Optimization of the methods for extraction of chitin in crab shell and preparation of chitosan
摘要
A combination of both acid and alkali treatments was used to extract chitin from crab shell in this study. Then, a three factors ( NaOH solution concentration, reaction time, reaction temperature) and three levels (35, 45, 55; 2, 6, 10; 70, 105, 140) L9 (34) orthogonal experiment design is further adopted to conduct a de-acetyl treatment to prepare chitosan by considering the viscosity and de-acetyl degree of the chitosan as the main performance indexes. Determination of de-acetyl degree of chitin complys with the procedures given by the reference and the viscosity meter was used for determination of viscosity of chitosan. The results show that the extraction of chitin shall use pulverized crab shell as the raw material and such raw material shall be immersed in 10% HC1 solution for 6 hours and washed with water for one time in every 2 hours, then heated in boiled water for 2 hours by the use of 10% thin NaOH solution. Afterwards, the said material shall be washed with water to become a neutral solution and dried over a stove. When chitin is mixed with 55% NaOH solution in a proportion of 1: 10 (W/V, g/mL) and the reaction takes place at a temperature of 105℃ for 6 hours, chitosan having a de-acetyl percentage of 94% and viscosity of ＞ 200 cps can be available.