Bottle Conditioning

  • September 9th, 2019
  • By Stephen Rich

In modern breweries, packaging beer is as much about science as it is engineering. Temperatures, pressures, speeds and flow rate all mix together with tanks, equipment, brewers and beer to create that perfect bottle or a can of beer, carbonated precisely and without oxygen added. This may be the case most often today, but it was not always so. It is common within the brewing industry to refer to old world brewing and fermentation as art, but packaging as engineering.

Bottle conditioning, also known as bottle or package re-fermentation is how beer and other sparkling beverages were given their characteristic carbonated snap in the package for hundreds of years. Many would argue that while it is perhaps not as predictable as modern methods, it may in fact create a more stable, and higher quality finished beer by the time you enjoy it. These are some of the reasons why Cowbell Brewing’s Anniversary Beers - Almanac and Reunion (our Solera Vintage Beers) - are all bottle conditioned.

Nearly all the beer we package at Cowbell is carbonated and packaged in a high quality oriented and modern process. First, towards the end of fermentation the tank is shut, so that the final creation of CO2 from fermentation is captured and begins to carbonate the beer naturally. After cold maturation, the beer is centrifuged on its way to a brite beer tank (BBT) to remove hops and most or all yeast. On its way to the BBT, the beer also passes through an in-line-carbonator that injects food-grade CO2 at precise levels. Then the beer rests in the BBT, perfectly carbonated and ready to be filled in cans, bottles, or kegs in a modern fashion.

For the very special Cowbell beers which are designed to mature over time, we choose bottle conditioning. At the end of fermentation, all CO2 is released from the tank before closing and cooling. After maturation and centrifugation, the beer collected in BBT will have no yeast in it, and also no CO2. This is where the science begins again.

We will calculate, then dose into the tank, a specific quantity of simple sugars (dextrose, maple syrup, Belgian Candi Syrup, wort, etc.), along with a very specific yeast strain chosen for that beer. Then the beer is recirculated; sugar and yeast mix gently to ensure perfect dissolution. Quickly then, we fill bottles and kegs – this time manually by hand.

The result is a bottle of beer with fresh yeast and sugar inside. Soon the fermentation process will begin again, and over the next 2 to 6 weeks, just a small amount of fermentation will happen in the bottle, ie. re-fermentation. The re-fermentation is not enough to add detectable alcohol, but it is enough to create carbonation. Newly produced CO2 is trapped inside the bottle – and when created at precise amounts will produce an equilibrium in pressure in the head space in the bottle, and the beer itself. And now, you have traditionally carbonated beer!

The bottle conditioning process is more laborious, time consuming, and less predictable than modern methods. So why bother? Yeast is the answer! That special single cell living organism, that is responsible for the creation of beer in the first place, once again gets to star in the picture.

During re-fermentation in the bottle, one of the first things the yeast does is consume oxygen. This reduction in harmful oxygen could be the most valuable contribution of bottle conditioning. Now the resulting beer will not oxidize and deteriorate as it would even under high quality modern filling techniques – and therefore the beer will be delicious for a longer period of time.

Many people also contend that the feeling of natural carbonation is more fine and delicate than modern carbonation techniques. This is a very subjective opinion, but I happen to believe in it. There is always something special about the feeling of a bottle conditioned beer. It can’t be confirmed by analytical methods. It just feels better.

Finally, the presence of healthy yeast in the bottle can contribute to more complex and interesting long-term maturation of the beer – just as it does in fine wine, port and champagne. The science of how these beverages mature overtime is still a little-researched subject, but the subjective opinion is very consistent. Bottle conditioned beers develop more complementary flavours over time compared to non bottle conditioned beers.

At Cowbell Brewing, we bottle condition because of the romance, tradition and quality. We appreciate the added depth, feeling and longevity that the resulting beer will showcase. It’s a challenging process reserved for only a small subset of appropriate styles. Is it worth it? Yes.