Words by Nick Brading and Iain Kenny
As early as 200BC Romans noticed beverages stored in swim bladders of sturgeon fish had magical clarity. Fast forward a few centuries and via a bit of processing and a nifty German / Dutch naming, isinglass became the linchpin of the British cask beer. Authentic isinglass still enjoys unrivalled status as “premier league” in cask fining but despite the production process removing any “fish material” from the collagen, there are sections of consumers preferring a vegan route.
As brewers search for alternatives, Murphy’s Super F is proving a popular option for the fining of cask beer.
There are two principal components of beer that require clarification following end of fermentation. The first of these is protein which comes from the malt and other cereal adjuncts in the grist. The amount of protein varies according to barley variety, growing conditions, malting skill and the brewers own processing techniques. Protein is required in beer for yeast growth, flavour, colour, aroma and foam all desirable characteristics. However, there is usually an excess in the final beer which unless removed, accelerates the deterioration of beer quality in the form of loss of flavour and development of haze. Other troublesome processing conditions present themselves in the brewery with slow fining and difficult filtration.
The second component that needs clarification is the removal of the yeast. In cask beer, a small amount is required to maintain or “cask” condition the beer to give the beer a pleasant mouthfeel when consumed. This amount is so small that the beer will appear bright even though some yeast cells may still be in suspension. However, the removal of yeast once the fermentation is over needs to be done quickly in order to preserve the freshness of the beer and to stop the dying yeast from autolysing and contaminating the fresh beer with off-flavours.
Understanding these two components and balancing a finings regime to suit is critical if the brewer is going to get high quality fresh cask beer to trade quickly or to filter the beer for kegging or small pack. When fining beer, the objective is to coagulate the protein particles and yeast cells to increase their density hence increase settling speed. The larger particles are called flocs. The principle of attraction is based upon molecular electrical charge where opposites attract.
At the pH and temperature of green beer, proteins have an excess of positive charges so a finings that carries a negative charge is used. These can be polysaccharide or silicaceous in origin. They are acidified so complement beer pH and create the right conditions to make flocs.
In the same way, live yeast cells fresh after fermentation carry a negative cell charge so a finings agent like isinglass is used. These are also acidified; the lower the pH, the more negative charges they carry.
Super F is manufactured in a similar way to some auxiliary finings but during the production, the solution is alkalised instead of acidified. The high pH causes a reversal of polarity in the silica sol so that it carries a positive charge like isinglass and attracts the yeast. Handling and addition points in the process are the same as for isinglass – normal auxiliary finings can be added to remove the protein then the Super F added to clear the yeast.
Isinglass is a huge collagen molecule with space to attract many yeast cells forming large flocs whereas Super F is a much smaller molecule forming smaller flocs so it takes a little longer to settle after each movement but when used properly supported with regular optimisation Super F is a go to product for vegan friendly cask beer.