Methods, processes and wort compositions related to vicinal diketone evolution and especially diacetyl formation in brewing

A method for predicting late fermentation production of diacetyl in a brewing process comprises determining the ratio of FAN (free amino nitrogen content) to sugar (fermentable) to gravity in an initial wort composition. In addition there is provided a process for preventing incipient late fermentation production of diacetyl in a brewing process, comprising measuring and variously adjusting the initial FAN, sugar and gravity of the wort such that the ratio 1 [ f . sugar ( g / L ) ] initial [ FAN ( g / L ) ] initial [ Gravity ( °P ) ] initial , (g f.sug /g FAN /°P) for the adjusted wort has a value of 37 or less.