The Blue crab (Calilinectes amnicola) which belongs to phylum arthropoda, is an important food item in coastal West Africa. Its by-products for example the shells can be used for the preparation of value added products like chitin, chitosan and carotenoid pigments. Chitosan is one of the most important derivatives of chitin and is a major component of the shells of crustaceans such as shrimps and crabs. The present study was undertaken to study the physicochemical parameters from the crab shell waste from Lagos Lagoon, Nigeria. The physicochemical properties like 1) Ash content was obtained by heating the sample in a muffle furnace at 550°C for 2hrs until constant weight was achieved. The crucible was then cooled, weight and the ash content calculated in % which was found to be 0.3%, 2) Moisture content was determined by gravitational method and found to be 10.99%, 3) Solubility was determined by placing 0.1 gm in centrifuge tube with 10 mls of 1% acetic acid, the solution was then centrifuged and the supernatant decanted, the undissolved was dried at 60°C, weighed and % solubility determined which was found to be insoluble, 4) Yield of prepared chitosan was determined by taking the dry weight of crab shells before treatment and the dried weight of prepared chitosan after treatment and found to be 13.00%, 5) Degree of de-acetylation was determined using a Fourier Transform Infra Red (FTIR) instrument with frequency of 4,000–400 cm-1 and found to be 49.65, 6) Protein content was determined by AOAC 2005 method and found to be 31.62%, 7) Fat content was determined by continuous extraction method using Soxhlet extractor apparatus and found to be 2.4%. The minerals contents were determined using AOAC and showed negligible amount as some of them were undetected except zinc and iron which showed a value of 4.77 and 5.28 respectively. Our result indicated the value of different parameters of chitosan from crab shell waste from Lagos lagoon.

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