Abstract:
Sensory, microbiological, biochemical and physico-chemical methods were used to assess freshness and quality of fresh
Lake Malawi Tilapia (Local name: Chambo) to compare their effectiveness and reliability. Fresh Chambo samples were rejected by
the sensory panel after 16 days from day of catch with a strong linear correlation (P < 0.01, R2 = 0.95) between sensory quality scores
and storage time in ice. Highest bacterial load of 1.6×107
cfu/g, cfu/cm2 was observed on day 15 coinciding with sensory rejection
time. TMA-N and TVB-N for freshly caught fish was 0.7 and 5.1 mg/100g, which increased to 3.4 and 26.4 mg/100g respectively at
the time of sensory rejection also correlating with increased bacteria load in the fish. Initial pH of the fresh fish muscle was close to
neutral (6.47), and reached its lowest point (5.84) on day 16 which was sensory rejection time. Findings suggest that sensory
evaluation is reliable in the absence of the other methods. TMA-N is not a reliable method for assessing freshness quality of Lake
Malawi Tilapia due to insignificant readings. pH showed to be a quick freshness indicator with an understanding that muscle pH for
live fish is generally neutral and increases as deterioration of the quality of fish progresses in storage. Rejection of fish samples
before reaching unacceptable microbial limits in this study, underpins the need for using more than one method for accurate freshness
and quality assessments of fresh fish.
