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17-04-2011, 19:50
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In the comments on my previous blog post (http://thebeerboy.blogspot.com/2011/04/now-drinking-salopian-darwins-origin.html#comments), Dom of Thornbridge brewery asked: "Do you believe force carbonation gives a different kind of fizziness as opposed to bottle conditioning?". This is the sort of question that is so innocently placed that it must be a trap, but nevertheless, I'm going to have a stab at answering it.

I'll preface this by saying that I'm going to talk in broad-brush terms, employing generalities to which there may be exceptions. However, what I say is what I think, and it's born of experience and education, although perhaps someone more expert than may might chime in with an opinion. It's also appallingly geeky, for which I don't apologise, but I do warn you that unless you find the title of the post interesting, the next 400 words will be a tad dry.

My gut feeling is that force-carbonating and bottle-conditioning do produce different types of fizziness. There may be some overlap between them – bottle-conditioned beer can be overcarbonated, and a filtered beer that is undercarbonated is particularly lifeless, and vice-versa - but in the main, they are different.

My drinking experience tells me that bottle-conditioned beers generally have a finer, softer carbonation than force carbonated beers. That's not to say that it's always preferable – I find the supersaturation of CO2 in many Belgian beers a bit hard to deal with, but again, this is a fine, small-bubble type of carbonation, whereas I find force carbonated beers tend to have larger, rougher bubbles. This is my experience, but there's also a bit of science behind it.

When sparkling wine is made, it can gain carbonation either from being fermented in a large closed container (tank, cuve close, or Charmat method), or it may be refermented in bottle (the so-called methode Champenoise). While both of these processes make fizzy wine, the methode Champenoise is generally accepted to produce smaller, more persistent bubble than the tank method. That's the science – I don't know exactly why, but I'd guess it's something to do with ratios of gas to liquid, and overall pressures producing a certain style of saturation, but that's only a guess.

One other thing I've learnt from homebrewing: the way a beer carbonates has a definite gradient to it. When you bottle a beer with a bit of sugar and live yeast, the yeast eats the sugar and produces CO2 in the the tightly capped bottle. What I've found is that the yeast produces CO2 faster than the beer can absorb it. So after two days, the beer is a riot of barely-dissolved CO2. In fact, I'd guess that the CO2 to conditioned the beer is produced within three days of capping the bottle – the rest of the conditioning process is about the CO2 dissolving into the beer.

Of course, what is actually happening in the bottle is just one thing. How the beer arrives in the glass is another. You can always pour a non-BC beer a bit more roughly, knocking the gas out of it. This does two things (for me) – it makes it less gassy (duh), and it makes it more tasty. It's more tasty because when the beer hits the tongue, if you've knocked a lot of the gas out of it, it doesn't erupt in a riot of bubbles, more beer stays on your tongue, and the flavour is more apparent.

So yes, I do think that force carbonation gives a different sort of fizziness than bottle-conditioning, and that's why.

Geek-out over.


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