N. Paster et al., ANTIFUNGAL ACTIVITY OF OREGANO AND THYME ESSENTIAL OILS APPLIED AS FUMIGANTS AGAINST FUNGI ATTACKING STORED GRAIN, Journal of food protection, 58(1), 1995, pp. 81-85
Essential oils from oregano and thyme were applied for 24 h as fumigan
ts against the mycelia and spores of Aspergillus flavus, Aspergillus n
iger and Aspergillus ochraceus, as well as against natural microflora
of wheat grains. The minimal inhibitory concentration (MIC) of oregano
oil needed to inhibit the mycelial growth of the fungi was 2.0 mu l/L
, while spores were eradicated following exposure to 2.0 to 2.5 mu l/L
. The thyme essential oil was less efficient in controlling mycelia an
d growth was observed even following exposure to 4.0 mu l/L. However,
the thyme essential oil was fungitoxic to spores (MIC=3.0 mu l/L). In
another set of trials the efficacy of the oils and two of their consti
tuents (carvacrol and thymol) in controlling natural microflora of sur
face-sterilized wheat grain was studied. Of the four materials investi
gated, only oregano essential oil exhibited fungicidal activity and, f
ollowing 24 h exposure to 20 mu l/L, a significant reduction in the pe
rcent of infested grain was observed even after 5 days of incubation o
n potato dextrose agar. A reduction in the germinability of the grains
was evident following exposure to the materials tested. When the fung
icidal activity of oregano essential oil was evaluated using grains wi
th different moisture contents (MC), data revealed that the better inh
ibitory effect was achieved in grain with a high MC. The findings emph
asize the toxicity of oregano and thyme essential oils as fumigants ag
ainst fungi attacking stored grain and strengthen the possibility of u
sing them as an alternative to chemicals for preserving stored grains.