Wort filtration process

The wort filtration process mainly includes seven processes: enter hot water, mash, quiescence, turbid wort reflux, first wort filtration, grain washing and draining. They are detailed below.

(1)Hot water entering
Before pumping the mash, the lauter tank must be checked. First, the filter sieve should be laid, compacted, and cleaned. At the same time, the drain mandoor of the lauter tank should be closed to ensure that the temperature of the mash remains unchanged. Then check whether the raker blade is in the normal position, and check the open and closed state of the pipeline valve connected to the lauter tank. After the inspection, hot water at 78°C is injected from the bottom until the filter plate is just flooded to discharge the air between the filter plate and the bottom of the tank to prevent the oxidation of the wort. At the same time, the sieve plate and the lauter tank can be preheated. 

(2)Mash entering
Saccharified mash is quickly pumped into the lauter tank while stirring, and the mash is evenly distributed by using a raker.Otherwise, it will lead to uneven leaching of extractives and decrease the leaching rate. During the pumping of the mash, the stirrer of the mash tank should be constantly stirred to ensure that the mash is stable. The discharge speed of saccharified mash is generally not more than 2~4m/s, and the pumping speed should be slow in the early stage. After the mash has a certain height in the lauter tank, pump it in at full speed.

(3)quiescence

After the mash is pumped into the lauter tank, the heavy grain husk and light grain husk fragments quickly settle to form a 30-40cm thick filter layer (if wet crushing is used, the lees layer will reach 60-70cm). After the end of quiescence, three filter layers are formed: the bottom layer (composed of coarse grains and heavy grains), the main layer (composed of grain hust, which is the thickest layer and the natural medium for wort filtration) and the upper layer ( It is made up of light particles such as protein and grain husk crumbs separated from the liquid, and this layer is thinner). The first wort is gathered on the upper part of the grain layer. This shows that the quiescence process is essential. The whole quiescence time is about 10~20min.

(4)Wort backflow
The clear and transparent wort contains about 4mg/L of C6-C16 fatty acids, and the fatty acid content in the turbid wort is more than 10 times that of the super clear wort. If the turbid wort enters the boiling kettle, it will cause problems such as increased iodine value, poor protein flocculation, and unreasonable wort composition, which will adversely affect the foam and flavor of beer, and will easily cause abnormal fermentation. Therefore, at the beginning of filtration, a turbid wort reflux operation should be carried out to improve the clarity of the wort and prevent the occurrence of the above problems.

The operating procedure is: first open the valves of the wort outlet pipe in order to discharge the air in the pipe, then close them immediately, and then open the wort outlet valves in sequence. At the beginning, the wort flowing out is turbid and unclear. At this time, it must be carefully pumped back to the lauter tank. The return wort must be pumped from below the wort surface of the lauter tank, so as not to damage the formed filter layer, and it also minimizes the amount of oxygen inhaled. The backflow time is generally about 10 minutes, until the wort is clear.

(5)First wort filter
The filtration time of the first wort is generally 75~105min. If an advanced new filter system is used, coupled with good tillage operation, the filter time can be reduced to less than 60 minutes. When the reflux wort is clear and the reflux is over, open the valve that enters the boiling kettle or the wort grant tank to allow the wort to enter. In order to maintain the porosity of the grains layer, the filtration pressure difference should be kept as small as possible. When the filter valve is opened, it should not be too fast. At the beginning, control the opening at 1/4~1/3, and then gradually open the valve according to the brightness of the wort.

During the filtering period, the agitator raker can be activated to loosen the filter layer and increase the filtering speed. However, the rotation speed of the raker should be slow, preferably 1/5-1/3r/min. When filtering for 25-30 minutes, measure the concentration of the first mash to determine the amount of washing water added In order to ensure the wort concentration at the end of filtration, the first wort concentration must be higher than the wort concentration to be fermented, approximately 40%~ 80% higher. For the production of 12°P beer, the wort concentration must be 16~20°P.

(6)Grain washing

When the first wort filtration is nearing the end, the extract is still retained in the spent grain. In order to improve economic efficiency, it should be washed out thoroughly. This process is called grain washing. The water used for washing the spent grains is called the spent grain washing water, and the washed extract is called the second wort.

The higher the temperature of the washing water, the faster and more thorough the washing. However, the water temperature must be controlled within the saccharification temperature range, generally 75°C to 78°C, and the highest temperature should not exceed 80°C. The whole process of washing the spent grains lasts for 90-120 minutes. When the spent grains just leak out, the filtration of the first wort should be stopped, and the spent grains washing water should be added according to the process requirements.

(7)Spent grain removable

When the concentration of the wort of the grain washing reaches the specified value, the grain washing is stopped. Open the drain valve to drain the residual liquid of the spent grains and dry it. Then open the drain manhole, turn on the raker knife and drop the blade to drain. After draining the spent grain, clean the rakerr and the sieve plate and set aside.

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