ASSESSMENT OF THE MICROBIAL INHIBITORY ACTIVITY OF SELECTED PLANT EXTRACTS ON SPOILAGE ORGANISMS OF SOME LOCAL BEVERAGES

Abstract

The effect of water and alcohol extracts of bitter cola (Garchinia kola), bitter leaf (Vemonia amugdalina), neem (Azadiachta induca) and utazi (Gongronema latifolium) on spoilage organisms and sensory properties of kunnu, pito and zobo drnks were investigated. Morphological and biochemical characterization of isolates from the drinks show the presence of Staphylococcus aureus, Bacillus subtilis, Lactobacillus plantarum, Saccharomyces cerevisiae, Saccharomyces ellipsoids and Candida sp.  Aqueous and ethanolic extracts of bitter leaf, biter cola and neem exhibited  broad spectrum activity against S. aureus. Subtilis and L.plantanum at concentrations of 50mg/ml and 100mg/ml. The highest zone of growth inhibition was obtained for 100mg/ml of both water and ethanol extracts of biter leaf and neem against S.aureus. Utazi had lowest activity against the organisms tested. The minimum inhibitory concentration of the ethanolic extracts of bitter leaf against organisms tested range from 250 μg/ml (L plantarum) to 1000 μg/ml (S.ellipsoides) while it is 250 μg/ml (S. aureus, L. plantarum and B.subtillis) to 500 μg/ml (S. erervisiae and S. ellipsoids) for neem extracts. The organisms were found to be more sensitive to alcohol extracts than aqueous extracts of the vegetables. Sensory evaluation showed no significant difference (P > 0.05) in the sensory attributes measured for zobo and kunnu treated with the water and alcohol extracts. However, significant difference (P < 0.05) were recorded in the taste, aroma and mouth-feel of pito treated these extracts.

 Anti-microbial screening, Plant Extracts, Spoilage organisms