As a hobby homebrewer, I know that when I bottle my beer there is a small amount of yeast left in the bottle that produces carbonation when under pressure with the small amount of sugar added. After the beer has conditioned in the closet for a few weeks there is a thin layer of sediment at the bottom of the bottle. I usually pour the beer off the sediment into a chilled pint glass to avoid stirring up the sediment.
With commercial beers however, there is no sediment. Without sediment, I assume they have filtered their wort so that there is no residual yeast left in the bottle. How, then, are they carbonated in bottles?
Yep. Force-carbonated in the bottle line. You can do the same thing with home-brew: keg it, crank in about 15psi CO[sub]2[/sub] and roll the keg around for an hour. Let stand overnight and you have carbonated beer. The pros just do it quicker and faster with specialized equipment. IIRC, the beer goes from Holding tank to Carbonator to Bottling Line to Capper.
We carbonate post-filter. As the beer leaves the filter, it enters a sort of flattened section of stainless steel pipe on its way to the Bright Tank. In the middle of this section of pipe are a pair of sintered stainless steel “stones” that force a stream of CO2 bubbles into the beer.
The operator adjusts the pressure of the CO2 depending on the speed of the beer through the pipe, and tests the beer in the Bright Tank repeatedly throught out the run to make sure the amount of CO2 in the beer is in the proper range.
Back in the “good old days” some of the breweries used a method called krauesening.
In this method, “ruh” beer, which is beer that is almost finished fermenting, is tranferred to an unvented tank. The ruh beer gets a bit of freshly fermenting wort, sometimes called “gyle” or “spiese”, added to it. This kick-starts a second fermentation that produces new CO2 that is trapped in the unvented tank and creates “natural” carbonation.
But I think the term “natural” is misleading, as in either method, it’s real, genuine CO2. It’s just a difference in whether it’s produced internally or externally.
As USCDiver says in his OP, there is still yeast in suspension when they bottle. At bottling, (he didn’t mention), they also add a bit more fermentables prior to putting in the bottle and capping the beer. Fermentables can either be wort (pre-fermented beer), or sugar. Most homebrewers use corn sugar (dextrose), or some dried malt extract added to some water, to provide the food for the yeast, which will then turn it into a bit more alcohol, and the CO2 needed for carbonation. As the bottles are capped, and all the pressure remains inside, the CO2 is absorbed into the beer… until you remove the cap. Alternative sugars can be used at bottling to change or enhance the flavor of the beer. (maple syrup for example in a maple ale)
One of the joys of homebrewing, is that if you completely screw up the amount of sugar you add at bottling, or bottle before the initial fermentations are complete, you can overpressurize your bottles, and they can either explode in storage, or foam up massively when you open it. (Doesn’t happen often, but it can/does happen to some newer brewers)
The main reason that some breweries use a “natural bottle conditioning” is that it can provide some additional blending of flavors in the beer, where a “forced carbonation” is usually done in “dead” beer (pasturized).
Some breweries go so far as to bottle with a different yeast than they used in fermentation, so that other breweries, and homebrewers can’t reculture their “house yeast.”
This isn’t new-thread worthy, but butler1850 just reminded me of something. Anyone know of a good use for corn sugar aside from natural carbonation? I always force carbonate in my cornie kegs, so I never have a use for the packets of corn sugar. I’ve got about five pounds now, and don’t just want to throw it away.
I’m going to have to look into the yeast reculturing idea! That’s brilliant! I usually use the kits’ dry yeast, or sometimes buy liquid, ready-to-pitch, but I’ve never thought of propogating my own or even taking someone else’s. Actually… I actually have a yeast culture in the fridge, but that’s for bread making. I started that sponge with a mixture of some liquid yeast that passed expiration, and man!, does it ever give a great flavor to bread that you don’t get from the Red Star or Fleischman’s.
Do you force-carbonate extremely (like, one-hour)? Or do you let the CO2 have several days to do its work? I’ve had fun experimenting with how much sugar I can add relative to how much time/CO2 it takes to get the beer fully carbonated, and then try to see a taste difference.
you can use the corn sugar as a brewing adjunct, eg a flavorless way to boost the alcohol content.
Once, when living in Japan and lacking yeast, I recultured Erdinger yeast from a bottle. But if you’ve got easy access to a yeast you like already, it’s easier than messing around with reculturing. That said, if you make beer very frequently, you can just keep reculturing when you bottle one batch for the next batch.
The greatest benefit of bottle conditioning is that the resulting fermentation uses up all of the available O2 in the bottle. Dissolved oxygen is the major contributing factor in deterioration of the packaged product.
In a commercial bottling operation, wouldn’t this be handled (if force carbonation is used) by displacement of O2 by CO2 during the filling process? I’m fairly sure that even in homebrewing, where the dissolved CO2 in the flat fermented beer comes out of suspension during bottling, and pretty nearly purges my bottles of O2. Not all of it of course, but pretty close, and I’m not dealing with an already carbonated product being dispensed into the container.
Yes. The bottles are actually purged with CO2 twice, then filled under pressure. Then they are hit with the jetter, which causes them to foam over just before being crowned.
But there is still a small amount of air in the headspace, at our facility we are typically somewhere around 0.1 ml of air in a 355ml bottle. Larger breweries strive for even lower than that.
