& W ries ild e li h fe is S F , c Pires et al., Poult Fish Wildl Sci 2017, 5:1 y i e r Poultry, Fisheries & t n l c u e DOI: 10.4172/2375-446X.1000181 o s P ISSN: 2375-446X Wildlife Sciences Research Article Article Open Access Chemical Characterization of Cancer Pagurus, Maja Squinado, Necora Puber and Carcinus Maenas Shells Pires C1,3*, Marques A1,3, Carvalho ML2 and Batista I1,3 1Division of Aquaculture and Upgrading (DivAV), Portuguese Institute for the Sea and Atmosphere, Rua Alfredo Magalhães Ramalho 6, Libson, Portugal 2Center of Atomic Physics, University of Lisbon, Lisbon, Portugal 3Interdisciplinary Center of Marine and Environmental Research, University of Porto, Av. General Norton de Matos, Matosinhos, Portugal Abstract The present study is a characterization of the chemical composition of crab shells from brown crab, spider crab, velvet crab and green crab. The chitin content of crab shells varied between 9.7 and 16.4% and the protein content was in the range of 13.2 to 20.7%. Ash was the major constituent and accounted for more than 70%. The total carotenoid content ranged between 0.6 and 9.3 µg/g depending on the crab species. Concerning macro elements their content followed the descending order in all species: Ca>P>S>Sr>Cl>K. In the case of trace elements content the descending order in brown crab was: Br>Fe>Rb>Cu>Zn; in spider crab was: Br>Fe>Rb>Zn>Cu and in velvet and green crab was: Br>Fe>Zn>Rb>Cu. The level of contaminants was relatively low and the descending order of their content was the following: As>Pb>Cd>Hg. Crab shells are a potential source of chitin and the levels of macro and trace elements together with the low contaminants concentration make them a raw material for chitin production or utilization as feed ingredients or fertilizers. Keywords: Crab exoskeleton; Chemical composition; Chitin; of the shell of brown, spider, green, and velvet crabs. The chemical Protein; Carotenoids; Mineral fraction characterization of shells involved the determination of chitin, protein and ash content, total carotenoids and mineral fraction (macro and Introduction trace elements and contaminants). The crustacean exoskeleton presents several functions including the Materials and Methods stabilization of the whole body of the animal, resistance to mechanical loads, and protection to the environment and against predators [1]. Brown crab males and females (Cancer pagurus) caught during The structure of crustacean exoskeleton consists of an organic matrix spring (n=24), summer (n=20), autumn (n=20) and winter (n=20) in constituted by α-chitin, proteins and carotenoid pigments and an the Scottish coast and during summer in French waters (n=18) were inorganic fraction where calcium carbonate is the main constituent [2]. purchased alive from a local importer. Males and females from green The relative percentages of these constituents depend on the species crab (Carcinus maenas, n=48) and velvet crab (Necora puber, n=46) and within a certain species they present seasonal changes and also vary caught in the Scottish coast during summer and spider crab (Maja among different parts of the skeleton [3]. The crustacean skeleton is a by- squinado, n=20) during autumn were purchased alive from a local product from processing of crustaceans and represents a valuable raw importer. The muscle was separated and shells were hand washed material for different applications. Crustacean shells have been utilized with hot tap water to remove flesh residues, lipids and other materials. in the preparation of fish feeds [4-5] and broilers [6]. The presence of Washed and dried shells were crushed to small pieces or powdered and chitin in crustacean shells may be a relevant factor as it is recognized stored at -20°C until further analysis. its role in activation the innate immune system of fish [4]. This muco Chitin extraction polysaccharide polymer can also modulate the fish gut microbiota [7]. Moreover, this by-product is also a source of carotenoid pigments [8] Chitin was extracted by acid treatment (demineralization) followed as well as the main raw material for the extraction of chitin [9]. Its by alkaline protein extraction (deproteinization) [9]. The quantity of the utilization to uptake and removal of metal ions in solution was reported chitin expressed as percentage of the shell was calculated after this process. [10] but it can be simply used for composting [11]. About 20% of all crustaceans caught or farmed worldwide are crabs. Brown crab (Cancer Protein content pagurus), European spider crab (Maja squinado), green crab (Carcinus The protein content of brown crab shell was calculated by the