The relationship between fermentation variables and flavor volatiles by direct gas chromatographic injection of beer.

Barker, R.L., Irwin, A.J. and Murray, C.R.

Abstract
The use of a rapid analytical method for determining the volatile substances composition of beer samples directly injected into a gas chromatograph to study the relationship between varying fermentation parameters and beer flavour is described. Compared with the previously used procedure, the method is faster (1 hour rather than 8), simpler (since the samples need no preparatory treatment, not even filtration) and more comprehensive (since it includes ethyl acetate and acetaldehyde, which were not covered by the previous method, among the compounds determined). Fermentation parameters studied include temperature, wort oxygen level, pitching rate and yeast aging. It was found that increasing the fermentation temperature raised the concentrations of esters and higher alcohols in beer and lowered the acetaldehyde level. Variations in wort aeration and pitching rate appeared to have little overall effect. Pitching with yeast freshly propagated from a laboratory culture resulted in higher acetaldehyde and ethyl acetate concentrations than were found after some generations of propagation from the fermenter yeast crop.
Keywords : analysis beer fermentation flavour gas chromatography pitching yeast propagation temperature volatile compound