Zoom in on microorganisms


Vines at the L’Orpailleur wineryZoomZoom
© Nicole Catellier, Cinémanima inc.
Wine preparationZoomZoom
© Nicole Catellier, Cinémanima inc.
Wine preparationZoomZoom
© Nicole Catellier, Cinémanima inc.
Barrel of wine at the L’Orpailleur wineryZoomZoom
© Nicole Catellier, Cinémanima inc.
WinemakingMovie ClipMovie Clip
© Production Cinémanima inc. and Armand-Frappier Museum

Winemaking : a job for yeast

Without yeast, there is no wine, there is only grape must. Yeast plays a role of paramount importance in the winemaking process. It converts the sugar in the must, obtained by pressing the grapes, into alcohol. The yeast also produces minor constituents, which modify the aroma and the flavour of the wine.

The multiple stages of winemaking

Grape harvesting
Grape harvesting generally starts in September and lasts for a period of about three weeks. Grapes are harvested by hand, bunch by bunch. The white wine, Orpailleur, is the product of a type of vine known as Seyval Blanc.

The harvested grapes are pressed. The must is stored in a vat in the fermenting room. The grape pomace and the skins of the grapes are recovered and recycled as compost for the grower’s vines.

For two days, the must is kept at a temperature below 10°C while adding proteolytic enzymes (they lyse proteins) and sulfur dioxide (SO2). The enzymes degrade the large protein particles and the SO2 contributes to the preservation of the mixture due to its anti-oxidant and anti-bacterial properties. The must deposits that result from this process are eliminated by racking, a clarification process.

Storage in tanks
The clarified must, which resembles juice more than wine, macerates at low temperature for two or three days.

Dry active yeasts are the ones mainly used for inoculating the must. They are obtained by freeze-drying a concentrated yeast culture. Sold as a powder, these yeasts must be reconstituted with water and sugar by the cellar master. Each gram of this powder contains approximately thirty billion yeast cells. The Lallemand Company in Montreal is one of only six plants in the world that produce these yeasts.

The cellar master adds the reconstituted yeasts to 10% of the contents of the fermentation vat, or leaven, and then incorporates this mixture into the total contents of the vat. This reduces the latency time before the fermentation process begins. The yeast, Saccharomyces cerevisiae, in the case of Orpailleur white wine, then goes to work converting the sugar into alcohol, a process that lasts about twelve days. During this time, the cellar master carefully controls the temperature (between 14°C and 17°C), which must be suitable for the yeast and yet not alter the distinctive quality of the wine, which comes from the type of grape used in its fabrication. Yeast activity must also be carefully monitored as it can be linear or have peaks. The cellar master must therefore be vigilant in order for everything to unfold as it should, leading to the desired results.

It is sometimes necessary to add sugar to the must to obtain a complete fermentation or to prolong it until the desired alcohol level is attained (17 g of sugar gives 1% of alcohol).

Some years, because of climatic conditions, the fruit does not reach perfect maturity and the acidity of the must is too high. The acidity can be corrected to approximately 4.5 grams of H2SO4 per liter using calcium carbonate.

Bentonite (clay) is added to clarify the wine, facilitate filtration, and ensure stability. It acts by precipitating and dragging along with it most of the suspended particles and proteins.

The deposit found at the bottom of the vat is called “lees ” This can be eliminated by racking, a process which consists of recovering only the clear portion of the wine.

Refrigeration or cold-stabilization
Wine contains tartaric acid, which can eventually crystallize. To avoid this happening in the bottle, the wine is refrigerated (0 °C) for a few days before bottling. This triggers a crystallization also known as tartaric stabilization.

Depending on the desired end products, and after tasting, some vats are blended while others are not.

Oak barrel maturation
Some wines are left to mature for several months in oak barrels. The wood fibre adds vanilla and wood flavours to the wine.

Before bottling, the wine is filtered to eliminate bacteria and yeasts.

Some wines are aged for several years in wine cellars before reaching the desired maturity for consumption.