Article

Bulk Aging

Aging your wine is not the most exciting winemaking topic, but it is a critical topic. Aging wine is considered from the time after your fermentation is completed through the time spent in the bottle before consumption. The three basic goals of aging your wines are to assure stability, to correct a flaw or fault, and to evolve the wine style by increasing complexity, flavor, and aroma. The goal of this article is to give you a deeper insight into the benefits of aging your wine, no matter your winemaking style or skill level.

Bulk vs. Bottle Aging

It has been said by many winemakers that complexity increases in the bottle. However, there is a point where the wine in bottle will start to lose its luster. This has to do with the type of wine, its SO2 levels, pH level, storage temperatures and its exposure to light. Winemaker Frank Renaldi of Musto Wine Grape Company says, “I am a big believer of aging wines in bulk — either tanks or barrels. I find the wine develops much better as a “team of bottles” in one vessel. Once the wine hits the bottle, it ages as a single entity. It ages in a different way, especially reds, but does it on
its own.”

Harry Hansen, Winemaker at Calistoga, California’s Sterling Vineyards, says, “Aging in bottle is subjective. Wines that are bigger and blacker generally can handle more cork time than light reds, which in turn can handle more cork time than delicate whites. At some point, tannins are softened, fruit characters have receded, and youth is a memory. Wines can still be very good, because what is lost in freshness is often replaced by layers of aroma. The eventual fate of every wine is to become vinegar, but as slowly as possible, please.”

Considerations of Aging Wine 

Let’s start with looking at each of the factors that affects the aging process: Time, temperature, oxygen, oak, yeast lees, pH, the composition of the wine, and wine stability.

Time
Different aging styles require different allotments of time. A Bordeaux with high acid and high tannins will take much longer to age than a softer California Cabernet. Grapes grown in cooler climates tend to need more time to age due to their higher acid and tannin structure, whereas grapes from a hotter region can usually be enjoyed earlier. Of course, as I write that, I am left thinking about how subjective that sentence is. Normally we are ready to bottle our whites 7–8 months after fermentation. I like my reds to go one year of bulk aging before bottling, and longer is better.

Temperature
Just as all chemical reactions are influenced by temperature, so are the reactions during wine aging. Wine aging is best from 58–70 °F (14–21 °C). You don’t want to over chill or over heat the wine during the aging process. You could lose a lot of positive aromas and flavors that way. If you don’t have a natural “ideal” temperature in your cellar, I would suggest installing an air conditioning unit in your wine cellar to handle those warm summer days. The colder winter temperatures will not hurt the wine as much as the summer heat. The biggest factor is to avoid temperature fluctuations from hot to cold. Wine likes to age at a steady temperature.

Oxygen
Excessive exposure to oxygen during aging can have a negative effect on your wine. The introduction of small amounts of oxygen during the aging process can help soften your wine and stabilize the color in red wine. This is the benefit of the barrel, as it allows micro-oxidation through the staves. Too much oxygen can lead to off flavors (acetaldehyde) and the browning/pinking of the color. Too much oxygen will cause your free SO2 levels to drop, which can then cause oxidized qualities in your wine (acetaldehyde — nuttiness, Sherry characteristic). The more phenolic material in the wine, the more oxygen the wine can safely absorb. This is why white wines are so susceptible to oxygen contact such as browning, whereas red wines carry more phenolic properties and are less likely to brown or have negative effects so quickly.

It is said that a wine is “saturated” with oxygen at about 6 mL of oxygen per liter of wine, or 8 mg/L, or 8 ppm. Single saturation examples include racking, movement to tank or barrel, fining, filtration, and bottling. How do you measure this? With a dissolved oxygen meter or, some wine grape and juice wholesalers have the testing equipment to do it for you on site. How do you control these saturations and not oversaturate your wine? Limit headspace, stay vigilant about topping off your barrels, utilize inert gas to flush out air, measure and adjust your SO2 levels every six weeks, and monitor your saturation levels.

