Fusarium graminearum in Stored Wheat: Use of CO2 Production to Quantify Dry Matter Losses and Relate This to Relative Risks of Zearalenone Contamination under Interacting Environmental Conditions

Abstract

Zearalenone (ZEN) contamination from Fusarium graminearum colonization is particularly important in food and feed wheat, especially during post-harvest storage with legislative limits for both food and feed grain. Indicators of the relative risk from exceeding these limits would be useful. We examined the effect of different water activities (aw; 0.95–0.90) and temperature (10–25 °C) in naturally contaminated and irradiated wheat grain, both inoculated with F. graminearum and stored for 15 days on (a) respiration rate; (b) dry matter losses (DML); (c) ZEN production and (d) relationship between DML and ZEN contamination relative to the EU legislative limits. Gas Chromatography was used to measure the temporal respiration rates and the total accumulated CO2 production. There was an increase in temporal CO2 production rates in wetter and warmer conditions in all treatments, with the highest respiration in the 25 °C × 0.95 aw treatments + F. graminearum inoculation. This was reflected in the total accumulated CO2 in the treatments. The maximum DMLs were in the 0.95 aw/20–25 °C treatments and at 10 °C/0.95 aw. The DMLs were modelled to produce contour maps of the environmental conditions resulting in maximum/minimum losses. Contamination with ZEN/ZEN-related compounds were quantified. Maximum production was at 25 °C/0.95–0.93 aw and 20 °C/0.95 aw. ZEN contamination levels plotted against DMLs for all the treatments showed that at ca. <1.0% DML, there was a low risk of ZEN contamination exceeding EU legislative limits, while at >1.0% DML, the risk was high. This type of data is important in building a database for the development of a post-harvest decision support system for relative risks of different mycotoxins.

Influence of storage environment on maize grain: CO2 production, dry matter losses and aflatoxins contamination

“…A comparison with previous studies on oats colonised by F. langsethiae (T-2, HT-2 toxins), maize and F. verticillioides (fumonisins), wheat and F. graminearum (ZEA and related toxins) and paddy and brown rice colonised by A. flavus and F. verticillioides (Garcia-Cela, Kiaitsi, Medina, Magan, 2018;Martin Castaño, Medina, & Magan, 2017a,b;Mylona & Magan, 2011;Mylona, Sulyok, & Magan, 2012) could be made. In these previous studies, DML of between 1 and 2% in cereals (rice, wheat, maize) contaminated with Fusarium toxins (FMs, DON and ZEA) resulted in levels exceeding the EU legislative limits.…”

“…Consequently, a relationship exists between small DMLs and the potential risk of exceeding legislative limits especially for human consumption. Intermediate tolerances to DMLs may be possible for commodities destined for animal feed use (Garcia-Cela, Kiaitsi, Medina, Magan, 2018).…”

“…According to Seitz et al, (1982), the contribution to DML from fungi increases during storage at a rate dependent on moisture, temperature, amount and type of kernel damage and level of fungal inoculum on the grain. Recent studies have examined the use of CO2 production during storage of maize, wheat and rice as an indicator of the level of AFs, FMs, deoxynivalenol (DON), ZEA and trichothecenes A (TCT-A) contamination (Garcia-Cela, Kiaitsi, Medina, et al, 2018;Martín Castaño, Medina, & Magan, 2017a,b;Mylona & Magan, 2011;Mylona, Sulyok, & Magan, 2012) These studies proved that it is possible to utilise the progressive increase in the respiration rate under increasingly conducive conditions for mould growth due to the oxidation of carbohydrates and hence CO2 production, water vapour and heat during aerobic respiration to calculate quality losses as DML. DML can be quantified based on CO2 production and respiration rates using Gas Chromatography (GC) and these data sets are used as a "storability risk index" to predict overall quality changes in stored grain.…”

“…Seitz et al, (1982) showed that a loss of 0.5% DML in stored maize was enough to downgrade this commodity from food to feed, with associated increased risks of aflatoxin contamination. DML of between 1 and 2% in cereals (rice, wheat, maize) contaminated with Fusarium toxins (FMs, DON and ZEA) resulted in contamination levels which exceeded the EU legislative limits (Garcia-Cela, Kiaitsi, Medina, et al, 2018;Martin Castaño, Medina, & Magan, 2017a,b;Mylona, Sulyok, & Magan, 2012).…”

The effect of storage temperature and water activity on aflatoxin B1 accumulation in hull‐less and hulled spelt grains

“…24,25 Also, it was indicated that production of secondary metabolites might be altered by atmospheric carbon dioxide (CO 2 ) content. [26][27][28] RNA-sequencing data demonstrated that several genes, involved in the biosynthesis of AFB 1 , exhibit different responses to a w or temperature depending on the atmospheric CO 2 content. 27,28 To date several studies on the effect of temperature and a w value on aflatoxin production in stored grains such as maize, 25 rice 29,30 and sorghum 31 have been published.…”