ABSTRACT
Crayfish are fresh water crustacean that look like a tiny lobster, fresh water crayfish [Procombarus clarki] had been introduced accidentally and appear in the River Nile and its resource all over Egypt during the last years. The objective of this study was to evaluate the chemical quality and composition of crayfish as a human food, and to introduce a new high quality crustacean organism as a new cheap source of animal proteins. Total thirty crayfish samples collected from different markets in Alexandria were analysied for total protein, amino acids using amino acids analyzer, fat, cholesterol, fatty acids [using GLC], ash, minerals, and some heavy metals [using atomic absorption spectrophotometer]. Also, total volatile basic nitrogen, pH, free fatty acids, and thiobarbituric acid value as a chemical quality index were mmeasured. The obtained results revealed good freshness and high chemical quality of crayfish, with regard to their ranges of total volatile basic nitrogen [28-35 mg/100g], pH [7.01-7.21], thiobarbituric acid [0.084-0.412] mg molanaldhyde/kg, and free fatty acids [0.56-0.93] mg/kg. Chemical composition and nutritive value of crayfish revealed mean values of total protein, fat, ash, and cholesterol contents 18.076%, 1.057, 1.48%, and 22.417 mg/100g, respectively. Minerals concentrations level were 0.61%, 443.22, and 356.45 micro g/g for phosphorous, iron, and magnesium, respectively. Amino acid pattern showed that Glutamic, Aspartic, Arginine, and leucine were abundant essential amino acids and oleic acid represented 44% of total fatty acids. Crayfish evoked high nutritional value as respect to higher content of total unsaturated fatty acids [73.689%] with 56.56%, and 15.08% monoioneic and polyioneic [with [greek small letter omega] and [greek small letter omega]] fatty acids also, high quality of protein which contain 55.703% essential amino acids. Also, this investigation showed that heavy metals concentration residue decreased in this order zinc > manganese > copper > chromium > cadmium > lead > nikie. Copper, chromium, and cadmium concentration were within the Egyptian permissible limits in all samples, but lead levels exceeded the maximum permissible limits in all samples and zinc exceeded this limit in 75% of examined samples. Information obtained in the present study can assist in developing quality standard for fresh crayfish in Egypt and recommended rules for its safety were mentioned