Growth Inhibition of Grain Spoilage Fungi by Some Herb and Spice Essential Oils Grown in Ethiopia

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Addis Ababa University


Microbial food contamination is an on-going limiting factor in crop production that can determine the shelf life of processed and unprocessed foods. Spice plants and herbs are commonly used as food flavoring and seasoning agents. Their antimicrobial properties as food preservatives are also well documented. In this study, essential oils of seven spice plants were tested for their antimicrobial properties against Aspergillus flavus and A. niger, two of the most important food and feed spoilage organisms. Agar disk diffusion assay was used for screening of the most effective essential oils, agar dilution assay was used to determine Minimum Inhibitory Concentration (MIC) of the essential oils and broth dilution assay was employed to the spore germination inhibition assay. Tests were also conducted to examine the effects of the essential oils for sorghum kernel protection against the tested fungi, and the optimal protective dosages on the sorghum grains were also determined. From the preliminary tests, essential oils of Cinnamomum zeylanicum (Cinnamon) and Thymus schimperi (thymus) were found to be the most effective. However piper nigrum (black pepper) had no effect on the test organisms. In MIC, spore germination inhibition and grain protection assay, cinnamon essential oil was found to be superior where its MIC on the isolates was found to be 0.0156% and its optimum protective dosage on the grain was 5%. It inhibited spore germination at a concentration of 3 _L/ml. The effect of thymus oil was also very much comparable to these results (no significant difference at P < 0.05). Finally, it could be concluded that some plant essential oils can be a useful source of antifungal agents for protection of grain spoilage by fungi.



Growth Inhibition, Grain Spoilage, Fungi, Some Herb and Spice Essential, Oils Grown