Effect of citrus lemon (Citrus limon) essential oil on microbial load of smoked clupeids (Ethmalosa fimbriata and Sardinella maderensis) during storage

This study examined the microbial load of smoked clupeids (Ethmalosa fimbriata and Sardinella maderensis) during a 12-week storage. One hundred and sixty samples (160; 80 each of both fish) of freshly smoked Ethmalosa fimbriata and Sardinella maderensis were procured from Makun Omi, Ogun Waterside, Ogun State, Nigeria. The fish samples were divided into two parts and a part coated with the essential oils while the other part was not. The coated samples were put in white polyethylene bags and placed in cartons and the second part (uncoated) was packed in polyethylene bags and placed in cartons. These cartons were then stored at ambient temperature (±25°C) for twelve weeks. The samples were assessed weekly for spoilage organisms in a twelve-week shelf-life study (to know the types and number of microorganisms per sampling time). Preserved fish samples had significantly (p<0.05) lower microbial load (Bonga:9.50−2.20 x 106 CFU/g and Sardine:6.25−1.30 x 106 CFU/g) than unpreserved samples (Bonga: 12.50−26.25 x 106 CFU/g, Sardine: 10.65−25.35 x 106 CFU/g). Eight (8) bacteria (Bacillus subtilis, Klebsiella aerogenes, Escherichia coli, Bacillus megaterium, Staphylococcus aureus, Enterobacter cloacae, Lactobacillus fermentum and Staphylococcus saprophyticus) were isolated from both samples, with the unpreserved having pathogenic micro-organisms (Klebsiella aerogenes, Staphylococcus aureus and Escherichia. coli). Lemon essential oil is therefore recommended as a potent natural preservative for smoked clupeids. Packaging essential oil preserved smoked clupeids in polyethylene bags before being placed in a box is also recommended as a way of keeping out microorganisms that can spoil fish.