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November 2015 WINES&VINES 105 WINEMAKING substances. Values between 25° and 30° C (77°-86° F) mainly favor tannins that increase their solubility, while the anthocyanins do not show any significant improvement. The tem- perature allows the extraction of flavanols to be regulated and, for young red wines with a limited structure, the temperature should not exceed 25° C. In addition, high temperatures favor the formation of polymeric pigments (various types of tannin-anthocyanin copoly- mers) with a consequent increase in the color intensity of the wine. The maceration time generally determines an increase in the polyphenolic substances extracted, especially tannins. In fact, as has already been observed, the concentration of anthocyanins reaches a maximum a few days after the start of fermentation, whereas longer contact with the pomace stimulates the forma- tion of polymeric pigments. Some authors also have reported that the kinetic diffusion of the less-stable disubstituted anthocyanins is faster than that of the trisubstituted ones. Maceration that lasts more than two weeks favors an accumulation of polymers with a larger molar mass, which is naturally more difficult to dissolve. Although it depends on the type of grape, it has been observed that the extraction phenomena tend to peter out during the fifth to sixth week of maceration. The formation of ethanol during fermenta- tion alters the solvent capacity of the liquid phase; this increases the solubility of tannins with a larger molar mass. Furthermore the ethanol, disrupting the external lipid layer that protects the seeds, favors more extraction of flavanols from them. Consequently, the contri- bution of tannins and flavanol monomers re- quires longer maceration times. A recent study by Spanish researchers (2012) has shown, however, that the dispersion of flavanols in seeds also occurs in the aqueous phase, al- though the presence of ethanol intensifies and speeds up extraction in the first stage of mac- eration (six days). Under ordinary conditions with healthy grapes, the use of sulfites does not generally show effects on the extraction of polyphenols, with other parameters (temperature, time, mechanical action, etc.) clearly having more effect. The extractive contribution of sulfur dioxide, however, turns out not to be negligible in the preparation of rosé wines. Finally, the indirect role of sulfites in protecting and pre- serving the anthocyanins from possible oxida- tive degradation should be remembered. Technological operations Finally, the winemaking practices used are particularly important, and it's worth mention- ing the classic operations of punching down and pumping over, alongside more recent prac- tices such as pre-fermentation cold maceration, the use of maceration enzymes, partial freezing of the must and practices that fall outside the classic scheme of red wine vinification such as thermomaceration. The start of fermentation in the must, with the formation of large quantities of CO 2 , causes the "cap" to rise, which minimizes contact be- tween pomace and the liquid phase and creates a slight warming of the mass. The first aspect is very limiting for extraction in the mixed phase. The periodical punching down (manual and mechanical) and pumping over solve the problem by remixing the mass. In the case of pumping over, the efficiency of the spraying process is fundamental for avoiding the formation of preferential routes in the cap, which would frustrate the efficiency of the operation. Numerous experimental works show that the performance of the two techniques strongly depends on the cultivar. In general, results are linked to the frequency and duration of the operations as well as the type of equipment used. Undoubtedly, the shape and size of the vi- nification containers play a decisive role in managing maceration, just like other condi- tions. In order to exploit space in the cellar, fermentation vats generally tend to be taller rather than wider, with the consequent diffi- culty in managing maceration, especially for larger quantities, and making the extraction process less efficient, all other conditions being equal. An alternative to classic maceration is the use of rotary fermentors or the practice of délestage. The extraction of polyphenols is par- ticularly fast in the case of rotary fermentors, which enable higher levels to be achieved (see tables above). It has often been noticed that punching down is less effective in terms of quantity when compared to pumping over, but we would like to underline the value of less haziness from lees in the wine. The use of maceration enzymes (essentially pectinase) contributes to the degradation of the cell walls (through partial hydrolysis of the polysaccharides of the pecto-cellulosic struc- ture of the wall), which favors the diffusion of the components present. Different authors do not always agree on the real efficacy with re- gard to the effect on anthocyanins. These in- consistencies can be explained by the different polyphenolic composition of the grape, the different extraction speed and the reactions in which the anthocyanins are involved. The pres- ence of a secondary and not entirely negligible β -glycosidasic activity in commercial prepara- tions could also explain the loss of anthocya- nins due to the formation of the less soluble aglycone. The possible influence on the antho- cyanic profile has also been observed, with an increase in more stable trisubstituted antho- cyanins such as malvin. Moreover, is has been 2,000 1,800 1,600 1,400 1,200 1,000 800 600 400 200 0 mg/L 0 1 2 3 4 Days n = TA n = TF Monitoring of the extraction of total anthocyans (TA) and total flavonoids (TF) from Barbera grapes in fermentation tanks where height (table at left) prevails, or with horizontal rotary fermentors (table at right). Source: Gerbi et al., 2011 2,000 1,800 1,600 1,400 1,200 1,000 800 600 400 200 0 mg/L 0 1 2 3 4 Days n = TA n = TF LEVELS OF EXTRACTION OVER TIME Vertical Tank Rotary Fermentor