What irreversible change occurs when beer temperature exceeds 22-23°C (71-73°F)?

When beer temperature exceeds 22-23°C (71-73°F), one significant irreversible change is that finings lose their ability to coagulate. Finings are additives used in the brewing process to clarify the beer by binding with proteins and other particles, causing them to settle out and improving the clarity of the final product.

At elevated temperatures, the proteins may become more soluble and alter their behavior, which affects the effectiveness of finings. As a result, the finings may not be able to aggregate and settle out properly, leading to a beer that lacks clarity or is hazy. This change is considered irreversible because once the ability of the finings to coagulate is compromised due to temperature, they cannot regain their effectiveness even if the beer is subsequently cooled.

Understanding this phenomenon is crucial for brewers, as maintaining proper fermentation and conditioning temperatures is vital for achieving the desired quality in the final beer product.