Oak
Many wine styles depend on oak aging. Oak aging highly impacts the aroma and flavor profile of the wine. This is because of the flavor the oak imparts by itself and the complexity added to the wine through micro-oxidation. Barrels can be challenging — you need to properly clean them, swell them, and consistently keep track of them by topping off your wine. If you have the funds and the time to monitor and cultivate your barrel I would highly suggest purchasing one. If you do not, there are some great alternatives we will discuss later.

Why is aging in an oak barrel so great? Wood vessels allow limited oxygen exposure, allow for slight evaporation (hence needing to top off your barrels), and add flavor components and complexities. Something to consider is the size of the oak barrel you purchase. If you purchase a new barrel smaller than 30 gallons (114 L) then you need to taste from your barrel every couple of weeks. This is because the less surface area you have, the more flavor extraction you will get from the barrel. Obviously, the younger the barrel the more flavor extraction will occur. As time goes on (after 3 or 4 years), the barrel will become neutral, meaning the oak extraction is greatly reduced. However, the barrel itself is still useful, as it allows the wine to mature and adds complexity to the wine. 

Cleaning your oak barrels is VERY important. Barrels can harbor microbes and it can be difficult to sanitize them if not properly cleaned.

Yeast Lees
Aging on the lees is a great practice for white wines. The most popular wine to age on the lees is Chardonnay, but winemakers are aging Sauvignon Blanc (France), Albariño (Spain), Muscadet (France), and Champagne (France) on the lees too.

I spoke with Kristen Parsons of Chamard Vineyards in Clinton, Connecticut about her Estate Reserve Chardonnay crafted in the French Meursault style and why she ages it on the lees. After aging in barrels for primary fermentation, a secondary malolactic fermentation is carried out along with sur lie aging. 

“The wine remains on the fine, silky lees that are composed of mostly autolyzed yeast cells. I stir the barrels mixing up these lees into the wine, daily, weekly, and then monthly for ten months. All of this is carried out for stylistic reasons. This attention creates a wine with a smoother structure and mouthfeel, increased body, and aromatic complexity. The resulting wine is layered with a rich and creamy mouthfeel,” Parsons said. “Another bonus it that the lees absorb oxygen, which not only enhances the character of the wine but aids in protection as well.”

pH
pH is a very important factor in all stages of winemaking. If you adjust anything in your grapes before fermentation, it is the pH. When it comes to aging your wine, a high pH is dangerous as the wine is vulnerable to spoilage organisms. It is important to make sure the SO2 is in balance with the pH. The SO2 effectiveness is critical to color and freshness, especially in white wines. The SO2 and pH balance also inhibits the growth and activity of microorganisms. A pH of 3.8 is considered a critical range for Brettanomyces (barnyard), Lactobacillus (mousy/acetic acid), and Pediococcus (overly diacetyl). You do not want to be in that range. So make sure to keep track of your pH and SO2 levels. For red wines you want to be around a 3.5 pH and for white wines you want to be around 3.1–3.3 pH.

Composition of the Wine
Starting with a good wine is key to your wine aging and finishing success. Starting with a faulted wine will result in an uphill battle. Always pay attention to your fermentations and cleanliness in your home winery. If you have a wine with negative characteristics, get it tested to see what exactly is going on. Some suppliers offer sensory tests, there are also companies that can give you the chemical breakdown of your wine that you can utilize. Sometimes a little micro-oxidation is exactly what the doctor ordered. Other times you might need to introduce a chemical over time to help clean up what’s going on.

Wine Stability
The wine needs to be stable — meaning proper SO2 binding, pH levels, cold stability (tartrate stability), heat stability (protein haze), combination of tannin molecules (“polymerization”), and the combination of color molecules (“polymerization”), and stabilization of color. Adjusting and aging your wine properly helps ensure that your wine stays safe in the bottle.

Benefits of Bulk Aging 

There are many benefits to aging your wine in bulk. One, is the ability to correct a problem. Do not bottle your wine until you have removed faults and flaws. If you have bitter or astringent tannins in a young red wine, you can bench test fining trials. 

