Lesson 4 - Clarification – Centrifugation
This lesson discusses beer clarification via centrifugation. Clarification removes yeast and solid particles from the beer in order to make it ‘bright’ or reduce the amount of haze. Centrifugation is one method that we can use to clarify beer. This lesson looks closely at the physics of centrifugation and the concept of accelerated gravitational force. By the end of the lesson, you should understand the importance of this process and its impact on final beer quality.
Key Beer Quality Parameters Post-Centrifugation
What quality parameters are we trying to achieve post-centrifuge? What determines a well centrifuged beer? Let us re-cap and discuss the desirable outputs and the positive effects that they have on the rest of the brewing processes and beer quality. We will start with the critical parameters:
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Minimal oxygen pick-up during centrifugation. High dissolved oxygen can negatively affect flavour and reduce shelf-life through oxidation and premature staling in the beer. Maintaining a hermetically sealed process, packing all transfer pipes with deaerated water, and maintaining an inert atmosphere in the centrifuge during operation, will all mitigate oxidation.
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Minimal temperature pick-up during centrifugation. The final colloidal stability of the beer is significantly influenced by the beer’s temperature during the maturation phase. To achieve a bright end-product, temperature pick-up during centrifugation should be minimised as much as possible.
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Improved colloidal stability of the beer through the removal of cold break (which contains polyphenol protein complexes). Lowering the haze-forming particle component of the beer reduces the risk of haze formation in the final pack.
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Improved sensory stability due to the removal of fatty acids, again a component of cold break. Fatty acid removal promotes foam stability and improves the beer’s presentation in glass.
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Reduction in filtration inhibitors, e.g. fewer proteins on the filter. Proteins can increase the beer’s viscosity, which can negatively impact filtration run lengths. Reducing protein loading can extend filter run lengths.
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Clean, ‘sterile’ beer. By having a hygienic design and an ability to fully integrate the centrifuge into the existing CIP system, this will reduce any risk of product cross-contamination or microbiological infection.
We have discussed beer centrifugation, mainly within a standard brewing process. However, centrifuges can also be used to recover entrained beer from spent yeast and other waste products.