We are getting to the part where you will need to be patient. The next two posts will be the hardest, due to having to wait.
Let me give you some background information on yeast. Thank you science.HowStuffWorks.com for the great explanation of yeast.
Yeast, a microscopic, one-celled organism belonging to the group of organisms called fungi. There are many kinds of yeasts, some of them of great importance to humans. Yeast is necessary to make leavened bread, beer, cheese, wine, and whiskey. It is rich in B vitamins; a form of yeast called brewer’s yeast is used as a diet supplement.
Yeasts obtain food from fructose, glucose, and other monosaccharides (simple sugars), which are found in most fruits. Yeast enzymes chemically break down the sugars into products that the cell can use. Other yeast enzymes can make simple sugars out of disaccharides (double sugars), which are found in certain organisms.
The breaking down of sugars, or fermentation, produces ethyl alcohol and carbon dioxide as by-products. Fermentation turns fruit juices into wine and helps turn wort (diluted grain mash) into beer or whiskey. The carbon dioxide produced by fermentation makes the bubbles in beer and some kinds of wine, and causes bread to rise. As bread bakes, the alcohol produced by fermentation evaporates.
There are two basic types of yeast: Ale and Lager.
- Ale yeast is a top fermenting yeast that works best at temperatures between 59˚ to 77˚. Ale yeasts ferment faster and are typically done with-in a week to ten days.
- Lager yeast is a bottom fermenting yeast which ferments best at a temperature less than 50˚. Due to the lower temperature lager yeasts typically take longer to complete the fermentation process, however they do produce more alcohol and have a dryer finish to the beer. Typically lager yeast takes several weeks to months depending on the alcohol content of the beer.
Now that we have that information, let’s get back to our brewing process. The last installment we left off at turning off the heat and transferring the wort to the fermenter.
The fermenter is usually a carboy made of either glass or plastic. Glass is the best way to go due to its non porous surface; it does not stain or scratch; although they are much heavier and fragile. Another option that homebrewer’s use is a 5 gallon bucket with a lid. The lid will need a hole to vent the carbon dioxide build up. For the advanced brewer there are conical fermenters that come to a point on the bottom so all of the solids (trub) go down to the bottom and the beer is able to be drained without disturbing the trub. Trub is the used and dead yeast cells that end up on the bottom of the fermenter after fermentation is complete.
***After the wort is in the fermenter the gravity is checked using a hydrometer. A hydrometer is an instrument for measuring the relative density of a liquid, usually consisting of a sealed graduated tube with a weighted bulb on one end, the relative density being indicated by the length of the stem that is not submerged. This reading will be known as your Original Gravity. In recipes this will be listed as the OG. number.
After the gravity has been documented and the temperature is below 77˚, the yeast may be added to the wort. The larger the batch, or the higher alcohol content batches, a yeast starter may be needed or add multiple yeast packets. Yeast needs oxygen to get going. After adding the yeast to the wort, agitate the carboy to mix the needed oxygen into the wort, this can be done by shaking or rocking the fermenter vigorously.
Your fermenter will need to be covered and vented to prevent any wild yeast or bacteria to take hold before the yeast is able to do it’s job. If there is plenty of head space in the fermenter, an airlock may be used. If there is not much space, a blow-off tube will be needed. A blow-off tube will allow the foam and hops; that get kicked up from the active fermentation to get released into a bucket or pitcher of sanitation solution. Without the venting of these gasses it is possible for the lid or cap to be blown off and the foam and hops to be sprayed all over the walls and ceiling of the fermentation area.
The fermentation area should be cool and dark. For an ale an area like a basement, that maintains a temperature of 65˚ –70˚F is optimal. Ales will ferment quicker at warmer temperatures, but off flavors will be present in the resulting beer. Lagers will need to be held under refrigeration with temperatures between 40˚- 50˚F.
After fermentation is complete the bubbling in the airlock or pitcher will be almost nonexistent. To be sure that fermentation is complete; take hydrometer readings over three consecutive days. If the readings haven’t changed, the fermentation is complete. If it’s not done give the fermentation a few more days. Document the final reading when it has completed. In your recipe this would be the FG (final gravity) number.
To figure the alcohol in your beer; ABV (alcohol by volume) – Take the difference between the OG and the FG, divide the result by 0.0075 and there is your ABV.
Example: 1.080 – 1.010 is a gravity difference of .07. .07 / 0.0075 = 9.3 ABV.
In the next post we will cover bottling your beer.