Effect of cleaning, milling, and baking on deoxynivalenol in wheat

Samples of wheat naturally infected by Fusarium graminearum Schwabe were obtained from mills in Oklahoma, Missouri, Kansas, and Minnesota and fields in Nebraska and Kansas in 1982; they were analyzed for deoxynivalenol (DON). The wheat was milled, and DON was found throughout all the milling fractions (bran, shorts, reduction flour, and break flour). The DON recoveries for each mill run ranged from 90 to 98%. These samples, regardless of DON concentration, also gave similar fractional distributions of DON. The greatest (21 ppm [21 micrograms/g]) concentration of DON was found in the bran, and the smallest (1 ppm) was found in the break flour. Cleaning and milling were not effective in removing DON; DON was not destroyed in the bread baked from the naturally contaminated whole wheat flour, but the effect on its concentration in the samples analyzed varied, the reduction ranging from 19 to 69%. The percent reduction found in the cleaned wheat ranged from 6 to 19%. DON concentrations in the following commercially made breads, caraway rye, seedless rye, and pumpernickel, were 45 ppb (ng/g), 39 ppb, and 0 ppb, respectively. The limits of detection by gas chromatography-mass spectrometry and high-pressure liquid chromatography for DON were 0.5 and 10 ng, respectively.     

Effect of cleaning, milling, and baking on deoxynivalenol in wheat.

Samples of wheat naturally infected by Fusarium graminearum Schwabe were obtained from mills in Oklahoma, Missouri, Kansas, and Minnesota and fields in Nebraska and Kansas in 1982; they were analyzed for deoxynivalenol (DON). The wheat was milled, and DON was found throughout all the milling fractions (bran, shorts, reduction flour, and break flour). The DON recoveries for each mill run ranged from 90 to 98%. These samples, regardless of DON concentration, also gave similar fractional distributions of DON. The greatest (21 ppm [21 micrograms/g]) concentration of DON was found in the bran, and the smallest (1 ppm) was found in the break flour. Cleaning and milling were not effective in removing DON; DON was not destroyed in the bread baked from the naturally contaminated whole wheat flour, but the effect on its concentration in the samples analyzed varied, the reduction ranging from 19 to 69%. The percent reduction found in the cleaned wheat ranged from 6 to 19%. DON concentrations in the following commercially made breads, caraway rye, seedless rye, and pumpernickel, were 45 ppb (ng/g), 39 ppb, and 0 ppb, respectively. The limits of detection by gas chromatography-mass spectrometry and high-pressure liquid chromatography for DON were 0.5 and 10 ng, respectively.     

Deoxynivalenol and nivalenol in wheat and by-products in Argentina

The deoxynivalenol and nivalenol contamination in wheat and by-products obtained through milling was analized by Trucksess method slightly modified in the proportion of acetonitrile—water (3:1). Only one sample of wheat showed deoxynivalenol contamination, 1,200μg/kg. No samples obtained in different stages of the milling were contaminated with deoxynivalenol or nivalenol. In the commercial wheat flours the levels found ranged between 400 and 800μg/kg, as follows: 400μ/kg, 5 samples; 800jug/kg, 1 sample.     

Decontamination ofFusarium mycotoxins,nivalenol, deoxynivalenol,and zearalenone,in barley by the polishing process

Korean dehusked and unhusked barley naturally contaminated withFusarium mycotoxins were polished using a Satake Grain Testing Mill. The pearled barley and bran fractions with different degrees of polishing were analyzed for nivalenol (NIV) and deoxynivalenol (DON) by gas chromatography with an electron capture detector, and for zearalenone (ZEN) by high-performance liquid chromatography with a fluorescence detector. NIV was detected in all the pearled barley fractions, but DON and ZEN were not detected in ≥27 % pearled barley fractions from dehusked barley and ≥36% pearled barley fractions from unhusked barley. However, for all degrees of polishing, NIV, DON, and ZEN were detected in bran fractions. The levels of NIV, DON, and ZEN in the bran fractions increased several fold over the original barley. Polishing was effective in removing DON and ZEN from the naturally contaminated barley, but not NIV.     

