Aspergillus carbonarius growth and ochratoxin A production in irradiated dried grapes under different water activity and temperature conditions.

ASTORECA A.,; FERNÁNDEZ- JURI M.G.,; MUZZOLÓN J.,; MAGNOLI C.,; DALCERO A.M.

Tulln, Austria

Congreso; ISM Conference 2009. Worldwide Mycotoxins Reduction in Food and Feed Chains; 2009

Grapes are products which have different destinations. The most important in the national and international market is the wine production but other destination of the grapes is their dehydrated to elaborate the dried grapes. Thus, dried vine fruits are at greater risk of OTA contamination than wine grapes because the ratio of A. carbonarius to A. niger increases during drying. Growth of Aspergillus species and consequently OTA production can be influenced by intrinsic ecophysiological factors, such as water activity (aW), pH, composition of the substrate, and extrinsic factors as relative moisture and temperature, being the two most important the aW and temperature. Therefore, the determination of the optimal conditions environmental is essential to keep the quality of raw materials and finished food. Thus, the objectives of the present work was to evaluate the lag phase, growth rate and OTA production by two strains of Aspergillus carbonarius on irradiated dried grapes at different aW, temperature and incubation time. No significant differences between the growth rates reached at 25ºC and 30ºC were observed by both strains. Fungal development and OTA production occurred at all aW and temperature condition assayed. The highest growth rate was observed at 0.995 aW and 25 and 30ºC, without significant statistical differences between both strains. Optimum condition for OTA production was detected at the maximum aW and temperature assayed at seven days of incubation. In general OTA concentration increased as aW increased with no significant production at 0.93-0.90 aW under all temperature levels tested. These results show the marked influence of aW and temperature on fungal growth and OTA production by A. carbonarius in irradiated dried grapes. This study confirms that fungal ochratoxigenic development in this substrate could be prevented by an adequate control of certain environmental factors such as aW and temperature, which are important in the development of Aspergillus carbonarius species on substrates destined to human consumption.