| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 86 === Abstract
Maillard reaction was used for preparation of water-soluble chitosan. Their
physico-chemical properties, such as yield, solubility, degree of
deacetylation, degree of Maillard reaction, stability of solution, and
particle size distribution, were measured. Both the water-soluble and acid-
soluble chitosans prepared were used as coagulants in the treatment of
aquacultural wastewater to compare the effects on turbidity, suspended solid,
chemical oxygen demand, and aquacultural pathogen of wastewater. Dosage,
range of most suitable dosage, effect of solvent pH and wastewater pH of
both chitosans were also determined.
On the basic properties of water-soluble chitosan, yield of water-soluble
chitosan made from α-chitosan was about 15%, while it was 28%-33% when made
fromβ-chitosan. However, the highest solubility of α-water-soluble
chitosan among different reaction times was 0.79g/dL(3-days reaction), then
that of β-water-soluble chitosan was only 0.4g/dL in water. For this reason,
all experiments in this study were all performed withα-water-soluble
chitosan.The absorbence at 420nm in 1% water-soluble chitosan was 0.6 after
2-days reaction, and was not raised later. It was seemed Maillard reaction
was finished in two days. Water-soluble chitosans was clear and transparent
in the solution among pH3 to 12. Two or three peaks appeared in the chart
of particle size distribution. It means that modification, polymerization
and chain-breakage might happen to chitosans after Maillard reaction. On the
effects of different chitosans on treating aquacultural waste water, with
dosage of 3ppm, water-soluble chitosans reacted for 1, 3, and 5 days and
β-chitosan(DE84%) made turbidity, suspended solid, and COD of wastewater
decreased from 15.2NTU, 122ppm, and 81.5ppm to about 3NTU, 25ppm and 20ppm
respectively. But addition of 3ppm α-acid-soluble chitosan lowered the
turbidity, suspended solid, and COD of the same wastewater to 7NTU, 56ppm,
and 41ppm respectively. The reason could be that 3ppm was not in the range
of most suitable dosage of α-acid-soluble chitosan. About effects on
aquacultural pathogen, addition of α-acid-soluble chitosan and water-
soluble chitosan solved in 0.2M acetic acid made Aeromonas & Pseudomonas
too few to be counted by plate count when dosage was more than 300ppm, but
it seemed part of antimicrobial effect was came from acetic acid. If water-
soluble chitosan were solved in pure water, the more the dosage was, the
larger the number of Aeromonas & Pseudomonas were. The range of most
suitable dosage of water-soluble chitosan was wider, but the dosage needed
was more than those of acid-soluble chitosan. When solved in acetic acid
solution of pH3, 4, 5, and 6, the lower the pH of solvent of water-soluble
chitosan was, the less the dosage was needed. The reason was that the ratio
of ionized isolated amino group to non-ionized isolated one is less at
higher pH. The results also showed that water-soluble chitosan would work
normally, while acid-soluble chitosan would not.
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