Results
The chart of picture 3 shows the extraction of the phenolic compounds, measured at the wavelength of 280 nm, determined with the TPI index (Total Polyphenol Index). The data obtained and shown in the chart refer to the same moment of the winemaking on the control tank (A) and on tank B equipped with oxyfl ow, even if for reasons of harvest organization, the winemaking processes did not take place at the same moment. This explains the different starting data of the two masses. On the contrary, it is worth highlighting the different extraction profi le: classical for the control tank, with plateau development where the dissolution of the phenols happens gradually and quite rapidly in the starting phase to stabilize around a maximum value; the development is more homogeneous in the case of oxyfl ow where the extraction is more regular in the time taken into consideration in the experimentation. The extraction profi le shown in picture 3, combined with the evaluation of the total anthocyanins and the colour measured at 520 nm, highlights an interesting modifi cation in the classical kinetics of the extraction of anthocyanins and tannins. This increases the contemporary presence of the two classes of compounds in solution, an essential factor to promote the stability of the colour in the wine already in the maceration phase. The general features determined on the products sampled at the racking show different values in the two wines as to alcohol developed, total and volatile acidity (table 2), which witnesses the difference of the masses of grapes processed as “control” and as “test”.
The data allow inferring that the ripening degree of the grapes was more advanced in the case of the raw material of the control wine. Taking this aspect into account, it is possible to formulate some considerations as to the chromatic parameters and some indexes concerning the forms of combination of the phenolic compounds summarized in table 3. The wine obtained with the aid of the “oxyfl ow” device (B) shows higher levels of all phenolic indexes (total polyphenols and couloring intensity) and of the concentrations of anthocyanins and tannins (picture 4). The combination of the latter ones in condensed structures and linked to polysacarides is higher in the reference product obtained with the classical Selector winemaking equipped with Oxyplus device. As to the combination structures of the anthocyanins, the forms of copigmentation favoured by higher levels of cofactors prevail in the “oxyfl ow” wine, on the other hand, the entity of the pigments present in polymeric form is lower. Therefore, it can be stated that the wine obtained through punctual insertion of must-wine into the marc, if compared to the one obtained through a classical Selector winemaking, presents an important structure of the phenolic map, even if the kinetics of extraction are slower. This modifi cation of the kinetics of the extraction of phenolic material, positively re-distributed with more regularity and homogeneity during the whole maceration period, leads to an advantage in the chromatic stability of the fi nal wine.
Bibliography
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by *Milena Lambri, Angela Silva, Marco De Faveri
* Institute of Oenology and Food Engineering, Faculty of Agriculture, Università Cattolica del Sacro Cuore, Piacenza