Concentration of ergosterol in small-grained naturally contaminated and inoculated cereals

Ergosterol (ERG) is a major sterol constituent of most fungi. Its concentration is negligible in higher plants, but can be used as a chemical marker of the presence of fungal contaminations. In this study, ERG concentration was assessed in randomly collected samples of naturally contaminated grain (wheat, barley and oat) and in samples of grain (wheat, barley, triticale and oat) harvested after inoculation of heads with conidia of different Fusarium species. Wheat samples were analysed at three stages of grain development. The lowest ERG concentration was found in non-inoculated samples at the first stage of grain development. This concentration was increasing with grain ripening. In naturally contaminated samples collected after harvest, ERG concentration was lower in wheat than in barley and oat. ERG concentrations in inoculated samples varied significantly, but were always significantly higher than in naturally contaminated samples. In the above cereal samples it was much lower than the levels assayed in laboratory cultures inoculated with fungi from genus Fusarium. The content of ERG was also analyzed in milling products of small-grained cereals and other foodstuffs, where a considerable variation was observed. The lowest ERG amounts were assayed in flours with a high degree of purification, while the highest ones in case of flours and products with a low purification rate. The results indicate the potential application of HPLC combined with microwave-assisted extraction both when assaying samples with low ERG concentrations (naturally contaminated) and those characterized with high contents of fungal biomass (strongly infected, artificially inoculated). It also facilitates analyses of fungal biomass in technological processes, where results may be expected to vary considerably.     

Fractionation of the rice bran layer and quantification of vitamin E, oryzanol, protein, and rice bran saccharide

Value-added processing with respect to rice milling has traditionally treated the rice bran layer as a homogenous material that contains significant concentrations of high-value components of interest for pharmaceutical and nutraceutical applications. Investigators have shown that high-value components in the rice bran layer vary from differences in kernel-thickness, bran fraction, rice variety, and environmental conditions during the growing season. The objectives of this study were to quantify the amount of rice bran removed at pre-selected milling times and to correlate the amount of rice bran removed at each milling time with the concentration of vitamin E, gamma-oryzanol, rice bran saccharide, and protein obtained. The ultimate goal of this research is to show that rice bran fractionation is a useful method to obtain targeted, nutrient-rich bran samples for value-added processing. Two long grain rice cultivars, Cheniere and Cypress, were milled at discrete times between 3 and 40 seconds using a McGill mill to obtain bran samples for analysis. Results showed that the highest oryzanol and protein concentrations were found in the outer portion of the rice bran layer, while the highest rice bran saccharide concentration was found in the inner portion of the bran layer. Vitamin E concentration showed no significant difference across the bran layer within a variety, though the highest magnitude of concentration occurs within the first 10 seconds of milling for both varieties. To extract the higher concentration of oryzanol and protein only the outer portion of the bran layer requires processing, while to extract the higher concentration of rice bran saccharide, only the inner portion of the bran layer requires processing. Rice bran fractionation allows for the selective use of portions of the bran layer and is advantageous for two reasons: (1) bran fractions contain higher concentrations of components of interest with respect to the overall bran layer average, and (2) less bran needs to be processed to obtain components of interest.     

The use of trichothecene-contaminated grains in feeds

A review is presented describing the relative efficiencies of the various technologies that have been proposed to permit incorporation of mycotoxin-contaminated grains into animal diets without adversely influencing growth rate or resulting in hazardous residues in edible animal tissues. When the degree of contamination is modest, it may be possible to dilute the contaminated materials with uncontaminated grain to lower the concentration of trichothecenes below the threshold of significant biological activity. A less useful alternative to dilution is the other mechanical approach of milling to remove the most heavily contaminated fractions of the grain. Chemical destruction of triochothecenes is also a possibility. An example is the use of sodium bisulfite treatment to destroy deoxynivalenol in contaminated corn. Such treatments may, however, reduce palatability and nutritional value. When the biochemical mechanism of trichothecene toxicity is known, in vivo therapeutic treatments may be possible. It has been shown, for example, that T-2 toxin-induced changes in brain prostaglandin production can be overcome by treatment with dexamethasone resulting in increased survival. A similar effect was seen using the selective platelet activating factor antagonist BN 52021. Another approach is the use of dietary treatments to either promote in vivo detoxification of mycotoxins or to reduce absorption from the digestive tract with the aid of nonnutritive binding agents.     

Antioxidant activity and phenolic content of the Indian wheat varieties

In this study, Indian wheat varieties grown under different agro-climatic zones were evaluated for their antioxidant potential. Different grain fractions (bran, flour, shorts) and the whole meal were tested using two free radicals (ABTS and DPPH) for their radical scavenging activities. More variation was observed in the antioxidant activities from different zones using DPPH assay. Irrespective of the method used, the whole meal and the bran of central zone varieties showed the highest and the north western plains zone varieties showed the lowest antioxidant activities. Within each growing zone, both the effect of genotype and environment was observed on the antioxidant activity. Both free and bound phenolic compounds were extracted from the bran of varieties representing different zones. Total phenolic content (TPC) varied from 2,900 to 5,650 μg Gallic acid equivalents/g of bran. Bound phenolic content was found to be more strongly correlated to the TPC than the free phenolic content. Highly significant genotypic differences were observed in the total phenolic content. This study therefore indicates that Indian wheat varieties have good antioxidant activity and high content of phenolic compounds and can be used further in breeding programmes to increase the content of phytochemicals responsible for antioxidant activity.     

