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Brewing technology

Introduction

History of Brewing

Malting and brewing have its origin in ancient times. The Babels are believed to be leaders in brewing even in the 7thcentury BC. The Sumerians wrote brewing recipes and tax regulations on clay plates in 6thto 4thmillennium BC. It is clear that even then beer was not only a drink but also income of the state budget. It is also historically known that brewing procedures were known not only in ancient China, Egypt, and Greece, but also among the Celts, Gaels, Slavs, Germans, Jews, etc.

The first written records on beer and its production in our countries have appeared since 1000 AD. The analysis of their texts shows that developed and long-time applied methods of brewing and growing of crops for beer production have already existed. The right to brew beer was gradually granted to towns or noble seats and home brewing was forbidden. In this regard the burgenses acquire more and more rights, which resulted in disputes with nobility as brewing in castles went into decline.

In 1040, in the small town Weihenstephan, near Munich, in Bavaria, one interesting brewery started its production. What is interested about it that it is still working, therefore, it is the oldest operating brewery in the world. Also people from other breweries came to the brewery to learn brewing. As time passed, Brewing Research Institute was established at the brewery, with its biggest collection of brewer´s yeasts in the world, and world-wide known Technical University was established, specialised especially in brewing.

Even our countries, i.e., Slovakia and Bohemia, were not left behind in brewing. In Bohemia more historical documents were preserved, as they are archived in their country. Slovak documents are mainly in archives in Budapest and Vienna, only partially in Bratislava or other cities. Many of them got lost during wars. However, relatively enough information can be found in trade guild books. The first brewers guild in Slovakia was established in 1450 in Bardejov and the oldest maltsters guild was established in 1506 in Prešov.

Ingredients for Beer Production

Water:

Water for brewing must be always drinking water, however, not only that. Each brewing water is drinking water; however, not each drinking water may be suitable for brewing. Brewing water minds mainly iron and manganese, but especially free C02, it means that mineral waters are not allowed. Brewing water should be soft with low alkalinity. Such water is necessary mainly for preparation of light beers; dark beers stand also harder water. However, also for this type of beers softer water is better. Therefore, during the first negotiations it is good if the potential customer provides us with at least basic data on water to be used. Small shortcomings of the quality of brewing water may be usually eliminated or reduced by small adjustments of technological procedures; however, in some cases water treatment equipment will be required. Water treatment equipment will always be necessary for steam production. This treatment equipment is a part of the standard offer of PSS, as well as a steam generator.

Similarly, it is inevitable to know if sufficient amount of water is available for brewing (8to 10 times more than the volume of produced beer); with sufficient pressure in the system, because short inrush intake of bigger amount of water is very often. Similarly, the sewage system must be well dimensioned to be able to take inrush bigger amount of water.

Water was mentioned as first, as beer consists of 90% of water, and the type of beer depends on it. It is also used for purification and sanitation. The requirement of its microbiological purity results from it.

 

Malt:

It is produced from barley, eventually from some other kinds of cereals (wheat, rye, oat, etc.). I will describe in short the technological procedure of malt production:

There is sufficient amount of high molecular starch in a cereal grain; however, there are no substances which could convert the starch into solution and then convert it into simple sugars.  These substances – let´s call them enzymes – have to be “produced” in the cereal grain. I will further speak about barley but it applies generally. Common barley contains humidity between 13 and 15 %. With this humidity, almost nothing is going on with barley. However, if we steep it to humidity between 36 and 42 %, it begins to germinate. In the first stage of germination rootlets start to grow on the grain. It lasts between 5 and 7 days. To avoid mutual twisting of rootlets and enable sufficient amount of air for germinating grains the germinating barley is turned around twice a day (dug trough, ploughed up, vibrated). About a day before a stalk begins to grow from the grain, the process is stopped. It is stopped by drying of the grain; first at lower temperatures, but with strong blowing of dry air. When humidity of barley drops from 40 under 20 % drying temperature may be increased. At the end of drying to 80°C, while humidity drops under 5 %. Rootlets of the grain are very fragile so when turning in the drum they break off. After cooling the malt is stored for 6 to 8 weeks and then it can been used for brewing. What has happened during the process? During germination enzymes were formed, which are able to split above mentioned macromolecules of starch to simple sugars. This process was stopped by drying, however, enzymes are still present, and from such grains, now malt, beer can be produced.

