Effect of short ultrasound treatment as a chitin pre-treatment: a strategical step to transform shell wastes in chitooligosaccharides

Chitooligosaccharides (COS) are innovative bioactive oligosaccharides obtained from chitin with applications in many areas such as in food and health as a bioactive ingredient. Québec has a huge potential in the production of these molecules because of its relevant role in the processing of marine products such as snow crab and American lobster, which generates huge amounts of shell wastes, rich in chitin. Although chitin from marine shells constitutes an interesting source of COS, the latter high crystallinity hinders the transformation of chitin into COS without the use of toxic and pollutant chemicals.

The objective of this work is to assess the effectiveness of ultrasound (US) treatment on the diminution of chitin crystallinity and relaxation of the hydrogen bonds in it. Particle’s size distribution was standardized and then 1% (m/v) chitin suspensions were UStreated at 40 W for 15 min (30s cycle, ON/OFF), in an ice-bath, in a high-intensity ultrasonic processor (model Vibracell VCX 750 Sonics, Sonics and Materials Inc, Newtown, United States), with a 13 mm tip and an amplitude of 40%. Two commercial chitins: from crab (naturally more crystalline) and from squid (less crystalline structure) were compared to extracted chitins from shell wastes of crab and lobster. Differences in water solubility, crystallinity (X-ray diffraction, XRD), deacetylation degree and chain bonds relaxation (FT-IR) were monitored in treated and non-treated samples. The US treatment was able to promote a higher increase in solubility in squid chitin, followed by the commercial crab chitin, crab and lobster. Characteristic chitin peaks (2θ) at nearly 10° and 20° in the XRD analyses indicated a decrease in crystallinity in US-treated samples in different extents for each chitin source.

These results encourage the investigation of emergent and green technologies such as US in the transformation of food wastes into high added-value ingredients.