African Journal of Microbiology Research Vol.(2) pp. 037-041, February, 2007 Available online http://www.academicjournals.org/ajmr ISSN 1996-0808 ©2007 Academic Journals Full Length Research Paper Effect of some chemical preservatives on the shelf-life of sobo drink *Doughari J. H, Alabi G. and Elmahmood A. M Department of Microbiology, School of Pure and Applied Sciences, Federal University of Technology, P.M.B 2076, Yola 64002 Adamawa State, Nigeria. Accepted 8 February, 2008 The effect of some commonly used chemical preservatives (benzoic acid, sodium benzoate and sodium sulfite) on the shelf-life of Sobo drink was investigated by isolation of microorganisms before and during its ambient storage for 14 days. Three bacterial species, i.e. Lactobacillus acidophilus, Bacillus subtilis and Bacillus cereus were isolated. L. acidophilus was found only in the samples without preservatives, while B. subtilis and B. cereus were found in the samples with preservatives. Four fungal species, i.e. Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus and Trichoderma sp. were isolated. Trichoderma sp. was isolated only in the samples without preservatives, while A. niger, A. flavus, A. fumigatus were isolated in samples with preservatives. Antimicrobial activities of the chemical preservatives revealed that benzoic acid was the most effective against both bacterial and fungal species, followed by sodium benzoate and sodium sulfite. Of all the samples, only those treated with benzoic acid as preservative remained organoleptically attractive after preservation for 14 days. Key words: Antimicrobial activity, chemical preservatives, Sobo, microorganisms. INTRODUCTION Beverages are consumed for their nutritional value, thirst quenching properties, stimulating effect or for their medi- cinal values (Adegunloye et al., 1996; Elmahmood and Doughari, 2007). Sobo drink is a local beverage quite popular in northern Nigeria and is enjoyed at various social gatherings. Its popularity has recently spread across the entire country because of its purported medicinal value, as well as the increasing cost of other available soft drinks (Adegunloye et al., 1996). Sobo drink is prepared from the calyx of the roselle hemp plant Hibiscus sabdariffa (Malvaceae). Roselle, also known as Jamaican sorrel, is probably a native of West Africa and has been cultivated throughout India and part of Asia for centuries. Currently, it is grown through- out the tropics especially in Indonesia, Central Eastern Java, India-Bangladesh, Sri Lanka, the Philippines and the West Indies. Different ethnic groups call the vege- table plant various names. The Yorubas call the leaves ‘Amukan’, while the flower is called ‘Isapa’. The Igbos call it names like ‘Ojo’, ‘Akwaroazo’, while the Hausas call the fleshy calyx names like ‘Yakuwa’, ‘Sure’ or ‘Gurguzu’ *Corresponding author. E-mail: jameshamuel@yahoo.com. (Arthney and Dennis, 1991). In spite of the increasing popularity of Sobo juice, one of its limitations for large- scale production is that it deteriorates rapidly. In fact, its shelf-life is approximately 24 h, following production if not refrigerated. The shelf-life of a product is defined as the expected time duration that a product will remain organoleptically acceptable. It is a function of holding temperature and the number of microorganisms remaining in it after process- ing. It is possible to improve the shelf-life of Sobo by slowing down the fermentation process, thus inhibiting discolouration of the Sobo drink and possibly permitting large-scale production and preservation for longer period with maximum retention of its nutritive values. Prescott et al. (2002) defined preservatives as a group of chemical compounds deliberately added to food or that appears in food as a result of pre-processing treatment, processing or storage. These include simple organic acids (such as propionic acid, sorbic acid, benzoic acid) p-hydroxyl ben- zoate alkylester (parabens), ethylene/propylene oxides, sulfides, ethylene oxide (as a gas sterilant), ethyl formate and sodium nitrates. The sulphites inhibit yeasts, moulds and bacteria and are most effective as inhibitors of browning in foods. Sulphur dioxide and sulphites are metabolized to sulphate and are excreted in the urine