For Beer brewers: What is brewing cereal?!
Answers: I noticed that when people refer to a sour smell or taste or smell in a beer they refer to it as brewing cereal. What exactly is this and what is the benefit of using this if it produces sourness?
Cereal grains in general are mostly grasses cultivated for their edible grains. In beer brewing, Brewing Cereals usually refers to adjunct grains, especially corn or rice, although unmalted barley will fall into this category as well. Depending on the type of cereal grain, you will get a different flavor added to the beer, depending on how much was used. Corn is known to give a bit of a sour, cidery flavor in high percentages. Unmalted barley will give a grainy flavor. Oats and Rye both give their own respective flavors as well. Brewing cereals/adjuncts are sometimes used with the intention of cutting costs, but sometimes to create an additional feature, such as better foam retention.
Depending on the style of beer being made, sometimes that flavor given from the cereal grain is a goal. An oatmeal stout has a complex, bitterness to it, that you can't get in a normal dry stout. Same goes for a beer made with rye. Corn is usually used because it is usually more readily available as a grain, and can add alcohol content to the beer without adding much body, although larger percentages will give cidery flavors. Rice will give a dry, crisp flavorless addition to beer, and it is used to add alcohol to a beer without adding color or flavor.
I've never heard of "cereal" in the context of sour taste or smells, but ok.
In brewing, "cereal" refers to the grains that are used as the base ingredients i.e. "cereal grains" such as corn, wheat, barley, rye, oats, etc. "Brewing cereal" would be the grains in the brew.
When one refers to "sour" in brewing, it indicates a bacterial infection. This is in contrast to "tart" which would indicate an acidic (low pH) condition which isn't necessaryly bad, but may not be the flavor you're after. "Sour" is bad if it's unintentional...it's OK if it is intended (like in a Lambic or any other brew where malo-lactic fermentation is desired). The tart flavors that it creates may be desirable for the style of beer...not unlike lemons add tartness to iced tea. Just the right amount (like lemon in tea) is good, but too much would taste bad.