Classical brewing procedure

The classical double-mash decoction brewing procedure is ideal for brewing light beers of Pilsner type. The brewing set, however, allows for application of other brewing procedures, including also infusion brewing.

1. Raw materials

Czech malt - the quantity depends on the required alcoholic strength of the beer
Hops - the quantity depends on the content of α-bitter acids in the individual products
Brewer’s yeast - 0.5 litres per hectolitre of hopped wort

2. Grist preparation

The first stage before the brewing process itself is malt grist preparation. The malt is purchased pre-cleaned, free of stones, sand and metal impurities, in 25 kg and 50 kg bags. The weight of the malt in the bag is specified on the bag label by the supplier. The calculated bag content is fed into the malt press hopper. The malt is crushed in the malt press and transported to the interim storage tank and further by a worm conveyor to the extractor of the wort pan. 

In the routine operation of a mini brewery it is necessary to test the best setting of the crushing gap of the press according to the malt quality. Composition of the malt grist directly affects the straining time, insufficient saccharification and extract loss. 

3. Hopped wort production

Malt grist may be extracted either in water with a temperature of 37 °C with subsequent scalding at 52 °C or directly in hot water with a temperature of 52 °C.

The wort pan is filled with water at 37 °C in the required quantity. The volume of the water is calculated according to the pour, required alcoholic strength of the half-product, assumed extract loss in the brewhouse and assumed evaporation. The whole dose of the malt grist is filled. The grist passes through the extractor and soaks with another portion of water. The remaining required volume of the water is used for rinsing the extractor and the interior walls of the pan. In the course of the extraction process the product is intensely stirred for 15 minutes. In the course of another 25 minutes the mixture is heated to 63 °C and stirred for another 10 minutes. Then 2/3 of the volume are pumped to the extraction and straining tank and the rest, mash 1, is left in the mash and wort pan where it is heated to 72-75 °C at a speed of 1 °C/min. In the course of the saccharification delay of 25 minutes the product must be stirred constantly until the achievement of perfect saccharification, checked by iodine solution. The iodine solution contains 0.25 g of iodine and 0.5 g of potassium iodide in 100 ml of distilled water. In the presence of starch the solution is coloured blue, while in the presence of the saccharification process the solution is coloured red. The drop of mash to be tested must first be cooled on a ceramic plate. After completion of the saccharification delay the mash must be quickly heated to 100 °C and allowed to boil for 20 minutes. Then the mash is pumped to the straining tank by which the temperature in the tank rises to 78 °C. The second mash is pumped and processed in the same way as mash 1. After pumping mash 2 to the draining tank the whole product is then left to rest for about 30 minutes.

Straining the unhopped wort begins with the wort face. After about 5 minutes of pumping the turbid wort from under the strainers back to the straining tank, the actual wort face straining begins and takes about 90 minutes. The intensity of straining is monitored in the pipeline peephole and regulated with the straining pump frequency exchanger. The unhopped wort must be pure without suspended malt particles. The draff layer is cut as needed in the course of the straining process. After 10 minutes of the face straining the unhopped wort concentration is measured. The measured value should generally be about 3-4 % higher than the required hopped wort level. The concentration depends on the quantity of water used for extraction and extraction capacity of the malt. After removal of the face, i.e. when the draff appears, filling of the rinsing water begins. The water temperature should be 80 °C and the water is prepared in the hot water tank. For a good yield three rinses are recommended. Pumping is again performed by the wort pump. At the end of the straining process it is necessary to monitor the unhopped wort concentration in the wort pan for alcoholic strength before pumping to correspond to the alcoholic strength of the displayed (sold) beer. For example in the case of brewing a 12% beer the unhopped wort concentration after straining completion will be 11.2 %, with the assumed evaporation of 5 %.

