Proximate composition and mineral contents of the blue crab (Callinectes sapidus) breast meat, claw meat and hepatopancreas Free

Abstract

The objective of this study was to determine the nutritional composition of the breast, claw meat and hepatopancreas of the blue crab (Callinectes sapidus). Samples were subjected to proximate (protein, fat, ash and moisture) and calcium, magnesium, phosphorus, potassium and sodium (Ca, Mg, P, K and Na) analyses. Protein, fat, ash and moisture of the breast, claw meat and hepatopancreas of the blue crab averaged 19.05, 0.59, 2.10 and 76.85 g/100 g, respectively. The results have revealed that this species is a rich source of protein, Ca, Mg, P and Na. Claw meat had higher protein concentrations (19.55 g/100 g) than both breast meat and hepatopancreas (18.81 g/100 g). Na was predominant element among minerals analysed. There were significant differences between Ca, Mg, P, K and Na contents of claw, breast meat and hepatopancreas of the blue crab. Information on the nutrient composition is needed to facilitate the processing, utilisation and marketing of blue crab products. Blue crab could balance human nutrition and could be used as an alternative dietary supplement of proteins and mineral matter.

Introduction

Utilisation of marine resources for human consumption has increased rapidly worldwide. As a whole, seafood products, including crustacean shellfish, have been lauded for their health promoting characteristics. Shellfish are nutritionally valuable sources of various minerals and high quality protein (Leu et al., 1981; Connor & Lin, 1982; King et al., 1990; Skonberg & Perkins, 2002; USDA, 2003).

Blue crab is one of the most important of shellfish. The main distribution of blue crab is on the North American coast. At the beginning of this century, it was in the north-eastern Mediterranean Sea and surrounding waters, in which most of the species have been, recognised (Holthuis, 1961).

The blue crabs which have commercial value and are distributed abundantly in the north-eastern Mediterranean are processed at processing factories in the local region. These processed products are exported to European countries (Türeli et al., 2002).

Nutritive values of different crab species have been previously investigated in various parts of the world (Krzeczkowski & Stone, 1974; Krzynowek et al., 1982; Vigh & Dendinger, 1982; Anthony et al., 1983; Sheets & James, 1983; Tsai et al., 1984; Siddiquie et al., 1987; King et al., 1990; Gates & Parker, 1992; Lee et al., 1993; Perry et al., 2001; Skonberg & Perkins, 2002; Türeli et al., 2002). Very limited data are available on the biochemical composition of crab in Turkey (Türeli et al., 2000, 2002; Gökoğlu & Yerlikaya, 2003; Çelik et al., 2004).

The potential health benefits related to blue crab consumption are because of the presence of proteins, vitamins and unsaturated essential fatty acids. Blue crab is also good source of various minerals. Therefore, it is so important human health. From these minerals, Ca and P are necessary to maintain an optimal bone development, more of both minerals being required during childhood and growing stages to prevent rickets and osteomalacia (Valverde et al., 2000). It is known that several aberrations in bone mineral homeostasis and bone metabolism result as a consequence of severe Mg deficiency in experimental rats. These include reduced bone growth and bone volume (Carpenter et al., 1992).

Ca also has an essential role in blood clotting, muscle contraction and nerve transmission. P is also important to maintain the pH, storage and transfer of energy and nucleotide synthesis. Mg is cofactor for enzyme systems (Food and Nutrition Board, National Research Council, 1989).

Fundamental knowledge of nutrient composition is needed to facilitate the processing, utilisation and marketing of the blue crab for human consumption. The purpose of this study was to determine the proximate composition and the mineral content of the blue crab commonly caught from north-eastern Mediterranean.

Materials and methods

Materials

Adult crabs, Callinectes sapidus, were harvested from Akyazan lagoon on the coast of the eastern Mediterranean Sea of Turkey, in December 2002, and transported live to the laboratory. Crabs were cooked by steaming for 10 min, and claw meat, breast meat and hepatopancreas were picked by hand. Three samples were prepared by blending the meat from twenty crabs.

Proximate analysis

Samples were homogenised and subjected to moisture and ash analyses using Association of Official Analytical Chemists (AOAC 1995) methods. Crude protein content was calculated by converting the nitrogen content, determined by Kjeldahl's method (AOAC, 1995). Fat content was determined by the acid hydrolysis Soxhlet system (B-811; BUCHI, Brussels, Belgium) in the laboratory of Cukurova University Faculty of Fisheries, Adana, Turkey.

Mineral analysis

Calcium, magnesium, sodium and potassium content were analysed with an AAS (AOAC, 1995). Phosphorus was measured by spectrophotometer in Laboratory TUBITAK M.A.M., Izmit, Turkey (AOAC, 1995).

