Aflatoxins contamination

De Campos, M., Santos, J. C., Olszyna-Marzys, A.,K., Aflatoxin contamination in grains from the Pacific Coast in Guatamala and the effect of storage upon contamination, Bull. Environ. Contam. Toxicol., 24, 789, 1980. (CA93 89863z)... 

Sinha K K and Sinha A K (1991), Effect of Sitophilus oryzae infestation on Aspergillus flavus infection and aflatoxin contamination in stored wheat , 7. Stored Products Res., 27, 65-68. 

Soil populations and aflatoxin contamination are influenced by weather patterns, with hot dry soils favoring the Aspergillus section Flavi. In terms of geographic location, A. flavus incidence is correlated with high minimum temperatures and inversely correlated to latitude. For example, corn ears that develop at temperatures of 28 to 32°C are far more likely to be contaminated by aflatoxin than ears grown later in the season at lower temperatures. However, late planting is not economically feasible due to lower crop yields. Besides hot dry weather, the level of insect and rodent activity in an area may also substantially favor colonization and aflatoxin production. Plant fertility, density, and disease also play roles in the level of aflatoxin contamination. 

Humans are also exposed to the aflatoxins when consuming animal products that were contaminated because the animal ate feed containing aflatoxin. Aflatoxin contamination can be passed to milk and dairy products as aflatoxin M (Figure 9.1). 

None of the preharvest or postharvest techniques is completely effective and aflatoxin contamination continues to be a health and economic threat. 

Cotty, P.J., Effect of atoxigenic strains of Aspergillus flavus on aflatoxin contamination of developing cottonseed, PL Dis., 74, 808, 1990. 

Aflatoxins Contaminant (mycotoxin) Produced by Aspergillus flavus, especially grains, corn, and peanuts carcinogenic and hepatotoxic... 

After aflatoxin contamination, perhaps the next most important factor that has a negative effect on human health and food quality is the presence of food borne bacteria. Several routes for reduction of the risk are currently under extensive investigation. One such means of risk reduction is the utilization of ionizing radiation treatments on meat food products. Ionizing radiation has been demonstrated to be an effective method to reduce or eliminate several species of food borne human pathogens such as Salmonella, Campylobacter, Listeria, Trichinella, and Yersinia Chapter 23). If proper processing conditions are used, it is possible to produce high quality, shelf-stable, commercially sterile muscle foods. 

Cultural practices such as irrigation are effective in reducing aflatoxin contamination of peanut and com (54), but this practice is not always available or cost effective to growers. Other conventional disease control practices, such as the use of fungicides, are largely ineffective in controlling A. flavus infection of crops when utilized at concentrations that are cost effective as well as environmentally safe. 

Insecticidal control of the pink bollworm is yet another management practice used by growers in Arizona pink bollworm exit holes in cotton bolls might provide portals of entry for A. flavus (55). Unfortunately, it is not economically feasible to achieve 100% control of the pink bollworm in cotton through the hi -ftequency use of insecticides, and even relatively low levels of infestation by this insect pest is well correlated to high levels of A. flavus infection and subsequent aflatoxin contamination. 

Thus, conventional control practices are available that reduce aflatoxin levels in the field, but at a substantial and often unacceptable cost to the grower. However, the partial effectiveness of these control practices has suggested to researchers that "weak links" exist in the chain of events leading to aflatoxin contamination that could peiliaps be exploited even more effectively to interrupt the contamination process. 

Nonconventional methods. Novel biotechnological methods are needed to control aflatoxin contamination since conventional methods are only partially... 

Inhibit the biosynthetic or secretory processes responsible for aflatoxin contamination. This last approach could be the ultimate generic control method since the aflatoxin biosynthetic pathway is common to all aflatoxin contamination problems. 

The novel biocompetitive strategies outlined here will complement conventional agronomic techniques which result in only partially preventing aflatoxin contamination. 

Table L Prevention of aflatoxin contamination of cottonseed by toxigenic strains of AspergiUus flavus with a strain of the fungus which does not produce aflatoxins (Cotty, 1989. Proc. 38th Oilseed Processing Clinic, pg. 30)...

Several approaches are being explored and developed using new methods in biotechnology to eliminate pre-harvest aflatoxin contamination of food and feed. These approaches resulted from recent information acquired on 1) non-aflatoxigenic A. flavus strains that prevent aflatoxin contamination of cottonseed when co-inoculated with aflatoxigenic strains, 2) molecular mechanisms governing aflatoxin biosynthesis, and 3) plant-derived metabolites that inhibit aflatoxin biosynthesis. 

Agricultural fields often harbor strains of A. flavus that produce little or no aflatoxin during invasion of cotton bolls these strains greatly reduced aflatoxin contamination when the bolls were co-inoculated with a toxigenic strains. Therefore, non-toxigenic strains are potential biocontrol agents. 

Widstrom, N. W. "Breeding strategies to control aflatoxin contamination of maize through host plant resistance" In Aflatoxin in maize A proceedings of the workshop-, Zuber, M. S., et al., Eds. CIMMYT Mexico City, Mexico, 1987, pp. 212-220. 

Cole, R. J. Sanders, T. H. Domer, J. W. and Blankenship, P. D. "Environmental conditions required to induce preharvest aflatoxin contamination of groundnuts summary of six years research" In Aflatoxin contamination of groundnuts ICRISAT publication Patancheru, India, 1989, pp. 279-287. 

Biocides, use for elimination of off-flavor metabolites, 326-327 Biocompetitive agents, use for control of aflatoxin contamination, 280-282 Biosynthesis of geosmin adaptive advantages of production,... 

---