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GENERAL CONCEPTS
Beer is probably the most-consumed alcoholic beverage in the world, as well as being one of the oldest.
To put it briefly, beer is made by fermenting cereals, or more rarely other plants, and then adding yeast (which determines the level of alcohol and the formation of carbon dioxide) and other flavourings that influence the smell and taste.
This is a generic definition that includes practically all types of beer, but there are so many variables in the process that thousands of different beers can be produced.
First things first:
Of course, the main ingredient of beer is water, which makes up around 90% of the final product.
The second basic ingredient is the cereal to be fermented.
You can produce beer with any type of cereal, although the most commonly used is barley.
In some countries, for convenience, other plants are used instead of cereals.
Just as important as the ingredients, the fermenting is the fundamental process that differentiates between different types of beer. There are different types of fermentation. Usually, natural aromatic additives are used during the processing of the cereals in order to offset the sweetness of the malt and give particular flavours to the beer.
Hops is certainly the most well-known and most used, but in some cases other natural flavours are used.
Finally, whether the beer is pasteurised or not and the type of container it is stored in (bottle, keg, cask) can also influence the conservation and consumption of the final product.

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INGREDIENTS

Water
Of course, the main ingredient of beer is water, which makes up around 90% of the final product. To obtain a standardised product, large, industrial breweries treat the water they use before processing, so they can be sure of always producing the same base characteristics.
For example, very hard water is more suitable for the production of stout, such as Guinness, while soft water is more suitable for making lager-type beers.
Cereals
The second basic ingredient is the cereal to be fermented.
You can produce beer with any type of cereal, although the most common is barley.
As the sugars in many cereals in their natural state are not fermentable, a process is required to transform them. In a few cases, such as with corn or rice, cooking is sufficient, but in most cases it is necessary for the grain to go through a "malting" process.
Usually a mixture of various types of cereals is used, adding to or substituting the barley with other ingredients such as wheat, sorghum, millet, buckwheat and other grains.
Cereal substitutes
In some countries, other plants are used for convenience. This leads to beers made from potato or agave in South America, or beer made from some types of plant roots in Africa.
Yeast
Yeast is fundamentally important for fermentation, and depending on the type used, beer can be classified into three large families: -Ales, or warm-fermented beers;
-Lagers, or beers brewed using cool fermentation;
-Lambic beers, or beers brewed with spontaneous fermentation (these are mostly produced in Belgium).
Flavours
Finally, natural flavourings are used in order to offset the sugary flavour of the malt, and make the beer more fragrant.
-Hops
Hops is certainly the most commonly used.
There are different varieties. This ingredient influences the characteristics of the beer in different ways. If it is added in the initial boiling phase, it makes the beer more bitter, while if it is added in a later phase of production, it is used to give the beer a more aromatic flavour.
-Other plants
As an alternative to hops, you can also find beers flavoured with chestnut, tobacco, hemp, or other aromatic plants.
-Fruit
In many beers, fruit, fruit juice or fruit syrup is added during the brewing process. As well as adding flavour, they give the product a higher level of sugar, which encourages the fermenting process, increasing the amount of alcohol as well as changing the taste.
-Spices
Certain spices (pepper, ginger, nutmeg etc), were widely used until a few centuries ago, before the large-scale introduction of hops.
-Honey
A few French microbreweries use honey to produce a particular type of beer. -Grape must
With the diffusion of breweries throughout Italy came a new type of beer, using grapes or grape must, a basic ingredient of wine, as an additive.

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MALTING
The main steps in the malting phase are germination and kilning.
As the sugars in the grain (usually barley) are not suitable for the fermentation processes to follow, it is first necessary to carry out malting, which is a process that reduces the complex starches in the cereal into more simple sugars capable of feeding the yeast to be added for fermentation.
The process begins with germination, which involves steeping the grains in water until they germinate and start to grow shoots. This activates enzymes that, along with the effect of the grain's absorption of water, change its chemical structure. This steeping usually takes a couple of days, in which the cereal is immersed in an amount of water equal to about half the weight of the cereal itself. During this phase, the water must be changed several times to avoid mould growth. Afterwards, the cereal is spread out over a flat surface for one or two weeks, in a clean and aerated environment at a constant temperature, to fully activate the germination process. During this phase, the grains are turned over approximately every 12 hours.
When the shoot is longer than half the length of the grain, but still shorter than the entire grain, the germination is interrupted by drying the cereal.
