Can Chitosan Be Depolymerized by Thermal Shock?

Abstract

Chitosan is a biopolymer with a wide range of applications. It typically requires depolymerization to achieve a desired molecular weight for specific uses. This study investigated the potential for depolymerizing chitosan by thermal shock and grinding to produce nanochitosan. A series of thermal shock cycles combined with grinding were performed to assess the influence of drying temperature, residence time, and number of thermal cycles on the molecular weight, particle size, and crystallinity of chitosan. The thermal shock reduced the molecular weight and particle size of chitosan within the first hour of treatment, with optimal conditions achieved at a drying temperature of 90 °C and residence time inside the oven of 5 min. These conditions resulted in a molecular weight of 15.0 kDa with an average diameter of 136 nm. Thermal shock can be considered an effective method for chitosan depolymerization with grinding serving to standardize the particle size. This optimized process offers promising applications where low-molecular-weight chitosan is required, including biomedical, agricultural, and food industries, as well as the potential for reducing time and energy consumption.