Statistical analysis

The data were subjected to analyses of variance (one-way Anova) at the 5% level using SPSS 10.1 version (SPSS, 1999) and Duncan's multiple range test was performed to separate differences among means.

Results and discussion

Proximate composition

The results of proximate analysis of the blue crab are shown in Table 1. Protein, ash and moisture contents of the claw, breast meat and hepatopancreas of the blue crab averaged 19.05, 2.10 and 76.89 g/100 g, respectively. These values are similar to those for Dungeness crab (Cancer magister), reported as 17.8, 2.6 and 77.6 g/100 g, for protein, ash and moisture, respectively (King et al., 1990), and are somewhat higher in protein than values reported for blue crab composite (15.6 g/100 g) and claw mead (13.9 g/100 g) samples (Lee et al., 1993). Skonberg & Perkins (2002), found similar values in the green crab (Carcinus maenus) according to the present study.

Protein content was the highest in the claw meat (19.55 g/100 g) compared with the other parts (18.81 g/100 g) of blue crab and did not differ significantly between hepatopancreas and breast meat. Krzeczkowski & Stone (1974), reported similar result (18 g/100 g) in claw meat of snow crab (Chionoecetes bairdi).

Moisture value was significantly (P < 0.05) higher in breast meat (79.05 g/100 g) than the other parts (73.60–78.02 g/100 g). Siddiquie et al. (1987) found that moisture content of body and claw meats in the Portunus pelagicus is 78.15–79.05 g/100 g. Hepatopancreas samples had the highest content (2.15 g/100 g) of ash among the three groups. Anthony et al. (1983) reported a similar content in the raw blue crab (2.06 g/100 g) and cooked blue crab (2.42 g/100 g).

The hepatopancreas (0.90 g/100 g) possessed considerably higher fat content than the claw meat (0.44 g/100 g) and breast meat (0.44 g/100 g). Krzynowek et al. (1982) found average fat contents of 1.1, 1.2 and 0.9 g/100 g for jonah (Cancer borealis), roch (Cancer irroratus) and red crab (Geryon quinquedens) caught off in the north-west Atlantic region. But it is not clear which portions of the crab body were evaluated.

Mineral contents

The mineral contents of the blue crab are listed in Table 2. Significant differences in mineral content were observed between claw meat, breast meat and hepatopancreas samples. Na was the predominant element among minerals analysed. Hepatopancreas samples had significantly higher Na concentrations than the samples of breast and claw meat. Ca, Mg, P, K and Na concentrations in the blue crab meat and hepatopancreas averaged 432.53, 92.34, 180.94, 65.47 and 840.19 mg/100 g, respectively. Ca and P were the highest in the breast meat. Mg and K were the most concentrated in the claw meat.

The concentration of minerals in meat of crab species can be influenced by a number of factors such as seasonal and biological differences (species, size, age, sex and sexual maturity), food source and environment (water chemistry, salinity, temperature and contaminants). The differences in mineral contents of the crabs used in our study and those reported in the literature are thought to be due to the above mentioned reasons (Anthony et al., 1983; King et al., 1990; Lee et al., 1993; Skonberg & Perkins, 2002; Gökoğlu & Yerlikaya, 2003; USDA, 2003).

In the present study, high Ca (398.2–455.4 mg/100 g) and Na (663.9–1133.0 mg/100 g) values were observed in parts of the blue crab. Callinectes sapidus is a euryhaline organism and can, therefore, function in a wide range of salinities, as their migratory and reproductive habits indicate. They are also efficient osmoregulators, and maintain their internal environment within narrow realms over a wide range of salinities.

The blue crabs in low salinity seawater seem to overcompensate for this lower external salinity by maintaining a greater quantity of Ca in their haemolymph than would normally be expected if they simply osmoregulated postmoult to their normal condition (Sheets & James, 1983). Crabs used in this study were caught in Akyazan lagoon where salinity decreases considerably (about 11%) in some seasons of the year.

Ca and Na were deposited in the meats and hepatopancreas of the blue crab, because the samples used here were adult crabs. Vigh & Dendinger (1982) reported that there was a decrease in Ca concentrations from 0 to 3 days postmoult, probably because mineral was rapidly deposited in cuticle, with a gradual return to normal postmoult values, and Ca quickly returned to normal values.

Conclusions

The results reported here demonstrated that breast, claw meat and hepatopancreas of blue crab were rich in terms of protein, major and essential elements. Ca, Na, Mg and P are plentiful when compared the recommended daily allowances in the Food and Nutrition Board National Council. It is possible to infer that the blue crab could be used in the balance of human nutrition and as a supplement of protein and mineral matter. It is also hoped that this study will be important for the local fishing industry in the north eastern Mediterranean coasts.

Acknowledgments

This study was supported by the Cukurova University Research Fund.

References