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Carbonic acid levels and carbonation rate

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  • Carbonic acid levels and carbonation rate

    Hi experts,

    After perusing other threads about carbonation, pressure, temp, and method, I decided to throw this out there to get some comments from those of you who are more experienced. Quick rundown, we are a nano (2.5 BBL) in Latin America, where it's hard to get decent equipment, on a shoestring, with a simple self-designed and built to purpose brewhouse, fermenting in plastic conicals in a temp-controlled environment. Budget currently prohibits us from buying a bright tank, so for each run, we crash to 4C, keg whatever we need to fill keg orders, then whatever is left (to be bottled), we put into large 50L kegs and carbonate in those, for bottling. We leave enough headspace so the beer has at least a full "circle" of surface area to make contact with the CO2 in the headspace (not filling up into the neck or curve of the keg), apply CO2, to all the kegs, and wait.

    Our best and most consistent results obviously come from applying CO2 at the calculated pressure from the equilibrium charts, say 14 PSI @ 6C (43F) for 2.52 volumes, and just waiting until it comes into equilibrium, usually about 7 days. But, since sometimes we want to get the beer out the door faster, we have played with other methods, setting the PSI higher for an initial period, then reducing it to the final desired equilibrium PSI, for example, 40 PSI for 24 hours then down to 14 PSI, or 30 PSI for 36 hours then down to 14 PSI. Once we even left a keg at 40 PSI, checking it at short intervals, until (sensorially) we had the desired carbonation level.

    Obviously, overcarbed beer has more carbonic bite, but what we noticed is that the carbonic acid bite seems to be a function not only of pressure/temp/duration, but of *rate*. The beer that carbed at a lower rate to 2.5 volumes over the course of 7 days seems to have the same amount of bubbles and carbonation, just judging visually and with the palate (bubbles and mouthfeel), but is very smooth with little bite, whereas beer carbed quickly over only 24-48 hours to the same carb level (again, no dissolved CO2 meter here, just going by bubbles and feel), is almost undrinkable due to the carbonic acid bite. Same carbonation level, way more bite, and not in a good way. In that case the bite mellowed after about two weeks, but still the beer was never as nice as the ones that we carb up slowly. Again, I repeat, it didn't seem to have more carbonation, just more acidity.

    The questions:
    1.) Is there anyone out there with a background in chemistry, or anyone more experienced that can corroborate this? Is carbonic acid production a result only of the amount of CO2 dissolved into the liquid or is is also affected by the rate, the speed at which the gas is dissolved?
    2.) Is the carbonic acid level proportional only to the amount of CO2 that actually dissolves into the liquid or is it maybe dependent on the actual pressure used to get there?
    3.) Also, in the forums, here and homebrewing ones, you'll hear people say "the beer is green", "leave it in the keg a week to smooth out", "let it age", etc., but does carbonic acid really disappear (reabsorb, decompose, convert, morph, I don't know) somehow after generated? What's the chemistry there?

    I realize, a brite tank and carbstone are the final answer, and hopefully that will be in the cards later this year, but for the moment, this is our ghetto setup, and it has been churning out some pretty high quality beers. For the moment, we'd just like to understand the science behind this particular aspect a bit better, so we can tweak our process. If the only solution is carb it slow every time, we'll do that.

    Thanks in advance for any comments, and if you see some fatal flaw in the process as well, feel free to speak up.

    Last edited by LongRoadBrewing; 01-27-2020, 02:02 AM.