The drying process takes a couple of days, and is carried out in a ventilated environment at a temperature of around 40°, frequently turning the grains. After this, the kilning process starts, which takes another 2/3 days, toasting the grains at temperatures varying from 70 to 200°.
During the kilning phase, which varies a lot in duration and temperature depending on the recipe, some of the basic characteristics of the final product are already determined.
High temperatures produce a dark or black malt, and lower temperatures can produce a more caramel-coloured or pale malt; these characteristics will later translate into the colour of the beer.
If the shoot that sprouts during the germination phase is too rich in protein, it could chemically alter the wort produced and give the beer an unpleasant flavour, so it is usually removed after drying.
After this process, the barley has finally become malt, which can be turned into fermentable wort.
As well as barley, it is also possible to use wheat, rye, oats or buckwheat. Usually other cereals are used if barley is in short supply, or if the brewer wants to create a particular product. Otherwise, when it comes to malt for beer production, the best quality malt is made from barley.
For many beers, mixtures of cereals are used.
Particularly notable are German weizenbiers and Belgian bières blanches, which are wheat-based beers. The difference between these two types is that for the weizenbiers, the grains are malted, whereas for the bières blanches, the grains do not undergo a malting process.
Some cereals, such as rice or corn, do not need to be malted, and are simply cooked instead.
Once the malt has been produced, it is stored in silos or sacks and left to mature for up to a month, before being entrusted to the master brewers for the next phase: mashing, which produces the fermentable wort.

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MASHING AND LAUTERING
During the mashing process, the mixed, ground cereals (grains), which have already been correctly treated (malted or cooked), undergo hydration using water at set temperatures until the mixture becomes a thick, pasty liquid. This phase is used to further decompose the starches in the grains into more simple sugars.
The term "mash in" refers to the first phase when the grains are immersed in hot water, bringing the mixture up to a particular temperature and leaving it to sit for several minutes at that temperature, in order to activate certain processes on the sugars. The temperature is then raised, and the mixture is left to sit again, to activate other chemical processes on the sugars. This operation is repeated several times at increasing temperatures, according to the master brewer's recipe, until it reaches 78°, at which point all processes are interrupted, the mashing finishes, and we reach the "mash out".
Here are some explanations of the enzymes that act at various different temperatures.
Phytases - these work between 30° and 52° - the phase in which the pH of the mixture is lowered (between 4.44 and 5.5);
Beta-glucanases - these work between 36° and 45° - the production phase in which beta-glucans are broken down (by breaking them down a lot, you can obtain better filtration; by breaking them down less you get a better stability of the foam of the beer - it is therefore important to find the right compromise - pH between 4.5 and 5.0);
Proteases and peptidases - these work between 46° and 57° - the phase in which protein is broken down and FAN is produced (pH between 4.6 and 5.2);
Beta-amylases - these work between 62°and 65° - the phase in which starches are broken down into maltose (fermentable sugars);
Alpha-amylases - these work between 72° and 75° - the phase in which starches are broken down into dextrins (non-fermentable sugars)
At 78° the process finishes.
It is not necessary to let the mixture sit at all of the above temperatures - it depends on the recipe and the final product desired. The mashing phase is very important for the taste of the beer, as it determines the amount of body the beer will have, the availability of fermentable sugar, and the beer's foam.
During this phase, it is also essential to keep an eye on the pH, because if it goes over a certain threshold it can leave an unpleasant taste in the final product.
There are three main methods for mixing the water and grains and heating them to the various temperatures: infusion mashing, English infusion mashing and decoction mashing.
Infusion mashing involves immersing the grains in all of the hot water required, in a suitable container, and then raising the temperature using external heat sources.
English infusion mashing involves adding the water gradually instead. When the temperature needs to be raised, water already heated to the required temperature is added.
Decoction mashing is slightly more complicated, because part of the water and grain mixture is taken out, raised to the calculated temperature, and then mixed back into the rest in order to raise the temperature of the whole mixture. This operation is then repeated for all of the required temperatures. Of course, for this technique it is important to calculate the quantities, times and temperatures very accurately.
Once brought to 78°, the mixture is ready, and fluid enough to be filtered. This next phase is called lautering, and will create the wort, ready to be boiled.
At the end of the sugar extraction process, the mixture must be filtered in order to separate the solid grains from the liquid wort. Usually, to recover all of the sugars produced by the mashing process, after the first, simple poured filtering (known as running off), the remaining solids are rinsed again with hot water (known as sparging) until all the extract still on the grains is obtained. The spent grains can now be used for feeding livestock, thanks to their excellent nutritional quality.