In the course of the hop boil treated hops are added in three doses, at the beginning of the boil stage, after 30 minutes and 10 to 15 minutes before the end of the hop boil. In the course of the hop boiling the boil must be intense - to achieve the required evaporation. The hop boiling stage is complete when the minimum required concentration of hopped wort is achieved. The concentration is measured by saccharometer 10 minutes before the boiling stage end. If the hopped wort concentration corresponds to the requirements, the boiling stage is finished, the amount is measured in the settled pan with a bar and a hopped wort sample is taken for concentration measurement by the saccharometer. Directly before the hopped wort sample is taken, the hopped wort refraction is identified in a test glass with the use of coarse flakes suspended in perfectly pure wort. This ends the boiling process and the hopped wort may be transferred to the whirl tank, if included in the brewhouse line, or pumped by a wort pump via a tangential nozzle back to the hopped wort pan. 

4. Hopped wort cooling

Hopped wort is pumped by a wort pump to a whirl tank where it is stirred with a tangential nozzle to whirl. The hopped wort is then left to mature for 20 to 40 minutes. Then the hopped wort is pumped from the whirl tank via a flat cooler to the fermentation tank. In the wort cooler the hopped wort is cooled to the fermentation temperature. The cooling takes about one house and yields about 1.2 times the amount of hot water. The important aspect is the achievement of the fermentation temperature; the cooling time, quantity and temperature of the yielded hot water are not relevant. In the double-stage stainless cooler cold water from the water distribution system is used as the coolant together with ice water from an ice water generator. Hot water from the exchanger is accumulated in the hot water tank and subsequently used as rinsing or extraction water. 

5. Primary fermentation

Yeast for fermentation is added to the cooled oxygenated hopped wort pumped to the fermentation tank and the tank fill is allowed to ferment at a temperature of 7-12 °C, which is called "cold fermentation", for 6-12 days, depending on the required alcoholic strength. If more doses are to be filled in a single fermentation tank, they should be filled within a single day. The heat produced by fermentation is cooled with ice water from the ice water generator fed inside the double wall of the tank to maintain the fermentation temperature, i.e. 7-12 °C. This means in practice that the cooling is commenced on day 3 or 4, when the temperature in the fermentation tank rises to 9.5 °C. In the case of 12% beer the fermentation level established by saccharometer at the end of the primary fermentation should range between 60 and 65%, which corresponds to 4.0-4.8 % on the saccharometer scale. Completion of the primary fermentation is manifested by a decrease in the daily loss of the extract below 0.3 % measured by the saccharometer, a darker colour of the liquid, sedimentation of the yeast and ripple of the hopped wort. This may be observed in a test glass.

About 5 to 6 times the amount of yeast for fermentation can be obtained from every tank and used for further primary fermentation after washing.

6. Secondary fermentation

Young beer corresponding to the recommended fermentation level is pumped by a pump or by drive gas displacement to lager tanks where secondary fermentation takes place at 0-4 °C for about 21 to 60 days. 

The progress of secondary fermentation may be observed with the bunging apparatus. Secondary fermentation usually takes place under increased pressure. The bunging apparatus is used for increasing pressure. Tank cooling with ice water is to be started immediately after bunging and the tank temperature of 2 °C should be achieved as soon as possible and then maintained. In the course of secondary fermentation the young beer acquires a balanced taste, saturation with carbon dioxide and further ripple. 

7. Beer filtration and bottling

The ready beer is filtered through a diatomaceous earth filter and pumped to the bottling tank. It may however also be bottled directly (without filtering). The bottling tanks are filled against counter-pressure to prevent the release of CO2. 

In the bottling tanks the beer is kept under constant pressure under which it is also bottled to the transport containers (such as KEG barrels) or directly to the restaurant tap. Filtration and storage of the beer in the bottling tanks must be subject to assumed and assured sales. Beer should be pumped to the bottling tank at least 24 hours before bottling and should not be left in this tank for more than 3-5 days. 

8. Yeast storage

The collected yeast is mixed in a vessel with ice water, allowed to settle and the top dead yeast removed. This is repeated every day. Thus the yeast may be stored for about one week. One yeast dose may be used 4-5 times for fermentation.

9. Quality of brewed beer

The quality of the brewed beer depends on the quality of the raw materials used and, above all, on the technological discipline in the brewing and distribution. Perfect purity throughout the whole technological process is the basic assumption for top-quality production. This applies not only for the technology itself, but also for all other equipment, service areas, and raw material, half-product and finished product storage.

Instructions for operation of the individual machines and equipment are part of the accompanying technical documentation which is part of the mini brewery supply.