Biochemical Quality Indices of Blue Swimmer Crab ( Callinectes sapidus ) Meat

| This study was planned to investigate the proximate composition, quality indices, amino acids, fatty acids, volatile aromatic compounds and minerals content of blue swimmer crab meat. Blue crab (Callinectes sapidus) samples (average weight was 140.13±0.13g) were obtained from Baltim fish market, Kafar Elshaikh, Egypt during July, (2019). Blue crab meat samples were stored -18°C for 12 hrs. They were washed with tap water, manually dis-carapaces, then meat obtained was rewashed carefully and drained. The obtained results showed that the major constituents (wet wt.) of raw crab meat were 83.59% moisture, 9.12% crude protein, 1.80% lipid, 1.22% ash and 4.27% carbohydrates content. In addition, values of quality criteria of carp flesh were 7.35 pH, 47.42 mg/100g total volatile basic nitrogen (TVB-N), 0.19 mg/100g trimethylamine nitrogen (TMA-N) and 0.15 mg Malonaldhyed/kg sample thiobarbituric acid (TBA). Also, crab meat contained 19 volatile aromatics compounds, 8 essential amino acids (EAA), 9 nonessential amino acids (NEAA), 8 saturated fatty acids (SFAs) and 7 unsaturated fatty acids (USFAS). In addition, it contained high levels of Na, K, Ca and Mg. In general, this study confirms that blue crab meat is an important source of valuable nutrients AAS, FAs and major elements.


Advances in Animal and Veterinary Sciences
September 2020 | Volume 8 | Issue 8 | Page 862 sinensis) as reported by Gu et al., (2013). And also,Sodium,Potassium,Calcium,Magnesium and Zinc content were 102.8,136.4,216.8,79.5 and 9.84 mg\100g, respectively as reported by Silambarasan et al. (2016). In Egypt, total production of crab during 2017 was estimated about 5859 tons (3.21% of total catch 1.822.800 tons) as reported by the Generally Authority of Fish Resources Development (GAFRD, 2017). Therefore, this work aims to determine the biochemical analysis of raw blue crab meat.

CRab samples
About 25 kg of raw blue crab (Callinectes sapidus Rathbun, 1896) samples were purchased from Baltim Fish Market, Kafar Elshaikh, Egypt during July, 2019. The blue crab was transported immediately using ice box within 5 hours to Fish Processing and Technology Laboratory, Elqanater Elkhairia Fish Research Station, National Institute of Oceanography and Fisheries. The average weight (Mean ± SD) of blue crab was 140.13±0.13g. Crab samples were stored -18°C for 12 hrs, to remove their carapaces easily. They were washed with tap water, dis-carapaces and viscera were manually removed. Crab flesh were carefully rewashed, drained with plastic net and analyzed.

CHemiCal Composition
Chemical composition of crab meat; moisture content of crab meat by a drying oven, at 105°C for overnight, total crude protein (total N×6.25) by Kjeldahl apparatus, total crude fat by Soxhlet apparatus using petroleum ether, and ash content by a muffle furnace at 550°c till obtained a constant weight were determined according (AOAC, 2005).

Quality indiCes pH value
The pH values of raw crab meat were measured were estimated by pH meter (Orion pH meter Model 420 A) as the method described by Zaika et al. (1976). total volatile bases-nitRogen (tvb-n) Content TVB-N content was estimated by macro-distillation method of Person (1976) was determined as follows: 10g of minced crab meat was macerated with 100 ml. of distilled water. Two grams of magnesium oxide (MgO) and antifoaming substances were added and the distillation of ammonia was carried out. The ammonia received in boric acid solution (2%) containing methyl red as indicator and titrated by sulphuric acid (0.1N). The results were expressed as mg/100g sample. TVB-N mg/100g sample = (V × N × 14 / sample wt.) ×100 Where; V: Volume taken of H 2 So 4 ; N: Normality of H 2 So 4 (0.1 N); The results obtained were expressed as mg TVB-N mg/100g sample (wet wt.).

