Clarifying

Harvesting – In the Cellar

Winemaking may begin with the picking of the grapes in the vineyards, but when the picking is done it’s only the beginning of the work at the winery.

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Last Load of Grapes for the Day Arriving

Loads of grapes arrive multiple times a day at the winery. Depending on what time of day the harvest took place, this could be in the wee early hours of the morning or well after dark in the evening. In some location and at some wineries, the grapes are picked during the night when the temperature is the coldest and therefore the grapes remain as stable and healthy as possible. At the winery I work at, we picked during the day and often the last load of grapes wouldn’t arrive to the winery until 9:00pm.

DeStemming

So the grapes have arrived. First things first: are you destemming? If you have machine-harvested the grapes, this has already been done by the machine. Bitter tasting phenols exist in the stems of grapes, and while this can sometimes be desired for red wines, it is avoided with white wines. So into the destemming machine the grapes go. This machine also slightly crushes the grapes, releasing some juice and turning the grapes into “mash”.

Destemming Machine

Macerating

Next, are you macerating the grapes? Maceration is where the grapes (now in mash form) are left in containers to sit “on the skins”. This is particularly important with red wines, as the red colour, as well as flavours, aromas, and tannins, comes from the skins. If you were to press the grapes right away, you would lose these important characteristics.This red skin transfer can also be accomplished by heating the mash. Depending on how long the grapes were left to mingle with the skins, you can end up with a blanc de blanc, weissherbst, or rosé. With certain white grape varietals with very aromatic skins such as Sauvignon Blanc, maceration is also employed. Maceration can happen before, during, and/or after fermentation, depending on the desired outcome. As the mash begins to ferment, the CO2 pushes the grape skins to the top of the container. This can form as cake-like hard layer on the top. Since the point is skin-contact, the wine-maker must “punch” the grapes skins down to mix them.

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Pinot Noir Macerating

pressing

The next action is to press the grapes (or mash in the case of destemmed or macerated grapes). There are a few different types of pressing machines, however most these days work by applying pneumatic pressure to a ballon inside the machine’s vat and forcing the grapes up against the sides of the vat. The juice then flows out through screens and channels and if pumped into a tank.

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Pressing Machine

clarifying

Ta-da! You have grape juice (now referred to as “must”)! With white wines, before fermentation can occur you need to remove the floating suspended matter in order to turn the natural grey-coloured mash into the crystal clear liquid we expect. Bentonite, charcoal, Kieselgel, Flora Clair, sulfuric acid, and other clarifying products preform this duty. They attract the suspended participles and pull them down to the bottom of the tank. For more information on the clarification process, you can refer to my Clarification blog post.

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Clarifying Products

The next step is adding the yeast to begin fermentation and separating the sunken particles from the clarified must. To make this separation, the wine is pumped into a different tank, making sure not to transfer the bottom of the tank containing the settled particles. A second pressing can also occur using the juice from the bottom of the tank mixed with soluble cotton, making sure to squeeze every last drop of grape juice from the clarifying agents and sunken particles. This lower-quality juice is often kept separate from the main juice.

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Pressed Must + Clarifying Agents + Settled Particles + Soluble Cotton = Ready for Second Pressing

Fermenting

Fermentation is the process by which yeast eats the sugars in the grape juice and convert the sugars into alcohol and CO2. Either you are kicking it back old school and allowing the naturally occurring yeast on the grape skins and in the air at the winery to ferment your wine, or you are adding a known yeast strain that will optimize the rate of fermentation. If adding yeast, you mix the yeast with warm water, wait for it to activate (as seen in the photo below), and then add it to your must. Fermentation generally starts quickly, but should slow down and continue for a couple weeks losing less and less sugar everyday. If fermentation continues too quickly you can lose a lot of aromas. When the alcohol content of the wine reaches about 15 percent, the yeast dies. You can also stop the fermentation process yourself before the yeast has finished eating (thus leaving residual sugars) by cooling the wine down and/or adding sulfur. These decisions are up to the winemaker.

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Yeast Getting Into Action Before Being Added to the Must

Carbonic maceration is another fermentation option that is used to create really fruity wines such as Beaujolais. In this case the entire grape bunches are put in tanks without being punctured and without yeast being added. Fermentation then occurs within each berry separately and the natural weight of the grape bunches and gravity press the grapes.

chaptalizing & de-acidifying

Further decision the winemaker must make are whether or not to chaptalize or de-acidify the wine. Chaptalization is the process of adding sugar to the wine (before or during fermentation) to increase the alcohol content of the wine. *This does not increase the residual sugars in the wine.* Chaptalization is done in northern wine growing regions/countries such as Germany who don’t get enough sunshine and therefore have grapes with low-sugar. Not enough natural sugar = too low alcohol percentage in the final product. This is not allowed in every country, or with all quality levels of wines. In Germany, if a wine has the acid and sugar levels to qualify as a Grosse Gewachs (equivalent to “Premier Cru”), you are not allowed to chaptalize or de-acidify.

