The Preparation Of Carboxymethyl Chitosan And Application Research On Coating Fresh Strawberries

In this paper，using chitosan as raw materials，through the carboxy methylationreaction with chloroacetic acid preparation of N，O－carboxymethyl chitosan，andpreparation of carboxymethyl chitosan as antistaling agent， explore the rapidpathogens inhibition of strawberry．By dip coating to coating preservation ofstrawberry fruit，N,O－carboxymethyl chitosan on strawberry preservation effect，the expected development and preservation of high efficiency，good safety，wideapplicability，easy to use coating antistaling agent，and solve the problem that theacidic solution of chitosan coating is not easy to clean．Experiment investigatedN,O－carboxymethyl chitosan weightlessness rate in the process of strawberrypostharvest storage，soluble solids content，total acid content，vitamin C content，the influence of such changes for N,O－carboxymethyl chitosan for strawberryfresh-keeping provides a theoretical basis．The main research conclusions are asfollows：In the experiment，in aprotic solvent dimethyl sulfoxide as reaction medium，by chitosan carboxymethylated reaction with chloroacetic acid，preparation for thesubstitution degree of carboxymethyl chitosan0.81．Reaction conditions as follows:the quality of the chitosan， chloroacetic acid and sodium hydroxide than m(chitosan)：m (chloroacetate)：m (sodium hydroxide)=1：5：4.5，the reactiontemperature of60℃，4h，the dosage of dimethyl sulfoxide50ml．Characterized byFI－IR preparation of carboxymethyl chitosan， show that carboxymethylatedoccurred in chitosan molecules of N and O， namely the product is N,O－carboxymethyl chitosan．In this paper isoelectric point precipitation method is adopted to refine thereaction product，isoelectric point precipitation method after refining the productafter dealing with the sodium salt can completely soluble in water． By thedetermination of chitosan viscosity of raw material is211.6mL/g，the molecular weight of28W，the deacelation degree is88.53%．After carboxymethylated productviscosity of12mpa.S，substitution degree is0.81，isoelectric point around3~4．Three different kinds of bacteria are separate from strawberries，which areproduced in Wuhan．After the preliminary appraisal，they are Rhizopus stoloniferVuill，Botrytis cinerea Pers，and Penicillium sp．Compared with chitosan，N,O－carboxymethyl chitosan significantly reducesthe postharvest strawberry the happening of the disease in the process of storage，and in the certain concentration range， the higher concentration of N,O－carboxymethyl chitosan， its bacteriostatic effect， the more obvious．1.5%carboxymethyl chitosan solution three isolated bacteria inhibition of bacteriostaticring diameter：16.8mm，16.4mm and15.8mm．The experiment results of the N,O－carboxymethyl chitosan coating forstrawberry processing in fresh-keeping under4℃show that，1.5%concentrationof N,O-carboxymethyl chitosan solution can significantly reduce the strawberry inweightlessness rate in the process of storage，strawberry in storage after5d indifferent treatment，weight loss of the control group reached10.44%，however，1．5%carboxymethyl chitosan treatment group is6.25%；Carboxymethyl chitosancoating treatment can effectively inhibit the respiration of strawberry，a significantreduction in strawberry the wastage of the soluble solids and total acid and vitaminC， to a certain extent， improve the sensory quality of strawberry in the process ofstorage，improve the effect of preservation，prolong the shelf life of strawberries．...