Assessment of the antimicrobial effects of some spices on potential food borne pathogens isolated from deteriorated soy-bean cake

Abstract

The growth of potential pathogenic microorganisms in ready to eat foods like soy-bean
cake has been reported to shorten its shelf-life and cause food borne illnesses. Four commonly used spices in Nigeria were evaluated for their antimicrobial effects against potential food borne pathogens in an effort to discover natural preservatives. Five potential food borne pathogens (Salmonella spp; Escherichia coli; Enterobacter spp; Staphylococcus aureus and Mucor spp) were isolated from spoiled soy-bean cake and identified using standard microbiological methods. Extracts of Ginger (Zingiber officinale), Pepper (Capsicum annum), Turmeric (Curcuma longa l.) and Cinnamon
(Cinnamomum verum) prepared at various concentrations were tested against the food borne pathogens using agar well diffusion method. The results revealed that these spices had antimicrobial effects on the food pathogens. The diameter zone of inhibition of Cinnamon extract was found to range from 7.2±0.1mm – 16.3±1.9mm while that of Ginger extract ranged from 6.3±0.3mm – 11.7±0.9mm. Zone of inhibition of Turmeric
extract was from 7.3±0.7mm – 11.7±0.7mm and that of Chilli Pepper extract ranged from 7.3±0.7mm – 13.7±0.7mm. The finding also indicated significant difference in the treatment effect of all the four spices on the tests organisms. The analysis shows that the treatment has significant effect on Salmonella spp and Escherichia coli with the calculated F-value of 3.776 and 6.032 respectively and with the calculated P-value of .041 and .010 respectively. However, the treatment has no significant effect on Enterobacter spp, Staphylococcus aureus and Mucor spp because all their calculated Pvalues of 0.965; 0.083 and 0.155 respectively were greater than 0.05. These spices could be considered as potential source of natural food preservatives. Direct testing of the spices on the Soy bean cake is therefore recommended.