An overview is provided of the use of cyclic voltammetry and electrochemical detectors for HPLC to characterize antioxidants that are active as reducing agents at inert electrodes. Results are presented for cyclic voltammetry at a glassy carbon electrode in 50% methanol, 50% 0.1 M HClO4, a solution typically used in HPLC separations of natural antioxidants. The relative reducing strength of each antioxidant is estimated by the formal potential, and information is also obtained regarding the reversibility of the oxidation of the antioxidants, and the extent to which the carbon electrode is contaminated by the products of oxidation. Cyclic voltammetry of complex mixtures such as blood serum and wine produces a measure of the total antioxidant status due to antioxidants with a low oxidation potential. The results of cyclic voltammetry studies are relevant to interpreting the performance of carbon electrodes in electrochemical detectors for HPLC.

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Background and Aims Microoxygenation (MOX) is widely used in winemaking. Its impact, however, on Pinot Noir wines has not been well documented. We investigated the influence of MOX on colour parameters and on the anthocyanin and polymeric pigment concentration of a young Pinot Noir wine. The relationship between MOX, yeast growth and acetaldehyde production was also explored. Methods and Results Microoxygenation was applied before or after malolactic fermentation (MLF), and at two oxygen doses [10.8 and 52.4 mg/(L ·month)], for 30 days. The end result was reported after dissolved oxygen was depleted and 90 mg/L SO2 was added. Microoxygenation induced a higher yeast growth and acetaldehyde production, where the latter was associated with both yeast metabolism and chemical oxidation. A larger loss in total anthocyanins and malvidin‐3‐glucoside occurred under MOX but absorbance at 520 nm and colour intensity were higher. With the higher oxygen dose, MOX promoted the formation of large polymeric pigments. Conclusions Acetaldehyde formation was strongly induced by MOX, contributing to reactions between anthocyanins and acetaldehyde forming pigments in the red spectrum. Between MOX treatments, only slight variation was found for each parameter, indicating a less important effect of the timing and dosage of MOX on the young Pinot Noir wine than anticipated from prior work. Significance of the Study Microoxygenation caused a significant impact on the colour development of light‐coloured Pinot Noir wine, increasing the colour intensity.

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