Bread wheat milling behavior: effects of genetic and environmental factors,and modeling using grain mechanical resistance traits

Key message

Genetic (Pinb-D1 alleles) and environment (through vitreousness) have important effects on bread wheat milling behavior. SKCS optimal values corresponding to soft vitreous or hard mealy grains were defined to obtain the highest total flour yield.

Abstract

Near-isogenic lines of bread wheat that differ in hardness, due to distinct puroindoline-b alleles (the wild type, Pinb-D1a, or the mutated forms, Pinb-D1b or Pinb-D1d), were grown in different environments and under two nitrogen fertilization levels, to study genetic and environmental effects on milling behavior. Milling tests used a prototype mill, equipped with two break steps, one sizing step, and two reduction steps, and this enabled 21 individual or aggregated milling fractions to be collected. Four current grain characters, thousand grain weight, test weight, grain diameter, and protein content, were measured, and three characters known to influence grain mechanical resistance, NIRS hardness, SKCS hardness index, and grain vitreousness (a character affecting the grain mechanical behavior but generally not studied). As expected, the wild type or mutated forms of Pinb-D1 alleles led to contrasted milling behavior: soft genotypes produced high quantities of break flour and low quantities of reduction flour, whereas reverse quantities were observed for hard genotypes. This different milling behavior had only a moderate influence on total flour production. NIRS hardness and vitreousness were, respectively, the most important and the second most important grain characters to explain milling behavior. However, contrary to NIRS hardness, vitreousness was only involved in endosperm reduction and not in the separation between the starchy endosperm and the outer layers. The highest flour yields were obtained for SKCS values comprised between 30 and 50, which corresponded either to soft vitreous or hard mealy grains. Prediction equations were defined and showed a good accuracy estimating break and reduction flours portions, but should be used more cautiously for total flour.

     

Mycotoxins in cereal grain (part 15). Distribution of deoxynivalenol in naturally contaminated wheat kernels

The analysis of deoxynivalenol (DON) in naturally infected wheat samples, after having been separated into four fractions through laboratory sieves, showed very low levels of DON in the fraction of largest kernels >2.8 mm (0 up to 1 mg/kg). The highest concentration of DON was found in fractions 2.2 to 2.5 mm and <2.2mm with up to 14mg/kg and 15mg/kg DON, respectively. In two samples (fractions <2.2mm) nivalenol was detected in concentrations up to 1,4mg/kg.     

Mycotoxins in maize products of the 1994/95 marketing season

The levels of mycotoxins found were generally lower the more refined the maize products were. The highest levels of deoxynivalenol, nivalenol and fumonisins were found in maize bran and maize screenings. Ochratoxin A was found in a defatted germ meal sample at 50 μg/kg. Zearalenone was found randomly in samples at low levels (50 – 100 μg/kg). All other mycotoxins tested for, except in maize bran and maize screenings, were absent above the detection limits     

Susceptibility of Kenyan Wheat Varieties to Head Blight, Fungal Invasion and Deoxynivalenol Accumulation Inoculated with Fusarium graminearum

Fifteen wheat varieties commercially grown in Kenya were tested for their susceptibility to head blight and mycotoxin accumulation after inoculation with Fusarium graminearum in pot experiments. The strains of the pathogen used had been isolated from wheat collected in different growing areas of Kenya. Head blight susceptibility was assessed as the percentage of spikelets bleached and area under disease progress curve; kernel colonization by fungal mycelium was determined as ergosterol content. All varieties were found to be moderately to highly susceptible. However, the varieties differed in head blight susceptibility (29–68% of spikelets bleached; mean 54%), fungal colonization (67–187  μ g/g ergosterol content; mean 111  μ g/g) and the resulting mycotoxin contamination [deoxynivalenol (DON) 5–31  μ g/g; mean 13.5  μ g/g]. Grain weight reductions due to head blight ranged from 23 to 57% (mean 44%). The varieties could be therefore divided into partially resistant and highly susceptible genotypes. The kernels of highly susceptible varieties had higher mycotoxin and ergosterol contents. However, the kernels of some varieties contained more fungal mycelium (ergosterol) without the corresponding high amounts of DON, suggesting that they possess some resistance to DON accumulation. Less susceptible varieties showed resistance to fungal spread, as indicated by a slow disease development and lower content of fungal biomass.     