The wort obtained from the first filtering, and the rinsing water that has collected the remaining sugars, are mixed together before the boiling phase.

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BOILING AND FILTERING
Boiling is another fundamental stage in the production of good beer.
It involves bringing the wort to boiling temperature in a suitable container. During this phase, hops is usually added to give the beer the bitter taste that will offset the sugars. Of course, the amount added and the boiling time influence the final flavour. Some brewers immerse the hops at various different points. This step can also be called "hopping".
The boiling is also important for concentrating the wort, which can be too diluted.
Another phenomenon that manifests during this process is that the sugars tend to crystallise when exposed to high temperatures, taking on a characteristic caramel colour. Of course, here too the choices of the master brewers regarding cooking times and temperatures fundamentally affect the characteristics of the final product.
It is important to note that during the boiling or cooling, coagulations of protein can form in the wort, which, reacting with the tannins, create lumps. These are usually (but not always - it depends on the master brewer) removed so they don't alter the taste of the beer.
Thanks to the temperatures reached during the boiling process, the product is also sterilised. Today, this could seem unimportant, because the preceding processes are already carried out with an adequate level of hygiene and safety, but in the past this was not necessarily the case, and sterilisation through boiling was essential to make the beer safe to drink from a bacterial point of view.
To allow evaporation and reduce the wort, it is advisable to boil the mixture without a lid. This also helps some of the more unpleasant aromatic substances, which are created during the cooking process of the cereals, be carried away with the steam.
After boiling, it is important to cool the wort quickly, and bring it to fermentation temperature as soon as possible. In order to do this, you usually use heat exchangers, which can reduce the temperature from around 100° to below 25° in a very short amount of time.
It is also a good idea to shake, pour or mix the wort during the cooling process, aerating it so that it oxygenates. This introduction of oxygen into the enzymes allows them to activate the fermentation process. Now, we are finally ready for fermenting.

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FERMENTING
We have seen how important the choice of cereals is, how important the kilning is for the final colour, how the mashing temperatures influence the foam and the body of the beer and the availability of sugars, how the flavourings added during the boiling process affect the taste, and how important it is that all the steps are highly controlled for hygiene in order to protect against mould that would ruin the final product. But even after all this work, all we have so far is wort.
To make it into beer, the most important phase is needed: fermentation. This takes place thanks to the addition of yeast.
In more than 95% of breweries, fermentation is induced, while only a few use spontaneous fermentation.
Induced fermentation, once activated, is anaerobic, meaning that the enzymes work and transform sugars into alcohol without the presence of oxygen. However, the presence of oxygen is very important in the inital phase to activate the reaction, and if the wort has not been well oxygenated during the cooling process, the fermenting could fail to start.
There are two essential types of yeast used in induced fermentation: "Saccharomyces carlsbergensis" and "Saccharomyces cerevisiae".
Between them, these two enzymes produce over 95% of the beer in the world.
"Saccharomyces carlsbergensis" produces lagers, which are beers produced with cool fermentation.
"Saccharomyces cerevisiae" produces ales, which are beers produced with warm fermentation.
The difference between these types is in the temperature and the length of the process.
The yeast in beers made with cool fermentation works at 7-9°. Once the yeast is spent, it tends to settle on the bottom. The "Lager" family includes many types of beer, and it is by far the most brewed and most consumed beer in the world.
The yeast in beers made with warm fermentation works at a temperature between 12 and 23°. It needs less time to mature. Once this yeast is spent, it tends to float on the surface.
There are also a small number of beers produced using spontaneous fermentation, mostly in Belgium. In this case, the wort is kept in low, wide containers in order to have maximum exposure to the air. This way, lactic bacteria present in the environment are naturally introduced into the wort. These "Lambic" beers have a strong, sour flavour, which is quite different from beers made with induced fermentation.
When fermenting starts, in the initial stage (primary fermentation), the yeast reproduces fast and attacks most of the sugars present. Once more than 90% of the sugars have been transformed into alcohol, the beer is usually poured into another container, removing a lot of the solid residues and spent yeast. It then starts a second phase, known as conditioning, maturing, or aging. The fermenting process becomes slower, and takes longer than the first phase, and by the end the beer has already been gradually cooled. It is then usually filtered to remove any impurities.
These processes we have outlined so briefly can, in practice, vary a lot in terms of the amount of yeast introduced, the processing temperatures, the length of the process, and the reintroduction of yeast or flavourings during the maturing of the beer. Each brewery tends to prefer not to divulge its own recipes, which contain particularities that characterise the different styles of beer.
