Author(s)

Tsi Celestine Angu¹, Pride Ndasi Ngwasiri^2*, Lifoter Kenneth Navti¹, Diane Youmbi Yimta³, Fonteh Florence Anyanwe Angaba¹

¹Department of Biochemistry, Faculty of Science, The University of Bamenda, Bamenda, Cameroon.
²Department of Nutrition, Food and Bio-Resources Technology, College of Technology, The University of Bamenda, Bamenda, Cameroon.
³Labouratory for Phytobiochemistry and Medicinal Plants Studies, Yaounde, Cameroon.

Dried fish are susceptible to bacteria and fungi attack and are liable to chemical changes which cause losses in quality and reduction of shelf-life. It is important therefore to maintain the quality of fish because continuous consumption of contaminated fish and their products may predispose consumers to health hazards. Maintenance of high quality fish therefore calls for adequate and effective preservation techniques. The study examined the effectiveness of essential oils of Ocimum basilicum and Ocimum gratissimum from two Agro-ecological zones of Cameroon in limiting the microbial proliferation and preserving the quality of smoke-dried Oreochromis niloticus fish stored at 25˚C for two months. The plant materials were harvested from the Western Highlands and Monomodal Humid Forest agroecological zones of Cameroon. Extraction of the essential oil from the plants was done by hydro-distillation. The fish species (Oreochromis niloticus) used in this study was chosen based on a survey study on the most consumed species of freshwater smoke-dried fish in the Western Highlands and Monomodal Humid Forest Agro-ecological zones of Cameroon. Heterotrophic bacteria counts, fungi counts and Enterobacteriaceae counts were used to assess the level heterotrophic bacteria, fungi and Enterobacteriaceae respectively in the fish samples during storage and were done by culture techniques using total plate count agar, potato dextrose agar and violet red bile glucose agar respectively. Total volatile basic nitrogen, peroxide value, and thiobarbituric acid reactive substance assays were used as spoilage indices to assess the nutritional quality of the fish during storage. From the survey study, Oreochromis niloticus was the most consumed smoke-dried fish in the Western Highlands (35.45%) and Monomodal Humid Forest (34.55%) agroecological zones. All the EOs caused a significant reduction in the microbial loads, total volatile basic nitrogen, peroxide value, and thiobarbituric acid reactive substance of smoke-dried Oreochromis niloticus as storage progressed. However, the reduction in these values was more pronounced in samples treated with essential oils of O. gratissimum from the Western Highlands, with heterotrophic bacteria, fungi and Enterobacteriaceae counts being 5.89, 6.97 and 4.59 log₁₀ cfu/g respectively at the end of the storage period. This was followed by essential oils of O. gratissimum from the Monomodal Humid Forest with heterotrophic bacteria, fungi and Enterobacteriaceae counts being 6.11, 7.79 and 4.86 log₁₀ cfu/g respectively at the end of the storage period. Also, essential oils of O. gratissimum from the Western Highlands was more effective in preserving the fish quality as lowest total volatile basic nitrogen (12.29 mg/100g), peroxide value (2.79 mEq O₂·Kg⁻¹) and thiobabituric reactive substance (1.695 mg MDA/Kg) values were observed for fish samples treated with this extract at the end of the storage period. This was followed by essential oils of O. gratissimum from the Monomodal Humid Forest with total volatile basic nitrogen (14.95 mgN/100g), Peroxide value (3.23 mEq O₂·Kg⁻¹) and thiobabituric reactive substance (2.354 mg MDA/Kg) at the end of the storage period. From the results obtained, essential oils from O. gratissimum were more effective than that from O. basilicum in the two agroecological zones and should be considered as natural alternative to chemical preservatives for further application in food preservation.

Oreochromis niloticus, Essential Oils, Fish Quality, Ocimum basilicum, Ocimum gratissimum, Agro-Ecological Zone

Angu, T. , Ngwasiri, P. , Navti, L. , Yimta, D. and Angaba, F. (2023) Preservation Potentials of Essential Oils of Ocimum basilicum and Ocimum gratissimum from Two Agro-Ecological Zones on Freshwater Smoke-Dried Oreochromis niloticus Fish Sold in Some Local Markets in Cameroon. Advances in Biological Chemistry, 13, 192-207. doi: 10.4236/abc.2023.135014.