So we know that mashing causes starch in your malted grains to be converted to fermentable sugars. The things that are responsible for these conversions are malt enzymes. In this article I want to introduce the basics.

What Is An Enzyme

In short here is a definition from Wikipedia:

Enzymes ( /ˈɛnzaɪmz/) are proteins that catalyze (i.e., increase the rates of) chemical reactions.[1][2] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and they are converted into different molecules, called the products.

If we apply this to brewing in a round about way, the enzymes that are present in malted grains are what transforms the starches into sugar chains, which are then easily digestable by yeast.

Malt Enzymes and Starches

There are a number of enzymes in malt that become active at certain temperatures of the mash and the ones that are most important to the brewer are the enzymes that turn the starches stored inside the malt into fermentable sugars and dextrins.

Starches are long chains of glucose molecules. If you can imaging a big, thick tree branch with lots of smaller branches attached to it with smaller twigs coming from those, then that is what these starches would look like.

The main thick straight limb of this branch is called Amylose and a limb with lots of smaller branches emanating from it is an Amylopectin. These starch molecules need to be broken down in the mash to create sugars that the yeast can consume, the main enzymes to do this are Alpha Amylase and Beta Amylase

Alpha Amylase – Alpha Amylase will break the long amylopectin branches of the starches and create long sugars and amyloses. Alpha Amylase will become most active between temperatures of 67°C – 73°C and a mash favouring these temperatures creates a less fermentable wort with a fuller body.

Beta Amylase – Beta Amylase will eat the smallest twig ends, of straight branches of Amylose, they can only work from the end of a branch and for every cut they make they free a maltose molecule. They also work away at the amylose starches freed by the alpha amylase. Beta Amylase favours temperatures between 55°C and 66°C and will create a highly fermentable wort with less body and a drier finish.

A mash temperature that is a good combination to get both alpha and beta amylase enzymes working in balance is around 67°C and will make a wort that has a good balance between body and fermentability.

Mash Temperatures

There are other enzymes present in malt like protease and beta glucanase that are activated at lower temperatures, to activate these enzymes a step mash is required to take the temperature up through varying temperature ranges from low to high. Modern malt however is well modified and a single infusion mash targeted to balance or favour either alpha or beta amylase will work for most styles of beer.

If you know your beer is supposed to ferment out fully and finish dry you will want to adjust your mash temperatures slightly to target beta amylase to create sugars that are easier to consume by the yeast. A full bodied beer on the other hand requires you to mash a few degree higher and favour alpha amylase.

Other enzyme rests will break down various starches:


Temp °C Temp °F Enzyme Breaks down
40–45 °C 104.0–113.0 °F β-Glucanase β-Glucan
50–54 °C 122.0–129.2 °F Protease Protein
62–67 °C 143.6–152.6 °F β-Amylase Starch
71–72 °C 159.8–161.6 °F α-Amylase Starch

via wikipedia

(Need info on enzymatic rests here)