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Adding Sugar

Another outcome of grapes grown in northern climates such as Germany is high acid contents. Not enough sun means that the sugars don’t develop enough and the juices pressed from these grapes have much too high acid levels. High acid content is more palatable (and to an extent sought after) in certain white wines, such as Riesling. High acids in red wines are avoided as it exaggerates astringency. De-acidifying is the process of adding certain chemicals to remove the acid. The options are to use 2 different salt compounds: calcium carbonate and/or potassium hydrogencarbonate; or malolactic fermentation. Malolactic fermentation is the process by which harsh malic acid is transformed into soft lactic acid. De-acidification should occur prior to fermentation in order to maintain harmonious aroma compounds.

Measuring & Tasting

Cellar tastings are an important aspect of the wine-making process. Faults in the wine can be discovered and rectified. Aging and cuvée decisions can be made. Frequent measurements of the wine tells you when fermentation has stopped (and whether you need to try and re-start it or or not) by analyzing the remaining sugar levels. Newly fermenting wines have their own unique aromas and flavours; nothing but a hint of the finished product exists. The fresh fermenting wines taste more like grape juice, with flavours of juicy, sweet fresh fruits such as pineapples and peach. Now you have a cellar full of wines-in-the-making, the fruits of the harvest labour.

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Cellar Tasting

Making Bubbly

A few weeks ago I harvested a small number of Müller-Thurgau grapes, pressed them, and clarified and fermented the juice. The question then was to leave it as is, or to go through a second fermentation and make sparkling wine. In the spirit of experimentation and education, I chose to make bubbly!

In order to add the bubbles naturally (versus making a secco where carbon dioxide is simply added to wine), a second round of yeast and sugar is added to the wine, and the bottles are then capped and cellared to be left on the yeast.

Prior to fermentation, the juice had 77ºOechsle (total sugars), which equates to an expected alcohol level of about 10.3%. Using the handy dandy table below, we can see that this means there is 81g of alcohol/L. When making sparkling wine, one can legally add only 1.5% alcohol. 10.3 + 1.5 = 11.8. This means we are enriching just under 12g of total alcohol with sugar for this second fermentation. We must therefore add 2.93kg/100L, or 0.0293kg/1L of sugar to the wine.

IMG_1744-768x1024 — Handy dandy table used to convert units

We had 17.5L of wine, so 0.0293kg x 17.5L = 0.512kg. Grams are easier to work with, so 0.512 x 1000 = 512g of sugar needed to be added the 17.5L of wine.

A strain of Sekt yeast was also then added. The rule for this yeast was 20g yeast/100L liquid, or 0.2g/L/1L x 17.5L of wine = 3.5g yeast to be added.

Another thing to note is that the newly fermented wine was stinky. That’s right, really, really stinky. This is a common problem with wine and occurs when the yeast doesn’t have enough sugar to eat. When this happens, the yeast starts eating amino acids – some of which contain sulfur – and produces this farty smell. The way to combat this during the fermentation process is to add nutrients for the yeast to eat. We had done this, but alas we had really hungry yeast. After fermentation, the way to correct this smell is through aeration and copper. We did this and also again added additional nutrients.

IMG_1929-e1443430474798-1024x959 — Sterilizing the bottles with sulfur

The next step is to bottle and cap the soon-to-be Sekt. The bottles must first be sterilized. To do this, a sulfur-water solution is sprayed into the bottles. The bottles are then 95% filled with the wine and sealed with a bottle cap.

Sparkling wine bottles are thicker and stronger than standard wine bottles in order to hold up to the carbon dioxide pressure. Even with these specially designed bottles, you can only have 7.5 bars of pressure within the bottle. Doing our due diligence, we checked this. You get 0.47g of CO2/1g fermentable sugar (and 0.46g alcohol). We had added 512g of sugar. 512g x 17.5L = 29.25. 29.25 x 0.47 = 13.75g CO2. Using a specific table, this equaled exactly 7.5 bars of pressures. Phew!

Finally, the bottles are placed on their sides in a cool, dark place. The amount of time the now sparkling wine remains aging on the yeast cells differs according to country, quality level, and desired flavours. For this experimental wine we plan on only waiting for a minimum of 3 months. With this 3 month wait-time, in December the spent yeast cells will be removed through a process called degorgement, corks inserted, and I will be able to cheers to the new year with my very own bubbly!

