| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 90 === The aims of this study are to explore the effects of molecular weight, degrees of deaectylation, concentrations of chitosan and gelling pH on physical-chemical properties of complex hydroges prepared from chitosan and alginate. Physical-chemical properties includes dynamic viscoelastic, water absorptivity and thermal properties. Chitin was extracted from red shrimp (Solemocera prominenitis) process waste. Three different degrees of deacetylation chitosans were prepared by hot alkali deacetylation from prepared chitin. The same degrees of deacetylation but different molecular weight chitosans were produced by ultrasonication treatment on three different degrees of deacetylation chitosans. The effect of the same degrees of deacetylation but different molecular weight or the same molecular weight but different degrees of deacetylation, their concentration and gelling pH on physical-chemical properties of complex hydrogels of chitosans and alginate were explored and results obtained are as following:
The viscoelastic properties especially the storage modulus (G) of complex hydrogels of chitosans and alginate increased with increasing concentration, molecular weight, degrees of deacetylation of chitosans and gelling pH. This may be due to the conformation, chain flexibility of the chitosan molecules and entanglement between chitosan and alginate were affected by increasing concentration and molecular weight of the chitosan. The electrostatic interaction between chitosan and alginate and hydrogen bond of intra-molecular and inter-molecular were then play their role to form hydrogels. The absorptivity of these hydrogels were also affected by these factors, but in the opposite trends. Increasing of these factors, the absorptivity of the hydrogels decreased. The maximum melting point and enthalpy also increased with increasing the molecular, degree of deacetylation and concentration as well as the gelling pH. This may be owing to that these factors enhanced the interactions of chitosan and alginate. The infrared spectra data show that increasing the concentration of chitosan would facilitate the electrostatic interactions and hydrogen bond between chitosan and alginate. But increasing the molecular weight of chitosan did not result in significant difference in infrared spectra. These results indicated that the main factor that increased the mechanical strength of the hydrogel of the same concentration were the entanglement of the molecular chains between chitosan and alginate.
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