MICROFLORA OF THE SOUR DOUGH OF WHEAT-FLOUR BREAD .14. CHANGES IN VOLATILE COMPOUNDS DURING FERMENTATION OF DOUGHS PREPARED WITH PURE MICROORGANISMS AND THEIR MIXTURES

Wheat doughs elaborated with microbial mass from Saccharomyces cerevisiae, Candida boidinii, Lactobacillus plantarum and Streptococcus faecium, individually and in up to 13 combinations have been investigated for: (a) changes during fermentation in short chain (C3-C6) volatile organic acids, and (b) headspace gas composition (alcohols, esters and carbonyl compounds) of fermented doughs. Lactic acid bacteria, when used individually, did not produce C3-C6 volatile organic acids, but when added to doughs with yeasts promoted an increase in propionic and isobutyric acids and a decrease in isovaleric acid concentration in relation to the amounts produced by the yeasts alone. n-Butyric and n-valeric acids were present in very low amounts that did not change during fermentation in any of the samples studied. The headspace gas from doughs with lactic acid bacteria contained very small amounts of volatile flavor compounds; diacetyl was the most relevant component. Yeasts had the same qualitative headspace composition, but they differed quantitatively. S. cerevisiae produced larger amounts of all the components than C. boidinii. Ethanol was the most abundant compound followed by acetaldehyde, n-propanol, hexanal+isobutanol and isoamyl alcohol. In general, the addition of lactic acid bacteria to dough with yeasts did not significantly modify the head-space flavor fraction. Doughs with both yeasts and lactic acid bacteria produced more ethanol than expected from the proportion of each yeast. When C. boidinii was inoculated in higher concentration (70%) than S, cerevisiae several components not detected in the other samples could be identified: isoamyl acetate, n-butanol, amyl acetate and n-pentanol. © 1990 Springer-Verlag.