Isinglass: A fishy tale!

To label or not to label, that was the difficult decision facing the brewing industry when new food labelling directives were introduced by the European Commission in 2003. The EC wanted to tighten the labelling legislation surrounding food and drink so that the consumer, especially those with food allergies, had a greater level of information about not only the ingredients present in food and drink, but also those used in its production.

It is widely accepted that the prevalence of food allergies is increasing and, since there is no cure, those who suffer sensitivity to particular foods have to adopt management strategies to ensure that they do not consume even small amounts of the foods to which they react. To be able to do that food allergy sufferers need very precise information about the ingredients contained in the food and drink that they are likely to consume.

The labelling of most food and drink in the United Kingdom is governed by the provisions of the Food Safety Act 1990 and The Food Labelling Regulations 1996. In addition to these provisions the European directive 2000/13/EC set out more general requirements for the listing of ingredients used in food. However, this legislation contained a number of exemptions. A particular shortfall was a provision known as the 25 per cent rule which meant that if a compound food, such as a sponge cake used in a trifle, made up less than 25 per cent of the finished food the manufacturer was not legally obliged to label the ingredients that made up that compound food.

Understandably there was a high degree of dissatisfaction from a number of consumer groups representing food allergy sufferers who felt that this labelling practice should be changed. Thus a new EC directive was introduced in 2003 requiring full ingredient listings for ‘common food allergens.’ In all, 12 common food allergens were identified including nuts, milk, eggs, and cereals containing gluten. Also included in the list were ingredients derived from fish, which presented the brewing industry with a dilemma.

Beer which is ready to be racked into casks typically contains around one million yeast cells per millilitre. This creates an undesirable haze in the beer, and has to be separated out. If the beer is to be brewery conditioned, where secondary fermentation is carried out in conditioning tanks in the brewery, there are a number of methods that can be employed to remove the yeast prior to packaging such as centrifugation and filtration.

However, for cask conditioned beer, yeast must remain in the cask after it leaves the brewery to enable secondary fermentation to occur in the cask.

If a cask of beer is left for long enough, the yeast will eventually settle naturally leaving the beer bright and clear. However, thirst breeds impatience, and of course economic realities facing the busy pub landlord require that this sedimentation has to be a lot quicker.

To achieve cask conditioning, but also allow the landlord to serve a clear pint, brewers add a processing aid known as finings, and in particular isinglass finings, to the cask.

Over the years a wide variety of substances have been employed to aid the clarification of beer

including oyster shells, chalk and fullers earth. However, before the advent of earthenware, beer and wine was often stored in dried animal skins and other containers derived from animal sources such as stomachs and fish swim bladders.

It was the Romans who first noted that wine stored in just such vessels was much less opaque than wine stored in other vessels. Isinglass, the product of fish swim bladders in a more purified form, was found to be particularly effective at clarifying wine and beer. So when commercial brewing expanded at the end of the 18th century, its use became routine to clarify beer in the cask.

At that time isinglass was sourced from the sturgeon, a common fish found in many of the rivers surrounding the major brewing cities. Today isinglass is generally obtained from the swim bladders of fish such as catfish, drumfish and threadfins caught in tropical and subtropical waters.

The swim bladder, located in the dorsal portion of the fish allows the fish to control its depth without having to expend energy by swimming.

The size of the swim bladder and its quality as a fining agent varies between fish species and can also be affected by where the fish are caught. Thus the dried bladders have gained rather exotic names such as Long Saigon, Pennang and Brazil Lump and some brewers may insist on using isinglass finings made from a particular type of swim bladder.

So how are isinglass finings prepared and how do they work?

To prepare finings suitable for brewery use, the isinglass is removed from the fish and dried naturally. If dried too quickly a lot of the clarification potential can be lost. Once dried the finings are cleaned, sterilised and ‘cut’ in acid. The cutting process results in a white liquid or emulsion of isinglass which is ready to add to beer.

The mechanism by which the action of fining beer works can be explained by a mathematical formula derived by George Gabriel Stokes in 1851. Stokes was interested in how particles moved in fluids, particularly how they settled or sedimented at the bottom of a liquid.

Rather unsurprisingly Stokes observed that one of the key factors that determined how quickly particles settled was their size. The bigger the particle the quicker it would settle. Therefore if you can get small particles to somehow coalesce and form bigger particles they will settle quicker. That is the principle that underpins how isinglass works in beer.

The important constituent of isinglass that makes it effective as a fining agent is collagen. Collagen is a protein that has a helical shape rather like the structure of DNA but whereas DNA has a double helix collagen has a triple helix. The triple helix of collagen winds itself together to form a complex mesh or net like structure.

Furthermore collagen contains numerous sites within that helical structure which are electrically charged in beer and are a key factor as to why isinglass is so effective at clarifying beer.

Article continues in Beers of the World magazine Issue 19

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