Mini Harvest – picking, pressing, clarifying, fermenting

Today, I went through the entire process of collecting grape bunches, separating the good grapes from the bad, pressing, clarifying, and starting the fermentation process. What a crash course for the harvest season!

The winery that I work at has a small amount of grapes vines directly on the property itself. These grapes have been attracting unwanted wasps for the past weeks, so it was time to take them down and make wine! Let me tell you, it takes nerves of steel and a very zen head-space to remain calm while cutting grapes off vines surrounded by wasps. Surprisingly, I did not get stung once. Not even close. I am a zen master.

After the grapes were cut off the vines, I went through the time-consuming process of cutting out bad, vinegary, blackened, unwanted sections of grapes on the bunches.

Screen-shot-2015-09-01-at-10.32.55-PM — Separating the good from the bad

I then took the grapes and was shown how to press them. First we used a traditional press. This was a very lengthy process, requiring time for gravity and pressure to press the juices from the grapes, through the cloth, and out of the filter. I couldn’t believe the dirty grey/brown looking colour of the juice that came out! A degree of murkiness is necessary to give the yeast something to eat and something to hold on to.

IMG_1692-e1441139751708-873x1024 — Colour of the must

We then switched to a hydraulic press. This went much faster and we were able to press three times. This press works through water pressure. The cylindrical tub is filled with the grapes, then a balloon in the center of the machine is filled with high-pressure water, pressing the grapes against the tub, through the cloth filter and out of the machine.

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After each press, the grapes (or what’s left of them) are moved and stirred by hand. By the third press, grape seeds started to come out of the machine!

When the pressing was done, we measured the sugar and acid levels of the must. Our readings were:

79 Oechsle after first press
77 Oechsle after third press (after the smaller, more acidic grapes are pressed)
5 Acid level
15L must

Then we added the clarifying agents:

7-8g charcoal (5-10% charcoal/ estimated 5-10% rot)
15g Bentonit (50/150g/ 100L)
3g Floral Clair (10-20g? 100L)
8ml Kieselsol (30-100ml/ 100L)

IMG_1703-e1441140864601-1024x544 — Clarifying products used

Then it was time to ferment. A Riesling strain of yeast was added to 1 litre water and 1 litre wine. Because the juice was so cold, we left the yeast to begin the fermentation process in the small glass until the larger container warmed up, at which point the contents of the small container were added to the entire 15 litres of must.

Screen-shot-2015-09-01-at-10.40.59-PM — Starting the fermentation

Now each day I must check the sugar level and the temperature of the fermenting wine. I write my findings on a graph and track the changes. Updates to come.

(Also, apologies for mixing German and English terminology. It’s strange learning something new for the first time in a foreign language-I don’t even know some of these terms in English!)

Clarifying

The clarification of wine must (juice) works through positive and negative electrical charges or through absorption in order to drag suspended particles down to the bottom of tanks to settle. Various products are used before filtration, during filtration, or just before bottling. Attention! Too much filtration can strip the wine of its flavour and character.

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The following are brief descriptions of the clarifying products that I have seen used:

Bentonite (negative charge) is added to remove large particles. It comes as a powder-clay consisting of calcium and sodium. After being mixed with water, the slurry is added to the wine. The bentonite chemicals react to the protein elements in the wine (mainly dead yeast), bonding to them, making them heavy, and dragging the now large particles down to the bottom of the tank. The riper the grape, the more bentonite is required.

Activated charcoal (neutral charge) absorbs bad odors and browning colours caused by oxidization.

Silicagel/Kieselgel (negative charge) removed bitterness from wine and clears out haze. It is most commonly used in combination with gelatin.

Egg Whites (positive charge) or the technical term for the protein found in egg whites, Albumin, is used to reduce astringency and decrease spoilage. It is often used in red wines as it doesn’t react with the tannins and also keeps the red colour intact. You can quite literally use the whites of eggs separated from the yolk, but powder form is safer as you reduce the risk of bacteria contamination.

Flora Clair (positive charge) is derived from plant proteins. It is also a gelatin replacement and thus when used can make the wine, technically speaking, vegan.

Sulfuric acid is added to reduce the affect of Acetaldehyde in wine. Acetaldehyde is a naturally occurring organic chemical compound and a by-product of yeast fermentation. It produces a butter-like smell and can cause wine spoilage. Adding sulfuric acid to wine can protect against this. It is a preservative, antibacterial and antioxidant. Sulfites are found naturally in fruits (and thus wine). Therefore, even wines proclaimed to be “sulfite-free” do contain the chemical, it’s just not deliberately added. Fun fact: dried fruits contain much higher quantities of sulfites than wine. Unsurprisingly, sulfite-free wines retain this peculiar scent to some degree.

IMG_1743-768x1024 — Example of visible separation