Length-based variations in deposition of chitin in the exoskeleton of Penaeus monodon and P. indicus

Shrimp waste produced at the processing factories is a burden to the environment. Nevertheless, it is a raw material for extraction of chitin which is with more commercial uses. In this study chitin was extracted from shrimp waste collected from three different length ranges (5-10cm, 10-15cm, 15-20cm) of Penaeus monodon and P. indicus from a local small-scale processing factory, to determine the most suitable length class of shrimps to obtain a higher chitin yield. Dried shrimp waste was preconditioned by soaking in acetic acid, demineralized by treating with HCl and deproteinized by treating with NaOH.  Extracted chitin was odourless, and pinkish white and off-white in P. monodon in P. indicus respectively. Highest chitin yield was from the largest size range of both species, P. monodon (30.5%) and P. indicus (27.86%). Ash, moisture, fat and nitrogen of extracted chitin were 0.98%, 5.80% and 6.16 % in P. monodon and 0.98%, 5.72% and 6.22% in P. indicus of dry weight respectively, which were matched with the moisture content (5.5%), ash (0.3%) and nitrogen (6.9%) of chitin available in the market. The chitin extracted from P. indicus of 5-10 cm length range had a moisture content of 5.72% and a nitrogen content of 6.22%, which were the closest to the moisture and crude nitrogen in the pure commercial chitin. Ash content (0.98%) of all the extracted chitin were comparable to those of pure chitin. This indicates that chitin extracted from shrimp waste in the processing industry is comparable to commercially available chitin and therefore shrimp waste is a suitable source for extraction of chitin for commercial purposes.