Purpose: This study aimed to investigate the occurrence of patulin contamination and the incidence of patulin-producing Penicillium spp. on decayed apples and to determine the effect of mechanical removal of decayed portions on patulin reduction.
Methods: Fungi on 53 decayed apples were isolated on Potato Dextrose Agar plates. To identify the fungal isolates, morphological and molecular examinations (sequencing of ITS1 and 4, and beta-tubulin gene) were carried out. Thirty Penicillium sp. were grown on apple agar plates for 7 days at 25℃ to evaluate intraspecific variability of growth and patulin production. After incubation with Penicillium expansum KUFMNS 21 for 14 days, the decayed parts of apples were scooped out and analyzed for patulin by HPLC-UV (276nm).
Results: A total of 58 fungi were isolated from 41 apples, of which 17 were contaminated with patulin (0.1-2.0 ㎍/g). Thirty isolates were classified as Penicillium spp. (29 P. expansum, 1 Penicillium echinulatum). Twenty-eight fungi were categorized into genera such as Alternaria, Fusarium, and Collectotrichum. All of the 29 Penicillium expansum produced patulin (0.2 ㎍/g– 1.1 ㎍/g) on apple agar plates within 7 days. Penicillium expansum KUFMNS 21 produced patulin up to 0.8 and 0.7 ㎍/g on 2 apple cultivars (Royal and Mishima) within 14 days, respectively. Patulin reduction in the apples was 92.9% (Royal) and 95.7% (Mishima) after removal of the decayed parts of apples on the seventh day.
Significance: The majority (41 out of 53) of the decayed apples were contaminated with fungi. Twenty-nine P. expansum out of 58 fungal isolates produced patulin. The mechanical removal of decayed apple parts effectively reduce the patulin contamination.