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.
The objective of this study was to perform a systematic review of risk factors for contamination of fruits and vegetables with Listeria monocytogenes , Salmonella , and Escherichia coli O157:H7 at the preharvest level. Relevant studies were identified by searching six electronic databases: MEDLINE, EMBASE, CAB Abstracts, AGRIS, AGRICOLA, and FSTA, using the following thesaurus terms: L. monocytogenes , Salmonella , E. coli O157 AND fruit, vegetable. All search terms were exploded to find all related subheadings. To be eligible, studies had to be prospective controlled trials or observational studies at the preharvest level and had to show clear and sufficient information on the process in which the produce was contaminated. Of the 3,463 citations identified, 68 studies fulfilled the eligibility criteria. Most of these studies were on leafy greens and tomatoes. Six studies assessed produce contamination with respect to animal host-related risk factors, and 20 studies assessed contamination with respect to pathogen characteristics. Sixty-two studies assessed the association between produce contamination and factors related to produce, water, and soil, as well as local ecological conditions of the production location. While evaluations of many risk factors for preharvest-level produce contamination have been reported, the quality assessment of the reviewed studies confirmed the existence of solid evidence for only some of them, including growing produce on clay-type soil, the application of contaminated or non–pH-stabilized manure, and the use of spray irrigation with contaminated water, with a particular risk of contamination on the lower leaf surface. In conclusion, synthesis of the reviewed studies suggests that reducing microbial contamination of irrigation water and soil are the most effective targets for the prevention and control of produce contamination. Furthermore, this review provides an inventory of the evaluated risk factors, including those requiring more research.