Production of patulin by Penicillium expansum.

Twenty-seven isolates of Penicillium expansum Lk. ex Thom obtained from Europe, Australia, and North America from seven different fruit hosts all produced patulin in culture. Six isolates were essentially nonpathogenic in apple fruits. In culture, patulin generally accumulated to much higher levels than in apple fruits. At all temperatures permitting fungus growth, patulin was produced. However, only small amounts were observed near the maximal temperature for growth (30 C). At 0 C, patulin accumulated but slowly in culture. Modified atmospheres suppressed both fungus growth and patulin accumulation in apples. After varying incubation periods to obtain similar total growth, the patulin concentration was low in modified atmospheres and high in air.