Preparation Of Novel Derivatives Of Chitosan, Evaluation Of Their Preservation And Antioxidant Activity

Chitosan is a natural macromolecules polysaccharide which has unique physical and chemical properties,and has good water absorption, moisture resistance, film-forming, thickening, gel, etc.. It does not produce toxic for food preservation side effects, and its antioxidant properties has an good function on human health. However, some of chitosan itself properties such as its poor water solubility, film preservation performance alone is not higher shortcome its application. In this study, chitosan and other natural medicines reinforced composite daub feature on freshing fruits and vegetables; by modifing chitosan group got Citronellal chitosan Schiff,ethyl vanillin Chitosan Schiff base,methyl benzoyl chitosan, p-methoxy benzoyl chitosan, methyl benzoic acid esters of chitosan, p-methoxy benzoic acid esters of chitosan.In this paper,the influence of chitosan, sodium benzoate and potassium sorbate preservative composite film on fruit is studied and studied the influence of chitosan and alginate double films on freshing fruits,the sciff base chitosan effect on fruits is studied. Fruit weight loss rate, sugar content, Vc content and acid content varies with time are as important index evaluation on freshing fruit. The synthetic routes of chitosan derivatives is studied. The structure of the derivatives were characterization by FT-IR analysis, XRD analysis; by the elements analysis and thermal gravimetric analysis method we get the degree of substitution of the product and thermal stability; By measuring free radical derivatives on DPPH radical scavenging activity and reducing power hydroxy size, assessed the strength of its antioxidant capacity, and through comparative study of the differences of antioxidant capacity between the different samples. The main conclusions are as follows:1 Preparation and characterization of chitosan derivativesChitosan reacted with citronellal and ethyl vanillin respectively under ultrasound-assisted, and get respectively citronellal chitosan Schiff base, ethyl vanillin chitosan schiff base, FT-IR analysis, XRD analysis verified the derivatized product structure. By elemental analysis to calculate the degree of substitution products, in the reaction temperature 70 C, reaction time 10h, reactant ratio of 1:6, the optimal degree of substitution was 92.3%. Thermal stability is higher than chitosan before 320 ℃, after 320℃is lower than chitosan. Ethyl vanillin and chitosan at reaction temperature 80℃, reaction time 10h, reactant ratio of 1:6, the degree of substitution was up to 62.1% under the conditions, and its thermal stability is higher than chitosan.Chitosan respectively reacted with methyl benzoyl chloride and p-methoxy benzoyl chloride respectively generated methyl benzoyl chitosan derivatives, p-methoxy benzoyl chitosan derivative, and they were verified the structure by FT-IR analysis, XRD analysis. Calculated the degree of substitution product by elemental analysis. At 60℃, the reaction time was 4h, reactant ratio of 1:2 under conditions the degree of substitution of methyl benzoyl chitosan derivatives, p-methoxy benzoyl chitosan derivative were 14.3% and 16.7%.Under the precondition of chitosan amino-protected, chitosan respectively reacted with methyl benzoyl chloride and p-methoxy benzoyl chloride synthesized p-toluic acid esters of chitosan and chitosan-methoxybenzoic acid sugar esters. By FT-IR analysis, XRD analysis verified the structure of the derivatized product. By elemental analysis method to calculate the degree of substitution. At 70℃, reaction time was 6h, the ratio was 1:2, methyl benzoic acid esters of chitosan and p-methoxy benzoic acid esters of chitosan degrees were respectively 23.6% and 26.8%.2 The performance of freshness on fruits of chitosanPreservation of Chitosan and potassium sorbate, sodium benzoate and other composite film on grapes indicated that:1% chitosan and 1% sodium benzoate complex films had the best weight loss reduces, Vc content and keep mitigate the effect of grape acid content decreased; and 1% chitosan,1% potassium sorbate and 1% sodium benzoate composite coated had the best reducee on the effect of the decay rate on grapes. While fresh orange sugar test showed that:1% chitosan and 1% sodium benzoate group having sugar orange best reduce decay rate, the effect of keeping Vc content; and 1% chitosan has the best reduced sugar orange the effect of weight loss.double-coated chitosan and alginate showed that:Compared with the control group chitosan and alginate double coated cherry tomatoes had better reduce weight loss, reduce the decay rate and the effect of Vc content, chitosan itself had good acid content to keep the effect of cherry tomatoesIts derivatives citronellal chitosan Schiff base and ethyl vanillin chitosan Schiff bases filming Cherry experiments showed that:1% chitosan compound 1% ethyl vanillin chitosan Schiff had the best weight loss reduces on cherries, and the best reduce the effect of the rate of decay and it had the better keep cherries Vc content of results,and 1% chitosan has the best maintained cherry acid content results.3 Study on the antioxidant properties of chitosan and its derivativesThe six derivatives of chitosan clearing DPPH, clearing Test of hydroxyl radicals and their reducing power showed that the antioxidant activity of each sample with the sample concentration increased, and different derivatives had a significant impact on its antioxidant capacity, esterified chitosan derivatives had a better antioxidant capacity than other derivatives, followed by acylation chitosan derivatives, and finally Schiff base derivatives. The same substituent in different location on chitosan affeced their abilities, the esterified product was greater than the acylated product, the same types of derivatives by different substituents had different antioxidant capacity, methyl benzoic acid esters of chitosan was greater than p-methoxy benzoic acid esters of chitosan, methyl benzoyl chitosan chitosan was greater than p-methoxy benzoyl chitosan, the citronellal chitosan Schiff base is greater than ethyl vanillin chitosan seats Schiff base.