Effects of processing on bacteriological, proximate, hydrocarbon content and organoleptic indices of Scomber scombrus

Abstract

Effects of boiling, smoking and frying on the organoleptic quality, bacteriological count, proximate composition and total hydrocarbon contents of  Scomber scombrus fish sold in Ikot Ekpene Metropolis were investigated. Fillets of fresh S. scombrus were made, and processed by smoking, boiling and  frying methods. Portions of the fish sample were aliquoted, and used to carry out sensory evaluation, plating aliquots of diluents onto nutrient agar  plates (for total viable count (TVC), and on Manitol Salt agar (for total staphylococcal count (TSC). Standard methods were used to determine moisture,  ash, total lipids and crude protein contents. Total hydrocarbon content was determined by toluene extraction and measurement of absorbance of filtrate  spectrophotometrically. Sensory quality obtained using smoke-drying and frying methods scored significantly higher than that of boiling and the control  (p<0.05). TVC of samples were lower than in the control fish sample after processing, increasing over the 4-day period, although negligible when  compared to the control. TVC were lowest in samples processed by frying. TSC decreased in all fish samples after processing, except in the control fish  sample. Fried Scomber scombrus samples also showed no trace of S. aureus. Moisture, lipid, crude protein and ash contents of control S. scombrus were  68.78±1.02, 2.03±0.11, 20.14±0.06 and 0.09±0.32 respectively. The changes in moisture, lipid, crude protein and ash contents were statistically significant  (P<0.05) in processed fish samples. Total hydrocarbon content also increased in processed fish; 2.914±0.005 for smoke-dried, 2.168±0.001 for fried and  1.538±0.009 for boiled, as against 1.412±0.011 in the control sample. Overall bacteriological quality indices, the proximate content and total hydrocarbon  contents of samples demonstrated frying and smoking as preferable processing methods for Scomber scombrus.