Journey to Harvest…and Beyond!
By Squire Fridell
This is part two in a continuing account of how red wine is made here at GlenLyon. Hope you enjoyed part one, printed in the Jan. 15 issue of the Kenwood Press, where I talked about everything that happens up until fermentation begins.
What happens during fermentation?
Fermentation is the amazing, natural phenomenon created by Mother Nature that’s been converting fruit sugars to wine for the last 8,000 years. Yeast (store-bought or natural, in our case) consumes the grapes’ sugars and creates two byproducts: carbon dioxide (CO2) and alcohol. When fermentation becomes active, the massive amount of CO2 pushes all the grape skins to the top of the tank, forming a thick, firm cap. (Suzy, wearing swim fins, can walk across that cap!)
A quick word about the dangers of CO2: It is a very heavy, odorless, colorless gas produced in abundance during fermentation. If you are in a winery where CO2 makes up a greater percentage of the air than oxygen, you will get dizzy, and you can easily pass out and then fall to the floor … and falling on the floor could be fatal! Why? CO2 is very heavy and will be most concentrated on the floor. You need to be very careful during fermentation and use every precaution. If you feel dizzy at all, run to the door! (Enough of that …) Since all the color, character, and personality of the eventual wine comes from the red skins, we need to submerge the thick cap into what is fermenting below. That needs to happen one to three times every day and night, depending on the stage of fermentation. For a couple of decades, we physically “punched down” that cap using a very heavy, stainless-steel punch-down tool (look for a future KP column entitled “My Rotator Cuff Surgeries!”). When we punch down our smaller T-bins or macrobins, we can still do use the tool and it’s pretty easy, but with the big tanks, it is not.
How did we resolve that issue?
About 10 years ago we installed a Pulsair Pneumatage system, where we can pump small blasts of filtered air under the thick cap into the fermenting must. Because we have a catwalk around the tanks, it makes the punch-downs a lot easier. As the air we pump under the cap rises to the top, the thick cap gently rolls over. An added benefit is that Pneumatage also adds some oxygen (21% of air is oxygen) down where that hard-working yeast likes it.
We’ve found that Pneumatage is very effective in turning the cap over and is much less strenuous than physically punching down the cap. Many winemakers choose to “pump over” the fermenting juice from the bottom of the tank to the top to wet down the cap, but we love our Pulsair system because it mixes things up quite well and also it’s very gentle on both the berries and the rotator cuffs of the workers.
Fermentation also creates a lot of heat (internal temperatures can go well into the 90s), so it is imperative that I check the temperature of the must multiple times every day and night. With fermentation of red grapes, we like the temperature to stay in the mid 70s, so if I need to bring the must temperatures either down during fermentation (or up to begin fermentation), I can circulate either cold or hot glycol through the tanks’ jackets. We also, at least once every day, check the declining sugars (Brix) with a hydrometer. Our target is a loss of about two Brix per day, and the speed can be pretty much controlled by altering the temperature. Once my hydrometer says the sugars have all been converted to alcohol (from 10 to 15 days), it’s now “dry,” which simply means no residual sugar (RS).
At this point, is it now “wine”? Yes! By definition, we now have “wine” … but it wouldn’t be very much fun to drink. Lots of solids are mixed in with the liquid, so you’d have to chew it …
How do you remove the solids?
Now that the wine is “dry,” it’s time to separate the newly created wine from the solids (the skins and seeds). We used a small basket press when we pressed our first wines many years ago, but we upscaled to our current bladder press, which is rated to hold up to 10 tons of fermented solids and liquid for each press load. It is truly an amazing piece of equipment … when it works. (See our November 2021 KP article: “Our 35th Harvest! What could go wrong?”) The bladder press’s job (think of a pressurized colander) is to inflate the internal bladder and squeeze out the liquid from the solids. That liquid is then pumped into another argoned and covered tank to let that cloudy wine sit for a day or two. The cloudiness (caused by spent yeast and tiny pieces of skins) will sink to the bottom of the tank.
After one more day, we transfer the wine to another tank, leaving the solids and cloudiness behind. To that tank we add an “ML starter” (Oenococcus bacteria culture), which will begin the MLF (malolactic fermentation) conversion of the tart malic acid in the wine to the much smoother lactic acid. ML is one of the complexities in red wine maturation and will eventually give the red wine a better mouth-feel.
MLF can most likely happen by itself over a lengthy period of time if no ML starter addition is made, but since its progress is unpredictable, we choose to add the ML starter. The day we add the ML starter to each tank, we begin to prep our new and used French oak barrels (see future KP article on “Barrels”). When the barrels are spick-and-span, smell “sweet,” and don’t leak, we rack the wine from the tanks into the barrels, leaving any remaining solids behind. We leave an inch of “head space” at the top of the wine so the liquid doesn’t overflow during MLF, when more CO2 will be produced. We put a water-filled air-lock bung on each barrel, allowing the gas to bubble out without allowing a stupid fruit fly to sneak into the barrel to swipe a sip of wine. The wine, at this point, is interesting to taste, but it’s immature, a bit rough, and doesn’t yet have all the complexities that will occur as the wine matures into adulthood.
Maturing into adulthood
We have the barreled wine tested once a week to check for any remaining malic acid as it converts to lactic acid. Once results come back indicating all the malic acid is gone, we’ll rack the wines once again from the barrels into a covered, argoned tank. Depending on the variety, we’ll add a couple of all-natural products to help preserve the wine, optimize the mouth-feel, and improve the overall wine quality. Once the empty barrels are thoroughly cleaned again, we’ll rack the wine back into those barrels, this time filling the barrels completely, replacing the air locks with airtight hard rubber bungs to keep out any possible air and oxidation.
Then, while we patiently wait for the wine to mature and be perfect for bottling, we will top off each barrel with wine every two weeks to make up for any volume loss due to evaporation and osmosis through the wood of the barrels. No matter where you travel in the world, that wonderful evaporating wine smell in a winery (or distillery) has a name … it’s called “the angels’ share.” Sort of says it all, huh?
As I type this, all our red wines (and our whites and rosé) are in barrels. Almost all the reds are hardbunged because they are finished with MLF, but we still have a couple with air locks as they continue to slide toward MLF completion. After one or two more rackings, in about a year’s time (or more) we’ll bottle those red wines.
After 35 years of doing this, what have we learned about wine making? Simply that good wine making is an ever-evolving craft with a touch of art. We feel the innovations and technology given to us every year are there to help us make the very best wine we possibly can.
Whew! It is definitely time for a glass of fine Sonoma Valley wine … methinks a nice, fruit-driven pinot noir tonight! Hope you’ll be joining me!
Squire Fridell is the Winemaker, Vineyard Manager, CEO, CFO, COO, EIEIO, WINO & Janitor at GlenLyon Vineyards & Winery Two Amigos Wines