Effects Of Injections Of Large Amounts Of Air During Fermentation

Abstract

Aim: Evaluating the effects of high amount of air injection during red wine fermentation process, on phenolic extraction dynamics, oxygen dissolution, phenolic compounds evolution, and oxidation of red wines.MethodsRed grapes musts were fermented in 100.000 L stainless steel tank, equipped with Parsec SRL “Air mixing” gas injection systems. For this experiment, treatments with two injection regimes, high and low intensity, and high and low daily frequency, were used. Oxygen analyzer was introduced into the tank to evaluate the gas concentration evolution along the fermentation. At the same time samples were taken at inoculation (time 0), day 2, 4, 6 and after running off. Soluble solids, titratable acidity, and pH were measured in the samples according to OIV-MA-AS313-01 and OIV-MA- AS313-15 methodologies. The content of glucose- fructose, malic acid, tartaric acid, cooper, iron, glycerol, anthocyanins and catechins in musts were analyzed by commercial enzymatic kits. Phenolic composition was evaluated by tannins methylcellulose precipitation assay (1), short and large polymeric pigments total phenolics by bovine albumin precipitation (2), total phenolics by Folin-Cioacalteu (3), and low molecular weight phenolics by HPLC-DAD were analyzed (4). Color was also determined in CIELAB parameters by absorption spectra at 280, 450, 520, 570 and 630 nm by using software MSCV developed by the Research Colour Group at the University of La Rioja, and 420 nm to evaluate browning index. 

Results: Our results show significative differences mostly in phenolic evolution, as we expected the highest intensity and frequency of air injection, produced the most elevated peaks of oxygen dilution and the highest increase in total phenolics, anthocyanins, short polymeric pigments, and tannin concentration. For all treatments was observed the increase of phenolic compounds extraction during fermentation. The total phenolic, tannins and anthocyanins concentration were high in second place by the treatment with low intensity and low daily frequency. Formation of short and large polymeric pigments were more associated with the high frequency than the intensity, these treatments at the same time had less browning index than the other treatments associated with chemical stability in wines. These results can be associated to the oxygen treatments, although, there is clear differences associated to the temperature during the air injection, the grapes origin and phenolic extractable capacity.

Conclusions: Contrary to some investigations of micro-oxigenation, the injection of high quantities of air or oxygen into musts has no investigated before, and its unknown the real effects in the phenolic extraction and the final stability in wine. These is an introduce to the investigation in these alternatives of overpumping musts.

References

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