BEER BREWING PROCESS

During the milling process, the husk is separated from the grain, which is broken into smaller pieces until flour is obtained. A typical mill consists of at least two rollers: one fixed and one rotating. The dry and brittle malt is crushed as it passes between them. If a finer product is required, the milling continues through additional pairs of rollers. The more roller pairs a mill has, the more finely the endosperm is fragmented; however, as the complexity of the mill increases, so does its purchase cost.

At this stage, the malt is mixed with water and heated at specific temperatures for a set period of time, allowing the enzymes to convert starch into fermentable sugars. This conversion of starch into simpler sugars is called saccharification.

There are three main mashing methods. The first is infusion mashing, which takes place at a single fixed temperature. The second is step infusion mashing, during which the temperature is increased once or twice. The third is decoction mashing, in which part of the mash is removed, boiled, and then returned to the mash tun. This final method is traditionally used for producing Lager-style beers.

In decoction mashing, the malt-water mixture is initially heated to 50°C, activating the malt’s proteolytic and cytolytic enzymes. Proteolysis is essential for breaking down proteins into amino acids that yeast will later consume for growth. Cytolysis improves the efficiency of the subsequent filtration process. At the same time, part of the mash is removed and boiled. After 10 to 60 minutes, the temperature of the main mash is raised by reintroducing the heated portion. The mixture is then held at the achieved temperature for another 10 to 60 minutes.

The temperature is then increased again to 75°C. At this stage, the starch-degrading enzymes α-amylase and β-amylase become active. These enzymes hydrolyze starch into fermentable sugars. Once the desired enzymatic activity has been completed, the mash is heated one final time to 75–77°C, causing the enzymes to become inactive.

The mash is then transferred to a vessel for filtration, where the liquid wort is separated from the insoluble malt solids. The remaining solids are used as animal feed. Filtration must be carried out quickly to avoid the extraction of tannins from the husks and unwanted darkening caused by oxidation.

The boiling of wort can be carried out in several ways: either through direct heating with a flame beneath the boiling vessel or by steam injection using internal or external calandrias. The choice of heating method depends on the brewer’s preference.

At this stage, hops are also added. Their compounds undergo chemical transformations due to the heat. Clarifying agents such as kappa-carrageenans are also introduced, forming a mesh that traps proteins and allows them to be more easily removed from the wort by sedimentation after boiling.

The reasons for boiling are:

Extraction of resins from the hops.
Isomerization of humulone into soluble isohumulone.
Evaporation of most — but not all — volatile hop oils.
Termination of any possible enzymatic activity.
Sterilization of the wort.
Concentration of the wort.
Removal of raw malt grain odors.
Development of a darker color in the wort.

At the end of the boiling process, the wort is filtered to remove hop leaves if whole hops were used. Otherwise, it is transferred directly into large vessels where it remains undisturbed for 20 to 30 minutes, allowing sediment composed of resins, proteins, and tannins to settle.

The now-clear wort is then passed through heat exchangers and cooled to 6–10°C, the appropriate temperature for fermentation. Immediately afterward, it is aerated to create an ideal environment for yeast growth.

Yeast is added to the cold wort, which contains oxygen, fermentable sugars, and various nutrients. The yeast quickly consumes the oxygen along with part of the nutrients, such as phosphorus, sodium, magnesium, and zinc. Fermentation temperature is maintained at 4–9°C for bottom-fermenting yeasts and 15–20°C for top-fermenting yeasts, usually lasting 5–9 days. In theory, the yeast population approximately triples through repeated doubling, ultimately becoming about seven times larger than the amount initially added.

When reproduction is complete, it means that all the oxygen has been consumed. At this point, the yeast begins to develop in an anaerobic environment, producing alcohol and CO2. The CO2 bubbles are collected, purified, and either reused or released into the atmosphere. The collection and reuse of CO2 involves a very high cost in industrial brewing.