At this point, we are finally ready for packaging.

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PACKAGING
You might think that by this point the beer is complete and has all of its final characteristics, but in fact, there are still many variables that can modify the eventual taste of the beer when it reaches the consumer's glass.
Firstly, the beer can either be pasteurised or left raw. In fact, beer is not really a product that can be defined as raw, because the grains have already been brought up to 78° during the mashing, and then the wort has even been boiled before fermentation.
However, after fermentation and before packaging, almost all beers are brought up to a temperature of around 60° in order to go through a process of pasteurisation. Those that are not put through this process are conventionally called raw beers. Of course, pasteurised beers keep for longer (many months), and almost all industrially produced beers are pasteurised. Unpasteurised beers, instead, if not preserved well, can develop bacteria that make them turn sour after a few weeks. Furthermore, once opened, a 20/30 litre keg of pasteurised draft beer keeps for much longer than a similar keg of raw beer, which needs to be consumed within a few hours.
Since beer is such an ancient product, those who lived in times before the studies of the chemist Louis Pasteur would have only known raw beer, and they were probably used to the changes in flavour if they didn't drink it fresh.
In defence of raw beer, however, it has many more live enzymes when consumed fresh, and has better sensory qualities and natural flavours that haven't been altered by processing. For this reason, many brewers maintain that its taste is decidedly fuller and more satisfying. As we will soon see, being unpasteurised is one of the characteristics of many artisan beers.
Another process that beer must undergo after fermentation is carbonation.
Beer is not naturally a particularly fizzy drink, even if the fermentation process produces CO2. If it were water, it could be defined like some naturally effervescent mineral waters - that is to say that it is not completely flat, but nor is it fizzy as we know it to be.
When packaged in bottles or cans, the carbonation be produced in two ways.
The fastest method is to directly add carbon dioxide (forced carbonation), but this is usually used only in industrial breweries due to its cost and the technique required. In this case, the product is ready for consumption as soon as it is packaged.
Microbreweries, artisan breweries and home-brewers (those that make beer at home using the special kits commercially available) usually use the method of natural carbonation, or "priming". This involves adding a small amount of sugar at the moment of bottling the beer, which activates a further fermentation process, creating carbon dioxide that stays trapped in the closed bottle. This way, pressure is created, which is released on opening the bottle, producing the necessary "fizziness". This process requires further maturing time in the bottle, so the beer cannot immediately be consumed. It also requires precise calculations to determine the quantity of sugar to add to the bottle in order to obtain the desired fizziness, or the fizziness appropriate to the type of beer produced.
One very important consideration to make is that there must still be active enzymes available for the re-fermentation of the beer inside the bottle to be possible. If, after its fermentation, the beer has undergone processes of microfiltration and pasteurisation, it will be very difficult to activate any natural carbonation.
Here, the substantial differences between artisan and industrial beers become noticeable.
Industrial breweries need to follow standardised procedures in order to always guarantee the same characteristics of the product. Therefore, after fermentation, they carry out microfiltration to give them a clear product with no impurities, and pasteurisation to guarantee the long life necessary for large-scale distribution.
Artisan production, which is on a much smaller scale, has different requirements and can therefore take advantage of the characteristics of raw beer.
Sometimes with artisan beers, brewers make the choice to not even filter them after fermentation, giving them a cloudy appearance due to the presence of substances in suspension.
As always, when different opposing methods exist, there are supporters and detractors on every side, and there is much open debate over which is the best type of beer.
Up to this point we have only considered bottle (or can) packaging, but for keg beer to be distributed for draft systems, the carbonation process is completely different.
Carbon dioxide is not added to keg beer, because the machinery of the bar where it is served injects gas into the keg through a small tube, pushing the beer out of a parallel tube to send it to the tap (draft) and then into the glass.
The pressure the machine is set at, and therefore the pressure at which the carbon dioxide enters the keg and mixes with the beer, determines the fizziness that the beer will have in the glass.
Most draft machinery uses a feed of exclusively carbon dioxide. But some beers (such as stout) are "drafted" with a mixture of carbon dioxide and nitrogen. These carbon-nitrogen systems, which are useful for certain beers, have slightly different taps, giving a different consistency and different foam to the beer.
The drafting, or the way the beer is poured into the glass from the tap, can also affect the consistency of the foam, and the body and fizziness of the beer. Therefore, paradoxically, two very different glasses of beer can come out of the same machine and the same keg, at the same moment.
