Application of water-soluble chitosan to shrimp for quality retention

Water-soluble chitosan produced using chitosanase enzyme was characterized and then applied to shrimp through vacuum tumbling. Untreated shrimp meat and shrimp meat treated with acetic acid solution and distilled water through vacuum tumbling were used as controls. All the shrimp were separately cryogenically frozen before frozen storage at -20 degrees C. The effect of water-soluble chitosan on the shrimp meat quality was evaluated during 120 days of frozen storage. Chitosanase enzyme shortened the polymer chain, reduced the molecular weight and particle size, and markedly improved water solubility of chitosan. Microscopy images showed that water-soluble chitosan penetrated into shrimp muscle tissue while chitosan was adhered on the surface of shrimp. At 120 days of storage, shrimp treated with water-soluble chitosan had lower aerobic plate counts, yeast and mold counts, and lipid oxidation compared to the controls. Also, there were no changes in color, texture, and moisture contents for water-soluble chitosan treated shrimp during frozen storage. Our results showed that chitosanase could process chitosan into water-soluble chitosan with a lower molecular weight and particle size. Our study also demonstrated that water-soluble chitosan could be applied to shrimp through vacuum tumbling for maintaining the quality characteristics of shrimp. (C) 2016 Elsevier Ltd. All rights reserved.