The raw materials used in the production of beer are four:
- barley (and / or other cereals),
- the water,
- and yeast (unless natural fermentation takes place).
After germination, the barley is dried (at 65 - 70 ° C, subsequently at 80 ° C or at higher temperatures for red and dark beers), with the aim of blocking the enzymatic activity which, perpetuating, would damage all carbohydrate and protein structures (important for subsequent processing steps). The drying also affects the rootlets, which are thus removed more easily.
In the following step there is the separation - by filtration - of the liquid part from the solid part; the latter, called threshing, is used in animal husbandry for feeding livestock and in fertilizing the fields, while the filtrate, still without aroma, is added to the typical flavoring substance, which is precisely the hops. This is added as a function of the flavor you want to give to the beer, after which you proceed with the boiling for a couple of hours of the filtrate. During the boiling process the aromatic components of the hops are solubilized (especially resins and tannins, which give the beer its typical slightly astringent taste); at this point, after the boiling process, the must is allowed to cool, with the formation of a bottom body to be removed then by filtration. In this way an aromatized drink is obtained, with a taste similar to that of beer, but free of bubbles and alcohol. The pleasure on the palate is therefore conferred by the subsequent fermentative passage, which gives the drink a certain alcoholic degree by adding selected microbial starters belonging to the Saccharomiceae family. The previous heating and boiling processes also have the purpose of inactivating micro-organisms that may be present in the must, which can give rise, in this phase, to secondary fermentations, thus altering the taste of the beer; thanks to these steps, therefore, the fermentation process is regulated only by the selected microbial stock.
Fermentation generally takes place in large silos, equipped with a heating jacket to keep the temperature constant; unlike those used for wine, these large cylindrical containers must be perfectly sealed (to keep the CO2 formed spontaneously dissolved during the fermentation process). The fermentation of the must, initially tumultuous, can be of two types: high (15-20 ° C for 3 or 4 days; high because in these conditions the yeast strains tend to reach the surface) or low (5-8 ° C for 10-12 days, during which the strains tend to settle on the bottom). From this moment on all beer passages must be made in adiabatic conditions, so as to maintain the same pressures in the various containers (steel barrels fitted with air release valves). In these barrels a slow fermentation continues, followed by filtration or centrifugation operations, packaging and ultimately pasteurization. This last step has the purpose of blocking the fermentation process and inactivating the enzymes of the microbial strains, which otherwise would continue to operate unwanted transformations on the product.
- SOFTENING (incorrect filtration, development of undesirable microorganisms, imperfect pasteurization)
- THREAD ASPECT (development of microorganisms of the genus Pediococcus, again due to incorrect pasteurization)
- LACTIC FERMENTATION (presence of microorganisms that have escaped pasteurization)
- SAPORE ASPRO (type of hops used in the preparation of beer or use of too sweet water).