Pathogenic Organisms in Pre-Brined Fresh and Stored Hot Smoked Clarias gariepinus (Burchell, 1822)

Abstract

This study was carried out to assess the microbial qualities of smoked catfish (Clarias gariepinus) pretreated with sodium chloride, hot smoked and stored for a 2-weeks duration at ambient temperature. The average body weight of fish was 700g and the fresh catfish were treated with salt (sodium chloride) at a rate of ¼w/v (700g of fish)(T1 and T2) and ⅛w/v) (700g of fish)(T3 and T4) i.e soaking in salt solution at rate of 1/4 or 1/8 of the fish body weight each for either 30 minutes or 1hour prior to smoking. Fish samples were selected, washed and distributed into five groups including the control sample (T5). The four groups were subjected to soaking treatment for 30 minutes and 1hour respectively before drying. The non-treated (without salt T5) catfish served as the control. After soaking treatments, all the catfish belonging to both treatment and control groups were subjected to hot smoking and slowly cooked with wood heat at 70oC. The control sample was smoke dried without prior soaking in salt solution. The smoked samples were stored for one and two weeks before analyses. The fresh fish, control and the treated samples showed different types of microbes. Smoke dried fish had the lower microbial loads during the weeks of storage. The results from this study revealed the presence of eight bacterial species namely; Staphylococcus aureus, Micrococcus luteus, Samonella sonnel, Enterobacter aerogenes, Bacillus cereus, Salmonella typhimurium, Escherichia coli , Proteus mirabilis and five fungi species namely; Aspergillis flavus, Aspergillis fumigatus, Rhizopus stolonifer, Rhizopus oryzae, and Candida krusei. Escherichia coli had the highest bacteria load of 3.5× 105 cfu/ml immediately after smoking while P. mirabilis has the least bacterial count of 2.3 x 103 cfu/ml after one week of smoking the fish. A. fumigates has the highest fungi of 7.3× 104 sfu/ml in fresh C. gariepinus while R. oryzae has the least fungi count of 1.1 x 102 sfu/ml after two weeks of smoking the fish. The result from this study revealed that common salt can extend the shelf life of hot smoked catfish (C. gariepinus) between one to two weeks under ambient storage condition, before the action and effects of spoilage microorganisms become significant.