Microbiological and chemical quality of kayabo a salted sun-dried nile perch lates niloticus from Lake Victoria, Tanzania
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Date
2017
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Publisher
Sokoine University of Agriculture
Abstract
Fish processing companies in Tanzania are basically for the export market with strict
control and monitoring of the food safety hazards. The major processors of fish for the
domestic market are small-scale processors often with limited knowledge on proper
handling of fish, inadequate hygienic facilities, lack of adequate raw materials which
compels them to purchase rejects (undersize, poor quality fish and fish frames) from fish
processing companies. The use of rejects and poor quality raw materials associated with
inadequate handling and processing conditions could result into food safety problems
and endanger the public health.
This study was conducted to assess the handling practices as well as microbiological and
chemical quality of salted sun-dried Lates niloticus (Kayabo) from Lake Victoria,
Tanzania. Structured observation checklist was used to collect information from thirty
Kayabo processors on the product handling practices along the processing chain.
Samples were collected from processors from two Municipalities of Mwanza City
namely Nyamagana (Kanyama) and Ilemela (Mwaloni). Analytical samples for
microbiological analyses were prepared according to Andrew and Hammac (US - FDA
BAM, 2001). Enumeration of total viable counts (TVC), total coliforms, E. coli, S.
aureus were respectively performed according to ISO 4833:2003, ISO 4831:2006, ISO
7251: 2005, ISO 6888 — 3: 2003, whereas detection of L. monocytogenes was done
according to ISO 11290-1:1996/Amd 1: 2004 methods. The total volatile basic nitrogen
(TVB-N) of Kayabo was extracted following the European official method (EC)
2074/2005. To assay nitrogen specifically generated by the trimethylamine (TMA),
distillation method was applied in presence of formaldehyde. Moisture content was
determined by AOAC method 985.14 (AOAC, 1995). Hierarchical cluster analysis was conducted on the handling practices of Kayabo from
the two locations. Three clusters were obtained; cluster I (15 companies), cluster II (10
companies) and cluster III (5 companies). All cluster I processors were from Kanyama,
whereas the rest of clusters contained processors from Mwaloni. The study showed that,
Kayabo value chain was associated with poor quality raw material, inadequate handling
practices, lack of food grade processing equipment, poor sanitation, lack of training and
education on hygiene as well as poor packaging and storage conditions. All clusters
exhibited TVC, 5. aureus, total coliforms with values ranging from 2.08 - 8.68 Log
CFU/g, 2.36 - 2.56 Log CFU/g, 0.6 - 1.36 Log MPN/g, respectively. Only TVC
indicated significant difference (P<0.05) among the clusters. However, E. coli and L.
monocytogenes were not detected in all samples tested.
Kayabo from the two locations varied significantly (P<0.05) in moisture content, TVB-
N and TMA-N contents. Samples from Mwaloni had highest mean scores of moisture
content (42.8%) compared to Kanyama (27.4%). The moisture content of Kayabo from
Mwaloni exceeded the 30% cut-off point for the dried salted fishery products. All
samples from Mwaloni had TMA-N and TVB-N values within the acceptable limit. The
higher concentration of TVB-N and TMA-N recorded beyond the freshness scale from
majority of Kayabo samples from Kanyama location gave an indication that the products
were made from the raw materials which had started to spoil.
The study showed that preservation of Kayabo with salt has varied effect on both quality
and safety parameters. The fact that salt can inhibit growth and proliferation of spoilage
and pathogenic microorganisms i.e. L. monocytogenes, S. aureus and E. coli, it is
therefore recommended that it is appropriately used. However, since growth of some
spoilage microorganisms was observed; it is further recommended to improve the handling practices by using cold storage from the fish supply sources to the processing
units, hygiene training and education, inspection of Kayabo processing facilities and
operations, adequate drying of Kayabo, appropriate final product packaging, labeling and
storage in order to improve significantly safety and quality of Kayabo.
Description
Dissertation
Keywords
Food, Fish processing, Fish products