Barley, which is the main raw material in beer, does not give, as such, a fermentable extract with the yeast. By brewing it in hot water we would obtain a poor result. It must first be left to begin to germinate. In this way enzymes are formed that attack the grain content and dissolve it in the water during the brewing process. A lot of the starch, particularly, is transformed into fermentable sugars, through the enzyme action during the brewing process.
This beginning of germination is called the malting. This prerequisite stage of production often forms an industry in itself, called the malting industry. During the malting process the grain is first steeped for approximately three days, then it is spread out in layers for a week to germinate and finally germination is halted by drying in a kiln or by a kilning process.
This serves to dissolve the starchy and proteinic matter in the malt. Three litres of water at 50°C per kilo of malt is put into a mash tun equipped with a powerful agitator. It is heated progressively in stages. Each temperature corresponds to the optimum action of an enzyme.
50-55°C is the optimum for proteolytic enzymes. Proteins ->Peptones ->Amino Acids.
62-63°C is the optimum for B amylolytic enzymes. Starch ->Maltose.
73-75°C is the optimum for amylolytic. Starch->Dextrins.
The brewer may act on the composition of his beer wort by his choice of stages.
As maltose is fermentable, but not dextrins, he may obtain beers that are more or less rich in alcohol. The brewing process lasts about two hours. Then, the mash is filtered in a lauter tun. The insoluble matter makes up the spent grain (25% of the weight of the malt).
The wort is sent to a boiler heated by steam pipes.
After reaching the desired volume, 150 to 300 g to the hectolitre of hops is added, according to the desired strength and degree of bitterness. The total boiling time is 1 hour. The wort is then clarified, cooled and oxygenated (to encourage yeast development). It is then sent to a fermentation tank.
Yeast is added to the wort, once it has cooled, and the fermentable sugars that dissolved
during the brewing process are transformed into alcohol and carbon dioxide. After about a week this fermentation is finished.
There are two main categories of beer here, “bottom-fermentation yeast” beers, which are fermented at a low temperature (8 to 12°C) with a yeast that sinks to the bottom of the beer, and “top-fermentation yeast” beers, fermented at 15 to 25°C, with a yeast which rises to the surface of the beer after fermentation.
The former originated in central Europe and spread to the rest of the world. The second are mainly brewed in England. Approximately half of the top yeast beer comes from Belgium. In France, the top yeast method is rare. The difference in taste and flavour between the two methods of production is very distinct.
The bottom yeast (Uvarum saccharomyces), having little flavour and a fairly neutral taste, lets the flavour and taste of the hops circulate and gives fine beers. This is the yeast used in classic Pilsner beers.
Top yeast (Cerevisiae saccharomyces) is an energetic yeast that reproduces strongly and only works well at a temperature of more than 15°C. It produces beers with much more aroma and flavour, appearing lighter and more digestible even when their specific gravity is very high. This yeast is ideal for speciality beers. It should be noted that top yeast beers should not be drunk too cool.
In both cases, there are many types available to the brewer. It is up to him to choose the one that best suits his particular needs. After fermentation, the beer goes into storage for several weeks at 0°C. The aim of this storage is to refine the taste, partially clarify the beer and to saturate it in CO2.
The beer is then filtered to giv brightness and take away the yeast particles. Biological stabilisation is obtained by filtration through a sterile filter.
After these processes, the beer is ready to be bottled.