Lesson 7 - Processing Aids and Additions SAQ
This lesson allows you to test yourself on the material covered in the Processing Aids and Additions lesson, and determine the level to which you have met the learning outcomes.
Suggested Response - Q2
** You want to improve the haze stability of your beer and remove polyphenols either in maturation or post filter. What treatments are available to the brewer?
Response:
The most common way of removing polyphenols from fermented beer is with polyvinylpolypyrrolidone or PVPP. Polyvinylpolypyrrolidone is an adsorbent stabiliser used to selectively bind haze, causing polyphenols. It is insoluble in beer and needs to be kept slurried or supported on a filter screen. Finer particle PVPP is cheaper and available as a single-use treatment.
For large breweries exporting beer with a long shelf-life (> 40 weeks), a regenerable PVPP system is cost-effective. This typically incorporates a horizontal leaf filter that is pre-coated with larger particle PVPP dosed from a regenerated PVPP holding vessel. Filtered beer is passed through the PVPP filter, which adsorbs the haze polyphenols present. At the end of the filtration run, the PVPP is spun off the filter screens, returned to the regeneration vessel and washed with hot caustic, which removes the trapped polyphenols.
Single-use PVPP can be dosed in the maturation vessel or pre-filter. Being insoluble, it forms part of the filter powder cake, trapping polyphenols during dosing and on the filter screen. After filtration, the PVPP is dumped with the spent kieselguhr.
Although PVPP is very efficient at removing polyphenols, it is expensive and incurs high capital cost; if a regenerable system is purchased, it also brings a high level of complexity. It may also be an unnecessary step when only a short shelf-life is needed, and where protein removal is otherwise usually sufficient.
The second and more novel way of removing polyphenols is by using the agarose based CSS filtration system. This is a system that uses a bed of agarose beads through which primary filtered beer is passed; it has a controlled bypass so not all beer is treated.
As the agarose becomes saturated with adsorbed polyphenols, more flow is diverted through the agarose bed. Like the PVPP filter, the bed is regenerated with caustic.
Whilst the filter system has a high capital cost, it is modular and can be adapted for different filter throughputs, so is generally cheaper than a PVPP system. It is also able to regulate to a defined polyphenol content using the bypass.