Chemical Characterization of Cancer Pagurus, Maja Squinado, Necora Puber and Carcinus Maenas Shells

The crustacean exoskeleton presents several functions including the stabilization of the whole body of the animal, resistance to mechanical loads, and protection to the environment and against predators [1]. The structure of crustacean exoskeleton consists of an organic matrix constituted by α-chitin, proteins and carotenoid pigments and an inorganic fraction where calcium carbonate is the main constituent [2]. The relative percentages of these constituents depend on the species and within a certain species they present seasonal changes and also vary among different parts of the skeleton [3]. The crustacean skeleton is a byproduct from processing of crustaceans and represents a valuable raw material for different applications. Crustacean shells have been utilized in the preparation of fish feeds [4-5] and broilers [6]. The presence of chitin in crustacean shells may be a relevant factor as it is recognized its role in activation the innate immune system of fish [4]. This muco polysaccharide polymer can also modulate the fish gut microbiota [7]. Moreover, this by-product is also a source of carotenoid pigments [8] as well as the main raw material for the extraction of chitin [9]. Its utilization to uptake and removal of metal ions in solution was reported [10] but it can be simply used for composting [11]. About 20% of all crustaceans caught or farmed worldwide are crabs. Brown crab (Cancer pagurus), European spider crab (Maja squinado), green crab (Carcinus maenas), and velvet crab (Necora puber) are the most popular crab species consumed in Europe. Brown crab landings attained around 51,247 tonnes in 2014 where those in the United Kingdom represented more 60% of total landings [12]. The European spider crab landings were around 6,538 tonnes in 2014, mainly in France [12]. Green crab landings in 2014 were approximately 1453 tonnes, mostly in France and United Kingdom [12]. The landings of velvet crab were around 2448 tonnes in 2014, mainly in United Kingdom [12].