SYNTHESIS OF AROMA COMPOUNDS BY WORT ENTEROBACTERIA DURING THE FIRST STAGE OF LAMBIC FERMENTATION

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Abstract
Lambic is a special type of Belgian beer obtained by a spontaneous fermentation. The fermentation is initiated by a growth of enterobacteria and non-maltose fermenting yeasts. These organisms die off after one to two months. To gain a clear insight in the relations between the enterobacteria and the aroma compounds formed in wort during this first period, several bacterial isolates were studied with respect to their metabolites formed in a synthetic medium and in two different lambic worts, using aerobic or semi-anaerobic conditions. The results showed that enterobacteria, especially Enterobacter species, are responsible for the production of 2, 3-butanediol, acetic, lactic and succinic acid and lower amounts of ethyl acetate and higher alcohols which are the main aroma compounds found in 1 to 2 months old lambic. Ethanol production is mainly due to yeast activity. The results are in agreement with previous determinations of entero-bacterial species present in first phase lambic18.