Extraction and Characterisation of Chitin and Chitosan from Irish Brown Crab Shell Waste

The conversion of seafood waste into valuable materials is essential for advancing seafood sustainability. Crab shells, which are a major byproduct, generate a large volume of waste annually and are a key source of chitin and chitosan. This study explores the extraction and characterisation of chitin and chitosan from Irish brown crab (Cancer pagurus) shell waste using chemical methods. Samples of crab shell waste (CSW), extracted chitin (CT) and chitosan (CTS) were analysed and compared to commercial chitosan (CTS-c) in terms of chemical, thermal and structural properties. The extraction process included steps of demineralisation, deproteinisation, decolourisation and deacetylation, yielding 17.60% CT and 50.45% CTS, which aligns with previously published values. FTIR analysis confirmed structural changes from CSW to CT followed by CTS, shown by distinct spectral shifts, with CTS exhibiting a degree of deacetylation (DD) of 78.53%, comparable to CTS-c (79.53%). DSC findings showed increased enthalpy, ΔH from 72.58 J/g (CSW) to 253.28 J/g (CTS), indicating improved thermal stability. SEM images displayed morphological transformations from porous CT to denser CTS, with porosity measured by ImageJ changing from 2.87% (CSW) to 18.60% CT before decreasing to 2.71% (CTS). These outcomes highlight the feasibility of valorising Irish crab shell waste into high-quality chitin and chitosan suitable for use in end-product applications, thus promoting the concepts of a circular economy.