Machines and malt house equipment in short:

  • receiving silos
  • transporters
  • steeping tanks
  • moving bulks (Saladin boxes, barns)
  • kilns
  • degerminators
  • chilling silos
  • malt silos

                                                                                                                                            

Above described procedure is applied for production of the most known and the most used malt of type pale Pilsner. Also other kinds of malt are produced, in our country mainly Munich, light caramel, dark caramel, and coloured malt. Combination of these malts is used for production of dark or semi-dark beers. Wheat malt becomes more popular for production of wheat beers, so-called weizenbier. About 200 kinds of malt are produced, which can be used also in bakery, distilleries, production of natural enzymes, cosmetics, etc.

 

Hop:  

It is the most expensive ingredient, but fortunately, only a little is required. While for one hectolitre of beer we need between 15 and 20 kg of the malt, only 100 to 300 grams of hops is required, depending on the kind of beer and concentration of bitter substances in hop. Hop gives beer the typical bitter taste, contributes to characteristic aroma, and has also other important technological attributes, for instance, stability of beer foam.

Hop species: From commercial and brewery point of view, hops are divided to fine hops, i.e., aroma hops, and bitter hops. Bitter hops are characterised by high content of hop resins, mainly alpha bitter acids (8 – 15%), but with small content of aroma substances. On the contrary, aroma hops have lower content of resins, but higher content of hop aromatic oils, which give beer mainly aroma. Both types of hops are used for production of beer.

Hops are very demanding for storing. At room temperatures they oxidise, loos their aroma, and their solubility at boiling decreases. Therefore, hops are adjusted in various ways. From hop heads so-called spindle are eliminated, or other ineffective substances, then they are milled, granulated, and packed in vacuum or modified atmosphere packaging.  Thus not only concentration of bitter and aromatic substances is increased, but also their shelf life. They shall be stored at low temperatures in dry and dark place.

 

Yeasts (Sacharomyces):

Yeasts belong to ingredients as they are directly added to boiled and cooled hopped wort and there would be no beer without them. They are single-celled microorganisms classified as members of fungus kingdom.  They are reproduced in vegetative way, by budding. Yeast metabolism is very significant for brewery industry. It concerns mainly transformation of fermentable sugars to alcohol, carbon dioxide (CO2) and energy, according to formula:

C6H12O6  = 2C2H5OH + 2CO2  + energy

Yeast metabolism of course relates to many other compounds of the hopped wort and a wide range of by-products.  Brewer´s yeasts, but also others, have one interesting characteristic. If they have enough nutrients and oxygen, their metabolism does not work according the above describe formula, but they use sugars and oxygen for their reproduction.  Yet after they consume from the boiled hopped wort all oxygen, they start to produce alcohol. This fact is used for fermentation of beer. We do not need to add a large amount of yeast at the beginning. We only add smaller amount and we aerate or oxidise the cold hopped wort.  At the beginning of fermentation yeasts reproduce and after they consume all oxygen they start to produce alcohol.  I used the notion yeasts only to explain the basic principle of fermentation. In brewery, we do not work with individual cells, but with biomass, which is also called yeasts.

 

Additional materials:

Carbon dioxide CO2 or nitrogen N2

Despite CO2 is formed at fermentation; we have to buy it for the brewery. Handling beer would be impossible without it.  If we want to transfer beer after fermentation into other tun (serving tun) or tank (KEG, bottle), beer would form foam in such tank and release CO2, the tank would be filled quickly with foam and the remaining beer at the bottom would be undrinkable. Therefore, it is necessary to create the same pressure in an empty tank as it is in the full tank (eventually little bit lower). Then, when we connect such tanks with piping, beer will be flowing without foaming. Of course, from the tank to be filled the pressure is being released, and CO2 is being added to the tank from which beer is taken. The same is achieved by use of pressurised nitrogen.  It has also other advantage. Beer transferred this way at racking to glasses forms less foam and its foam is thicker and more lasting. Brewery doesn´t have to buy nitrogen, there is equipment for production of pressurised nitrogen from air, which may be a part of supply. Pressurised air may not be used for these purposes, because beer oxides, and therefore its taste is getting worse and durability decreases.

 

Sanitation detergents:

  • Alkaline
  • Acid
  • Disinfection

I will not speak about that much, just that it is impossible to run the brewery without sanitation and disinfection. Precise sanitation procedures apply for that.

Technological procedures

Milling:

Milling is a mechanical and at the first sight simple process.  However, grain structure of the milled malt significantly influences mashing, lautering (filtering) and boiling extract. The aim is to damage paleae as less as possible and mill the inner grain well. With fine milling paleae are damaged to greater extent and during filtering throughput of the filtering layer decreases and filtering is inadequately prolonged. At the same time, during longer influence of hot water, undesirable substances are leached out from damaged paleae to beer. With rough milling filtering is quick; however, rough particles of endosperm, mainly in grain tips, do not dissolve and remain in the spent grains. Therefore, it is important to find a reasonable compromise. Setting of the malt mill and roughness of milling depends on the quality and type of the malt, therefore, new setting of the malt mill is required when processing a new batch or when several types of the malt are milled for dark beers.  Types of malt mills: two-cylinder, four-cylinder, and five-cylinder mills.