After this brief explanation of how many variables can influence the types of beer that are produced, and what they are, we will now look at what the most famous styles (as they are defined) are.

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STYLES OF BEER
Beers are classified according to different characteristics.
The most common feature recognized by all is the colour.
A seconda del tipo di cereale e di tostatura si hanno malti più chiari o scuri che influenzano molto il colore finale. So we can speak generically of blonde, amber, red or dark beer.
Un other classification concerns alcohol content determined by fermentation.
Birra "leggera" identifica una birra poco alcolica, mentre "birra doppio malto" (definizione che non ha uno specifico significato tecnico) identifica una birra abbastanza alcolica.
There is also a measurement scale of bitterness called IBU (International Bitterness Unit). Beer bitterness depend on relationship between malt (malt gives sugar and makes the beer sweeter) and hop (flavouring that make beer bitter).
The features described (colour, alcohol and bitterness) are recognized by all people and are reasons that influence choice of all beer lover (less demanding or more demanding).
The goal here is not make a complete list of the hundreds of existing beer styles because there is no universally agreed list of featured and sets of criteria. But with history of technology and geography of raw materials let's try to say which are the main beer styles.
The three large groups in which the beers are classified are related to fermentation: ALE, LAGER, LAMBIC.

Ale or top-fermented beer
At the beginning of the history of beer probably fermentation was spontaneous. Today this is true only for certain Belgian beers named LAMBIC.
Since ancient times was isolated a specie of yeast: Saccharomyces cerevisiae. It is a family of unicellular microorganisms of the fungi kingdoom. Over the centuries it has been instrumental to winemaking, bread-making, and brewing. It is the microorganism behind the most common type of fermentation, still used today and commonly called brewer's yeast.
Beers produced with this yeast are called ALE or top-fermented beers. For many centuries probably ALE was the name that meant beer.
Roasting malt until the seventeenth century produced dark malts and beer was broun or dark. In the seventeenth century use of coke to roasting cereals produced lighter malts, so beer colour was lighter than before. This beer was named PALE.
At the same time the technique of flavoring beer with hops from central Europe was imported and PALE ALE (called BITTER) was top fermentation beer with blonde colour and hop flavour. Was an alternative of typical beers of that time PORTER or MILD (darker, more malty and less bitter). PORTER identified a beer brewed initially in London and then exported through the British colonies around the world. It was enough alcoholic dark malt beer, the first beer to be aged at the brewery and dispatched in a condition fit to be drunk immediately. For these characteristics it was very important as a food for humble population groups. The production cost was limited so for a long time it was the workers' beer. The name originate from porters in ports. Probably in the nineteenth century it was the most drunk beer. Names STOUT-PORTER or DOUBLE-PORTER or PORTER-EXTRA meant very strong PORTER. After the world wars with shortage of raw materials these beers have become lighter and have disappeared from many countries except Great Britain the homeland of ALE.
The term STOUT PORTER would later be shortened to just STOUT. GUINNESS called originally EXTRA SUPERIOR PORTER later was named only EXTRA STOUT. May be geographical origin contributed to this diversification. PORTER in GREAT BRITAIN, STOUT in IRELAND.
Today PORTER mean dark beer little alcohol slightly hoppy like STOUT. STOUT can be different for coffe flavour, cacao flavour or other flavour and a different carbonation.
MILD originally meant a dark brown colour beer, less hopped than BITTER, young and not aged as opposed to a PORTER for people who liked not strong beer.
Today again MILD is a young beer, lightly hopped, of amber red or brown colour and alcohol content not more than 4 grades.
Other definitions of ALE are BROWN ALE produced from 100% typical malt called brown. It's a beer with a dark amber or brown colour, similar to MILD. OLD ALE is a beer aged, malted, not hopped, dark with a high alcohol content.
BARLEY WINE are similar to OLD ALE because aged. In the past differences were minimal. Perhaps name BARLEY WINE appears as a brand of some brewery. Today OLD ALE are darker then BARLEY WINE but less alcoholic. BARLEY WINE are STRONG ALE (beer very alcoholic). However, they are not very popular beers.
Some ALE mix PALE malt (light) with a piece of caramelised or toasted malt and have red or amber colour. These are named AMBER ALE. An example of AMBER beer is the SCOTCH ALE typical of Scotland, a beer bodied and flavored with various herbs for historical difficulty of finding hops in Scotland.
