Week three on the job at Guigal was basically all about fermentation and extraction. We finished Domaine Guigal’s harvest on Thursday and the negociant grapes came in until Sunday. We would have finished sooner; however, rain forced us to cancel Wednesday’s harvest.
… a refactometer, which measures the potential alcohol level of incoming grapes. The meter measures the reflection of light in a sample grape must, which is affected by the changing sugar content. This year’s harvest came in roughly between 12.5% and 13.5% potential alcohol. In theory, according to viticulture and vinification characteristics in the Rhone Valley, the higher the alcohol level, the better the harvest, up to about 14%. This differs in Burgundy, for example, where the focus tends to be more on acidity.
… a little over 2 tons of table sugar, the same thing you may put in your coffee in the morning. However, this sugar is used for chaptalization, which is the process of adding sugar to the must in order to increase the alcohol level. As most of you probably know the yeast cells feast on sugar, producing CO2 and alcohol as a byproduct. So the more sugar the yeast has to eat, the more alcohol will be produced. Although at a certain temperature and alcohol level, the yeast will die and fermentation will cease, even if sugar remains in the must. This of course must be avoided as Guigal makes strictly dry wine. Based on the refactometer reading, among other measures, Philippe and Marcel Guigal will decide whether or not to chaptalize.
… a density meter. Every day we must measure the density of the must and fermenting wine. As a reference, at 4 degrees Celsius H2O has a density of 1,000 grams per liter. At 20 degrees Celsius pure ethyl alcohol has a density of 789 g/l. As a gross simplification the must enters the tank with a density of around 1,100 g/l. As fermentation commences, the sugar content drops and the temperature rises. Additionally, the resulting density slowly drops and the alcohol level slowly rises. Within about one week the density reaches roughly 990 g/l, meaning that all of the sugar has been consumed and the alcoholic fermentation is completed.
… oak barrels filled with Condrieu white wine that is well into the fermentation. In order to ensure proper balance and structure in the resulting wine, the temperature must be cooled. A hot ferment would impart unwanted characteristics.
… a “turbo pigeage” pump resting in between extractions. Based on the the density readings, daily tastings, and other analyzes, the Guigals will decide how much extraction to carry out for each individual fermenting vat. In a very brief and general sense, extraction is the process of mixing the upper level cap (grape skins and seeds) with the lower level juice or wine. Generally speaking the most extraction is done at the peak of the fermentation when the yeasts are most active. The least extraction is done after fermentation is completed and when maceration ensues. Extraction is essentially only done for red wines, as the process requires the interaction between the juice or wine and the grape skins, seeds, and sometimes stems. In this particular case turbo pigeage is the process of pumping the juice/wine from just below the cap, over the cap. The process is similar to “pumping over”; however, the exact technique and mechanics are different and in the case of pumping over, the juice/wine is typically pumped from the bottom of the vat.
… the turbo pigeage in action!
… a liquid nitrogen tank. Another extraction technique. Nitrogen gas is pumped into the must from the bottom of the vat, generating bubbles, which force the juice up through the cap.
… “pumping over” in action! As I already mentioned, pumping over is an extraction process where the must is pumped from the bottom of the vat over the cap on the top. In summary, regarding all of the above extraction techniques, there are countless theories as to what to do, when to do it, and how much to do. At Guigal, the vinification style entails a lot of extraction, two times a day for 2 to 20 minutes, using as many as four different extraction methods in each individual vat. Of course the extraction ceases as soon as the wine is pumped into barrels. Three general techniques were not covered in the above photo montage–(1) punching down or “pigeage”, (2) continuous extraction through thermal kinetics, and (3) rack and return or “delestage”. Briefly, pigeage is the punching down of the cap into the must, either by hand or by a pneumatic device. Continuous extraction is done on the “La Landonne” label and was briefly described in last week’s post. An additional tank is attached over the main vat, allowing for the juice/wine to naturally collect on top, due to liquid expansion during fermentation. Since the cap is not allowed to pass through to the attached tank, the cap is trapped between the juice/wine on the bottom and the juice/wine on the top and thus soaks perpetually in the must. Additionally as the temperature of the must rises on the bottom the must ascends through the cap and as the temperature of the must lowers on the top the must descends back through the cap. An endless cycle of extraction is created. Finally, delestage is very similar to pumping over, except that the entire vat is racked, leaving only the cap. Then the juice/wine is returned to the vat, mixing back in with the cap. Delestage is the only extraction technique not performed at Guigal.
… I don’t know if you can appreciate it from the photo, but these are “clean” wine hands, after about 5 repeated washes. The red wine is temporarly tattooed on my hand, regardless of repeated washes. Typically it’s a lot worse than this! A small price to pay I guess for making one of the world’s top wines!