Compositional Evaluation of Local Smoked Nigerian Mackerel (Scomber scombrus)

Abstract

Effects of different energy sources using sawdust, melon husk, rice bran and electric oven (control) were investigated on the chemical composition of local fresh mackerel (Scomber scombrus). For this purpose, proximate, mineral and amino acid compositions of the smoked fish were determined using standard analytical technique. The results showed the range of crude protein, crude fat, crude fibre, ash, moisture and carbohydrate contents (%) as; 57.80 – 70.20, 7.41 – 17.51, 8.48 – 11.25, 4.20 – 5.70, 3.33 – 5.28 and 0.79 – 3.42, respectively. Sodium was found to be more abundant in all the samples (7.10 – 12.25 mg/100g) compared with potassium (4.40 – 9.90 mg/100g) and magnesium (5.05 – 9.70 mg/100g) while phosphorus was the highest concentrated mineral (12.90 mg/100g) recorded in fish sample smoked with melon husk heat source. Harmful heavy metals such as lead and cadmium were not at the detectable range of atomic absorption spectrophotometer (AAS). The amino acid revealed that only Scomber scombrus fish sample smoked with melon husk enhanced the contents of total amino acid (TAA) and total essential amino acid (TEAA) by 1.05 and 1.20%, respectively while sawdust and rice bran heat treatments reduced TAA and TEAA. The essential aromatic amino acids (EArAA) and total sulphur amino acids (TSAA) contents were increased in all the samples smoked with different heat sources. Predicted protein efficiency ratio ranged between 2.21 and 2.61. The first limiting amino acid (LAA) for all the smoked samples was Ile except sample smoked with rice bran which has Val as LAA. Although the results of smoked fish samples showed deviations in nutrients from the results of sample dried with electric oven but over 80% of the mineral and more than 85% of the protein were still retained in smoked fish.

Keywords: Agricultural wastes, Heat sources, Scomber scombrus, Chemical composition.