During malolactic fermentation in wine by Oenococcus oeni, the degradation of citric acid was delayed compared to the degradation of malic acid. The maximum concentration of diacetyl, an intermediary compound in the citric acid metabolism with a buttery or nutty flavor, coincided with the exhaustion of malic acid in the wine. The maximum concentration of diacetyl obtained during malolactic fermentation was strongly dependent on the oxygen concentration and the redox potential of the wine and, to a lesser extent, on the initial citric acid concentration. The final diacetyl concentration in the wine was also dependent on the concentration of SO2. Diacetyl combines rather strongly with SO2(Kf = 7.2 × 103M−1 in 0.1 M malate buffer [pH 3.5] at 30°C). The reaction is exothermic and reversible. If the concentration of SO2 decreases during storage of the wine, the diacetyl concentration increases again.

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Ten laboratories participated in a collaborative study of a method for the determination of deoxynivalenol in wheat by gas chromatography with electron capture detection. Each laboratory analyzed 6 samples in duplicate. Each collaborator received samples spiked at the 100.3, 501.3, and 1002.6 ng/g levels; a control sample; and 2 naturally contaminated samples. The average recovery (outliers excluded) for the spiked samples was 92.2%. The mean repeatability and reproducibility, respectively, were 32.2 and 41.3% for the spiked samples and 30.9 and 47.6% for the naturally contaminated samples. The method was adopted official first action.

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