J. Agric.
Food Chem. 1906, 3 4 , 461-465
461
Reduction in Levels of Deoxynivalenol in Contaminated Wheat by Chemical and Physical Treatment J. Christopher Young,* Lionel M. Subryan, Donald Potts, Margaret E. McLaren, and Fakhry H. Gobran
Ontario soft white winter wheat naturally contaminated with deoxynivalenol (DON, vomitoxin) at ca. 1pg/g was treated with a variety of aqueous and gaseous reagents. Of those reagents investigated, aqueous sodium bisulfite effected the greatest reduction in DON levels, with the extent of reduction dependent upon concentration and contact time. Flour resulting from milling of bisulfite-treated wheat contained only low (ca. 5% of original) levels of DON. However, when this flour was baked into a variety of products, DON levels increased to 50-75% of that in the untreated wheat due to alkaline hydrolysis of the DON sulfonate intermediate. Because of detrimental effects on the rheological properties of the dough, flour resulting from the treatment level employed (33 mL of an aqueous solution containing the equivalent of 10% SO2 (w/w) per kilogram of wheat) would not be suitable for commercial use. Although reaction between pure DON and aqueous bisulfite occurred rapidly at room temperature (half-life 5.6 min, in the presence of 10% SO2 equivalents), DON was unaffected by treatment with gaseous SOz.
as modified by Young et al. (1984). GC of (heptafluoroThe trichothecene mycotoxin 4-deoxynivalenol (DON, vomitoxin, 3cu,7~~,15-trihydroxy-12,13-epoxytrichothec-9-butyry1)imidazole- (Regis Chemical Co.) derivatized extracts was carried out on a Hewlett-Packard Model 5710 en-8-one) is a naturally occurring metabolite produced by GC equipped with a 63Nielectron-capture detector and 183 the fungus Fusarium graminearum Schwabe on a variety cm X 4 mm i.d. glass column packed with 3% OV-3 on of cereal grains and is known to be associated with several Chromosorb W-HP (80-100 mesh). The column, injector, diseases in humans and animals (Ueno, 1983). and detector temperatures were 190, 250, and 300 OC, The majority of studies on attempted decontamination respectively, and the nitrogen carrier gas flow was 30 of cereals containing trichothecenes have dealt with the mL/min. Estimations of DON were made by comparison food-processing aspects (cf. Scott, 1984). Several recent of peak heights from injected samples with those of studies on the effects of milling wheat showed that the standards. The results were then corrected on the basis extent of distribution of DON was related to the level of of recoveries from samples spiked at the 0.1-0.35 pg/g contamination. At relatively high concentrations (ca. 5 level. Aliquots from reaction mixtures of treated pure pg/g), DON was fairly uniformly distributed among the DON were analyzed by high-performance liquid chromavarious mill portions (Hart and Braselton, 1983; Scott et tography using a Waters Scientific Radial-PAK cartridge at., 1983), whereas at concentrations of 0.6-1.0 pg/g, packed with C18 Novapak (5 pm) coupled to a Perkinmilling led to increased levels in the outer kernel (e.g. bran) Elmer LC-85 W detector set at 220 nm. The column was portions and decreased levels in the inner flour portions eluted at 2 mL/min with methanol-water (1:l). (Young et at., 1984). Wet milling of corn has been reported to remove two-thirds of T-2 toxin (Collins and Rosen, Analysis for Sodium. Flour samples (5-10 g) were ashed at 400-600 “C for 4-6 h. The residue was dissolved 1981). The effects of further processing (e.g., baking) of wheat are variable (ranging from 0 to 50% reduction) and in 3 M HC1 and analyzed for sodium content on a Varian AA6 atomic absorption spectrophotometer. depend upon the mycotoxin and products (El-Banna et al., 1983; Kamimura et al., 1979; Scott et al., 1983, 1984; Treatment of Wheat with Aqueous Chemical Young et al., 1984). Since millers usually add water to Agents. Samples of contaminated or sound wheat (1kg) wheat prior to milling, we wanted to determine whether were treated with aqueous chemical reagents to achieve it was feasible to add some reagent(s) to the water during a final moisture content of 16%. The reagents were this so-called “tempering” stage and effect a substantial sprayed in four equal portions onto the wheat in a Vreduction in the DON content. The results of such studies shaped Twin Shell dry blender. The wheat was mixed for on the effects of chemical treatment of DON-contaminated 5 min after the addition of each portion of agent. When soft white winter wheat prior to milling and subsequent all of the reagent was added, the wheat was mixed for a baking of the resultant flour are presented in this paper. further 1 h, transferred to a glass jar, which was sealed, and stored at 22 “C and 54% relative humidity. After 24 MATERIALS AND METHODS h, the wheat was ground on a Wiley Laboratory Mill, Wheat. Samples of contaminated (225 kg) and sound Model 4, and passed through a 0.5-mm screen prior to (45 kg) Ontario soft white winter wheat were obtained from analysis. When a large volume (500 mL) of reagent was Reid Milling, Mississauga, Ontario, in 45-kg jute bags and used, the wheat (1kg) was soaked in the reagent for 24 h stored frozen (-20 “C). and air-dried for 24 h prior to grinding. Analysis for Deoxynivalenol. Subsamples from Treatment of Contaminated Wheat with Gaseous ground blended samples were analyzed in duplicate by the Chemical Agents. Initially, dry SO2 gas was passed for gas chromatographic (GC) method of Scott et al. (1981) 3 h through 1kg of wheat in a gas-tight container. The gaseous SOz treatment was repeated on another sample of whect, but the gas was bubbled through water prior to Chemistry and Biology Research Institute, Agriculture being passed through the wheat. Ozone was also used as Canada, Ottawa, Ontario, Canada K1A OC6 (Contribution a reagent. After being generated, the ozone was bubbled No. 1552) (J.C.Y.), and Diversified Research Laboratories through water prior to being passed through the wheat. Limited, Toronto, Ontario, Canada M4W 2L3 (L.M.S., For all these experiments, the gases were passed through D.P., M.E.M., F.H.G.). the wheat for 3 h. The wheat was then left in an atmo~~~
0021-856118611434-0461$01.50/0
Published 1986 by the American Chemical Society
462
J. Agric. Food Chem., Vol. 34, No. 3, 1986
Young
et al.
Table I. Relative Amounts of Deoxynivalenol Remaining in Contaminated Wheat” after Treatment with Aqueous Reagents %
reagent hydrogen peroxide hydrogen peroxided hydrogen peroxided sodium hypochlorite sodium bisulfite ascorbic acid ammonium hydroxide hydrochloric acid
concn 5% 6% 6% 1%
10% soz 2% 5% 0.1 M
reagent v01,~ deoxynivalenol‘ mL/kg remaining 33
92 102
750 33 750 600 600 600
124
