Aplicaciones de la microoxigenación. Efectos sobre el color y la composición fenólica de vinos tintos

Resumen

In the early nineties the beginnings of the micro-oxygenation technologies came up. The use of these technologies has spread widely all over the wine world industry. Nevertheless the number of references which deal with the potential of these technologies in the scientific literature has been scanty up to very recent dates. The controlled oxygenation on red wines can be applied in different moments of the wine's life and with different purposes, like the reduction of astringency, the stabilization of colour, the elimination of reduction off odours, etc. In this work, the effect was studied in short and long-term treatments of micro-oxygenation applied before and/or during and/or after the malo-lactic fermentation on the colour and the phenolic composition, principally the anthocyanic composition of red wines was evaluated. This thesis is divided up into in 6 chapters. First Chapter was carried out as a bibliographical review. In the four following chapters, the aims, planning, materials and methods, results and discussion of the experiences performed in the application of this technology along four consecutive campaigns from 2004 to 2008 were described. All the experimental essays were carried out on an industrial scale, in the facilities of Piedemonte wineries (Olite, Navarra). Finally, in Chapter 6, the conclusions obtained in this thesis were summarized. In general lines the incident of micro-oxygenation on the characteristics of the wines was lower than the expected. None of the applied treatments had an incident on the volatile majority composition and neither on the sensory characteristics of the evaluated wines. The most prominent effects appeared on the anthocyanic composition and on the colour. Results showed that the above mentioned effects are not easily predictable, differences were observed depending on the moment of application and the dose of oxygen used. The higher doses of oxygen modified significantly a higher number of parameters. The positive effects were observed in the applications both before both after the MLF. The most evident consequence of micro-oxygenation was a clear increase on the process of transformation of the free anthocyanins, which leaded to obtain wines with a more stable colour opposite to agents like the modifications of the pH or the discoloration from sulphur dioxide, and sometimes this technique has become a colour more intense. The effects were more immediate and more permanent in long term when the oxygen was applied before the MLF, than when the treatment was applied only after. The stabilization of the wine colour using micro-oxygenation was not accompanied by an acceleration of the evolution on the tonality of the wine towards the yellowish tones. Rather on the contrary, in some occasions the micro-oxygenated wines showed a slower evolution with regard to the control wines. Key words: micro-oxygenation, stable colour, anthocyanins, oak barrels, chips, malo-lactic fermentation.