EFFECT OF BOILING ON THE COLOUR OF LABORATORY MALT WORTS

Abstract

Investigation of the effect of boiling on malt worts obtained In routine analysis using the Recommended Methods of the Institute of Brewing has indicated that an increase in colour of 50% may normally be expected. The presence of excess air up to a certain level will produce an increase in colour of some 75%, but air above this level has no further effect. If air can be excluded from the boiling wort the increase in colour can be diminished. Most of the colour increase takes place during the first hour of boiling. A broad relation appears to exist between the formation of colour and the permanently soluble nitrogen fraction; the ratio of permanently soluble to total soluble nitrogen is highest when the boiling takes place in excess air and lowest when air is excluded during the actual boil. Heating wort at 150° F. has the same effect on colour as boiling; subsequent boiling of heated wort can produce higher colours than boiling alone. The proportionate increase in colour is not Influenced by either the original colour or the specific gravity of the wort. It is concluded that the malt has little or no influence in determining colour increase, but that variations in the mashing process and in the handling of wort in the under- back, copper, hop-back and wort receiver are responsible for the wide range of colours which may be observed in beers made from the same malt.