| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 94 === Abstract
Chitin and chitosan possess typical characteristics of polysacharide's and alkaloid's reaction. Moreover, chitin and chitosan degrade before melting, which is typical for polysaccharides with extensive hydrogen bonding. Thus, these make it necessary to dissolve chitin and chitosan in an appropriate solvent system to impart functionality.
However, their solubilities relate to many factors, such as degrees of N-acetylation, distribution of N-acetylation, and molecular weights. Among them, acyl groups can provide intermolecular and intramolecular hydrogen bonds, which have influences on their physicochemical properties. Therefore, it is one of the most important parameters.
This study shows that ultrasonic treatment in the acid hydrolysis stage can help H+ to asscess chitinous molecular cores, leading the chitinous samples to hydrolyze homogeneously. This prevents the lower results for highly acetylated samples by using the previous reported HPLC method.
As to the application of infrared spectroscopy (IR), improved HPLC (B) method can be used to establish the calibration curve. This can be used to replace the NMR method in which the high-cost instrument is not available in most laboratories.
In the IR method, KBr pellets are prepared by mixing about 2 mg of sample with 100 mg of KBr. The degree of N-acetylation is calculated from the absorbance ratio of two bands (pb 1320/ rb 1420) by using a best chosen calibration curve. If the DA of the sample is less than 20％, it would be better to use the absorbance ratio of pb1660 b3/ rb2880 b1 or pb1660 b8/ rb 2880 b1.
Both improved HPLC (B) method and proposed IR method are suffered from obtaining weak signals for samples of low DA. They are not suitable for samples having degrees of acetylation less than 10％.
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