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The fate of the Fusarium mycotoxins deoxynivalenol and nivalenol during the milling of Japanese wheat cultivars artificially infected with Fusarium was investigated. Grain samples with different mycotoxin concentrations were milled using a laboratory-scale test mill to produce eight fractions: three breaking flours (1B, 2B, and 3B), three reduction flours (1M, 2M, and 3M), wheat bran, and wheat shorts. Patent flour for human consumption was made from the 1B, 2B, 1M, and 2M flours, and low-grade flour was made from 3B and 3M flours. The four resulting samples (patent flour, low-grade flour, bran, and shorts) were analyzed for deoxynivalenol and/or nivalenol with an in-house validated analytical method using high-performance liquid chromatography with UV absorbance detection. In samples with different mycotoxin concentrations, the distribution of those toxins differed among the milling fractions. Grains with a lower level of contamination produced bran and shorts samples with a high relative concentration of nivalenol. A high percentage of nivalenol was found in patent flour, followed by bran. Contrary to the less-contaminated sample, the concentration of nivalenol in moderately contaminated grain was high only in the shorts sample. The highest percentage of deoxynivalenol and nivalenol was observed in the patent flour. The results of this study indicate that the distribution of deoxynivalenol and nivalenol in milled Japanese wheat could be influenced by the contamination level of the original grain, and the milling process is not always effective for removal of toxins from wheat grains.

The occurrence of mycotoxins in small grain cereals and their retention in final products are serious concerns for food safety. Previously, we investigated the fate of deoxynivalenol and nivalenol in a Japanese soft red winter wheat cultivar during milling and we found that deoxynivalenol and/or nivalenol was readily distributed among flours for human consumption. In the present study, we analyzed the ergosterol concentrations in the milling fractions as an index of fungal biomass to elucidate the relationship between deoxynivalenol/nivalenol accumulation and fungal invasion into the grain, after the in-house validation of an analytical method for quantifying ergosterol in the resulting milling fractions (patent flour, low-grade flour, bran, and shorts). Using three samples with different levels of deoxynivalenol and/or nivalenol contamination, the contents of deoxynivalenol/nivalenol and ergosterol in the resulting milling fractions were evaluated. The concentration of ergosterol was always lowest in patent flour and highest in bran or shorts, indicating that most of the fungi is retained in the outer layers of grain (bran and shorts) even in highly contaminated grain. On the other hand, the concentrations of deoxynivalenol and nivalenol were similar in the low-grade and patent flours and only slightly lower than in the medium-level and high-level contaminated grains. Moreover, the percentage distribution of ergosterol was higher in bran than in other fractions in all cases, which differed from that of deoxynivalenol/nivalenol. This result indicates the diffusion of deoxynivalenol/nivalenol inside the grain that is independent of fungal invasion.

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The physiology of starch degradation in relation to ripening and ethylene was investigated using 'Tsugaru' (earlymaturing) and 'Fuji' (late-maturing) apples (Malus domestica Borkh.). Fruits were harvested at immature and mature stages, and treated with ethylene and 1-methylcyclopropene (1-MCP). In immature fruit of both cultivars, starch content rapidly decreased during storage at 25°C, and 1-MCP had little effect on this change. Ethylene treatment slightly stimulated the degradation of starch, but differences in starch among treatments were small. The respiration rate gradually decreased and ethylene production remained low during storage irrespective of the treatments and cultivars. These results showed that fruit at this stage could not respond to endogenous and exogenous ethylene for inducing the climacteric, and starch degradation did not relate to the climacteric or ethylene. In mature 'Tsugaru', 1-MCP treatment significantly inhibited ethylene production and reduced the respiration rate and starch degradation. The effects of 1-MCP and ethylene on starch degradation in mature 'Fuji' were small, and starch content decreased drastically in all treatments, although 1-MCP significantly inhibited ethylene production and the respiration rate. It is suggested that ethylene is partially involved in starch degradation in mature 'Tsugaru', but not in 'Fuji'. These results showed that the role of ethylene in starch degradation differs between cultivars and their harvested stages, relating to ripening and physiological characteristics of the fruit.

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