Ethanol fermentation/alcohol fermentation. Yeasts break pyruvate molecules—the output of the metabolism of glucose (C6H12O6) known as glycolysis—in starches or sugars down into alcohol and carbon dioxide molecules. Alcoholic fermentation produces wine and beer.

Fermentation is usually divided into three stages: primary, secondary, and conditioning (or lagering).

Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide, and thereby turns wort into beer. In addition to fermenting the beer, yeast influences the character and flavour.

In commercial production, the yeast works in anaerobic conditions to convert pyruvate into ethanol, and does not carbonate beer. Beer is carbonated with pressurized CO2. When beer is poured, carbon dioxide that is dissolved in the beer forms bubbles.

Skunked beer is caused by a specific chemical reaction triggered by exposure to light, as explained in the latest Reactions video by the American Chemical Society. They’re added to the wort, or not-yet-beer, during the brewing process. When boiled, hops release iso-alpha acids into the liquid.

Though the amount of time from start to finish can be as little as a month, most of that time is spent allowing the beer to ferment and condition. In general, expect to spend 6-10 hours of hands-on time brewing, and 2-4 months between brew day and drinking.

Even contaminated homebrewed beer can’t make you sick, he said. “There are no known pathogens that can survive in beer because of the alcohol and low pH,” Glass said. “So you can’t really get photogenically sick from drinking bad homebrew. It could taste bad, but it’s not going to hurt you.”

If you are brewing a hoppy IPA, you want to drink it fresh. You could have it go into a bucket, and come out of the bucket for kegging or bottling in 2-3 weeks. Another 2-3 weeks might stand to help, but if you want fresh, that could do it.

The actual process of preparing the ingredients takes only a few hours, but your beer-to-be will need to ferment in your beer brewing kit for at least two weeks (or longer, depending on the type of beer you’re brewing), followed by two weeks of bottle conditioning after you’ve bottled your home brew.

If you leave the beer too long you have a higher chance of the yeast cells starting to break down in your beer (autolysis). This breaking down of cells releases the contents of the cells into your beer (this can include off flavours processed by the yeast).

I would say keep it in the primary for 2 to 3 weeks so fermentation can definitely finish and the yeast can clean up after itself. Fermentation time generally will take the same time regardless of batch size.

A beer is usually done fermenting when the krausen drops and the yeast and sediment drop out clearing the beer. This is hard to see with a bucket. I use glass carboys so it is easy to see when this happens. With out a hydrometer to test specific gravity extra time will be your safety net.

IT’S SLIGHTLY QUICKER For the most part, making a 3-gallon batch of beer takes almost the same amount of time as a 10-gallon batch of beer, although smaller batches can take less time (especially if you use the BIAB method).

5 Gallon homebrew kegs have about 45-50 12oz beers depending on how high its filled and then also how much sediment might be transfered from the fermentor.

Dividing these costs over 12 batches (one year) results in $2.25 per 5 gallons. If you even brew 10 times a year, your cost is $2.70 per 5 gallons. For the direct costs of grain (pre-crushed), liquid yeast, hops, priming sugar, propane and bottle caps, John estimates $46 for a robust recipe.