Have you heard of bottle fermentation but aren't sure what it is? We'll explain it to you briefly!
This process has become increasingly important in the craft brewing world (as well as in the world of homebrewing), both to increase carbonation and to extend the product’s shelf life. But let’s take it one step at a time! ?
What is secondary fermentation? As the name suggests, it involves a second fermentation of the beer, which takes place directly inside the container (bottle, can, keg, etc.) after the primary fermentation—which occurs in the fermentation tanks at the brewery—that is, the process that transforms the wort into beer.
So, the chemical reaction will be exactly the same, but it occurs after the beer has been bottled: sugars are added to reactivate the fermentation process, since the yeast (added to the tanks during fermentation) will naturally be attracted to the sugars: just as when making any leavened product, we can say that the yeast “eats” the sugars and begins to ferment, producing, among other things, carbon dioxide.
The new CO2 produced is what makes our beer fizzy and increases its carbonation. That wonderful “psssssst” sound we hear when we pop the cap off our beer is caused by the carbon dioxide inside the bottle!
Of course, this is a simplified version of the secondary fermentation process, which can actually be much more complicated—involving the addition of different yeast strains or fresh yeast along with sugar… in short, complex techniques and secrets known only to our master brewer!
It is said that the process of secondary fermentation in the bottle was perfected in Belgium, a country with a long brewing tradition. Trappist monks, who were far more educated than most other brewers of the time, developed techniques for nearly every type of beer, starting with Gueuze. The British, on the other hand, were at the forefront of producing sturdy bottles, specifically designed to withstand high pressure: in fact, by the late 1700s, newspapers in Calcutta were already carrying advertisements for bottled India pale ale (IPA).
Historical details aside, we know for certain that the key requirement is bottle cleanliness (our bottles actually go through a “rinsing machine” that cleans them with a jet of extremely hot air, eliminating all microbes) and temperature-controlled storage—in our case, for about two weeks—in a dedicated warehouse.
In short, why has it become so essential? What are the most important aspects that influence our beers?
The crispness, the denser head that clings to the glass, a longer shelf life, and even those wonderful little sediments in the bottle—all of which make the beer delicious and unique!
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