The second is the stylistic choices you get to play with and experiment with. All wines will evolve and release more complex flavors and aromas over time. Depending on if you decide to do any oak infusions or age in an oak barrel, these practices will help impart interesting and complex flavors to your wine. Conversely, if you decide to age in a stainless tank or glass, your wine will contain a bright freshness. 

The third benefit is that it allows for blending possibilities with other wines. This is one of the most fun parts about winemaking, in my opinion. If you age your wine you have time to do bench trials and figure out ways to try to impart more complexity in your wine by blending other wines in your cellar. The goal of aging is to increase complexity in your wine and you have a lot of options to play with to introduce complexities.

Equipment Options

Glass
There are a few options you can try when aging your wine in glass. However, if you are aging your wine in glass you want to keep in mind that you want to keep your wine away from the light. Too much light in your cellar can impact the color saturation of your wine. Whatever option you choose, always top off your storage vessel to avoid oxidation.

Demijohns are a great glass option. They have been used by winemakers for many years. They come in multiple sizes, can be used for winemaking, cider, and depending on the style, olive curing. Demijohns are a large glass bottle that is narrow at the top and curves out into a big tear shape at the bottom. Each demijohn is equipped with a plastic basket or braided plastic basket. Some demijohns come with spigots for tasting access to the wine. They come in a variety of sizes, the most popular for winemaking are 2.5 gallon (10 L), 6.6 gallon (25 L), and 14.3 gallon (54 L). 

It is easy to do an oak infusion with a demijohn. There are a few ways to do this. You can use fishing line and a muslin hop bag filled with oak chips, use an oak infusion tube filled with oak chips, or use fishing line and a stave, spiral, or WineStix® to impart oak flavors. 

Demijohns can be difficult to move around so I’d suggest getting a plant caddy and putting the demijohn on the caddy so it’s easier to move. Please note that the bottom of the demijohn is very thin glass so it can break easily, especially when filled with wine. Be careful when moving these, they are deceptively secure looking with the outside basket.

Carboys are one of my favorite options: They are inexpensive, come in an array of sizes, are easy to use, easy to clean, easy to add oak infusions, and you can see what’s going on with your wine. Carboys look like a water cooler water jug. They are a thicker glass than demijohns but do not come with spigots. Carboys come in a variety of sizes including 3 gallons (11.5 L), 5 gallons (19 L), and 6 gallons (23 L).

It’s important to see if you are accumulating a lot of sludge at the bottom of your carboy. This means it’s most likely time to rack your wine. Carboys can also be a little tough to move around when full. I’d suggest getting a plant caddy or putting your carboy inside a milk carton crate to help you move it around your cellar. 

“Carboys are a great storage vessel when you start making wine 5- or 10-gallons (19- or 38-L) at a time. I suggest you go to a variable capacity tank when you are up to three to five carboys of the same wine. It is easier to maintain one tank versus five carboys, such as racking, filtering, additives, and SO2 additions,” says Renaldi.

Food-Grade Containers
PET carboys are a popular vessel, especially for those who are working with kits. These are lightweight, making them easier to lift and move around your cellar, and they will not break like glass. However, cleaning these can pose a problem. When cleaning your PET carboy you can create grooves in the plastic that can eventually be a home for bacteria, no matter how much you scrub. Keep that in mind when cleaning these and try not to scrub too hard or scratch the inside of the PET carboy.

ROTO Barrels are food-grade plastic barrels. They are great because they give that barrel vibe to your cellar without breaking the bank. You can add oak infusions, it’s easy to rack in and out of, and gives a great look to your cellar. However, just like the PET carboy, you have to be conscious of how you clean it to help avoid creating any homes for bacteria.

Flex Tanks are created from a polyethylene food-grade plastic. They give the winemaker the ability to utilize it as an aging vessel that is permeable like a barrel but is in a shape that is easier to store in their cellar. There are two different maturation styles that allow the winemaker to decide how much oxidation they want released into their wine. These are maturation weight, which allows a level of oxygen transfer on par with a second-year barrel, and a heavyweight level that allows approximately 50% less oxygen transfer than the maturation weight.

