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The membrane of the filter cartridges was designed asymmetrically especially for beer filtration in order to reliably separate microorganisms Process optimisation in the filter cellar
The first step in the multi-stage filtration process is usually the (optional) use of a centrifuge after the young beer has matured in order to remove yeast and other particles that cause turbidity. The remaining, finer particles and yeasts are filtered out of the beer in the next step by clarification and precoat filtration or alternatively by cross-flow. Optionally, the first steps to stabilise proteins and phenols, which are otherwise undertaken before bottling, can also be taken in this phase.
It is important to note that each stabilisation must be followed by a further filtration step for particle reduction - usually with filter cartridges - in order to achieve a high degree of purity. In the following filtration steps with filter media that have increasingly fine separation rates, the aim is to remove any trub and unwanted microorganisms and to stabilise the beer against microbiological ageing processes. The final step in this process is membrane filtration, in which even the last beer-damaging microorganisms are removed with membrane filter cartridges specially developed for the brewery. It is carried out directly before bottling to ensure the longest possible shelf life with high quality.
Alternatively, flash pasteurisation (flash pasteurisation) can be used to kill microorganisms. However, this increases the energy requirement of the system, can lead to slight changes in colour and taste and may require a final trapfiltration before filling.
The process steps of the three most common production methods in beer productionThree processes, one goal: beer of the highest quality
While the individual process steps on the way to filtered, stabilised beer are basically the same in the majority of breweries, the methods used in the filtration process differ. Basically, three processes are common on the market that increase the quality of the beer and ensure the longest possible shelf life: classic beer filtration (precoat filtration), cross-flow filtration and 1- or 2-stage depth filtration without kieselguhr.
Which process should be chosen depends on the needs of the plant operator and the profile of the brewery. For example, users with a high level of process knowledge will come to different conclusions than operators with a strong desire for automation. The cost of investment and the factors of water and energy consumption in operation can also play a decisive role.
In classic precoat filtration, sheet and frame filters provide great flexibility through simple adjustment of the filter areaPrecoat filtration
Classic beer filtration is precoat filtration. Natural filter aids such as diatomaceous earth or perlite as well as cellulose are used as precoating agents. These are first washed onto a rather coarse filter screen so that a fine filter cake builds up, through which the beer then flows and which filters out trub substances such as yeast residues.
Precoat filtration with diatomaceous earth has been tried and tested in breweries for decades. The processes are well established and there is a large selection of filtration systems and media on the market. Changes tend to take place in the details, for example to reduce water consumption or to extend the service life of the filter media - important factors in the brewing process. Since filtration is particularly gentle, value-giving ingredients, colour and aroma can be retained very well.
To ensure the high filtration quality required, precoat filtration is followed by germ-reducing depth filtration with layers, modules or candles. Another method that is becoming increasingly popular due to the rising demands for efficient processes is trap filtration. It has been used in brewing for many decades and is experiencing a "revival" due to the changed requirement profiles. Trapfiltration is particularly suitable for breweries that use other technical additives for filtration - besides diatomaceous earth, for example, the stabilising agent polyvinylpolypyrrolidone (PVPP). The filtration process ensures that these substances are safely removed after use.
Cross-Flow-Filtration
Cross-flow filtration, also called tangential flow filtration, found its way into breweries in the 1990s. The beer to be filtered is conveyed parallel to a membrane and the filtrate is drawn off at right angles to the direction of flow. The suspended particles, solids and insoluble trub substances to be separated accumulate in the unfiltrate circuit. In order to avoid the formation of a filter cake or a cover layer on the membrane and a resulting drop in performance, regular rinsing and cleaning cycles are required during filtration. The frequency of these regenerations depends on the trub content in the unfiltered beer.
Originally, cross-flow filtration was mainly of interest to larger breweries and corporations with a very high annual output: The process is highly automated and, as a large-scale solution, allows remote operation and maintenance. The cleaning of a cross-flow filtration system can also be fully automated. On the other hand, there are high investment costs and higher energy and water costs, as cross-flow systems have to be cleaned more frequently and for longer periods than other filtration systems. Breweries with large production volumes that aim for a high degree of automation and do not shy away from the costs and challenges of the technology can benefit from lower labour costs in return.
In trap filtration, depth filter cartridges reliably separate particles 1- or 2-stage depth filtration without diatomaceous earth
In layer filtration after centrifugation, depth filter sheets are inserted between a variable number of plates that have a trub side and a clear side. The filtration mechanism combines mechanical and adsorptive separation. In the sheet filter, the depth filter sheets are hydraulically pressed together so that they seal against each other. The great advantages of modern, pure cellulose depth filter sheets include not only their mechanical stability but also the fact that they can almost completely avoid drip losses. In the compact design of a depth filter module, filter sheets can be used alternatively after the centrifuge.
To achieve the highest possible degree of clarification, depth filtration with filter sheets or modules can be carried out in two successive stages. While larger particles are first removed from the beer in the first stage, significantly finer filter media separate even the smallest beer-damaging particles and microorganisms from the filtrate in the second stage. Depth filter sheets made of high-purity cellulose, to which no mineral components are added, are particularly suitable for this purpose.
Due to the simple design, uncomplicated operation and low investment costs, 1- or 2-stage filtration with depth filter sheets or modules is particularly recommended for small and medium-sized breweries. It is no longer an insider tip for craft beer brewers either, but a popular option. But some large breweries also successfully use the 2-stage filtration process.
Value-preserving premium depth filter sheets made of high-purity cellulose and depth filter modules do not require any mineral components even for sterilising filtration Flash pasteurisation or cold sterile filtration
Which filtration process is ultimately chosen depends mainly on operational aspects such as annual output and energy management. But the brewmaster's philosophy also plays a role - similar to the question of whether flash pasteurisation or cold sterile filtration should be the last step before bottling. Due to the growing importance of factors such as carbon footprint and energy consumption, breweries should consider the advantages and disadvantages of each process in terms of resource and energy consumption: The brewhouse already has a high thermal energy demand, which until now has virtually always been met with fossil fuels. Breweries that want to save costs and CO2 emissions can use cold sterile filtration and thus reduce their thermal energy costs.
Another factor in terms of costs and environmental compatibility is the issue of water, which is needed for cleaning and sterilising in membrane filtration. Here, for example, there are initial approaches to recovering the process water, treating it and feeding it back into the filtration cycle. This significantly promotes environmental compatibility and reduces water consumption, but is in turn associated with energy costs. In case of doubt, it can be decisive which costs are more significant according to local conditions: those for energy or those for water.
The choice of the optimal filtration process
In Germany, Europe or worldwide: with few regional exceptions, breweries today are confronted with high investment requirements. In this field of tension, the choice of filtration process not only contributes to a tasty, high-quality product - it can also have a decisive influence on costs and resource expenditure. There is no one solution that fits all operators perfectly - each of the three variants presented has its justification and must be weighed against each other. These depend heavily on the operational and economic circumstances of the brewery: this includes throughput as well as investment possibilities, personnel expenditure and automation requirements. Especially in times of ever-increasing competition, breweries have to gear their processes to economic efficiency and quality.
Those who identify the right filtration solution for their operation can benefit in the long term from stable, reliable processes and a high-quality product that is convincing in the market. In the brewery, filtration processes are thus essential factors for quality, taste and shelf life - properties where it is never wrong to take a second look.
