Here we are, the day after pitching the yeast into the wort for our Robust Porter. It may look like nothing is going on here, but that is far from true. In order to understand what's really going on in this picture, we're going to have to get into a bit of science, so hold on to your beer-geek hat.
Within an hour or two of completing your brew day, the yeast got acclimated to their environment and realized it was time to get to work. Their first project is to get healthy. They absorb vitamins, minerals, and a type of amino acid known as free amino nitrogen in order to build their strength. Beer has a natural fermentation advantage over wine, cider, or mead because vitamins and nitrogen are readily available in wort, where they often need to be added to other fermenting beverages. Oxygen is also essential in this stage, which is why we vigorously agitate the wort after it has been cooled. The agitation causes oxygen to be dissolved into the surface of the wort, and it is vital to yeast health.
After the yeast become strong, the next thing they do is fill the entire space of the beer. They reproduce rapidly, because they need to spread out in order to eat all the sugar they can get. This phase of the life cycle is where a lot of the yeast-driven flavors are produced. Proper temperature is important here so that we don't encourage the yeast to produce unwanted flavors. For the American Ale yeast that we're using, maintaining an ambient temperature between 64°F and 68°F should be the right range to produce a clean tasting beer with a very subtle fruity character. I keep my beer fermenting in a closet that stays about 66° F in the Chicago winter.
In the photo above, you can see a very thin layer of foam on top of the wort. This means the yeast are probably just in between reinforcing their strength and reproducing to fill the space. They are starting to expel a little bit of CO2, which causes the foam. The light foam is a good indication that the yeast will be working in full force by the end of the day. By this time tomorrow, we're going to see some serious fermentation action.
If your beer isn't showing a light foam by this point, it's not a cause for worry. There are a lot of complex biological factors at work here, and this phase can take as long as 48 hours to achieve. We're going to keep tracking the progress of this beer throughout this week.
Check back here tomorrow to see what happens next!
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