Influence of chitin purity on its dissolution behaviour in alkaline solvent

The biopolymer chitin is a promising ingredient for bioplastics due to its strength and stability. Chitin fibres must be isolated from biomass by stripping away tightly bound minerals, proteins, and pigments. Depending on the desired chitin purity, this isolation process can be long and cost-prohibitive on industrial scale. Following isolation, chitin fibres must be dissolved or separated which is challenging due to chitins recalcitrance. Cryo-assisted dissolution in potassium hydroxide has been identified as a fast and non-toxic approach. However, to date, this method has not received widespread attention and has not been evaluated for chitins from different species. The present study demonstrated the dissolution of Northern pink shrimp (P. borealis) chitin using KOH solvent and the influence of residual impurities on dissolution behaviour was investigated for the first time. Three chitin samples with purities ranging from 84 to 97 % w/w were compared, and results confirmed that chitin with lower purity can be successfully dissolved in KOH solvent, provided that minerals were removed prior to dissolution. However, dissolution behaviour and physical properties were strikingly different between the samples. Microscopic analysis of chitin particles allowed the differentiation between exoskeleton features and the identification of insoluble particles, providing potential new avenues to improve dissolution processes.