 

Mixing:

It is mixing the milled malt with water of a certain temperature. The temperature of the water depends on the quality of the malt and requested splitting of proteins. The temperature is achieved by mixing cold and hot water. Such mixed water is added to the milled malt and goes into a mash tun, where the requested temperature shall be achieved. If not, it can be heated up.

 

Mashing:

For mashing the following temperatures are important:

38 °C achieved at mixing.  At this temperature peptidases start to work and stop to work at 50°C (they split proteins to peptides);

 

52 °C at this temperature phosphatises mainly work, they release phosphoric acid into the solution and decrease pH;

 

63 °C enzyme beta-amylase works mainly at this temperature. It splits simple sugars from ends of starch units. Rest is important for formation of fermentable sugars.

                                                                                                                                                          

73 °C  optimal for working of alpha amylase. It splits macromolecules of starch in the middle of chains in a non-specific way. 

                                                                                  

At these temperatures rests are introduced to enable operation of individual enzymes. Mashing in fact means heating to above mentioned temperatures to enable dissolution of starch and proteins in malt grains and enable their transfer to simple sugars.  Two methods exist:

  1. a) Infusion method–malted substance up to 38 °C is left to rest for 10 min., then heated up to 52 °C, again rest for 10 min., heating up to 63 °C, 20 min. break, heating up to 72 °C, 15 min. break, heating up to 76 °C and pumping to a lauter tun. It can be used for all types of beers, but it is mainly used for dark beers. It is the simplest method.
  2. b) Decoction method –one-, two-, or three-mashing; for PSS equipment mainly one-mashing is applied. Until heating up to 63 °C it is similar to infusion method. Then about 2/3 of the volume is pumped to the lauter tun and left to rest. The remaining part is heated up to 72 °C and left to rest for 15 – 20 min. Then it is heated to boiling and boiled for 15 – 20 min. After boiling the mash is slowly pumped to the lauter tun while continuously mixed in both tuns. Then the entire volume is quickly given back to the mash tun. The temperature of the entire volume should rise to 72 °C. If higher, during further boiling decrease the volume of the first mash, if lower; increase the volume of the same. At temperature 72 °C it is left to rest for 10 min., heated up to 76 – 78 °C and pumped into the lauter tun while both mixers working. After 20 min. rest lautering starts.

 

Lautering (filtering):

It is a physical process separating liquid containing sugars from solid parts. The filtering layer consists of individual porous solid parts of the mash. These are mainly paleae from the malt and non-liquefied remains of starch, mainly in unmilled grain tips. At the beginning of filtering a dull liquid flows out.  It is returned back to the lauter tun. By rhythmic increasing and decreasing of flow the filtering layer is gradually settled and flowing out liquid (wort) is purified. The liquid is also called first wort run-off. Then the wort is transferred to the mash tun and flows until a layer of spent grains shows (solid parts). This layer with thickness between 20 and 40 cm still holds great amount of the extract. Therefore, the top of the layer is sprayed with hot water (about 76 °C) and filtering continues. Spraying with hot water is repeated about three times until flowing out water (sparging) contains less than 1% of the extract. Should the filtering flow in course of flowing of the first part or sparging slows down, blender turns on (rotary rakes) in the tun and the layer is cut by very slow run. Thus throughput of the filtering layer increases and filtering continues. In meantime, the first wort run-off and sparging in the tun are heated in a way so as at the end of filtering achieve about 100 °C.

 

Hop boiling:

At temperature of 100 °C required amount of hop is added to the wort. At the beginning of hop boiling bitter hops are added so as bitter substances have enough time to dissolve. During the entire hopt boiling the blender has to be turned on to provide for intensive boiling and to avoid burning on walls. Aroma hops are added about 10 min. before the end of boiling. They could evaporate from the wort during longer boiling. Boiling period is determined by many factors. It is mainly necessary to achieve requested precipitation of nitrous substances, dissolution of bitter hop substances, and requested concentration of hopped wort. After hop boiling it is necessary to arrange for separation of solid particles.

