Microbial assessment of Clarias gariepinus fillets fed defatted and non-defatted sundried black soldier fly larvae meal
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Date
2025-08
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Abstract
Aquaculture production in Nigeria is hindered by the dependence on fishmeal as the main protein source in
fish feed. Consequently, there is a need to explore alternative protein sources that is cost-effective, sustainable and pose
no risk to consumers. This study evaluated the microbial loads and isolates in Clarias gariepinus fillets fed defatted (DF)
and non-defatted (NDF) sundried black soldier fly larvae meal (BSFLM) diets over a period of 21 storage days with
assessments at day 0, 7th, 14th and 21st, after 168 days of feeding trials. Fishmeal was replaced with DF and NDF
sundried BSFLM at varying inclusion levels of 0%, 25%, 50%, 75% and 100% in the diets of Clarias gariepinus, which
were fed for a period of 168 days. Following the feeding trial, the fish were saline-rinsed, filleted, and sealed in double
polyethylene bags. The fillets underwent boiling for 20 minutes, after which the fish were foil-wrapped, grouped in ziplock
bags, labelled and stored at 4°C for 21 days in a chest freezer. Microbial analysis was estimated for each labelled ziplock
bag sample at days 0, 7th, 14th, and 21st of the storage period, assessing total bacterial count (TBC), total coliform count
(TCC), mould yeast, and microbe isolates. The results obtained showed that at day zero of storage, the highest TBC (8.0
x 105 CFU/g) was observed in fillets fed 75% defatted BSFLM, with Bacillus and Candida spp. dominating the isolates. At
seven days of storage, the TBC ranged from 1.02 x102 CFU/g (0% defatted BSFLM) to 9.6 x105 CFU/g (75% defatted
BSFLM), with Staphylococcus, Bacillus, and Candida spp. being the most persistent isolates. At the twenty-first day of
storage, TBC in fish fillets fed 0% and 25% defatted BSFLM were more than 300 colony counts, which were recorded as
too numerous to count because they exceeded permissible limits for consumption, and a broader spectrum of
microorganisms, including Staphylococcus spp., Bacillus, Aspergillus spp., and Klebsiella spp., were isolated. This study
concluded that catfish fillets fed defatted and non-defatted sundried BSFLM diets should be consumed within a shorter
storage period due to the potential microbial risks associated with prolonged storage.