An example of AMBER beer is the SCOTCH ALE typical of Scotland, a beer bodied and flavored with various herbs for historical difficulty of finding hops in Scotland. Famous for their red color due to the mixture of malt are IRISH RED ALE, low alcohol beers. IRISH RED ALE like STOUT are tipically irish. Let's go back to PALE ALE, today the most popular top fermentation beers.
Produced from light malt have a color from golden to copper. The massive use of hops makes beers bitter. Different hops levels have resulted in a range of different tastes. Famous in history have been IPA (INDIAN PALE ALE), exported from England to India. Ships that imported spices from India at return could carry beer in India at low cost. The journey was long and since hops is a good preservative IPA was highly hopped and very bitter beers. This beer style spread in America and borned APA (AMERICAN PALE ALE) produced in America with local hops.
Still today IPA and APA are synonyms of top fermentation beer, pale and bitter beers. ENGLISH PALE ALE (in the past called BITTER to distinguish them from PORTER and MILD), are Enlgand beers flavored with hops but not as IPA and APA.
So far we have seen top fermentation beers of Grat Britain (the ALE's homeland), but there are other situation due to some geographical areas.
ALTBIER (or simply ALT) is brewed with caramelized malt and top fermentation old recipe in the Dusseldorf area in Germany. Color is amber-brown.
Always in Germany KOLSCH is a blonde beer known only for a few decades in the Colonia's area, low alcohol and slightly hoppy.
For BELGIAN ALE see chapter dedicated.
To finish the ALE beer speech we need to talk about beers produced with a high percentage of wheat in malt (over 50%). They are not defined ALE. In germany they are called WEISS BIER or WEIZEN BIER, in Belgium they are called BLANCHE or WHITE.
The name white is given to the beer not for the color, but for the foam produced during fermentation. They are unfermented beer and contain yeast cells that make the beer cloudy.
The Belgian BLANCHE beers compared to the German WEISS beers are lighter color because malt is unroasted and are typically flavored with coriander and orange peel.
The German WEIZEN are divided into further styles.
Classic WEIZEN beers are HEFEWEIZEN (hefe means yeast in german), with golden color and suspension yeast.
KRISTALLWEIZEN are like WEIZEN but being filtered they have a clear and crystalline color without yeasts in suspension.
WEIZENBOCK are beers already produced in the Middle Ages by monks during Easter and Christmas periods with dark malt and long fermentation for having high alcohol content. Due to its high nutritional value WEIZENBOCK help monks in fasting periods.
WEIZENBOCK today means a WEISS beer with high alcohol content, non necessarily dark like in the past, very malted and not hoppy.
DUNKELWEIZEN is produced with ancient method of roasting the cereal which gives a darker malt. It has amber or brown color, but lower alcohol than WEIZENBOCK.
BERLINER WEISS is a Trade Mark of the Berlin Brewers Association. It's an old beer style with lower alcohol but very sourn, a rare and not always appreciated characteristic today due to the presence of spontaneous wheat lactic bacteria.
You can drink it in and around Berlin. To correct the strong acid taste it's often mixed with raspberry syrup or woodruff which give it a characteristic bright red or green color. It's a very fresh, crisp and light refreshing drink.
Lager or bottom-fermented beer
If for the ALE beers Saccharomyces cerevisiae yeast is used, for the LAGER beers the yeast Saccharomyces pastorianus is used. Saccharomyces carlsbergensis and Saccharomyces monacensis are synonyms not correct of Saccharomyces pastorianus. For the name origin see https://en.wikipedia.org/wiki/Saccharomyces_pastorianus. Already in the fifteenth century bottom fermentation beer was produced probably without know yeast property.
LAGER beer ferment at a lower temperature than ALE and yeast at the end settle on the bottom. This process can last a few weeks and allows the beer to mature and filter. At the end at the bottom there are yeasts, hops, tannins, suspended particles and the beer remains clear.
The demonstration that in the past the properties of yeast were not known is the "German beer purity law" adopted in Bavaria in 1516 and then in Germany. According to the law, the only ingredients that could be used in the production of beer were water, barley and hops. The text does not mention yeast. This law was changed only in the 20th century with laws of the European Union and German reunification, but still today many Bavarian brewery follow this specification.
It is evident therefore that the homeland of the ALE beers is Great Britain and its related countries and the LAGER beers are typically German and central Europe.
Obviously over time contaminations between styles have been important for the production of the beers we drink today.
For example, hops, the typical flavour of LAGER beer is today used also for ALE beer. But some features of ALE have conditioned LAGER production.
