Patulin Production by Some Fungal Species in Relation to Water Activity and Temperature

Abstract

The combined effects of water activity (aw) and temperature on growth and patulin production by strains of Penicillium expansum, Penicillium patulum, and Aspergillus clavatus were determined. Malt agar media were used, in which the aw was adjusted by addition of sucrose or glycerine. The minimum aw values for patulin production by P. expansum, P. patulum, and A. clavatus were 0.99, 0.95, 0.99, respectively. The temperature ranges for patulin production by P. expansum, P. patulum, and A. clavatus were 0–24, 4–31, and 12–24 C, respectively. The optimum temperatures for patulin production by P. expansum and A. clavatus were low compared with those for growth. Optimum temperatures for patulin production at high aw by P. patulum varied with the strain tested and were 8 or 31 C. The temperature range for patulin production in apples by P. expansum was determined. The minimum temperatures for rotting and patulin production were 1 C in Cox Orange cv. and 4 C in Golden Delicious cv. The amount of patulin accumulating in rotten tissue of six apple varieties differed greatly. The invasiveness of and patulin production by various strains of four patulin-producing fungal species were tested. All P. expansum strains tested caused rot containing patulin. The increase of rot and patulin production by P. crustosum and A. clavatus depended on the strains tested. None of the P. patulum strains was able to invade Golden Delicious apples.