Bulk Aging Wines
I made my first batch of wine in the spring of 1981, a completely forgettable rhubarb wine. I used bread yeast and a “recipe” published in the local newspaper. The result was drinkable … although only if desperate. A few years later I picked up my first wine making book, and was off into wine making as a planned activity rather than a “guess and hope”.
My early wine making techniques were picked up from the few books on the market, and from the owner of the supply shop I frequented. [I later became a partner in the shop.]
Note: I updated this post significantly on 10/17/2018. The gist is the same, but I expanded on many points.
The conventional wisdom I was taught was “1 week, 3 weeks, 3 months”.
This means ferment for 1 week (more or less, depending on the whim of nature). Rack into a carboy and let settle for 3 weeks. Rack again and let settle for 3 months before bottling. Essentially, wine making took about 4 months from start to bottle. We typically let the wine age at least 3 months before consuming.
Sure, the common myth is that wine takes years to age properly (and some does), but many wines are completely drinkable at 3 months in the bottle. Sure, most will improve given another 6 to 12 months of aging, but we’re talking drinkability, not perfection. [The “perfect” timespan to age wines is a completely separate discussion.]
In this wine making methodology, the wine is “bulk aged” for 3 months. What is “bulk aging”? This means the wine stays in a large wooden, glass, or stainless steel container for extended periods of time, say 6 to 18 months, before bottling.
In speaking with amateur wine makers today, many are convinced that bulk aging is an absolute necessity. In the not too recent past, I agreed wholeheartedly with that concept.
Bulk aging is normally accomplished by placing the wine in a large container made of wood, stainless steel (commercial wine makers), or glass (home wine makers). The common choice of wood vs. glass or steel is outlined as follows.
Bulk aging in barrels has two obvious benefits:
- The wine leeches constituents from the wood of the barrel itself, adding a oak flavor. [wine barrels are normally made from various types of oak.]
- Since barrels are porous, the wine is subjected to evaporation, requiring that the barrel be topped up on a periodic basis.
Oak flavoring is a desired trait in many red and some white wines, so the use of barrels for aging makes sense. It should be noted that newer barrels provide more oak character, while barrels that have been re-used provide less character.
Barrels are gas permeable. Wine evaporates from the barrel, requiring regular checks and topping up when the wine level gets below a safe threshold. Oxygen is the enemy of wine, so too much air space produces oxidation which destroys the wine.
So why barrel age?
In addition to the oak character, evaporation concentrates the non-water/alcohol compounds in the wine, concentrating them. This provides for a more intense aroma and flavor, even when using older barrels that don’t contribute much oak character.
Glass or Steel
What does bulk aging in glass or steel containers give the wine? There’s no wood so no wood character is imparted to the wine. Glass and steel are not gas permeable, so there’s no evaporation.
Bulk aging, in general, gives the wine time to settle, and for heavy particles to drop as sediment. With a few exceptions (such as nigori sake) a clear wine that lacks visible suspended particles is desired. Without the use of fining agents (substances that cause suspended particles to drop) the settling process can take months, hence the need for bulk aging.
I recently read an opinion which stated that the bulk aging provides a more consistent wine, from bottle to bottle, as the wine goes through a more significant part of the aging process in bulk. The wine has the potential to diverge in aging once bottled, so the longer in bulk, the more consistent the bottles will be long term.
This makes some sense, but in my experience, I have had little variation between bottles. Additionally, it’s known that wine ages faster in smaller quantities, so wine will typically be drinkable faster if bottled sooner.
Due to dissatisfaction with grapes available in North Carolina, I’ve been making mostly kit wines since the late 90’s. Kit wines typically are advertised at taking 4 to 8 weeks from start to bottling, basically 1/4 to 1/2 the time the “conventional wisdom” says.
In the past I thought it had to do with the fruit — which is mostly grape concentrate in lower end kits, and may be 100% juice in high end kits. But after so many batches of kits, I decided that idea doesn’t match my experiences. Kits work the same, regardless of brand or quality level – full concentrate and full juice kits are produced using the same method with the same additives.
If it’s not the fruit, what is the cause?
In my experience, all kits call for adding bentonite as a fining agent when the batch is started, and adding a combination of kieselsol and chitosan when the wine is stable (fermentation ceases). Additionally, the instructions call for vigorous stirring after the wine is stable and before adding the kieselsol/chitosan. If the instructions are followed, the wines turn out completely clear. I’ve had kit wines in the bottle for 7 years without dropping any sediment.
The fining and stirring are the reasons why the kit wines are ready to bottle so much sooner. Let’s look at what each does:
The addition of bentonite at the start, when yeast is added, causes heavy particles (including proteins) to drop sooner.
Stirring the wine vigorously when fermentation is complete drives out trapped CO2. I use a powered stirring rod and stir wines typically for 4 minutes, reversing direction every 30 seconds. The wine can foam wildly, but subsides within a few minutes. If I stir the same wine the following day, I get very little foaming. Practical experimentation indicates that stirring drives out the CO2.
This accomplishes in minutes what takes weeks or month in bulk aging. With the CO2 gone, clearing works faster as the CO2 keeps solids in suspension.
Kieselsol and chitosan use negatively and positively charged ion, respectively, to capture remaining solids in the wine and precipitate them. With the CO2 gone, these substances function to clear the wine quickly and more effectively.
Use all three of the above techniques in sequence, and the result is a remarkably clear wine in just a few weeks, rather than months.
I recently started a mead and decided to use kit wine technique in the making. I added bentonite at the start, stirred vigorously when fermentation was complete, and added kieselsol/chitosan. In just a couple of weeks my mead was crystal clear.
I racked it off the sediment after a few weeks. Although I could bottle it now, I’m going to age it another couple of months in the carboy to see if it drops more sediment. My expectation is that it won’t.
My take-away from this is that extended bulk aging is unnecessary.
Please note that this does not indicate that bulk aging should not be done — the point is that there is no wine making requirement that wine be bulk aged. A totally clear wine can be produced and bottled in 1 to 4 months. Stirring and modern clearing agents dramatically reduce the time necessary for the wine to clear.
Bulk aging in wood, steel, or glass does not harm the wine (assuming normal wine making hygiene is implemented). Barrel aging takes time or the wine maker may desire to monitor a wine and make adjustments, including oak (in numerous forms) to change the taste of the wine.
Bulk aging is the wine maker’s decision, not a requirement.