EXPERIMENTAL PRODUCTION OF AFLATOXIN IN CITRUS JUICE AND PEEL1

Abstract

Grapefruit juice and grapefruit peel each supported growth of and aflatoxin formation by Aspergillus parasiticus and Aspergillus flavus. Grapefruit peel was a better substrate than grapefruit juice for toxin production; amounts of aflatoxin B1 and G1 were 5–10 times higher in the peel when the same mold strain grew at 28 C in both substrates for up to 62 days. In juice, amounts of aflatoxins B1 and G1 produced by A. flavus markedly decreased after 18 days and then became stabilized, whereas amounts of aflatoxin G1 formed by A. parasiticus increased to 34 days then declined and stabilized. When the molds grew on grapefruit peel, amounts of aflatoxins B1 and G1 produced increased for 38 days (A. flavus) and 26 days (A. flavus and A. parasiticus), and then declined and became stabilized. Amounts of aflatoxin B1 (A. parasiticus) increased rapidly early during incubation and then remained relatively constant through an extended holding time. Concentrations of aflatoxins B2 and G2 formed by both molds in each substrate did rot significantly change during extended incubation. A. parasiticus grew in grapefruit juice for 14 days at 28 C after which the juice was separated into three fractions. The solids fraction contained 72.8%, mold 16.9%, and filtrate 10.3% of the total amount of aflatoxin produced. Similar results were obtained with lemon and orange juice. Frozen storage (−18 C) of grapefruit juice samples containing aflatoxin did not significantly affect the amount of aflatoxin recovered until after 18 weeks.