Microbiology and Spoilage Trail in Nile Perch (Lates niloticus), Lake ...

The excellent freshness fish grade (QIM score) was scored during 15 days and good quality
fish were scored during 3-4 weeks of storage in ice. QIM scores characterized with a
constant increase (from 2-14 score) through out the 33 days storage time (figure 4). The
quality of fish after 3 weeks of storage in ice was observed and was graded as not fit for
processing prime quality fresh chilled fillets for export.
Figure 4: QIM score for whole Nile
perch during storage in ice.
4.2.1.2 Microbiological analysis
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Figure 5: Main contributing attributes
to QIM score for whole Nile perch
during storage in ice, (GA: General
appearance).
The test results for specific spoilage organisms (SSO), total viable counts (TVC) and
Enterobacteriaceae counts for Laboratory iced whole Nile perch stored in ice at 0-3 o C are
shown in figure 6. The SSO counts were low up to 4 th day of storage in ice and then rapidily
increased from 2.75 - 6.15 log10 cfu/g after 15 days of storage. Similary the TVC counts
were low but higher than the SSO counts on the 4 th day of storage but increased from 4.12 -
7.88 log10 cfu/g after 15 days of storage. The Enterobacteriaceae counts were similar to
TVC counts after 4 days of storage i.e. 4.40log10 cfu/g and increased up to 6.22 log10 cfu/g
after 15 days of storage. These counts corresponded well to the excellent freshness quality
scores for the same period of whole Nile perch for processing into very good quality fillets
and or other products. After 15 days of storage and up to 22 days of storage of whole Nile
perch in ice all microbiological counts slowly increased to 9.49log10cfu/g (SSO);
9.84log10cfu/g (TVC) and 8.22log10cfu/g (Enterobacteriaceae). Then the counts increased up
to a stationary phase during the fourth and fifth weeks of storage and reached maximum