Lesson 3 - Wort Boiling Theory SAQ

**What raw materials and process aids do we typically add during wort boiling; what role do they play in wort and beer quality?

Response:

Additions made during the boil include adjuncts, hops/hop products, kettle finings, gallotannins, silica sol, PVPP, antifoams, yeast food, calcium or magnesium salts, sour wort and acids.

Adjuncts could include solid or liquid sugars. We use these to increase wort gravity and influence beer flavour, colour and flavour stability. Adjuncts can increase or reduce colour levels, add specific flavour or dilute malt flavour. They can also be used to produce high gravity wort and to increase brew size for the same weight of malt. 

Hops and hop products provide bitterness and aroma. They assist with trub formation by contributing polyphenols and hop vegetable matter. This vegetable material can also help reduce the rate of fouling on heating surfaces.

Kettle finings can improve trub formation and do improve the level of cold break. The increased removal of protein can improve beer filterability and colloidal stability.

Gallotannins are added to help improve haze protein removal and have the additional benefit of removing the prooxidant metal ions, copper and iron.

Silica sols also adsorb potential haze proteins and polypeptides, aiding their removal in trub.

PVPP can be used to help remove polyphenols that can take part in haze formation.

All additions that improve the removal of hot and cold break reduce the risk of fermentations and yeast health being negatively affected by high levels of suspended solids in the wort. However overdosing clarification agents can lead to excessive levels of cold break that can harm yeast crops and cause high beer losses.

Calcium ions react with phosphate to produce calcium phosphate. This precipitates out releasing H⁺ ions, which causes the pH to drop. A similar reaction occurs if magnesium ions are present but the effect is less significant.

Adding calcium also helps remove the oxalic acid derived from malt. If this is not removed, it forms calcium oxalate (CaC₂O₄) when the pH drops later in the process. Calcium oxalate forms scale on fermentation and conditioning vessels and can cause gushing in packaged beer.

Yeast food is a supplement added to wort to provide the nutrients that yeast needs during fermentation. All malt worts usually contain everything yeast needs apart from sufficient zinc. Worts made with sugar adjuncts can be deficient in some nutrients, so yeast food is required. Adding yeast food at the end of the boil ensures it is sterile at the start of fermentation. The nutrients it contains are usually unaffected by heat.

Acids and sour wort are used to adjust pH. Phosphoric acid might be used in some high gravity or high adjunct worts, which can suffer from a deficiency of phosphate. Lactic acid or sour wort is thought by some brewers to produce a smoother tasting beer than those acidified with mineral acids or high levels of calcium.

Antifoam is used to reduce foaming in the kettle. Foaming can lead to a loss of bitterness and some feel a reduction in foam stability.