Flax seed has become an increasingly popular food ingredient because of its nutrient richness as well as potential health benefits.  Flax seeds are often ground before consumption and flax seed cakes are used as animal feed.  Aflatoxin production may occur subsequently when the ground seeds are stored in an environment supporting fungal growth. The objectives of this study were to determine the growth of two  toxigenic fungi, Aspergillus flavus and A. parasiticus , and to quantify the concentrations of four major aflatoxins (AFB1, AFG1, AGB2, and AFG2) produced by the two fungi on ground flax seeds with 0.82, 0.86, 0.90, 0.94 and 0.98 a w incubated for 30 days at 20, 27 and 35°C. Results of the study showed that A. flavus was able to grow on ground seeds with 0.86-0.98 a w at all three temperatures, and the most rapid growth occurred at 0.90 and 0.94 a w at 27°C. Whereas A. parasiticus grew on seeds with 0.86-0.98 a w at 27 and 35°C as well as on seeds with 0.86-0.90 a w at 20°C, and the most favorable growth condition was 0.90-0.94 a w at 35°C. Aspergillus flavus produced aflatoxins on seeds with 0.90-0.94 a w at 27°C as wells as on seeds with 0.86-0.98 a w at 35°C and the maximum total aflatoxin (298 µg/kg), AFB1 (247 µg/kg) and AFG1 (51 µg/kg) were found on seeds with 0.90 a w at 35°C. Whereas, A. parasiticus produced aflatoxins under a wider range of conditions which included 0.86 a w at 27 and 35°C, 0.90 a w at 20 and 27°C, 0.94 a w at 27°C, and 0.98 a w at 35°C.  The maximum total aflatoxin (364 µg/kg) and maximum AFB1 (324 µg/kg) along with 34 µg/kg AFG1 and 6 µg/kg AFB2 were produced by A. parasiticus on seeds with 0.98 a w incubated at 35°C for 30 days. Linear regression models also indicated that high incubation temperature (35°C) was optimal for overall fungal growth as well as formation of high levels of aflatoxin by both fungi. Future studies should also address aflatoxin contamination in flax seed oil.

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