Function of Isinglass Finings
• Isinglass finings clarify beer by combining with yeast (net negative charge) and protein by electrostatic interaction and by physical enmeshment to form large aggregates which settle rapidly.
• Isinglass finings are available as solutions, pastes, flocs, shredded leaf, ribbons or whole leaf. The active principle is the protein collagen which becomes less ineffective over time or when subjected to heat, causing a degradation to gelatin.
The effectiveness of isinglass finings depends on:
• Type of finings, mixing and storage temperatures, storage time.
• Yeast strain and yeast count prior to fining.
• Dosage rate, time of addition, fining performance, type and quantity of auxiliary used.
• Temperature of beer on addition of finings.
Range of Values
• Yeast counts prior to fining are typically 0·5 x 106 – 2 x 106 cells per ml with a mean of 1·0 x 106 cells per ml.
• Samples taken 4 to 5 hours after adding finings should be visually bright with good floc formation
• Liquid isinglass finings should contain between 250 and 500 mg per litre of sulphur dioxide. For flavour considerations it is advisable to use the lowest practicable sulphur dioxide concentration commensurate with microbial stability of the liquid finings and leading to less than 30 mg per litre in the final beer.
• The rate of addition of finings is typically 11 – 14 mls per litre (3 – 4 pints per barrel).
• At temperatures below 4° C (39° F) liquid finings are stable for at least six months. Slight deterioration may occur after 12 months.
At temperatures of 13° C (55° F) a storage period of no more than 3 – 4 months is recommended, although after six months the deterioration would only be slight. In cases where finings are subjected to fluctuating temperatures, e.g. in summer, as a result of changes in atmospheric conditions, storage for periods greater than one month may cause deterioration to occur.
Preparation of isinglass finings from flocs, ribbons, shreds or whole leaf*
• Finings in the form of floc is treated with water at 13° – 14°C (55° – 57° F) and agitated for one hour to give a homogeneous solution. The mixture is then chilled to a temperature of 10° – 11° C (50° – 52° F) and is stored for at least 24 hours before use.
• Shredded or ribbon finings are treated for one hour with water at 13° – 17° C (55° – 62° F) containing organic acid (eg citric, malic or tartaric acids). Sulphurous acid should be added as a preservative The mixture is then diluted (three fold) and stored for 24 hours. Fining performance of the mixture may be improved by storage for three to four days at 10° – 13° C (50° – 55° F)
* Nowadays it is far more usual to use pre-made isinglass finings in the form of Triple strength concentrate or ready for use strengths. Where Isinglass finings is still prepared in the brewery it is now far more likely to be done from Isinglass Paste.
• At no time during mixing or storage should the temperature be allowed to exceed 14° C (57° F) or fall below 10° C (50° F)
• Finings should be injected into casks at racking or immediately prior to despatch.
• Every batch of finings should be inspected visually and examined for infection by micro- organisms.
• Fining action is monitored by making the equivalent addition of finings to appropriate samples of beer and noting daily the size of flocs, speed of fining action and clarity of fined sample
• A nine gallon cask is fined and stillaged in the sample cellar for a larger scale production check on the fining performance (see Topic 29).
• Finings contribute to sulphur dioxide levels in beer The levels of sulphur dioxide in samples of fined beer should be measured. Isinglass finings supplied by Murphy & Son Ltd. will add in the order of 3 – 4 ppm SO2 to the beer at typical addition rates.