Stabilisation of Beer
Stabilisation of beer is not a discreet operation. It is a gradual progression of procedures aimed at optimising the removal of= undesirable content at each stage of production. In dealing with physical, chemical and microbiological stability, the selection of raw materials and the design of the brewery and processes plays a significant role in ensuring the final product quality. However, even the best processes are at risk from particulate contamination and the ingress of spoilage micro-organisms.

domnick hunter routinely support international brewing groups in developing Hazard Analysis at Critical Control Point (HACCP) procedures to optimise filtration system effectiveness. domnick hunter filters are available to:

• Remove particles from incoming water and liquid additives;
• Provide trap filtration after ion-exchange and powder filtration processes;
• Sterilise gases and liquor;
• Prevent an ingress of airborne micro-organisms into process vessels, propagators and storage tanks;
• Remove particles from Clean-in-Place solutions;
• Provide culinary grade steam;
• Stabilise and ‘sterilise’ beer prior to packaging.

Our products are augmented by an unrivalled level of technical and administrative support, and an open-door policy that encourages domnick hunter customers to view how their filters are manufactured, and to take a part in continually improving the range of products available.

Intermediate Stabilisation
Bright beer is physically stable but is likely to have residual microbial content. Typical low levels of spoilage organisms and yeast present few problems during short term storage in the bright beer tank. These will be removed by either sterile filtration or pasteurisation during packaging. If the beer is to be stored for longer, for example transported to a packaging facility, or if it has been recovered, then the levels of spoilage organisms may be higher.

domnick hunter offer a range of filters for the purpose of intermediate stabilisation, that control microbial levels for short periods. These biologically stabilise the beer for long enough to prevent spoilage during storage or transportation. They are capable of complete removal of yeast and reduction of numbers of bacteria. This performance also makes them ideal for use as pre-filters to protect more expensive ‘sterilising’ membrane filters downstream.

Cold Sterilisation
Cold ‘sterilisation’ is the terminal microbiological stabilisation of beer prior to packaging. It involves the use of a microporous polymeric membrane to filter out yeast and spoilage organisms. The pore size of the membrane is closely controlled, 0.65µm or 0.45µm rated membranes being adequate to ‘sterilise’ beer. domnick hunter polyethersulphone membrane filters offer a number of advantages over other forms of filtration and pasteurisation:

• Flavour change is negligible, even where oxygen levels in the beer may be approaching upper limits;
• The technique will remove all spoilage organisms and is effective against heat resistant forms such as spores and cysts;
• Haze values will remain unchanged or will improve with filtration;
• Performance of the filter can be guaranteed by implementing a non-destructive integrity test on the filters prior to use.

The filters are positioned in the bright beer supply, as close as possible to the filler. This design, coupled with complimentary cleaning processes, combines to reduce the likelihood of re-infection from downstream process lines. The beer is essentially free of particulate content at this stage, having been previously clarified using fine powder, sheets and cartridge pre-filtration.

Trap Filtration
Powder filters, whether utilising diatomaceous earth, PVPP or any other powder will by their nature shed some of the particles into the beer. In extreme cases, total bed collapse can occur which results in mass unloading of the powder and contamination of downstream lines, equipment and vessels.

An effective means to handle powder seepage is to employ domnick hunter trap filters. Also known as police or guard filters, they effectively remove trace quantities of particulate otherwise destined for the bright beer tank. They will block in the event of major bed collapse, thereby protecting downstream processes.

Selection of the filter is a balance between its ability to remove the finest particles and its longevity of use. domnick hunter offer guidance to ensure that process operations, such as back-washing, can be optimised to maximise the filter’s lifetime and economy of use.

Incoming Water
Water entering the brewery comes from a variety of sources, natural and treated. The water is susceptible to seasonal variation in terms of particulate, micro-organism and dissolved content. It is unusual for the water to be useable without general treatment, whether it is intended for the brewing process or as plant water. Clarifying grade filter cartridges from domnick hunter are ideal for the protection of ion exchange columns and reverse osmosis membranes.