tRimetHylamine-nitRogen (tma-n) Content
TMA-N was determined calorimetrically using the standard method as described in the (AOAC, 2005). The results obtained were expressed as mg TMA-N mg/100g sample (wet wt.). tHiobaRbituRiC aCid (tba) value TBA value was estimated as the method described by (Tarladgis et al., 1960) as follows: Ten grams of sample were blended with 97.5 ml of distilled water and 2.5 ml of 4N HCL and distilled and then 50 ml of distillate into test tube, sealed were obtained. After that, 5 ml of the distillate was added to 5 ml of TBA reagent (0.2883 g TBA/100 ml of 90% glacial acetic acid) into stopper tube, and then the mixture was heated in a boiling water bath for 35 minutes. After cooling at the ambient temperature, the absorbance was measured at 538 nm using digital Spectrophotometer ( J.P. SELECTIA S.A) against a blank which carried out in the same manner using 5 ml distilled water with 5 ml. TBA reagent. Then, the TBA value was calculated as mg. Malonaldehyde /kg sample (wet wt.) according to the following equation: TBA value (mg MDA\kg sample)= 7.8×Absorbance (at 538 nm) Where; 7.8: constant.

amino aCids Composition
Total amino acids (TAAs) were determined according to the methods described by (Moore et al., 1958) as follows: Sample of 20-25mg was placed in glass hydrolysis tube containing 10 ml of 6 N HCl with 0.1% mercaptoethanol. The tube was sealed and heated in an oven at 110 o C for 24 hrs. The hydrolyzed sample was then cooled to room temperature and filtered through Whatman No. 1 filter paper. The tube and precipitate on the paper was washed with distilled water and the filtrates were then completed to a 25ml in a volumetric flask. Five ml of the filtrate were transferred to a 25ml beaker and placed under vacuum in a desiccator over Potassium hydroxide (KOH). The resulted dried residue was dissolved in one ml of sodium citrate buffer of pH 2.2 and stored at 4°C until analyzed by Beckman Amino Acid Analyzer Model 119 CL. The results obtained were expressed as g/100g sample (on dry wt. basis). This determination was done at amino acids Lab., Agricultural Research Center, Cairo, Egypt.

deteRmination oF Fatty aCids
The method of (AOAC, 2000) was conducted for lipid extraction from sample using chloroform methanol (2:1 v/v). The lipid samples were saponified over-night with

Advances in Animal and Veterinary Sciences
September 2020 | Volume 8 | Issue 8 | Page 863 ethanoic KOH (20%) at room temperature (Vogel, 1975). In order to have more representative samples, lipid extracts from crab samples were pooled together for preparation of fatty acid methyl esters (FAME) and two such pooled samples were analyzed. The lipids were trans methylated using ethanoic koh (20%) at room temperature to obtain FAME. FAME was analyzed by (a Pye Unicam series 304 Gas Chromatography) for identifying the individual fatty acids. The separation of fatty acid methyl esters was conducted using a coiled glass column (1.5m×4 mm) packed with Diatomite (100-20 mesh) and coated with 10 % polyethylene glycol adipate (PEGA). The column oven temperature was programmed at 8 o C/min from 70 º C to 190 º C, then isothermally at 190 º C for 25 min with nitrogen at 30 ml/min (Farag et al., 1986).

volatile aRomatiC Compounds
Volatile aromatic compounds were determination by Gas chromatography according to the methods described by Gu et al. (2013). Analytical of volatile compounds was performed by using a Perkin Elmer Auto system XL equipped with flame ionization detector (FID). A fused silica capillary column ZB5 (60m x 0.32 i.d.) was used. The oven temperature was maintained initially at 50°C to 240°C at a rate of 30°C/min. Helium was used as the carrier gas, at flow rate 1.1ml/min. The injector and detector temperatures were 230 and 250°C, respectively. This determination was done at Flavors, Taste and Smell Lab., National Research Center, Cairo, Egypt.

