Lesson 8 - Clarification – Filtration
This lesson discusses the process of beer clarification via filtration. The filtration process primarily removes suspended particles from the matured beer to produce a clear stabilised beer that is ready for packaging. This lesson also discusses the importance of this process, the different filtration technologies available to the brewer, and the impact of filtration on final beer quality.
Key Principles of Filtration Quality Control
To achieve a bright, clean, “brewery fresh” beer during a product’s pre-determined shelf-life, a brewer must control and carefully manage six key quality parameters at filtration.
Table: Filtration quality parameters
|
Parameter |
Importance of Control |
| Beer temperature to be maintained < 0°C |
High temperatures pre-filtration will cause dissociation of protein-polyphenol complexes, which then reform as a chill haze in package.
|
| Colloidal stability process aids addition rates (e.g. silica gel) |
Dose rates must be optimised. Low dose rates will result in reduced colloidal stability. This means the beer will become hazy prior to its pre-determined shelf-life.
|
| Colloidal stability process aids contact time |
Similar to dose rates, contact time must be optimised to avoid the beer becoming hazy prior to its pre-determined shelf-life.
|
| Deaerated dilution water oxygen level (target < 10 µg/L) |
High dissolved oxygen will cause flavour instability by create staling flavours. This will alter the beers’ sensory profile and reduce the brewery fresh character. Before beer is introduced into the filter system, the filter and associated pipework must be flushed with deaerated water to remove any oxygen.
|
| Beer oxygen content during the filtration process |
As with using deaerated water, to retain its brewery fresh character, the beer must not pick up dissolved oxygen during the filtration run (< 50 µg/L is desirable).
|
| Haze |
Haze must be constantly monitored during filtration to achieve 90° haze readings of < 1.0 °EBC and 25° haze readings of < 0.5 °EBC. Values greater than this cause the beer to become visually hazy.
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