Impact of extended acid hydrolysis on polymeric, structural and thermal properties of microcrystalline chitin

Abstract

In this study, microcrystalline chitin (MCCh) was prepared from commercial shrimp shell α-chitin by acid hydrolysis at ambient temperature for various treatment durations (30, 60, 90, 120, and 150 min), and their structural, polymeric and thermal properties were studied. Results showed that MCCh was distinct from native chitin structure, exhibiting loosened fibrillar structure with large pores and void diameter, increasing with treatment duration from <0.5 μm for native chitin to 1.653 μm for MCCh-150. The recovery rate obtained was in the range of 57.50 – 71.65%. The degree of N-acetylation reduced slightly from 89.86% for native chitin to 88.07% for MCCh-150 with increasing treatment duration. Crystallinity indexes increased from 85 to 92% after 30 min of acid treatment, then decreased slightly to 90% after 150 min. DSC analysis indicated MCCh were thermally stable. These results suggest that extended acid hydrolysis treatment can greatly improve MCCh polymeric and thermal properties. Furthermore, the method described is simple, easy, energy-efficient, and requires less acid compared to earlier studies, making it more practical and scalable for the production of MCCh.

Keywords

• Shrimp shell residue
• Degree of N-acetylation
• Microcrystalline chitin
• Crystallinity index