 

 

Separation of solid particles:

Solid particles consist of precipitated nitrous substances in form of flakes and insoluble parts from added hop. At present the process takes place in a vessel called Whirlpool. PSS had two types of the vessels. Smaller breweries use brew kettle. Solid particles are separated after termination of hop boiling by slow decreasing of rotation of the blender to allow it stopping in 5 to 7 min.  Solid parts in swirled wort settle down and in 20 min. they form a compact cone in the centre of the bottom of the tank. Larger breweries use a separate tank, whirpool, where the hopped wort is pumped by centripetal force. The hoped wort swirls and settlement of solid particles is the same as in the first case. Such hot purified hopped wort is ready for cooling.

 

Wort cooling:

It is also a physical process. The hopped wort is cooled in a plate heat exchanger to the fermentation temperature, about 6 to 8 degrees according to needs and type of yeasts. Small amounts of oxygen in form of sterile pressurised air or foodstuff oxygen are added to cold hopped wort during pumping. I have explained the reasons for that in the part on yeasts. This cold oxidised hopped wort is pumped into the fermentation tank.

 

Fermentation and maturation:

Yeasts are added into perfectly clean and disinfected tank. Amount of yeasts is determined mostly according to number of individual cells for a litre of wort, however, in small breweries we rely on former experience. For instance, if we use dried yeasts packed in vacuum, 0.5 kg of such yeasts is enough for 1,000 to 3,000 litres.  With higher volume, fermentation starts later. If we use yeasts from the operation plant, then about 10 litres of thick yeasts are enough for 1,000 litres of wort. Method of dosing of yeasts in PSS systems: small breweries – mixed yeasts in required amount pour into the fermentation tank from the top. Larger breweries, the same, however, it is difficult with tall tanks. Therefore, it is also possible to pour yeasts during hop boiling to a disinfected whirpool and pump to the tank through the wort heat exchanger. The hopped wort goes to the tank by the same way and it pushes out eventual remains of yeasts from piping. Tanks are usually dimensioned to double or quadruple volume of brew. Yeasts are added only to the first brew as well as oxidation is made only the first brew. Then main fermentation starts in the tank. As I have already mentioned with yeasts, in course of fermentation yeasts reproduce first, then they start to create alcohol, CO2 and energy in from of heat. Therefore, it is necessary to cool the tanks. It is made automatically, after achieving requested temperature in the tank, cooling starts and fermenting fresh beer is kept at the set temperature. Arising CO2 is firstly released out, then the blow valve is closed and fermenting plug is set to the required pressure. After achieving the pressure, CO2 starts to release by bubbling through the layer of water. This way one can determine visually intensity of fermentation and maturation. During the main fermentation it is necessary to control on daily basis apart from temperature and pressure, also concentration of the remaining sugar. Sampling is necessary, carbon dioxide is manually shaken out and sugar is measured by a sacharometer. After decrease of sugar concentration, to about two thirds of original degree, beer shall be cooled gradually. After termination of the main fermentation, when sugar dropped to about one quarter of original degree, we shall decrease the temperature to 1 °C and beer starts to maturate. Its taste starts changing and undesirable products of the main fermentation diminish.  Pressure has to be regulated similarly as the temperature. The content of carbon dioxide in beer depends on the temperature and pressure. If it is high, beer foams too much and problems with racking occur. If it is low, beer is tasteless, almost undrinkable. The ideal content of CO2 is 5 g/litre. The Slovak standard states 3 g/litre, however, with such content beer is slack. The content above 6 g/l causes problems with filling and racking into glass. Even taste is worse as it foams in the mouth and loses its natural taste.

 

Filtering:

Small breweries usually do not filter beer, however, PSS has this procedure in their supply. During filtering cloudiness of beer removes, caused mainly by diffused yeasts but also other colloids. Various kinds of diatomaceous earth are used for filtering. It is porous inert material of animal origin. It is formed of shells of various dead snail fish, which in some areas create several tens or hundreds meters thick layers.  This material in the bottom (stainless sieves, stainless candles, cellulose plates) creates filtrating layer, where above mentioned substances are caught. Purified beer is released with back pressure (the same pressure as in CKT) into a serving tun and from there to transportation tanks.

 

Filling:                                                                                                                                                                

PSS SVIDNÍK, a.s. produces also simple and effective washers of KEG barrels. Washing principle in short:

  • Pushing out remains of old beer by pressurised air
  • Rinse with cold water
  • Wash with hot solution of NaOH
  • Several times rinse with water
  • Steam sterilisation

The barrel prepared this way is filled with beer. In our offer we have also simple fillers. The principle of isobaric filling applies here as well. First, CO2 is pushed into the barrel, the same pressure as in the tank, from which the barrel is going to be filled. Then supply valves for beer are open and from the barrel carbon dioxide is released until the barrel is completely filled.