Effect of lemon grass (Cymbopogon citratus Stapf) powder and essential oil on mould deterioration and aflatoxin contamination of melon seeds (Colocynthis citrullus L.)

Abstract

Experiments were carried out to determine the potential of using the powder and essential oil from dried ground leaves of Cymbopogon citratus (lemon grass) to control storage deterioration and aflatoxin contamination of melon seeds (Colocynthis citrullus L.). Four mould species: Aspergillus flavus, A. niger, A. tamarii and Penicillium citrinum were inoculated in the form of conidia suspension (approx. 106 conidia per ml) unto shelled melon seeds. The powdered dry leaves and essential oil from lemon grass were mixed with the inoculated seeds at levels ranging from 1-10% (w/w) and 0.1 to 1%v/vt respectively. The ground leaves significantly reduced the extent of deterioration in melon seeds inoculat4ed with different fungi compared to the untreated inoculated seeds. The essential oil at 0.1 and 0.25% (v/w) and ground leaves at 10% (w/w) significantly reduced deterioration and aflatoxin production in shelled melon seeds inoculated with toxigenic A. flavus. At higher dosages (0.5 and 1.0% v/w), the essential completely prevented aflatoxin production. After 6 months in farmers' stores, unshelled melon seeds treated with 0.5% (v/w) of essential oil and 10% (w/w) of powdered leaves of C. citratus had significantly lower proportion of visibly diseased seeds and Aspergillus spp infestation levels and significantly higher seed germination compared to the untreated seeds. The oil content, free fatty acid and peroxide values in seeds protected with essential oil after 6 months did not significantly differ from the values in seed before storage. The efficacy of the essential oil in preserving the quality of melon seeds in stores was statistically at par with that of fungicide (iprodione) treatment.


Key Words: Aflatoxin, Cymbopogon citratus, essential oil, powdered leaves, melon seeds, mould deterioration, oil content, free fatty acid, peroxide values, seed germination.


African Journal of Biotechnology Vol.3(1) 2004: 52-59