maenas), and velvet crab (Necora puber) are the most popular crab following formula: 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 *Corresponding author: Pires C, Division of Aquaculture and Upgrading (DivAV), were around 6,538 tonnes in 2014, mainly in France [12]. Green crab Portuguese Institute for the Sea and Atmosphere, Rua Alfredo Magalhães landings in 2014 were approximately 1453 tonnes, mostly in France Ramalho 6, Lisbon, Portugal, Tel: +(351) 213 027 000; Fax: (+351) 213 015 948; E-mail: [email protected] and United Kingdom [12]. The landings of velvet crab were around 2448 tonnes in 2014, mainly in United Kingdom [12]. Received April 19, 2016; Accepted June 08, 2017; Published June 16, 2017 Citation: Pires C, Marques A, Carvalho ML, Batista I (2017) Chemical The available information on crustacean waste is very scarce. In Characterization of Cancer Pagurus, Maja Squinado, Necora Puber and Carcinus one report published by Sea Fish Industry Authority is estimated a Maenas Shells. Poult Fish Wildl Sci 5: 181. doi: 10.4172/2375-446X.1000181 quantity of 3,500 to 7,000 tonnes of crab wastes assuming that 25% to Copyright: © 2017 Pires C, et al. This is an open-access article distributed under 50% of whole crabs are processed in UK [13]. the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and The objective of this work was to evaluate the chemical composition source are credited. Poult Fish Wildl Sci, an open access journal Volume 5 • Issue 1 • 1000181 ISSN: 2375-446X Citation: Pires C, Marques A, Carvalho ML, Batista I (2017) Chemical Characterization of Cancer Pagurus, Maja Squinado, Necora Puber and Carcinus Maenas Shells. Poult Fish Wildl Sci 5: 181. doi: 10.4172/2375-446X.1000181 Page 2 of 6 P (%)=100–(Chitin (%)+Ash (%)). Victoria, Australia) [15]. Mercury was analyzed by atomic absorption spectrophotometry according to test method 7473 [16] using a Hg Carotenoid content analyzer Leco, AMA 254. In all analyses, a minimum of three replicates Total carotenoids were measured by UV/Vis spectrophometry at was performed per sample. a wavelength of 468 nm. One gram of ground crab shell was extracted four times with 5 mL of acetone for 30 min. and all extracts were pooled Results and Discussion and 2.5 mL of water added. The carotenoids were extracted twice with Chitin content 10 mL of hexane. Both hexane extracts were pooled and 5 mL of a 5% No significant differences between the chitin content of males NaCl solution were added and dried with anhydrous Na2SO4. The total of carotenoids content (using astaxanthin as a standard) in the extracts and females were recorded in the shells of all species except females was calculated using the formula: harvested in Scotland during the spring which have higher chitin V××1000 MW content than males (Figure 1A). Furthermore, the chitin content of Total carotenoid content (µgg-1 of biomass)= ext spider crab was significantly higher than that of other crab species. ε 1% ××1 W 1cm sample The chitin content of crab shell presents a wide variation within these species but the results obtained in the current work were of the same where A is the absorbance at 468 nm, Vext is the volume of the extract, 1% order of magnitude of those reported by other authors. Thus, chitin MW is the molecular weight of astaxanthin 596.84 (g/mol), ε1cm is the content in the range of 12.6% and 15% (dw) was reported for green crab coefficient of extinction of astaxanthin 124000 mol-1L.cm-1 and W sample shell [17,18]. Higher chitin content (27.4%) was referred for the shell of is the weight of the sample (g). Carcinus mediterraneus [19]. Different sections of the snow crab were Ash content analysed and obtained levels of chitin between 18.70% and 32.25% [8]. On the other hand, lower chitin content (6.83%) was determined in a Ash content was determined according to the AOAC freshwater crab shell [20]. methodology [14]. Protein content Elemental analysis and contaminants (Hg, Cd and Pb) The protein content of the different crab species shells was in the Energy dispersive X-ray fluorescence (EDXRF) was employed to range of 13.2% and 20.7% (Figure 1B). The level of this constituent in quantify Cl, S, K, Ca, Fe, Cu, Zn, As, Br and Sr [15]. Sodium, cadmium the male shell of all species was similar to that of female shells with and lead were quantified by Flame Atomic Absorption Spectrometry exception of winter brown crab harvested in Scotland. Lower protein (FAAS) in a Spectra AA 20 spectrometer (Varian Australia, Mulgrave, content between 4.31 and 7.06% was reported in the green crab shell 20.0 25.0 (A) F (B) F d d M g g M g 16.0 20.0 fg def ef c c bc bc cd cd cde abc bc abc bc