Lesson 9 - Clarification – Filtration SAQ
This lesson allows you to test yourself on the material covered in the Clarification – Filtration lesson, and determine the level to which you have met the learning outcomes.
Suggested Response - Q3
**Answer BOTH parts of this question:
a) When filtering your beer, you periodically see slugs of maturation tank bottoms in the inlet main to the filtration area. What measures can you take to ensure the tank bottoms do not blind the filter?
b) What is ‘absolute rating’ of a sterile filter, what is the pore size, and why is this important? How can the brewing process upstream be managed to reduce loading onto this filter?
Response:
a) Good practices in maturation will help alleviate tank bottoms in filtration. Before the vessel is transferred to filtration, systematic and effective removal of solids in the maturation tank will reduce the risk of slugs entering the filtration process.
Installation of a turbidity meter to detect tank bottoms will monitor the beer clarity during its transfer to filter continuously; it provides early indications of elevated solids in the transfer main. In addition to good practice in maturation, a brewer may choose to install a buffer tank to collect the tops and tails of the maturation vessel, which may be high in suspended solid particles. By collecting this volume in the tank, it can then be dosed back into the bulk beer stream in a controlled manner (5-10%) to reduce the solid loading onto the filter, which otherwise may blind or block it – reducing the filter run length. Another advantage of installing this tank is the beer recovery from the heads and tails, helping to reduce beer losses.
b) The ‘absolute rating’ is a term used to describe the degree of filtration of an absolute filter. A sterile filter pore size is 0.45 µm which is capable of trapping microorganisms. Absolute filters guarantee removal of all organisms larger than the pore size and are used frequently as a method to improve product stability. Loading should be reduced onto these filters to mitigate the breakthrough of microorganisms. Good hygiene and sanitation practices should be standardised throughout the brewing process to minimise microbiological activity and therefore reduce the loading on the sterile filter. CIP effectiveness should be validated and audited frequently, using rapid testing techniques, such as ATP bioluminescence to test rinse-water sterility.