Beer was treated with 2,4 dinitrophenyl hydrazine and the carbonyl derivatives were extracted with chloroform then with ethyl acetate. These extracts were poured on Celite ethanolamine columns and fractionated wtih 1% pyridine in benzene. Each of the fractions was streaked on a 250 um silica gel plate with a reference spot of butter yellow and developed in butyl acetate : dioxan : decalin : formamide (30:30:40:4), benzene : ethyl acetate : petroleum ether (34:1:5) and toluene (100%). After development the plates were dried and visualized on a blotter with diethylamine. Brewing raw materials, wort and beer were examined for the content of these carbonyl derivatives. All were found in one or more of the raw materials; 9 of them increased from the pitched wort stage and malonaldehyde, p toluoaldehyde and 6 methyl 5 hepten 2 one increased when the beer was aged. Malonaldehyde imparts a stale cardboard like character to beer and is probably derived from the autoxidation of methyl linolenate. p Toluolaldehyde which imparts a spicy flavour is present in the raw materials, especially maize, and increases throughout fermentation and in the ageing of the beer. Lists are given I of the sources of these compounds, II of their structure, MP, Rb values and colour with diethylamine, III of their aroma and of their flavour in beer, and finally IV of carbonyls whose concentration in beer increases with oxidation and staling.
Keywords: beer carbonyl compound flavour maturation