mineRals Composition
Minerals composition; Na, K, Ca, ph, Fe, Mg, Mn and Zn were determined according to the methods described by Walsh (1955) using an atomic absorption spectrophotometer (ICE 3000 SERIES, England). 1g of oven-dried crab sample was put in combustion degree oven 500°C for two days. The samples were digested with 3 ml concentrated nitric acid and 1 ml of perchloric acid. The mixture was placed on a water bath till a clear colour was obtained. So the sample is ready to estimate the concentration of the elements steps measurements device. This determination was done at Central Lab., Faculty Agriculture, Zagzig University.

statistiCal analysis
The results obtained were subjected to descriptive statistics and tested using analysis of variance and Duncan's multiple range tests using SPSS version 20 Statistical Package for Windows (Differences were considered to be significant when p<0.05). Table 1 shows the proximate analysis and quality criteria of raw blue crab flesh. The chemical composition (ww) of crab meat was 83.59% moisture, 9.12% crude protein, 1.80% lipid, 1.22% ash and 4.27% carbohydrates content. Our results are lower content of crude protein, lipid and ash than 18.53%, 3.27%, 5.74%, respectively of crab (Chiromantes boulengeri) (Khaled and Khafaji, 2018) and 15.30%, 2.30%, 5.70%, respectively of crab (Atergatis roseus) (Salama and Mona, 2018). However, moisture was higher content than (73.50 -76.40%) those findings by the same authors. Concerning carbohydrates, it is lowest content than 2.70% of estuarine crab (Scylla serrata) ( Jelin and Keerthika, 2017) and also 2.10% of swimming crab (Charybdis smithii) (Yogesh et al., 2019). This variation in chemical composition of crab is affected by season and location of catch, feeding, crab species, age, sex etc. . With regard to quality indices of crab meat (Table 1), values of pH, TVB-N, TMA-N and TBA of crab flesh were 7.35, 47.42 mg/100g, 0.19mg/100g and 0.15mgMDA/kg sample, respectively. The pH value was higher than 6.60 (Mehta and Nayak, 2017), 6.16 (AbouZeed, 2016) and 8.50 (Ibrahim, 2017) of some different crustaceans species. Also, the TVB-N content was higher than 4.06 and 4.86 mg/100g of crayfish and shrimp, respectively (Ibrahim, 2017). TBA content was lower than 0.63 and 0.79 mg/100g of crayfish and shrimp, respectively (Ibrahim, 2017). Also, the TBA content was lower than 0.25 MDA/kg sample (Shimaa et al., 2014). Our data showed that TVN value was high compared with previous studies, may be refer to handling steps of crab from catch to marketing.

Data in
volatile aRomatiCs Compounds oF blue CRab meat Figure 1 and Table 4 and show that 23 components of volatile aromatic compounds (ww) of raw blue crab meat were determined and identified. These compounds could be divided into 7 groups.     Wilson et al. (2017) and Yogesh et al. (2019); they found that Mg and P levels were 3.9 and 34.31 mg\100g of swimming crab (portunus sanguinolentus) and swimming crab (Charybdis smithii). concLuSIon Based on the results obtained, total volatile basic nitrogen (TVB-N) of crab meat was a high content but it does not exceed the permissible level of crustaceans. Crab meat contained 19 volatile aromatics compounds, 7 essential amino acids (EAAs), 9 nonessential amino acids (NAAs), 8 saturated fatty acids (SFAs) and 7 unsaturated fatty acids (USFAs). Also, total SFAs (was higher than total USFAs. In addition, it contained accepted levels of Na, K, P, Ca and Mg. Generally, this study recommends that blue crab meat is an important source of valuable nutrients, AAS, FAs and major elements.

AutHorS contrIbutIon
All authors contributed equally to this article.

conFLIct oF IntErESt
The authors have declared no conflict of interest.

rEFErEncES
• AbouZeed AS (2016). Utilization of Squilla for the production of some value-added fishery products. Ph.D. thesis, Fac. Saba Pasha Agric. Alex. Univ., Egypt. • AOAC (2000). Official methods of analysis of the association of