Brewer’s Perspective: More on Package Conditioning at Sierra Nevada

For much more about Sierra Nevada’s approach to this technique, see Package Conditioning for Beers that Live Longer. [PAYWALL]

How Much Yeast

We aim for what amounts to an extremely low cell count per 12-ounce bottle—about 1.1 million cells per milliliter of beer (1.10e^6 cells/ml).

It’s important to note that a yeast target for bottle conditioning would likely be different brewery to brewery, and it certainly would be different from yeast strain to yeast strain. At Sierra Nevada, we’ve arrived at our target level over years of fine tuning with our yeast. The goal is to add as little as possible and still get the job of bottle conditioning done.

For perspective: In 800 barrels of beer, that is usually about 150 pounds (68 kilos) of yeast slurry—but it depends on the cell count and viability of the yeast we’re using. This is something we calculate every time, taking those points into consideration. Also, our yeast-health and handling criteria for bottle-conditioning yeast are more rigorous than our criteria for using yeast for fermentation.

Because of the critical nature of bottle conditioning, we can’t afford to take any risks. The additional factors we use to set our criteria include, among others:

• yeast generation
• from which brand it was harvested
• the number of hours elapsed since the yeast’s source tank was chilled
• when the yeast was harvested
• yeast storage conditions in the brink

We do our very best every day to reduce risk and ensure the best quality and consistency.

Sugar

At Sierra Nevada we use dextrose, and we calculate it based on the actual CO₂ volumes in the brite tank versus the target carbonation level.

The rough calculation:

(target CO₂ v/v minus actual CO₂ v/v)  1.2 = pounds per barrel of dextrose

We apply a few nuance factors to that calculation, but that’s the basis that we further fine-tune to our process. This is derived from the classic equation from Joseph Louis Gay-Lussac, circa 1810—C₆H₁₂O₆ à 2 C₂H₅OH + 2 CO₂—which describes the fermentation of glucose into ethanol and carbon dioxide.

Of course, the theoretical is different from the practical in these situations. Our bottle conditioning today is strictly anaerobic, and Gay-Lussac’s equation includes respiration plus fermentation and is calculated as anhydrous glucose in laboratory conditions. We’ve figured out our actual efficiencies that we use every day, as described above. We have our ABVs dialed in a little under label target coming into filtration, so that we can be sure after conditioning it’s right on target, every time.

How Much Beer

It takes a lot of storage to manage package conditioning on a large scale. During Celebration season, when we’re brewing two of our most popular bottle-conditioned beers at the same time—Celebration and Pale Ale—we’ll have somewhere around 3,000 pallets in the warm-conditioning warehouse at any given time.

There’s a constant rotation of new pallets coming in and finished pallets going out. After Celebration season, the number of pallets goes down to about half that, and we maintain the same process. There are a lot of factors that determine warehouse inventory and how much buffer we maintain, which changes throughout the year.

Conditioning Temperature

The warm-conditioning warehouse is about 62°F (17°C), and the average hold time needed for conditioning to be completed is 10 days. We won’t ship any of that beer before the conditioning time is complete. Once the beer has met its holding-time criteria, it will go out on a refrigerated truck to be delivered to our distribution network and onward to be enjoyed by drinkers.