Method for preparing chitosan from shrimp and crab shells

Abstract

The invention discloses a method for preparing chitosan with shrimp and crab shells as the raw material. The method includes the following steps of decalcification, dissolution, removal of insoluble impurities, mild heat treatment, high temperature treatment, solid-liquid separation, dilute acid neutralization and dissolution, dilute alkali treatment and separated washing and drying. The method for preparing chitosan with shrimp and crab shells as the raw material has the advantages that deproteinization and deacetylation are conducted simultaneously, the process procedure is shortened, consumption of alkali is reduced, the reaction condition is mild, less damage is caused to a chitosan polymer main chain compared with a traditional method, it is convenient to obtain a chitosan product of a high molecular weight, and the cost of separating a chitosan product out of a solution is low; the obtained chitosan product is in cotton white color, the chitosan product is dissolved, and viscosity of the solution with the concentration being 1% is 400 mPaS or above.

Description

technical field [0001] The invention relates to a method for preparing chitosan, more precisely, a method for preparing chitosan with shrimp and crab shells as raw materials. Background technique [0002] Chitosan, the chemical name is poly(1,4)-2-amino-2-deoxy-β-D-glucose, as a biopolymer compound with a huge amount in nature, it is widely used in medicine, pharmacy, health care products, environmental protection, etc. field has great application potential. [0003] In the prior art, the preparation of chitosan is generally based on the chitin-containing shell of shrimp, crab or insect, etc. The process mainly includes decalcification with dilute acid→cooking and deproteinization with dilute alkali under heterogeneous conditions→oxidation Decolorization→deacetylation→filtering→cleaning→drying with concentrated alkali under heterogeneous conditions. But the method for preparing chitosan in the prior art has following several defects: [0004] 1. Deproteinization and deace...

AI Technical Summary

Problems solved by technology

[0004] 1. Deproteinization and deacetylation are carried out independently in two steps, which increases the alkali consumption and prolongs the production process;

[0005] 2. The intermediate product (i.e. crude chitin) after dilute alkali deproteinization contains more pigments, and special decolorization steps are required. Generally, potassium permanganate, hydrogen peroxide and other oxidants are used to oxidize and remove the pigments. Because potassium permanganate and hydrogen peroxide Oxidants such as oxidants have strong oxidizing ability, and they also have a strong destructive effect on the main chain of the chitin polymer while removing the pigment, resulting in a decrease in the molecular weight of the final product chitosan;

[0006] 3. It is difficult to deacetylate under heterogeneous conditions, so the severe reaction conditions of using 40%~60% high-concentration lye to cook at high temperature for a long time are the long-term methods used in traditional production, although concentrated alkali and high temperature Long-term treatment can remove acetyl groups, but it will also damage the main chain of chitosan polymers, and is also highly corrosive to equipment