• The time of boiling affects precipitation of coagulable nitrogen, pH, colour, utilisation of hops and flavour of beer.
• Total evaporation during the boil controls the elimination of volatile compounds some of which are deleterious.
Range of Values
• Boil time is usually between 45 mins and 1 hour 30 mins.
• Reduction in pH during boiling is typically 0·05 – 0·15 units
• Development of colour is typically 2 – 4° EBC
• The range of evaporation for cask conditioned beer across the industry is 3% – 12% but typically 7% – 9%.
• Boiling time and rate of evaporation should be kept constant for a particular brand.
• Boiling should be sufficiently vigorous to ensure flocculation of protein
There are several methods to measure the extent of evaporation which include:
Measuring the level of wort in the copper before and after boiling. The level should only be measured when conditions in the copper are flat calm. Measurements should be made at 100°C (212°F) or else allowances have to be made for expansion/contraction ot the wort.
Measuring changes in gravity of the wort. Because of the errors in hydrometer readings this method is only suitable for measuring high rates of evaporation.
Measuring the flow of steam during boiling using a steam integrator. This is the preferred method and is suitable for measuring all levels of evaporation.