MOLD GROWTH AND AFLATOXIN PRODUCTION ON OLIVES AND OLIVE PRODUCTS (OLIVE OIL, SUNLIGHT, HEAT)

Tunisian olives were shown to contain potential aflatoxigenic molds. When inoculated onto damaged whole olives, A. flavus grew extensively, but did not produce aflatoxins. Asp. flavus also grew extensively on pastes made from commercial olives, but produced little aflatoxin on pastes of black and green canned olives. Asp. parasiticus also grew extensively and produced moderate amounts of aflatoxins on paste of black canned olives, little on pastes of canned and pickled green olives, and very little on pastes of fresh frozen then heated California olives. Potassium sorbate and natamycin delayed and prevented growth in fresh olive paste at 15 C. However at 25 C only sorbate (6,000 ppm) delayed growth. Aflatoxin B1 was not detected in any of these samples. Supplementation of fresh olive pastes with zinc, sucrose, asparagine and proline together; a combination of zinc, sucrose and amino acids and Yeast extract (YE) alone, then inoculated with Asp. flavus and Asp. parasiticus, showed that Asp. parasiticus produced aflatoxin in highest amounts with the combination and in moderate amounts on the amino acids and YE. No aflatoxins were produced on pastes supplemented with zinc or sucrose alone. Growth of Asp. parasiticus and Asp. flavus was extensive in all samples. Fresh, frozen, heated or lye-treated olives inoculated with Asp. parasiticus supported little growth and no aflatoxin on fresh and frozen olives, and heavy growth, but little toxin on heated and lye-treated olives. Asp. flavus grew similarly to Asp. parasiticus but produced no toxin. Media containing Yeast Extract Sucrose Agar (YESA) mixed with olive pastes (50:50), and inoculated with A. parasiticus, showed that frozen and fresh olive pastes partially inhibited aflatoxin production, while heated and lye treated pastes stimulated aflatoxin production. Cole aqueous extracts of frozen olives when added to YESA strongly inhibited aflatoxin synthesis, while cold aqueous extracts of fresh and lye-treated olives stimulated toxin production by Asp. parasiticus. Aflatoxin B1 was stable in olive oil given heat treatments up to 250 C, lost on exposure to sunlight, and moderately stable on longterm storage at 25 C. Foods fried in olive oil contaminated with aflatoxin, absorbed more toxin than the theoretical amount contained in the oil that was absorbed during frying