Abstract
This study was conducted to investigate the microbial and physico-chemical qualities of salted sun-dried Nile perch (Lates niloticus) products and frozen fish from various storage facilities in Mwanza, Tanzania. The bacterial flora, moisture contents (MCs), and water activity (Aw) were investigated using standard methods. A total of 120 samples were collected for microbiological analysis with 90 of the samples additionally analysed for MC and Aw. Findings showed that the mean total viable counts (TVCs) in salted sun-dried products sampled during rainy season was 4.5 log cfu/g in fish heads with MCs of 38.0% and Aw of 0.682. This was significantly higher (P 0.05). Fish belly flaps had TVCs of 3.3 log cfu/g at 26.4% MCs and 0.669 Aw in rainy season which were comparable (P>0.05) to those dried in the dry season. The microbial species recovered were Staphylococcus spp., Enterobacter spp., Psychrobacter spp., and Bacillus spp. Neither Escherichia coli nor extended-spectrum beta-lactamase producing Enterobacteriaceae were detected. Frozen Nile perch had TVCs of 5.7 log cfu/g on skin, 5.4 log cfu/g in gills and 2.9 log cfu/g in flesh and were within acceptable limit set by Tanzanian standards. These results reveal that dried Nile perch products are generally safe for human consumption; however, the recovered bacteria indicate a need of implementing hygienic procedures during processing of products for improved quality and safety. Key words: Salted sun-dried fish, microbial quality, food safety, physico-chemical parameters.
Highlights
Findings showed that the mean total viable counts (TVCs) in salted sun-dried products sampled during rainy season was 4.5 log cfu/g in fish heads with moisture contents (MCs) of 38.0% and Aw of 0.682
High TVCs were reported in salted sun-dried Nile perch products collected during the rainy season with mean counts ranging from 3.3 to 4.5 log cfu/g while those collected during the dry season had lower mean counts ranging from 2.9 to 3.1 log cfu/g (P
The study shows the relationship between TVCs, MC, and Aw obtained in salted sun-dried Nile perch products collected in the rainy season and dry season, in that, the increase of MCs and Aw was proportional to the increase of TVCs in samples
Summary
Nile perch (Lates niloticus) from Lake Victoria is one of the most important fish species for fisher folks in Tanzania as well as for the nation due to its economic and nutritional health benefits (Kirema-Mukasa, 2012).Fish are an important source of animal protein and other essential elements to sustain human health (Ikwebe et al, 2017; Immaculate et al, 2013; Majumdar et al, 2017). Nile perch (Lates niloticus) from Lake Victoria is one of the most important fish species for fisher folks in Tanzania as well as for the nation due to its economic and nutritional health benefits (Kirema-Mukasa, 2012). Nile perch of good quality are processed as fillets for export markets especially to the European countries and Asia while other fish parts are processed for domestic and regional African markets (Kabahenda and Hüsken, 2009; Kirema-Mukasa, 2012). The salted sun-dried Nile perch products are mostly exported to countries such as the Democratic Republic of Congo, Rwanda and Burundi (Kirema-Mukasa, 2012). The salted sun-dried Nile perch products have been widely marketed in East and Central African regional markets, limited information is available on their microbiological quality and safety aspects
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