In the mid-nineteenth century travel of a member of SPATEN brewery family throughout Europe was important because at return to Bavaria he applied techniques he had seen for the production of PALE ALE and produced a more substantial and stable LAGER. This new beer recipe was very successful, but the German malts still toasted on the fire gave an amber or dark beer.
The blonde beer like we know today born in 1842 when this new recipe of SPATEN arrived in BOHEMIA in the city of Plzeň (Pilsen in German). The use of a light malt toasted at low temperature (still today named PILS) with local hops produced a beer named PILSNER in honor of the city of origin. In a short time it spread throughout Europe. Today PILS is one of the most famous and produced beer styles in the world. Is known for featuring hops, so it's a bitter beer.
The method created by PILSNER URQUELL (the first PALE LAGER) has spread everywhere giving rise to what is considered the modern industrial brewing.
In Dortmund, historically a large beer production and export center, DORTMUNDER style use pils malt, but less hops flavour than PILS.
Also HELLES beers in BAVARIA like DORTMUNDER beers use pils malt, but probably hops flavour is further less.
These are the most popular beers today, but there are others historical styles of LAGER beers.
SCHWARZBIER is a dark German beer like STOUT and PORTER, less bitter, but with same flavours of cocoa and coffee. The alcohol content is not high.
DUNKEL are beers amber or brown, less dark than SCHWARZBIER. It's an old recipe that requires triple-decoction mashing. So DUNKEL is a very malted beer, more than SCHWARZBIER. With the same method applied to WEIZEN beer get DUNKELWEIZEN.
A bodied and alcoholic beer style is BOCK. Originally was produced in Einbeck town in Saxony in certain periods during the year from monks to resist fasting for alcoholic and sugary properties of this beer style. Historically were very dark beers. Today there are BOCK beers amber or red.
BOCK recipe as for DUNKEL can be applied to WEIZEN to get WEIZENBOCK. Many TRAPPIST beers are WEIZENBOCK.
In addition to the classic BOCK that can reach 7.5% alcohol there are further BOCK styles.
MAIBOCK or HELLES BOCK with golden-amber color has same alcohol percentage, but is more bitter because has hops flavour.
DOPPELBOCK is a very alcoholic beer (can reach 9% alcohol). It's darker than others BOCK. EISBOCK is traditional of the area of KULMBACK. It is obtained by freezing a DOPPELBOCK and removing the ice. It's remain a very bodied and alcoholic beer (can reach 12% alcohol) with red-brown color and ruby reflection.
MARZEN is an historic style. In Bavaria in according to a law of 1539 from 23 april to 29 september boilers for boiling beer were sealed off to avoid fire and others security reasons. So beer produced in March (Marz in German) had to be kept until the autumn because it was not produced in the summer. In order to keep itself was an alcoholic beer and was the only available in OKTOBERFEST period. MARZEN color is amber-brown.
A style like MARZEN produced in Austria is called VIENNA LAGER.
>From some decades beers served at the OKTOBERFEST called OKTOBERFESTBIER are like HELLES and can be produced only from Munchen breweries where there is the event.
Also the VIENNA LAGER (the traditional Austrian beer) today is like a PALE LAGER probably more light-colored than the original recipe produced in 19° century.
To conclude the list of LAGER stiles we mention the KELLER. They are young beers not filtered, generally not pasteurized. This method can be applied to many styles, but generally are PALE LAGER turbid with yeast in suspensionand and about 5% alcohol.
Lambic spontaneously fermented beer
They are wheat beers not exposed to classical brewer's yeast (like ALE o LAGER), but thanks to a high exposure to the open air many types of microorganisms may inoculate the wort and start the fermentation.
Lambic beers are defined young if aged 3-6 months (no more than a year). They can also be aged for 2-3 years, in this case they are defined old. Usually aren't bottled, so are served on tap near the production place (the surroundings of Brussels).
Old lambic have dry, vinous and distinctly acidulous taste which makes them unique.
We also have some LAMBIC beers variants related to flavorings:
FARO are very young LAMBIC flavored with sugars or caramel to sweeten the taste.
GUEUZE are a blend of young and old to start a refermentation in the bottle. Bottles are generally 75 ml, plugged with cork and metal cage which protects from the CO2 that is produced directly in the bottles.
They are stored in the cellar lying down exactly like wine, unlike some ALE refermented in the bottle that are kept in an upright position.
FRUITS BEERS are produced with the addition of fruit before the second fermentation. The most used fruit is sour cherry.
