33A-23 |
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J.-E. SHIN, Q. Xu, and L.-F. Chen. Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009 Chitin is an abundant biopolymer found in the shells of crustaceans, the cuticles of insects and the cell walls of microorganisms. Chitosan is converted from chitin by deacetylation. Both chitin and chitosan have been used in agricultural, food, industrial, and medical fields. However, chitin is not soluble in water and chitosan is only soluble in acidic conditions. Various studies have been conducted to make water-soluble chitosan by chemical modification. However, chemical modifications change the fundamental skeleton of chitin and chitosan. As a result, the modified chitin and chitosan lose the original physicochemical and biochemical activities. It was hypothesized that the reaction time and alkaline concentration of the deacetylation process by using a twin-screw continuous processor could be reduced to a level that minimize the side reactions causing the loss of the original physicochemical and biochemical activities. The objective of this research was to optimize this deacetylation process by using a twin-screw continuous processor. Deacetylation of chitin was carried out using a continuous processor. Optimization operations were conducted with factorial combination of process variables: temperature, the ratio of chitin and NaOH, water content, and feed rate. Water-soluble and acid-soluble chitosan were isolated based on the difference in solubility at various pH ranges. Yield was calculated by gravity method. The results showed that water-soluble chitosan was produced with maximal yield in the conditions of 75 psi steam pressure, 50 % moisture content , NaOH/chitin ratio at 1, and 95 g/min feed rate. Acid-soluble chitosan was produced with maximal yield in the conditions of 55 psi steam pressure, 55 % water content, NaOH/chitin ratio at 2, and 140 g/min feed rate. These results suggest that using a continuous processor reduces the reaction time and alkaline concentration because this method provides more surface area on which chitin can react with NaOH. Therefore, the method may maintain activities of chitin and chitosan, and has significance for decreasing process costs.
Session 33A, Carbohydrate: General
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