| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 99 === Chitosans, generally obtained from chitin through partial deacetylation, are a group of polymers consisting of glucosamine and N-acetyl glucosamine. Chitosans are biodegradable, biocompatible, non toxic, and antimicrobial. The main objectives of this study are to prepare phosphorylated chitosan microparticles by reaction of chitosan with triphosphate, further to reduce the particle size by ultrasonication, and to evaluate the antimicrobial activity of chitosan microparticles and chitosan/gelatin composite films.
Microparticle of phosphorylated chitosan was formed via ionic gelation method by mixing sodium triphosphate with chitosan. After treated by sonication, the particle size was further reduced. The absorbance at 888 cm-1 (representing the group of -PO) in FTIR spectrum indicated that the crosslinking was formed between chitosan and sodium triphosphate. In addition to the particle size distribution, phosphorylated chitosan exerted significantly better antimicrobial activity when compared to the non-treated chitosan.
Gelatin and different type of chitosans (un-treated, phosphorylated, and phosphorylated/sonicated) were used to fabricate chitosan/gelatin composite films. Microstructure, mechanical properties, moisture content, water solubility, water vapor transmission ratio (WVTR), and antimicrobial activity of the resulting films were analyzed. Microstructure of film was observed by scanning electron microscope; the results showed that the films containing chitosan exerted more compact structure and higher tensile strength. The highest tensile strength was detected in the composite films with the ratio of gelatin/chitosan at 2:3.
No significant difference of water content was observed among different types of composite films. While water solubility decreased as the ratio of chitosan increased in the formulation, WVTR increased with the increase of chitosan proportion. Ranges of WVTR of composite films containing untreated, phosphorylated and phosphorylated/sonicated chitosan were 4.54-6.20, 4.54-5.78, and 4.54-5.24 (g/m2‧24 hr), respectively. Gelatin/untreated chitosan composite films showed greater antimicrobial capacity, after contact 180 minutes its inhibition measured up to 95%. However, the inhibition for phosphorylated and phosphorylated/ultrasonicated composite films at the same condition was 80-90%.
In conclusions, phosphorylated chitosan prepared by ionic gelation method had smaller particle size, better mechanical properties, and greater antimicrobial activity. The best ratio of gelatin/phosphorylated chitosan for preparation composite films was 2:3.
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