The Brewing Process

 

 

Milling

 

Milling breaks up the malt grains into much smaller particles. This will give a large starch surface area in the mash tun and allow the soluble sugar products to escape into the mash liquid more easily. The dry crushed materials is known as grist.
The skill in milling is to produce a grist which is fine enough to release the maximum amount of sugars from mash, but not so fine that it will cause clogging difficulties during extraction from the mash later on.

Mashing

Mashing is the stage of mixing the crushed malt with hot liquor. The purpose is to allow enzymes to "convert" the starch which dissolves in the hot mash. During conversion the long starch chains are chopped up into small sugars, most of which are fermentable. The hot liquid containing these dissolved sugars, when strained from the mash, is called wort.
Mash temperatures are critical if the enzymes are to be able to act efficiently (malt starch is best converted in the range of 149 to 156 degrees Fahrenheit). Therefore a great deal of care is taken at this stage to control, and if necessary adjust, temperature and mashing time. For example, as little as 1 degrees Fahrenheit increase in temperature can make the wort noticeably less fermentable and affect beer taste. Accurate control helps produce a brew that is of the same quality each and every time.

In the Copper or Boiling of the Wort

The wort is next sent to the copper or wort kettle for boiling. Even though in modern breweries this vessel is usually made of stainless steel, it is still referred to as the "Copper".
Wort is brought up to boiling point in the copper by means of a steam heater or fire and then given a vigorous boil. Boiling times vary considerably but are usually about one hour. This causes the wort to evaporate, so that the volume reduces, while it's strength increases. Both the time and vigour of boil are carefully controlled to ensure that evaporation, for any one type of beer, remains the same for every brew.

Hops

At this stage, another raw material is added - hops - to give the beer its characteristic bitter flavour and aroma.
There are many different varieties of hops, and each has its own particular flavour. In Britain, the famous hop growing areas are in Kent in the South-East of England, and Worcestershire in the Midlands. We use these together with other sources of hops from Germany and other areas. Hop cones are picked by machinery nowadays (the days of going on hop picking holidays are over), then kiln dried, and made into small Hop Pellets.
In the past, hops were added on a rather random basis. Chemists can now analyse hops to measure the ingredient which produces the bitterness in the beer, so that we know just how much hops to add to give the beer the taste we desire.

Wort boiling kills any organisms left alive after mashing, and stops all remaining enzyme activity. Boiled wort is therefore sterile and inactive. Boiling also causes much of the material, which would make the wort look cloudy, to clump together or "flocculate". This material will then sediment out later to leave the wort brilliantly clear.
Hop pellets are boiled with the wort which causes them to break up and release their bitterness and flavour. Unfortunately much of the hop aroma is boiled off up the stack, so if we are brewing "hoppy beers" it is common to add more, special aroma hops towards the end of the boil.
Developments have taken place to produce hop extracts which can add bitterness and flavour directly into the beer, with greater efficiency than copper hopping.

Cooling of the Wort

Yeast is a living organism and, like most of us, would be killed off at the temperature of boiling liquids! Therefore, we need to cool the wort to a temperature at which the yeast will ferment comfortably. This is usually in the range 60 to 70 degrees Fahrenheit, which means the wort must be cooled down a great deal as soon as possible.

Yeast

Brewing is a natural process which depends on a small, plant-like organism called yeast. Yeast grows and multiplies by feeding on various types of sugars, which it turns to energy. It needs small amounts of oxygen to do this. As well as energy to grow, yeast also produces energy in the form of heat, along with water and a gas called carbon dioxide. In fact we use sugar and oxygen in the same way ourselves, obtaining energy from our food. However, once the oxygen has been used up, yeast does something we certainly can't - it generates alcohol. This is fermentation and the sugars that the yeast can digest are called fermentable sugars.
Yeast is alive when it's used for fermentation. If it's treated badly - kept too hot or too cold for instance - it stops working, as you might do yourself! Neither can it survive being kept too acid or too alkaline; both will quickly damage it. The best conditions are known as the "correct pH".
This means that the whole of the brewing process has to be carefully controlled to allow the yeast to do its job; and this is a major part of the brewer's skill.
Yeast Handling And Recovery Skimming and cone removal are two methods by which yeast may be separated from the rough beer, and removed to storage vessels. However, rather than simply waiting until the yeast sinks and clears the beer, we can put the beer through a centrifuge. This is a machine like a spin dryer, which by rotating very fast causes much of the yeast to separate out immediately. This is then drawn off for recovery.

Fermentation

The yeast is now "pitched", usually by injecting the correct quantity, in slurried form, into the cooled aerated wort stream on its way to the fermenting vessel.
Once the yeast is pitched, there is a short delay while the yeast adjusts to its new surroundings. It soon sets about growing and multiplying to produce more yeast. As it does so, it uses up the sugars as a food source and produces alcohol and carbon dioxide. To the yeast, of course, these are waste products!.
Some of the carbon dioxide gas dissolves in the beer to give it the characteristic fizz, but large quantities are allowed to escape from the fermenter and must be vented away safely.
Fermentation is a process which gives out energy and this causes the temperature to rise. If this isn't controlled, the yeast can be damaged and the beer flavour ruined.
The progress of the fermentation is controlled by adjusting the temperature. As you might expect, the fermentation goes slower if it's cooler. Fermentation can take anything from three days to four weeks depending on the type of beer you are making, the original gravity of the wort, and the temperature.

Maturation

The next stage after fermentation is maturation, which is achieved by holding the beer for a period to improve its flavour. This also allows yeast and other solid matter to settle out before filtration. Until all the yeast is settled, the "rough" beer will still be cloudy. Because of the different ways in which ales yeasts operate, maturation of ales needs only a couple weeks of conditioning.