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.