Assessment of Microbiological and Bio-chemical Quality of Fish in a Supply Chain in Negombo, Sri Lanka

Abstract This study aimed to investigate quality of fish landed in Negombo area and distributed in suburban areas in Western province of Sri Lanka. Hundred samples of large fish ( Katsuwonus pelamis and Euthynnus affinis ) and 60 samples of small fish ( Amblygaster sirm, Pterocaesio chrysozona, Stolephorus commersoni , and Sardinella albella ) were sampled from different stages of a supply chain at five and six sampling visits, respectively. All fish samples (N=160) were analysed for aerobic plate counts (APC) at 37 o C, Coliforms, feacal coliforms, Escherichia coli , Salmonella spp., Listeria monocytogenes , total volatile base nitrogen (TVB-N) while 130 were analysed for histamine. Water from fishery harbor basin, fishery harbour, ice manufcaturing plants and ice used in multiday boats were also analysed for microbiological parameters. Large and small fish contained APC in the range of 2.0 x10 2 - 2.0 x 10 6 and 8.0×10 3 - 2.0×10 8 cfu/g, respectively. Faecal coliform counts ranged between not detected (ND) and 90 MPN/g in large fish and between ND and >1100 MPN/g in small fish. 5% of large fish were contaminated with E.coli and ranged from ND to 15 MPN/g. E.coli was present in 70% of small fish samples and ranged from ND to >1100 MPN/g. Of the 160 fish samples, tested Salmonella spp were detected in nine occassions. Of the 160 fish samples, L. monocytogenes was found in eight Katsuwonus pelamis and one Sardinella albella fish. TVB-N of large fish were found at range of 1-67 mgN/100 g and 79% samples contained unaccptable levels. Small fish contained about 25.10-104.30 mgN/100 g while 78% samples exceeded acceptable levels. Histamine level of large and small fish, 26% and 83% of samples exceeded the maximum acceptable levels, respectively. Harbour basin water was heavily contaminated with Salmonella spp. (50%), Faecal streptococci (100%), Faecal coliforms and E.coli (100%). Ice samples (20%) from one ice plant were found contaminated with Salmonella spp.