Use of the Weibull model to describe inactivation of dry-harvested conidia of different Penicillium species by ethanol vapours.

AIMS: This study aimed at modelling the effect of ethanol vapours, in the range 0.7-7.5 kPa, on the inactivation of dry-harvested conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum. METHODS AND RESULTS: Survival curves were modelled by a Weibull model: log (N/N(0)) = -1/2.303 (t/alpha)(beta). The shape parameter beta was different from one in all cases, indicating that the classical first-order kinetics approach is the exception rather than the rule. Survival curves exhibited upward concavity (beta < 1) with the notable exception of P. chrysogenum at ethanol vapour pressures 0.7 and 1.5 kPa. The scale parameter alpha (h) varied greatly depending on the ethanol vapour pressure and on the species. CONCLUSIONS: For safety reasons, it is recommended not to exceed an ethanol vapour pressure of 3.3 kPa. At 2.8 kPa, more than 4 log(10) reductions in viable conidia were achieved for all the species after 24-h exposure. SIGNIFICANCE AND IMPACT OF THE STUDY: Ethanol has GRAS status in the USA and represents an interesting alternative to fungicides. The effectiveness of ethanol vapours to inactivate dry-harvested conidia of some Penicillium was demonstrated in this study.