Lesson 5 - Beer Haze SAQ
This lesson enables you to test yourself on the material covered in the lesson on Beer Haze and to determine the level to which you have met the learning outcomes.
Suggested Response - Q1
** Discuss polyphenols in relation to beer haze. Where do they originate from and what reactions do they undergo in the brewing process?
Response:
Polyphenols in beer derive 70% from malt and 30% from hops. They contain more than one phenol ring and more than two hydroxyl (OH) groups attached to the rings.
Polyphenols that are important to beer haze are flavanols and their polymerised derivatives.
Flavanols constitute around 10% of the polyphenols in beer. They are principally catechin, epicatechin, gallocatechin, and epigallocatechin. They have three phenol rings and six hydroxyl groups and may exist as monomers, but more commonly as dimers and trimers – the so-called simple flavonoids or proanthocyanidins.
Monomers do not appear to be involved with haze formation; it is mainly the dimers that are haze promoting. Two of these, procyanidin B3 and prodelphinidin B3, constitute about 1/3rd of the flavonoids and are particularly reactive.
Protein binding is due to the number and position of the hydroxyl (OH) groups on the flavanoids aromatic rings. Prodelphinidin B3, as a result, is more reactive than procyanidin B3.
These molecules are, however, thought to be too small to bind to proline-rich haze proteins directly to form haze complexes. They need to polymerise (mediated through oxidation reactions, which can occur throughout the brewing process), enzymatically during mashing or non-enzymatically during wort boiling.
Oxidised flavanols that are haze active are termed tannoids. They form tannins that bind sensitive proteins. The association and growth of these complexes will result in haze particle formation.