are proteins possessing catalytic capability, i. e., the ability to accelerate chemical reactions without being changed themselves at the end of the reaction. The production of beer is critically dependent upon enzymes, whether endogenous enzymes native to raw materials such as malted barley and yeast, or exogenous (added) enzymes of commercial origin. There is a great diversity of enzymes, including amylases that break down starch, β-glucanases that hydrolyze β-glucans, pentosanases that degrade pentosans, and proteinases that catalyze the degradation of proteins. The molecules acted upon by the enzymes are called “substrates;” the materials produced are “products.” Traditionally, it is the enzymes naturally present in malted barley that will break down grain starches into sugars during the mashing process, and it is those sugars that will ferment into beer.

Optimizing enzyme activity is crucial to the brewing process and dependent on the style of beer brewed and the materials available. The brewer will carefully manipulate the temperature, time, ionic composition, and material concentrations in wort to ensure that the enzymes work in concert to create the perfect beer.

The more enzyme available, the faster the reaction. The relationship between the rate of an enzyme-catalyzed reaction and substrate concentration is not so simple. At a certain substrate concentration the system becomes “saturated” such that elevating the substrate concentration beyond this point does not lead to the reaction proceeding any faster. This is referred to as “saturation” and occurs because the enzyme binds to the substrate molecule to form an “enzyme-substrate complex” which then breaks down to re-form the enzyme and release the product(s).

The location where the substrate binds to the enzyme and where the reaction occurs is called the “active site.” The shape of the protein molecules determines this and the active site might comprise amino acids from quite distinct parts of the enzyme molecule. Stresses such as heat or changes of pH that will tend to change the interactions in the enzyme molecule will disrupt the active site, prevent substrate binding, and destroy enzyme activity. Enzymes differ in their tolerance of heat and pH.

Temperature and pH also impact directly on the rate of the reaction that the enzyme catalyses. All chemical reactions, including those catalyzed by enzymes, are accelerated by heat according to Arrhenius’ Law. However, heat also disrupts proteins’ three-dimensional organization, thereby deforming the active site. Thus the net rate of reaction observed is a balance dependent on how resistant the enzyme is to heat. Enzymes in mashes such as α-amylase andperoxidases are very resistant to heat, whereas others like β-glucanase, β-amylase, and lipoxygenase are much more heat sensitive. The enzyme α-amylase, essential in starch breakdown during mashing, is also stabilized by the presence of calcium ions.

pH also impacts the catalytic process as well as the stability of the enzyme. See ph. It is likely that the amino acids functioning within the active site will only do so under certain charge conditions and this will be directly determined by the local pH. Most enzymes of relevance in mashing tend to function optimally in the pH range of mashes (between five and six).

Enzymes are susceptible to inactivation by other agents (“inactivators”). One such substance is the copper ion that binds thiol groups. Other molecules (“inhibitors”) can block enzyme activity reversibly: i.e., if they are removed then enzyme activity is restored.

See also alpha amylase, amylases, and beta glucanase.