Differential inhibitory potentials of three plant extracts against Dermestes maculatus Degeer and microorganisms in smoked catfish, Clarias gariepinus Burchell

Abstract

Objectives: Three medicinal plants: Zingiber officinale rhizome, Allium sativum bulb, and Moringa oleifera seeds, were evaluated for progeny inhibition in fish beetle, Dermestes maculatus, and incidence of bacteria and fungi in smoked-dried Clarias gariepinus. Materials and Methods: Cleaned C. gariepinus were separately soaked in extracts of these selected plants (50 g/1000 ml) for 60 min before smoke-drying in a mud kiln at 105°C and later divided into lots. Sensory evaluation was conducted on uninfested fishes in lot A while fishes in lot B was artificially infested with five pairs of newly emerged adult D. maculatus for 10 days. Number of emerged larva, adult insects, and incidence of microorganisms before and following 90 days in storage after infestation were used as indices of potency of the extracts. Results: Results obtained showed that all the treated uninfested smoked-dried C. gariepinus retained high scores for taste, texture, aroma, and appearance within the first 5 weeks of storage after smoking when compared with the control. This implied that the tested extracts had no negative effect in terms of sensory attributes on the treated fish during storage and can therefore be used for fish preservation. Meanwhile, A. sativum among all the selected extracts had the least number of larvae (17.67 ± 1.45), adult (21.00 ± 1.53), fungi (9.00 × 102 ± 0.53 sfu/ml) and bacteria counts (11.33 ×102 ± 0.33 cfu/ml) following 90 days in storage after infestation. Conclusion: Allium sativum among the tested extracts proved to be most effective and could be recommended for control of D. maculatus and microorganisms in smoked C. gariepinus.