Investigations on the Origin of Secondary Products of Alcoholic Fermentation

¹ Laboratoire d'Oenologie et Chimie Agricole, Faculté des Sciences. Bordeaux, France

It was already established that in alcoholic fermentation secondary products other than glycerol arise from the acetaldehyde resulting from the decarboxylation of pyruvic acid formed by the glyceropyruvic fermentation. The first object of our work was to verify, by establishing numerous balances of secondary products, under very diverse fermentation conditions, the exactitude of the empirical equations of formation of each of the secondary products starting from acetaldehyde. Next and particularly our goal was to specify the mechanisms of these empirical reactions and the nature of the intermediate terms. The problem was studied simultaneously by several procedures; investigation of relations, quantitatively as much as possible, between two or several facts, for example between the presence or addition of one substance and the formation of another or the blocking of a reaction; evolution of the content of acetaldehyde as a function of time or of certain determined conditions and relationships with other concentrations or other variations; consequences of the addition or suppression of such growth factors, which are involved in the constitution of enzymes known to be catalyzers of such reactions, upon the levels of secondary products. We see, for example, acetic acid influencing contents of very diverse substances, as an intermediate in the formation of succinic acid, by blocking the dismutation of acetaldehyde whence an increase in the level of butanediol finally as a precursor of acetylmethylcarbinol with regeneration. Or yet we see diacetyl coming into play as the precursor of acetylmethylcarbinol and of butanediol; in support of this interpretation our work brings numerous and significant facts; presence of traces of diacetyl in the fermentation and the influence of thiamine.