Dojin Ryu

Stability of zearalenone during extrusion of corn grits

The effects of extrusion cooking on the stability of zearalenone (ZEN) in spiked (4.4 microg/g) food-grade corn grits were investigated using a twin screw extruder. A ground rice culture material containing a high level of ZEN was used to spike the corn grits. The extrusion variables were screw type (mixing and nonmixing), temperature (120, 140, and 160 degrees C), and moisture content (18, 22, and 26%). Both unextruded and extruded samples were analyzed for ZEN by high-performance liquid chromatography. Extrusion cooking of the corn grits resulted in significant reductions of ZEN in grits extruded with either mixing screws or nonmixing screws, but use of mixing screws was somewhat more effective (66 to 83%) overall than nonmixing screws (65 to 77%). Greater reduction of ZEN was observed at either 120 or 140 degrees C than at 160 degrees C. The moisture content of corn grits was not a significant factor affecting reduction of ZEN during extrusion with either mixing or nonmixing screws.

Development of a nanobody-alkaline phosphatase fusion protein and its application in a highly sensitive direct competitive fluorescence enzyme immunoassay for detection of ochratoxin A in cereal

A rapid and sensitive direct competitive fluorescence enzyme immunoassay (dc-FEIA) for ochratoxin A (OTA) based on a nanobody (Nb)-alkaline phosphatase (AP) fusion protein was developed. The VHH (variable domain of heavy chain antibody) gene of Nb28 was subcloned into the expression vector pecan45 containing the AP double-mutant gene. The Nb28-AP construct was transformed into Escherichia coli BL21(DE3)plysS, and soluble expression in bacteria was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot. Both the Nb properties and AP enzymatic activity were validated by colorimetric and fluorometric analysis. The 50% inhibitory concentration and the detection limit of the dc-FEIA were 0.13 and 0.04 ng/mL, respectively, with a linear range of 0.06-0.43 ng/mL. This assay was compared with LC-MS/MS, and the results indicated the reliability of Nb-AP fusion protein-based dc-FEIA for monitoring OTA contamination in cereal.

Effect of cycling temperatures on the production of deoxynivalenol and zearalenone by Fusarium graminearum NRRL 5883

The effects of three regimens of cycling incubation temperatures and incubation at constant 25 degrees C on the growth of Fusarium graminearum NRRL 5883 and production of deoxynivalenol (DON) and zearalenone (ZEN) on rice were compared. The effects of low-temperature stress were also studied by incubating rice cultures at a constant 15 degrees C for 4 weeks following incubation at constant 25 degrees C for 2 weeks. Both incubation temperature and time significantly (P < or = 0.05) affected growth of F. graminearum NRRL 5883 and production of DON and ZEN. The highest amount of free ergosterol (640 microg/g culture material) that was used as a measure of fungal growth was found in cultures incubated at temperatures cycling between 15 and 30 degrees C during a 6-week period. The highest amounts of DON (1,679 microg/g culture material) and ZEN (603 microg/g culture material) were produced in cultures incubated at a constant 25 degrees C for 2 weeks prior to incubation at a constant 15 degrees C for an additional 4 weeks. Under cycling incubation temperatures, maximum amounts of DON (850 microg/g culture material) and ZEN (98 microg/g culture material) were produced in cultures incubated at temperatures cycling between 15 and 30 degrees C for 6 weeks. Overall, there was no correlation between mold growth and production of either DON or ZEN. However, DON production and ZEN production were correlated.