Natural occurrence of deoxynivalenol, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol,nivalenol, 4,7-dideoxynivalenol,and zearalenone in polish wheat

Three wheat samples collected in 1987 in Central Poland and naturally infected withFusarium spp were analyzed for the presence ofFusarium spp andFusarium toxins. Heads were separated into three fractions: kernels with visibleFusarium damage, healthy looking kernels, and chaff + rachis. The samples contained deoxynivalenol (2.0 – 40.0μg/g), nivalenol (O.O1μg/g), 4,7-dideoxynivalenol (0.10 – 0.15μg/g). 15-acetyldeoxynivalenol (0.10–2.00 μg/g), 3-acetyldeoxynivalenol (O/1Oμg/g), and zearalenone (0.01–2.00μg/g). This is the first report about 15 - acetyldeoxynivalenol in European wheat and the co-occurrence of 3 - acetyldeoxynivalenol and 15-acetyldeoxynivalenol in the same sample of contaminated cereals.     

Effect of delayed harvest on contamination of pearl millet grain with mycotoxin-producing fungi and mycotoxins

The response to delayed harvest of fungal and mycotoxin contamination of grain of the pearl millet hybrid HGM 100 was examined in 1992 and 1993. Samples of grain were assayed from seven plantings at locations near Tifton, Georgia, USA. Grain was harvested at 30, 40, and 50 days after anthesis and evaluated for infection byFusarium species andAspergillus flavus, and mycotoxin contamination. Mean isolation frequencies ofF. semitectum (35.6%) andF. chlamydosporum (17.2%) increased linearly with delayed harvest.Fusarium moniliforme andF. equisiti were infrequently isolated (<0.5%) and did not increase in the grain when harvest was delayed. Low mean concentrations of zearalenone (0.17 ppm), nivalenol (0.42 ppm), and deoxynivalenol (0.01 ppm) were detected but were not affected by delayed harvest. Isolation frequencies ofF. chlamydosporum andF. equiseti were correlated (P=0.07) with levels of nivalenol.Aspergillus flavus was not isolated from the grain, and aflatoxin concentrations averaged 1.9 ppb.     

Simultaneous occurrence of deoxynivalenol, zearalenone, and aflatoxin in 1982 scabby wheat from the midwestern United States

Thirty-three samples of wheat of the 1982 crop year from Kansas and Nebraska were analyzed for deoxynivalenol, T-2 toxin, zearalenone, and aflatoxin. Deoxynivalenol was identified in 31 of 33 samples, zearalenone was identified in 3 of 33 samples, and aflatoxin B1 was identified in 23 of 31 samples. One 1982 wheat sample from Illinois and one from Texas were also contaminated with deoxynivalenol at 1,200 and 600 ng/g, respectively. None of the samples contained detectable T-2 toxin. The mean concentration of deoxynivalenol was 1,782 +/- 262 ng/g, and the concentrations of aflatoxin B1 ranged from 0.8 to 17.0 ng/g, with a mean of 3.37 +/- 0.7. Zearalenone concentrations of the three positive samples were 35, 90, and 115 ng/g. However, density segregation of two other samples which tested negative yielded light fractions, comprising less than 2% of the samples, contaminated at 230 and 254 ng of zearalenone per g; calculated zearalenone concentrations for these two samples were below the limit of detection of the method. The high frequency of aflatoxin B1 and deoxynivalenol in wheat from the 1982 crop is unprecedented, as is the simultaneous contamination of some samples with deoxynivalenol, zearalenone, and aflatoxin B1.     

Simultaneous occurrence of deoxynivalenol, zearalenone, and aflatoxin in 1982 scabby wheat from the midwestern United States.