Belgian beers.
This topic is treated separately because in 2016 the "Belgian Beer Culture" was inscribed by UNESCO in the intangible cultural heritage of humanity and many beers are typical of this area.
BELGIAN ALE (belgian top fermentation beers) are divided into important subgroups.
-TRAPPIST beers: it's not a real style of beer but the trademark of a consortium governed by a specification which involves the production of beer within the walls of a Trappist abbey or under the control of Trappist monks, not for commercial reasons, but for the sustenance of the monks or for charity. They can be light or dark beers and belong to the most varied styles. They are generally very full-bodied beers with a high alcohol content. Some TRAPPIST beers can also be brewed in some abbeys outside Belgium.
-ABBEY beers: like TRAPPIST beers styles can be very different, but are always alcoholic beers, lightly hopped, very spicy and full-bodied beers. They cannot have the TRAPPIST brand because the relationship with the abbey is only the concession for the use of the brand or recipe, but the production is industrial commercial purposes.
The name of many Trappist or abbey beers includes the style, for example DUBBEL, TRIPEL etc. -BLONDE or GOLDEN ALE: they belong to the PALE ALE family, (they are top fermentation blonde beers) and are produced with the same type of malt of PILS beer, but have a higher alcohol content.
-AMBER ALES: not bitter beers, amber and alcoholic beers.
-DUBBEL: dark beers. With caramelized beet sugar they are refermented in the bottle and take on fruity and spicy flavors.
-TRIPEL: a belgian variant of the british STRONG PALE ALES with high alcohol content.
-QUADRUPEL o GRAND CRU: dark top fermentation beers, refermented in the bottle or in the barrel. Usually are TRAPPIST beers with 9-10 degrees alcohol or more.
-FRUIT BEER: beers fermented a second time with the addition of fruit.
-FLEMISH RED: top fermentation beer with addition of lactobacilli (the yoghurt bacteria), a particular roasting of the malt and aged in oak barrels. The result is a red-brown color, a very sour taste and a very frothy beer.
-WHITE or WHEAT BEER or BLANCHE: it's a wheat beers like german WEISS. The difference is that WEISS beer is made from roasted malt, while BLANCHE beer is made from unroasted malt. The taste is fruity due flavoring like coriander and orange peel. The color is lighter tending to yellow. Usually BLANCHE beer like WEISS is cloudy beer due yeast in suspension.
These described above are top fermentation beers typical of Belgium, but are made also STOUT, BROWN ALE, SCOTCH ALE. (see dedicated chapters)
-CHAMPAGNE BEERS: beers produced with the champagne fermentation method. They have taste of beer but the perlage of the champagne.
-SAISON: it is typical of the Walloon region, created by Belgian brewers before the advent of refrigerators. Was made in the cool season so as not to damage fermentation with the summer heat. Ready to drink in late summer, today it is a very popular style of beer also in the USA.
Obviously are produced in Belgium also LAGER beers like PILS and BOCK. (see dedicated chapters)
Exclusives of Belgium are the spontaneously fermented beers: the LAMBIC. (see chapter LAMBIC)

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FINAL CONSIDERATIONS
For those who have read up to this point, we specify that this is not a complete and definitive manual on beer styles. Beer is produced all over the world so the geographical area and food culture influence local productions and diversify them a lot.
The evolution of technologies has also made changes to the recipes and the finished product. Today in the world it is estimated that about 80% of the beers produced are LAGER, and especially PALE LAGER. In fact, for many people the word "beer" suggests the classic glass of light and blond beer. Dark, highly alcoholic or flavored beers are often referred to as special beers.
This happened thanks to the post-World War II standardization and globalization. The creation of a global market has made consumption uniform.
Due to the industrialization of food processes, in the last century many recipes of historical beers have been put aside to favor commercial products.
Today, thanks to a new culture and easy access to information, raw materials and technologies to produce, microbreweries and craft breweries have sprung up in many countries. These often offer forgotten traditional beers, increasing the choice with usually high quality products.

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TO KNOW MORE
For those who want to learn more:
-The book of Fred Eckhardt: A treatise on Lager beers (1969);
-The book of di Michael Jackson: The world guide to beer (1977);
-The book of Fred Eckhardt: The essentials of beer style (1989);
-The website: Beer judge certification program (https://dev.bjcp.org)
-The website: Brewers Association Beer Style Guidelines. (https://www.brewersassociation.org/edu/brewers-association-beer-style-guidelines/)