Worldwide Occurrence of Mycotoxins in Cereals and Cereal-Derived Food Products: Public Health Perspectives of Their Co-occurrence

Cereal grains and their processed food products are frequently contaminated with mycotoxins. Among many, five major mycotoxins of aflatoxins, ochratoxins, fumonisins, deoxynivalenol, and zearalenone are of significant public health concern as they can cause adverse effects in humans. Being airborne or soilborne, the cosmopolitan nature of mycotoxigenic fungi contribute to the worldwide occurrence of mycotoxins. On the basis of the global occurrence data reported during the past 10 years, the incidences and maximum levels in raw cereal grains were 55% and 1642 μg/kg for aflatoxins, 29% and 1164 μg/kg for ochratoxin A, 61% and 71,121 μg/kg for fumonisins, 58% and 41,157 μg/kg, for deoxynivalenol, and 46% and 3049 μg/kg for zearalenone. The concentrations of mycotoxins tend to be lower in processed food products; the incidences varied depending on the individual mycotoxins, possibly due to the varying stability during processing and distribution of mycotoxins. It should be noted that more than one mycotoxin, produced by a single or several fungal species, may occur in various combinations in a given sample or food. Most studies reported additive or synergistic effects, suggesting that these mixtures may pose a significant threat to public health, particularly to infants and young children. Therefore, information on the co-occurrence of mycotoxins and their interactive toxicity is summarized in this paper.

Reduction of fumonisin B1 in corn grits by single-screw extrusion.

This study was designed to determine the efficacy of extrusion in reducing fumonisin B1 in corn flaking grits in the presence and absence of glucose. In addition, degradation products of fumonisin B1 during extrusion were identified and quantitated with a mass balance approach. Uncontaminated clean corn grits, grits spiked with 30 microg/g fumonisin B1, and grits fermented with Fusarium verticillioides M-2552 (40-50 microg/g fumonisin B1) were extruded in the presence and absence of glucose (10%, w/w) using a single-screw extruder. Extrusion decreased fumonisin B1 by 21-37%, whereas the same process with added glucose further decreased fumonisin B1 by 77-87%. LC-fluorescence and LC-MS showed that most fumonisin in the extruded samples without added glucose was the fumonisin B1 form, whereas the main degradation product in grits extruded with glucose was N-(deoxy- d-fructos-1-yl)fumonisin B1. The formation of hydrolyzed fumonisin B1 was not significant during extrusion. Results suggest that extrusion in the presence of glucose may reduce fumonisin B1 in corn grits significantly.

Effects of processing on zearalenone.

Zearalenone (ZEN), a common contaminant of all major cereal grains worldwide, is produced by some plant pathogenic molds including Fusarium graminearum and F. culmorum. The biological activity of this mycotoxin is mainly attributed to its estrogenic activity that modulates/disrupts endocrine function in animals and possibly humans. Efforts have been made to reduce the level of ZEN by various chemical, physical, and biological processing methods. Some chemical treatments were shown to be effective in reducing zearalenone content in artificially or naturally contaminated foods. During physical processing, the fate of ZEN depended on its distribution in the food matrix and its chemical properties such as heat stability and solubility. For example, wet milling of contaminated corn resulted in starch that was essentially toxin-free. In contrast, animal feed fractions such as bran and germ, by-products of the wet milling process, tended to concentrate ZEN. Extrusion cooking, a complex process where food is subjected to heat, high pressures and shear stress, reduced ZEN levels in food as well as its estrogenic activity. Fermentation of foods with bacteria and yeast resulted in reduction in ZEN levels. However, fermentation can result in the conversion of ZEN to more potent derivatives such as cc-zearalenol. Further efforts are needed to identify effective methods for removing/detoxifying ZEN in foods.

