E - like enzymes
What are enzymes?
Enzymes are mostly proteins which, as biocatalysts, can accelerate certain chemical reactions without themselves being changed. All enzymes have the suffix "ase" in common.
Where are the enzymes located?
Certain enzymes are already present in barley. However, they are usually in a dormant, i.e. inactive state. They are awakened or activated during germination. The majority of the enzymes are therefore formed during the malting process in the germination phase in the barley grain.
What is the goal of the enzymes?
The aim of the enzymes is to break down the starch contained in the barley into small, fermentable sugars so that in the next process step of whiskey production - fermentation or alcoholic fermentation - these can be converted into alcohol by the yeast.
What is strength?
Starch is a widespread organic biomolecule in the plant world and is present in barley in a proportion of about 60 percent. It is a giant or macromolecule - in the form of a multisugar - which is composed exclusively of the individual building block glucose (= dextrose). The individual glucose building blocks link up with each other at a specific point in the molecule, thus forming long sugar chains that form a spiral. This giant spiral structure is called amylose. However, the glucose building blocks can also link up with their neighbors at another point in the molecule. This results in long sugar chains that exhibit strong branching. This branched form is called amylopectin. Starch consists of about 20 to 30 percent amylose and 70 to 80 percent amylopectin.
How does biochemical starch degradation work?
Let's mentally make a cut through the barley grain. This reveals small globules, the so-called starch granules, which are surrounded by a protective layer and embedded in a protein matrix. First, these starch granules must be exposed. To do this, a specific class of enzymes, the cytases, biochemically degrades the starch-enveloping protective layer. The protein matrix in which the starch globules are embedded is degraded with the help of so-called proteinases. The degradation products of these enzymes are various amino acids, which in turn are required as a food and growth source for the yeast during subsequent fermentation. The exposed and now accessible starch globules can be degraded into smaller fragments by a third class of enzymes, the amylases. In this process, alpha-amylase breaks down the long glucose chains of starch into smaller fragments, so-called dextrins, as well as sugars with a lower molecular weight. Beta-amylase, on the other hand, always cuts off exactly two coherent glucose molecules (= maltose) from the end of a sugar chain. Alpha-glucosidase, in turn, always removes only a single glucose molecule from the ends of the sugar chains, while limiting dextrinase cuts off the branches in the amylopectin of starch. The shorter sugar chains formed in this process can be further degraded by the other enzymes in the same way to form fermentable sugar components.
At what temperature do the enzymes work?
Basically, the enzymes relevant for the mash act at temperatures between 40°C and 80°C, whereby each enzyme or enzyme class has its own optimum temperature range within which the biochemical processes take place as quickly as possible and with high yield. This means that for the enzymatic degradation of starch, both a certain temperature and a certain time are the relevant parameters and thus play an enormously important role for an optimal mashing process. The optimum temperature of some of the starch-degrading enzymes is 62°C to 65°C, which is approximately the temperature of the first mash water. This high temperature leads to swelling and bursting of the starch globules (= gelatinization), and thus facilitates the access of the enzymes to the starch and its degradation. After a reaction time of about 30 minutes, the formed, sugar-containing wort is drained off via the sieve bottom of the lauter tun - the mashtun - while at the same time fresh water is added from above at a now higher temperature. This has the decisive background that any remaining starch globules in the barley are also gelatinized and thus made accessible to the enzymes.
What happens to enzymes at higher temperatures?
Not all enzymes survive the higher temperature. But those that are not immediately thermally inactivated use the remaining opportunity to break down further starch into smaller sugar molecules.
Where are the temperature optima of the mash enzymes?
The alpha-amylase is stable in a temperature range of 65°C to 75°C. The other enzymes are somewhat less heat stable and denature earlier over time. Thus, the temperature optimum of beta-amylase is 60-65°C, that of limiting dextrinase is 55-60°C, and that of alpha-glucosidase is below 45°C.
How much starch is converted to sugar?
At the end of mashing, about 80 percent of the starch has been converted into fermentable sugars by enzymatic degradation.
What role does the protein content of barley play?
The protein content in the barley grain should not be too high. This is because a lot of protein simultaneously means less starch and this in turn means less sugar, which ultimately leads to less alcohol. However, the protein content should not be too low either, as the yeast needs the amino acids broken down from the proteins with the help of proteinases as a source of food and growth. A protein content of around 10 percent in the barley grain has emerged as a reasonable compromise.