Alphafloc Isinglass Paste
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Alphafloc isinglass paste is produced from the clean maws of certain types of fish. These fish maws contain about 98% collagen on a dry ash-free basis. The paste form of isinglass comprises finely divided isinglass in an aqueous base with sodium metabisulphite as preservative. The fish maws are subjected to vigorous cleaning followed by wet size reduction via processing which avoids heat generation (thereby avoiding thermal degradation of the collagen). The ready for use isinglass produced from the paste is added to beer at the end of fermentation to speed maturation and improve filtration by removing yeasts and protein particles. For ease of use Alphafloc paste is supplied with the necessary acid and preservative in a separate sachet. Alphafloc viscosity is typically around 50-60,000 cP.
The precise nature of the action of collagen on yeast and proteins is not fully understood, and many suggestions have been promoted. Collagen exists in solution as tightly bound triple helix strands which possess both positively and negatively charges sites along their length. It is clear that the amino acid make-up of collagen, and specifically the high proportion of proline and hydroxyproline, contributes to its remarkable ability to remove both yeasts and proteins so effectively. In a typical application greater than 95% of yeast and 90% of protein particles are removed.
A typical treatment rate of 1 -3 g/hl (as isinglass) is recommended. Typical addition rates of the ready to use liquid isinglass for beers prior to filtration are between 0.25 -1 L/hL of beer. For both performance and commercial considerations it is advisable to identify the correct addition rate. This will vary from beer to beer (a simple optimisation test is detailed later).
Isinglass has long been used in the clarification of traditional British cask ale. In this role its effectiveness has never been rivaled, although many attempts have been made to find alternatives over the years. The same ability to remove yeast, and more importantly, proteins makes it an ideal partner in the cost effective production of filtered beers. New generation centrifuges are being introduced into the brewing process. This has seen interest in Alphafloc increase, as the action of the centrifuge on large particulate solids and Alphafloc on the more troublesome smaller particles results in beers with excellent filtration characteristics.