Bulk Aging (WineMaker)

Wine aging storage vessels

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 versus 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 by looking at each of the factors that affect the aging process: Time, temperature, oxygen, oak, yeast lees, pH, the composition of the wine, and wine stability.


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.


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.


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.


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 smaller the barrel the more surface area where oak is in contact with wine, leading to more flavor extraction 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 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


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.

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