited, theactivity of POD, APX and GR were increased, thus,the increase of PPO activity wasdelayed. The treatment of coating before storage could extend the storage time of cucumberby increasing the activity of reactive-oxygen-scavenging enzymes which inhibited theperoxidation of membrane lipid.