Development of Detection and Reduction Methods for Mycotoxins in Corn and Herbal Plant Material

Abstract

This is a study of methods to reduce, eliminate or prevent fumonisins and aflatoxins in corn and to survey botanical supplements for aflatoxins. Gamma (Cobalt60) and electron beam irradiation were used to eradicate fumonisin B1. Fumonisin B1 in water was irradiated with 0.5 to 30.0 kGrays. The minimum dosage (0.5 kGray) reduced fumonisin 99%. When naturally contaminated whole and ground corn was exposed to irradiation (10.0-100.0 kGray), Aspergillus and Fusarium fungi were killed; whereas, the level of fumonisins was not changed.

Transgenic Bt and non-Bt (NBt) 2000 and 2001 corn were inoculated with Fusarium verticillioides and Aspergillus flavus at silking. At harvest, corn was rated for insect damage, mold populations and levels of fumonisins and aflatoxins. There were little aflatoxins in 2000 corn and none in 2001 corn. Levels of fumonisins in 2000 Bt corn were not significantly lower than the level found in Bt corn; however, 2001 Bt corn showed significantly higher levels of fumonisins than those found in NBt corn.

Whereas irradiated herbal material contained no microorganisms, non-irradiated material was contaminated with Aspergillus, Penicillium, and Rhizopus. All A. flavus isolates from herbal material produced aflatoxin B1 on rice cultures. Twenty-four of 25 irradiated and non-irradiated herbals contained AFB1, ranging from trace levels to 450 ng/g. An analytical method to detect aflatoxins in herbal products was developed for ginseng root, Panax quinquefolius. Aflatoxins AFB1, AFB2, AFG1, and AFG2 were added to toxin free ginseng at 2 ng/g, 4 ng/g, 8 ng/g and 16 ng/g. Based on HPLC analysis, mean recoveries ranged from 77% to 92 %.

This method was used to survey wild simulated and cultivated ginseng roots harvested after a dry growing season (2002) and a wet growing season (2003). Root samples were from UMD field plots, a commercial source, and from Appalachian growers. Levels of 5.5-32.0 ng/g AB1 were found in 4 samples from a wild simulated grower. One of nine cultivated samples contained trace amounts (0.10 ng/g) AB1 from the 2002 season, and no aflatoxins were found in 2003 samples. In the commercial fresh root sample 16 ng/g of AB1 was found.