The Aspergillus flavus inoculum was prepared by growing the
isolate in Potato Dextrose Agar (Sigma-Aldrich Co., St. Loius, USA)
for 3 d at 30 C to obtain sporulating cultures. Fungal spores were
collected in sterile bottles containing 0.5 g/L Tween-80. Spore
concentration was measured with a haemocytometer and adjusted
approximately to 104 spores/mL.
Pieces of untreated chiffon cake, chiffon cake added with 1.5 g/
kg CAP, and chiffon cake added with 3 g/kg CAP were sealed in
aluminum foil and autoclaved at 121 C for 15 min. Each chiffon
cake piece was inoculated with 1 mL of spore solution, using a
sterile needle, and packed separately in a sealed sterile plastic bag.
Each 20-piece batch of chiffon cake was used for one of the four
treatment batches: (1) ordinary chiffon cake (untreated), (2) chiffon
cake irradiated at a predetermined optimum dose, (3) chiffon cake
added with 3 g/kg CAP, and (4) chiffon cake with 1.5 g/kg CAP added
and irradiated at a predetermined optimum dose. All treatments
were performed in duplicate. Growth of A. flavus on chiffon cake
was monitored daily during the 10 d of storage at ambient temperature
(25 ± 5 C). A piece of chiffon cake was supposed positive
when more than 1% of the total surface area was covered with
fungi. From a total of 20 chiffon cake pieces, the number of pieces
covered with A. flavus during storage at ambient temperature
(25 ± 5 C) for 10 d was recorded and the percentage reported.