Monitoring the effect of Micro-oxegenation before malolactic fermentation on South African pinotage red wine with different colour and phenolic analysis
Geldenhuys, L; Oberholster, A; du Toit, Y L.
The use of micro-oxygenation and its effect on the quality of the red wine varietal, Pinotage, is largely unknown. The influence of adding different oxygen dosages before malolactic fermentation on the phenolic composition and colour stabifisation of wine made from Pinotage was studied, and the suitabifity of certain spectrophotometric and RP-HPLC analyses to determine these changes were assessed in tanks of commercial lengths. Total oxygen dosages of 0 mgfL, 16 mgIL and 32 mgfL were applied, after which the wines underwent malolactic fermentation and maturation in the same tanks for two additional months. Decreases in anthocyanin concentration showed a strong inversely proportional correlation with increasing polymeric pigment concentration. This suggests that the addition of oxygen contributed to the early stabifisation of wine colour in Pinotage red wine. Overall, tannin concentrations were not significantly influenced by the oxygen treatments, although lower levels were observed in wines treated with oxygen. An important finding of the study was that there appeared to be little difference in the colour and phenolic composition of the wines between the 16 mgfL and 32 mgfL oxygen treatments. Good correlations were found between certain spectrophotometric techniques and the RP-HPLC analysis used to study changes induced by micro-oxygenation (total anthocyanins, total phenols). The colour and phenolic composition of Pinotage wine can be influenced before malolactic fermentation by micro-oxygenation. Some spectrophotometric phenolic analyses showed the same tendencies as observed with RP-HPLC (anthocyanins, monomeric flavan-3-ols, tannins), indicating their suitabifity to follow phenolic and colour changes induced by micro-oxygenation in Pinotage red wine.
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