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Effect of freeze-thaw pretreatment on thermal drying process and physicochemical properties of chitosan

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ABSTRACT

The effect of freeze-thaw pretreatment on the thermal drying process and physicochemical properties of chitosan was investigated in this study. Results showed that the freeze-thaw treatment changed the form of chitosan paste and reduced 75.6–77.7% of the water content. The freeze-thaw treatment decreased the drying time of chitosan from 16–19 h to 2.75–4 h and the dried product was loosely packed powder. After freeze-thaw treatment, the molecular weight of chitosan was unchanged during the thermal drying. The heat-induced browning effect of chitosan during drying was greatly alleviated by the pretreatment. Furthermore, the pretreatment increased the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity of dried product by 40.4–59.8%. The molecular weight, color, and DPPH radical-scavenging activity of the pretreated dried chitosan product were close to those of freeze-dried product. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41017.

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