Effects of Ocimum gratissimum and Piper nigrum on microbial load and shelf life of Sarotherodon galilaeus

The freshness of fish degrades after death due to various biochemical reactions which may often result in deterioration of both sensory quality and nutritional value. This study was conducted to determine the effects of black pepper (Piper nigrum) and African basil, (Ocimum gratissimum) on the microbiota composition and shelf life of freshly smoked Sarotherodon galilaeus. A total of 60 samples of S. galilaeus (mean weight 21.85 ±7.02) were procured from Makoko fish market, Lagos. Fish samples were properly cleaned and treated with 0.0001g/l each of the additives. The control group was not treated with either of the additive. Both the control and the treated fish were smoked dried to a constant moisture level of 28.69% using the NIOMR smoking kiln at temperature of 50⁰C. The smoked fish samples were thereafter stored in respective cages for 4 weeks. During the 4-week storage period, fish were examined for microbial contents and organoleptic quality on a weekly basis following standard procedures. Results revealed that, after two weeks of storage, fish quality had deteriorated such that the assessors were unwilling to taste any of the fish samples further. Fish colour, odour and overall acceptance were significantly different (p ≤ 0.05) among treatment groups. Microbial load increased gradually in all the samples. The predominant bacterial organisms observed were Bacillus spp, Aeromonas spp, Pseudomonas aeruginosa, Staphylococcus aureus and Flavobacterium; while fungal organisms recovered were Aspergillus flavus, Penicillium spp, Saccharomyces spp, Rhizopus stolonifer, Fusarium spp, Aspergillus niger and Mucor spp. Inference from the study showed that O. gratissimum extract significantly delayed onset of spoilage in smoked fish samples and the shelf life of the smoked fish was observed to be stable between 0 and 2 weeks after smoking under room temperature.