Resumen de Influence of temperature, copper and CO2 on spore counts and geosmin production by Penicillium expansum

Daniela Corréai-Judet, Maurice Bensoussan, Claudine Charpentier, Philippe Dantigny

• Background and Aim Musts and wines produced from rotten grapes often have an earthy/musty odour, with geosmin the responsible compound. Penicillium expansum is considered a potential source of geosmin in rotten grapes from vineyards treated with copper-based fungicides.

  Methods and Results The laboratory study assessed the influence of temperature (10–30°C), copper concentration (0–76.50 mg/L) and CO2 in the headspace (0.03–3%) on the spore count and the production of geosmin by P. expansum according to a Doehlert design. The spore count and the production of geosmin (ng/mg biomass) were significantly correlated (r = 0.78). Copper had no significant effect on the spore count but was the most important factor for explaining geosmin production. The production of geosmin was enhanced at low temperature (15°C), 0.03% CO2 (i.e. atmospheric level) and high copper concentration (76.50 mg/L).

  Conclusion Penicillium expansum, grown on Czapek agar, produced a significant amount of geosmin at low temperature and in the presence of copper.

  Significance of the Study This study suggests a possible explanation for the occurrence of earthy/musty odours in musts and wines made from rotten grapes.