Variable Capacity Stainless Steel Tanks
Variable capacity tanks are another winemaker favorite. Hansen says he prefers using stainless steel or glass vessels for white wines because they are “impenetrable to oxygen, and the wines age most slowly. This is appropriate for delicate whites like Riesling or Sauvignon Blanc.”

Stainless steel tanks are also great for bulk aging red wines. They protect your wine, have variable levels of volume, have a sample tap you can utilize, are easy to clean, easy to infuse with oak or other products, and pretty much last forever. 

Oak Barrels & Infusions
Oak barrel aging is a hot topic for winemakers. There are many different thoughts on which oak to use and how long to age in an oak barrel. Rick Lanza of Wooden Valley Winery, in Fairfield, California says that he barrel ages his Cabernet Sauvignon first and then bottle ages it for up to a year. “We prefer barrel aging for red wines because it allows the tannins to refine and become finer grained, and you get the micro-oxidation through the barrel, so that helps soften the wine.”

When using oak barrels you definitely want to taste often to avoid over-oaking, make sure the barrels are topped-off monthly, properly manage your SO2 levels, and be patient — it will be time well spent. Hansen says, “Barrel aging allows for more rapid development and softening of tannins, while bottle aging allows development of secondary aromas. Wines like Cabernet Sauvignon, Petite Sirah, or Tannat can accept longer aging in barrel than Pinot Noir because they have more pigment and tannin to begin with, so generally Pinot goes to bottle younger.

Flavor considerations for oak barrels consist of the type of oak (French, American, or other), the age of the barrel, the toast level, if there was a different type of alcohol aged in there previously, and the number of times it’s been used. All of these factors impart different flavors.

Barrel alternatives include staves, chips, oak powder, spheres, oak spirals, WineStix®, and more. Each has its pluses and minuses, but just like an oak barrel you want to taste your wine regularly to make sure you are imparting the flavors you want in your wine. WineMaker digital members can read more about these options at: https://winemakermag.com/article/beyond-the-barrel.

Quick Tips: I’ve outlined a lot of equipment, but just as important as it is to find the right aging vessel for you, it’s also important to maintain your airlocks and bungs. If you don’t keep your airlocks full or bungs clean you are asking for bad things to happen with your wine. These may be small items but they can introduce big problems if not maintained. Also, always have different sized glass jugs in your cellar. This helps you manage your topping off needs without losing any wine to over-oxidation. Lastly, keep track of your SO2 levels. Oxygen isn’t your friend and you don’t want your wine to spoil while it ages. Remember wine always wants to turn to vinegar, and it is a living product. You need to protect it! 

Products to help avoid the need to age so long (sidebar)

Looking to impart age without aging your wines? No problem. I understand that sometimes you just want to enjoy your wine as soon as possible. If your wine has any harsh tannins or needs some “rounding out” I’d suggest looking into the following products.

Noblesse
Noblesse is a natural nutrient that is used to help soften wines. It can be used pre- or post-fermentation. It is great if you need to soften a high-alcohol wine or round out a wine that is too high in acid or tannin. Sometimes our grapes are high in Brix and we can’t help but have a high-alcohol wine. Noblesse will help soften your wine’s mouthfeel, giving the perception of a rounder, silky mouthfeel, while reducing any sulfur smells and burning sensation from the high alcohol.

Gum arabic
Gum arabic is a tartrate stabilizer that helps soften the perception of astringent and bitter tannins. It also helps stabilize your wine’s color. This is a great tool for when your wine tastes a little bit “too young.” It can help a wine taste another year older by just one simple addition.

Super-SmootherTM
Super-SmootherTM is a great tool that’s ideal for home winemakers because it comes in small packages intended for 6-gallon (23-L) batches. It contains glycerin and liquid oak extract. The combination of these two adds a subtle oak flavor while softening harsh tannins and smoothing out wine mouthfeel.

Tannin FT Rouge
Tannin FT Rouge is derived from highly reactive tannins from exotic woods and chestnut. I usually suggest using this pre-fermentation to help preserve the natural tannins from the grape, help stabilize color, and enhance mouthfeel. You can use this post-fermentation but you will have to wait 3–6 weeks for the addition to show up in your wine.