Thirty-three samples of wheat of the 1982 crop year from Kansas and Nebraska were analyzed for deoxynivalenol, T-2 toxin, zearalenone, and aflatoxin. Deoxynivalenol was identified in 31 of 33 samples, zearalenone was identified in 3 of 33 samples, and aflatoxin B1 was identified in 23 of 31 samples. One 1982 wheat sample from Illinois and one from Texas were also contaminated with deoxynivalenol at 1,200 and 600 ng/g, respectively. None of the samples contained detectable T-2 toxin. The mean concentration of deoxynivalenol was 1,782 +/- 262 ng/g, and the concentrations of aflatoxin B1 ranged from 0.8 to 17.0 ng/g, with a mean of 3.37 +/- 0.7. Zearalenone concentrations of the three positive samples were 35, 90, and 115 ng/g. However, density segregation of two other samples which tested negative yielded light fractions, comprising less than 2% of the samples, contaminated at 230 and 254 ng of zearalenone per g; calculated zearalenone concentrations for these two samples were below the limit of detection of the method. The high frequency of aflatoxin B1 and deoxynivalenol in wheat from the 1982 crop is unprecedented, as is the simultaneous contamination of some samples with deoxynivalenol, zearalenone, and aflatoxin B1.     

Ergosterol Content in Various Fungal Species and Biocontaminated Building Materials

This paper reports the ergosterol content for microbial cultures of six filamentous fungi, three yeast species, and one actinomycete and the ergosterol levels in 40 samples of building materials (wood chip, gypsum board, and glass wool) contaminated by microorganisms. The samples were hydrolyzed in alkaline methanol, and sterols were silylated and analyzed by gas chromatography-mass spectrometry. The average ergosterol content varied widely among the fungal species over the range of 2.6 to 42 μg/ml of dry mass or 0.00011 to 17 pg/spore or cell. Ergosterol could not be detected in the actinomycete culture. The results for both the fungal cultures and building material samples supported the idea that the ergosterol content reflects the concentration of filamentous fungi but it underestimates the occurrence of yeast cells. The ergosterol content in building material samples ranged from 0.017 to 68 μg/g of dry mass of material. A good agreement between the ergosterol concentration and viable fungal concentrations was detected in the wood chip (r > 0.66, P ≤ 0.009) and gypsum board samples (r > 0.48, P ≤ 0.059), whereas no relationship between these factors was observed in the glass wool samples. For the pooled data of the building materials, the ergosterol content correlated significantly with the viable fungal levels (r > 0.63, P < 0.0001). In conclusion, the ergosterol concentration could be a suitable marker for estimation of fungal concentrations in contaminated building materials with certain reservations, including the underestimation of yeast concentrations.     

The content and distribution of steryl ferulates in wheat produced in Japan

Oryzanol contained in rice bran is a complex mixture of steryl ferulates (SFs) with many identified health benefits. Recently, SF has been shown to exist in other cereals such as wheat, rye, and corn. In this study, SFs in several wheats produced in Japan were analyzed. For instance, SF content of whole wheat grain, Yumekaori (Japan) was 15.2 ± 1.4 mg-oryzanol-equivalent/100 g grain, while that of the imported one, 1CW (Canada) was 11.4 ± 1.3 mg-oryzanol-equivalent/100 g grain. The main SF components in the examined wheats were campesteryl ferulate, campestanyl ferulate, and sitostanyl ferulate. SF distribution in whole wheat grain was investigated using 14 fractions produced by a conventional test milling machine. SF was intensively accumulated in the four bran fractions (24 ? 95 mg-oryzanol-equivalent/100 g bran fraction). These results suggest that the wheat bran would be an important source of SF.     

Fungi in flour and refrigerated dough products

Summary Fungal counts of 19 flour samples and 11 wheat samples from 11 flour mills of the Kansas-Nebraska and Pacific Northwest wheat-growing areas were made over a period of 2 years. In addition, 50 spoiled and 22 fresh samples of refrigerated dough products were examined for their fungal content. Methods for obtaining counts of fungi from flour and refrigerated dough were improved through the use of tetracycline as a bacterial inhibitor. Fungal counts ranged from 85 to 8,100 per gram in flour and from 90 to 1,400 in wheat. Generally, mold counts were higher in the flour than in the wheat. Judging from earlier reports, improved handling of wheat and better milling practices are effecting a gradual reduction in fungal counts in commercial flours. More than 500 fungi were isolated from the flours and doughs and were identified. Except for a few Fungi Imperfecti and Mucorales, the majority of the species from the flours belong in the generaAspergillus andPenicillium. Not only do they belong to these genera, but to specific groups in each. In the genusAspergillus, representatives of theA. candidus, A. glaucus, A. flavus-oryzae, andA. versicolor groups were the only ones present. InPenicillium the series commonly found wereP. cyclopium, P. citrinum, andP. urticae, and the remaining species were scattered among various series. Fungal counts of both fresh and spoiled dough samples were comparatively low. Essentially, the fungal flora of the doughs was a reflection of the flour microflora. Spoilage of the dough products did not appear to be of fungal origin.This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.