ABSTRACT
The presented is a quantitative study of aromatic substances-carbonyl compounds: acetoin, glyoxal, methylglyoxal, diacetyl, acetaldehyde, propanal, isobutanal, isopentanal, hexanal in pre-ferment and in sour dough. During fermentation of pre-ferment and sour dough, L. bulgaricus produces greater quantity of acetaldehyde compared to L. brevis, L. casei and L. plantarum. It has been found that L. bulgaricus produces high quantity of acetaldehyde from the threonine amino acid during fermentation of pre-ferment and sour dough. Alongside, the threonine amino acid contributes to the increase of aromatic substances: acetoin, methylglyoxal, diacetyl, propanal, isobutanal, isopentanal, hexanal.