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Ale A type of beer generally characterized by an amber color and traditionally produced using a top-fermenting
yeast. (In medieval England, ale meant unhoped beer, but this no longer applies.)

Aleurone Tissue two to three cells deep that surrounds the starchy endosperm of the barley corn and is responsible for making the hydrolytic enzymes (hydrolases) that degrade the barley food reserves.

Alpha acids: Resins from the hop that are the precursors of the bitter compounds in beer.

Amino acids: Small molecules (there are around 20 different ones) containing nitrogen, which are the building blocks of proteins.

Amylases: Starch-degrading enzymes.

Amylose: A linear polymer of glucose that is a key component of starch.

Amylopectin: The second key component of starch, differing from amylase in that it has branches.

Anaerobic: In the absence of oxygen.

Aneuploid: Indicates that an organism contains more than two copies of its genetic blueprint. (Haploid organisms contain one copy; diploid organisms contain two copies; polyploid organisms contain many. There is no agreed-on point at which aneuploidy becomes polyploidy.)

Antifoam: A material added to fermentations to suppress excessive production of foam.

Antioxidant A material (either native to a raw material or added) that serves to protect against the damaging influence of oxygen.

Aroma hops: Hop varieties said to give particularly prized aroma characteristics to a beer.

Astringency: A drying of the palate. ATP bio-luminescence A technique for detecting microorganisms and soil by measuring the amount of light produced by the action of the enzyme luciferase acting on ATP present in the sample.