After the first wort (original wort) is filtered, a certain amount of leachate will remain in the lees layer, in order to ensure the utilisation of raw materials, this part of the leachate needs to be recovered, and hot water can be used to wash out these soluble components, this process is called lees washing. This process is called lees washing. The main contents of lees washing are lees washing water quantity, temperature, frequency, quality of lees washing water and lees ploughing. The operation and frequency of lees washing are affected by the concentration of the first wort, the thickness of the lees layer, the performance of wort filtration and the boiling intensity of the wort boiling pot.
So, how to ensure that the leachate is fully recovered and the quality of the wort is maintained during lees washing?
1. The amount and frequency of lees washing should be controlled to a certain degree.
The amount of water and the number of times of lees washing depends on the concentration of the first wort and the evaporation intensity of the boiling pot. The number of times to wash the lees is generally 3 to 4 times is good, in principle, not more than 4 times. Multiple recovery of residual sugar can certainly improve the utilization of raw materials, but too many times of washing, washing too much, will be harmful ingredients in the husk (such as polyphenols, pigmented substances, bitter substances, etc.) a large number of wash out into the wort, affecting the quality of the wort; In addition, too much washing will also make the boiling pot mixed wort concentration is reduced, the need to consume a lot of heat to evaporate the water, not only is the energy consumption increased, the production cost is also higher, but also affects the boiling pot evaporation intensity. It will not only increase the energy consumption and production cost, but also affect the appearance, flavour, taste and other quality problems of the finished beer. However, if the first wort concentration is higher, the evaporation strength of the boiling pot is stronger, the appropriate increase in the amount of lees washing water, the impact on the wort yield and quality is still acceptable, so according to the different first wort concentration, wort evaporation strength should be reasonably arranged to wash the amount of lees washing water and the number of times of lees washing.
2. The temperature of lees washing water must be suitable
Generally controlled at 78 ℃ ± 1 ℃ is good, should not exceed 80 ℃. Wash water temperature is too low, the lees are not thoroughly washed, residual sugar wash is not clean, but also reduces the temperature of the mixed wort; wash temperature is too high, not only will destroy the role of certain enzymes, but also lead to the residual macromolecular carbohydrates continue to decomposition of the obstruction, so that the wort viscosity, turbidity increases. Reasonable wash water temperature should be controlled than the filtration mash temperature 0.5 ~ 1 ℃, at least not below the filtration temperature.
3. The quality of washing water has a greater impact on the quality of wort.
The quality of lees washing water has great influence on the quality of wort, including the pH of lees washing water and the harmful ions contained in it. Generally, the pH value of lees washing water is about 6, but the adjustment of pH value in actual production is more troublesome. Therefore, it is required to control the pH value of the lees washing water below 6.5, so that less polyphenol substances and pigments can be dissolved in the wheat husk, which is also conducive to the coagulation and precipitation of proteins in the process of wort boiling. The presence of harmful ions can upset the compositional balance of the wort, leading to impaired fermentation and the quality of the final beer product. Therefore, in order to ensure the quality of the wort, the quality of the lees washing water should be strictly controlled.
4. The lees should be washed with the lees ploughed on as much as possible.
When washing the lees, ploughing should be turned on as much as possible, generally the first washing (up to and including the second) should be ploughed in principle, because at this time the residual sugar concentration in the lees is high, the lees layer is more compact, and ploughing the lees can help to wash out the leachate and loosen the lees layer. In the case of filtration difficulties, often with the top of the water to re-organise the dregs, but the top of the water, the dregs and unfiltered wort concentration has a certain degree of dilution, and the top of the water will be brought into a large number of water to the boiling pot, which affects the number of times the dregs can be washed and the amount of water used, prone to cause residual sugar is high.