Synthesis Of N- Succinyl-chitosan And Effect On The Quality Of Wheat Flour

Chitosan was applied in the study of food, medicine and chemical industry in recent years because of its excellent properties, such as non-toxicity, biocompatibility, biodegraded, etc. But because of chitosan only soluble in acid medium, insoluble in water, so the propertity restricts its application. First, in order to improve its solubility, we synthesised N-succinyl-chitosan(NSC), and physical and chemical properties of chitosan and NSC were studied and compared, included solubility, thermal stability, moisture absorption, moisture, emulsification and antibacterial propertity. Finally, we studied the quality of flour and steamed bread with chitosan and NSC.N-Succinyl-chitosan was synthesized by acylation with succinic anhydride. IR and 1H NMR showed the reaction occurred on the amine group of chitosan.Solubility results showed that compared to chitosan, N-succinyl-chitosan has greatly improved in solubility. NSC showed weak solubility in neutral condition, good solubility in acid and alkali conditions. Thermal stability of NSC was significantly lower than that of chitosan, and NSC thermal decomposition temperature is 287°C by thermogravimetric analysis. Moisture-absorption capacity of NSC in RH=81% and RH =32% environment and the moisture-retention rate in silica gel were all higher than that of chitosan; Chitosan and NSC had good emulsifying properties, within the first 120 min, emulsifying power significantly decreased, compared with chitosan the emulsion rate of NSC drops decreased, emulsion stability improved by emulsifying properties analysis. Both of them have different degrees of inhibition on Escherichia coli and Staphylococcus aureus, the inhibition effect of NSC on bacteria was more higher than chitosan. The minimum inhibitory concentration of chitosan and NSC on two kinds of bacteria were 0.05% and 0.025%.We studied the effects of chitosan and NSC on quality of wheat flour, Mixolab reflected the mixing characteristics of dough. With the increase in the proportion of chitosan and NSC addition, water absorption is gradually increasing, and the flour with NSC increased obvious than chitosan; the stability time was increased, compared with chitosan, when adding 0.4% NSC for the rub resistance of the dough was obviously improved. The pasting property was improved, peak time and setback value decreased, and under the same addition proportion, pasting properties of flour adding NSC is better than that of chitosan. Chopin alveograph test reflected tensile properties of dough,showed that with chitosan and NSC adding to wheat flour, P(the maximum tension stress of dough in the process of alveograph)、W( required energy within bubble expansion to the fracture) increased significantly than the blank dough. Compared with chitosan, the value of W increased obviously with flour adding NSC, and when the adding ratio is 0.4%, the toughness, gluten strength, ductility of the dough is greatly improved. Mixing and extension characteristics of dough data analysis results showed that when NSC in a ratio of 0.4% adding to wheat flour, dough rheological properties and pasting properties which have obviously improved. So 0.4% is the appropriate adding proportion produce steamed bread.Textural properties were studied using texture profile analysis. With the extension of storage time, compared with the blank steamed bread and steamed buns which added chitosan, elasticity, cohesiveness and resilience of the steamed buns with NSC were increased significantly in the storage first four days, and they had little change in the late storage time. The hardness and adhesion decreased slightly in the addition of chitosan and NSC. Thermal characteristics of wheat flour was determinated by differential scanning calorimetry(DSC) under different storage time. Through the analysis of thermal characteristics of steamed bread, found that because of the addition of chitosan and NSC,absorption peak of vaporization enthalpy of steamed bread decreased.So it can effectively reduce the retrogradation, and inhibited the ageing of steamed bread. So adding chitosan and NSC to steamed bread samples in a short storage time could improve the quality of steamed bread, and the improvement effect of NSC to the steamed bread quality is very obvious.