A pilot plant for different types of boiling was introduced within the context of a diversified research program. The experiments performed first comprised on a pilot scale the use of different temperatures in barometric external boiling (104-degrees-C, 107-degrees-C and 110-degrees-C) with evaporation figures varying from 3 - 15%. The results were as follows: The Strecker aldehydes 2-methyl-butanal and 3-methyl-butanal do indeed evaporate during wort boiling, however, they are formed increasingly when the boiling intensity rises. The situation is similar in the case of Maillard products such as 2-furfural and 2-furfural-OH. 1-hexanol is given off when boiling and is not formed anew. The nitrogen heterocyclenes are dependent on both thermal stress as well as the evaporation figure. The flavour of the beer was more favourable in the case of brews boiled at a temperature with a higher evaporation figure. Here there ie a parallel to the ester contents of the beer (acetic acid-hexyl-, -heptyl- and -octylester). These findings were confirmed by large-scale experiments in which double-bottom vessels require an overall hogher evaporation (11%) than an external boiler (approx. 8%). Insufficient evaporation gives the beer an unattractive husk or wort taste and a somewhat broader bitterness. It was also possible to derive an influence of boiling intensity on the flavour stability of the beer.
