Beverage Process

BEER FILTRATION

Beer filtration is normally carried out in 2 basic stages with first the production of a bright beer and second the production of sterile beer (if this is required).

Production of Bright Beer

A bright beer looks clear and the major amount of the yeast and suspended solids has been removed. It will contain a small amount of yeast.

For this filtration there are two types of beer filter for the brewer to consider:

1. D.E. (or kieselguhr) pressure filters using D.E. powder as a filter aid
2. Sheet filtration using coarse/medium grade filter sheets

D.E. PRESSURE FILTERS

These modern beer filters are efficient, versatile, compact and economic. They do require some training and experience in operation.
They are especially required where the beer is cloudy or hazy and will not settle well as they cope very well with suspended solid levels up to 0.5%.
They are not recommended for very small quantities (anything under 10 hl/6 Imp. barrels).
These filters consume D.E. (diatomaceous earth or kieselguhr) powder or Perlite powder as a filter aid. This is available in different grades of porosity and the correct grade must be used for the filter mesh size and the degree of clarity required. D.E. carries handling health warnings and masks must be worn when handling it. The discharged powder must also be disposed of to a suitable area.
The cost of powder is low and, with its high efficiency, this makes this process the one of choice for the majority of brewers, becoming especially important the larger the brewery.

VELO D.E. filters are available form 2 m2 up to 100 m2 and flow rates are typically about 5 to 8 hl/hr per m2 filtration area.

SHEET FILTERS

These beer filters are easy to use and require very little knowledge to run them but they do not cope well with hazy beers as the sheets will block, entailing replacement of the sheets prematurely. This can be costly.

This is a traditional method and requires the beer to be fined and well settled and the use of a standpipe in the tank to retain settled solids.

Filter sheets are consumable items. They are available in different grades and the correct grade must be chosen. The cost of the consumable sheets is considerably higher than the cost of D.E. powder. This is a drawback of this method together with its lack of versatility to handle anything other than a fairly clear well settled beer.

These are the filters of choice for quantities under 10 hl (6 Imp. Barrels).

Filters are available in a 40 x 40 cm or a 60 x 6 0cm format designed to take from 20 to 100 sheets depending on the flow rate required.

Production of Sterile Beer

This process removes practically all the yeast from a bright beer.

There are 2 main methods of sterile beer filtration:

1. Sheet filtration using sterile sheets
2. Cartridge membrane systems through 2 or 3 grades of membrane

SHEET FILTER

This is basically the same filter as above for the bright beer step but the filter should be designed and built to a higher hygienic standard than the one for the bright beer stage. (This up-graded specification filter can also be used for the bright beer stage.)

The filter would be used with sterilising grade of sheets.

Filters are available in a 40 x 40 cm or a 60 x 6 0cm format.

NB:
One major advantage of Sheet Filters is that the 2 stages of bright beer filtration and sterile filtration can be incorporated into the same filter by use of a change over or inversion plate. The unfiltered beer can be fed in one end and sterile beer comes out the other and so no intermediate tank is required. The beer passes first through the coarse or medium sheets then through the sterile sheets.

CARTRIDGE MEMBRANE SYSTEMS

The bright beer can also be pumped through a series of housings containing a suitable number of consumable cartridge filters to achieve the flow required for bottling. It is recommended that the first housing contains filters with a porosity of 5 or 10 micron followed by housings with 1 or 2 micron and finally 0.45 micron filters. For small systems this system could be reduced to a 2 stage system of say 2 and 0.45 micron.

This system can be installed directly before the filler which gives increased security as it avoids the risk of using a sterile beer tank.

NOTE: In practice both these sterilising procedures could be used in series as the beer could be sterile sheet filtered into a sterile tank before bottling and then the beer can be fed into the filler through one cartridge membrane housing of 0.45 micron. This belt and braces system is used to reduce risks of bottling beer particularly on fast lines and where a long bottled shelf life is essential.