Stability of Fumonisins in Food Processing

Fumonisins are mycotoxins produced by Fusarium verticillioides (moniliforme) and Fusarium proliferatum that are found in corn and processed corn-based food products. Although generally heat stable, fumonisin concentrations appear to decline as processing temperatures increase. At processing temperatures of 125 degrees C or lower, losses of fumonisin are low (25-30%), whereas at temperatures of 175 degrees C and higher, losses are greater (90% or more). Processes such as baking and canning, where product temperatures rarely reach 175 degrees C, result in little or no loss of fumonisin. Processes such as frying and extrusion cooking, where temperatures can exceed 175 degrees C, result in greater losses. Heating fumonisin in the presence of glucose results in an apparent first order loss of the toxin. Adding glucose to corn muffins and extrusion mixes results in high losses of fumonisins during baking and extrusion processing. Little information exists on the effects of chemical and bioprocessing on fumonisins. Alkaline processing of corn, such as in the nixtamalization process, hydrolyzes fumonisins and results in a more toxic product. Additional research is needed to identify and to determine the toxicity of fumonisin decomposition products.

Reduction of Fumonisin B1 in Corn Grits by Twin-Screw Extrusion

UNLABELLED This study was designed to investigate the fate of fumonisins in flaking corn grits during twin-screw extrusion by measuring fumonisin B₁ (FB₁) and its analogs with a mass balance approach. Food grade corn grits and 2 batches of grits contaminated with FB₁ at 10 and 50 μg/g by Fusarium verticillioides M-2552 were processed with or without glucose supplementation (10%, w/w) with a twin-screw extruder. Extrusion reduced FB₁ in contaminated grits by 64% to 72% without glucose and 89% to 94% with added glucose. In addition, extrusion alone resulted in 26% to 73% reduction in the levels of fumonisin B₂ and fumonisin B₃, while levels of both mycotoxins were reduced by >89% in extruded corn grits containing 10% glucose. Mass balance analysis showed that 38% to 46% of the FB₁ species detected in corn extruded with glucose was N-(deoxy-D-fructos-1-yl)-FB₁, while 23% to 37% of FB₁ species detected in extruded corn grits with and without added glucose was bound to the matrix. It was also found that the hydrolyzed form of FB₁ was a minor species in extruded corn grits with or without added glucose, representing <15% of the total FB₁ species present. Less than 46% of FB₁ originally present in corn grits could be detected in the fumonisin analogues measured in this study. Research is needed to identify the reaction products resulting from extrusion processing of fumonisin-contaminated corn products. PRACTICAL APPLICATION Twin-screw extrusion is widely used in food industry for its versatility. This technology may reduce the level of fumonisins in corn particularly with added glucose.

Significance of Ochratoxin A in Breakfast Cereals from the United States

Ochratoxin A (OTA) has been found in all major cereal grains including oat, wheat, and barley worldwide and considered as a potential concern in food safety. A total of 489 samples of corn-, rice-, wheat-, and oat-based breakfast cereal were collected from U.S. retail marketplaces over a two-year period, and OTA was determined by high-performance liquid chromatography. Overall, 205 samples (42%) were contaminated with OTA in the range from 0.10 to 9.30 ng/g. The levels OTA were mostly below of the European Commission Regulation (3 ng/g) except in 16 samples of oat-based cereals. The incidence of OTA was highest in oat-based breakfast cereals (70%, 142/203), followed by wheat-based (32%, 38/117), corn-based (15%, 15/103), and rice-based breakfast cereals (15%, 10/66). On the basis of the incidence and concentration of OTA, oats and oat-based products may need greater attention in further surveillance programs and development of intervention strategies to reduce health risks in consumers.

DON occurrence in grains: A North American perspective

In agricultural commodities, the occurrence of deoxynivalenol (DON) has been reported all over the world, with levels varying among grain types and years of production. The grain supply chain, including growers, buyers, and end users, have effectively managed DON with strategies to control this issue systematically. The safety of consumers is ensured through use of these management strategies. This is observed in this review of the North American systems. This article describes the occurrence and management of DON in North America, which is accomplished by 1) a review of the toxicological effects of DON; 2) a review of publically available data and introduction of new information regarding the occurrence of DON in wheat, maize, and barley in North America, including variability due to growing regions, grain varieties, and year of production; 3) an overview of industry practices to reduce DON contamination from field through milling when necessary; 4) a review of how all in the value chain, including growe...