VOLATILE COMPOUND AND ORGANIC-ACID PRODUCTIONS BY MIXED WHEAT SOUR DOUGH STARTERS - INFLUENCE OF FERMENTATION PARAMETERS AND DYNAMICS DURING BAKING

Lactobacillus brevis subsp. lindneri CB1, Lactobacillus plantarum DC40 0 and Saccharomyces cerevisiae 141 or Saccharomyces exiguus M14 were u sed as starters to produce wheat sour dough breads. Sour doughs with h igher relative percentage of yeast fermentation products (1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol and ethanol) and with higher t otal peak area of volatile compounds, or with a more complete profile (higher amounts of ethylacetate and lactic and acetic acids, and the p resence of carbonyl compounds) were produced by the associations betwe en lactic acid bacteria (LAB) and S. cerevisiae 141 or S. exiguus M14, respectively. Low temperature (25 degrees C) and sour dough firmness (dough yield 135) were appropriate for LAB souring activities but limi ted yeast metabolism. Raising the temperature to 30 degrees C and semi -fluid sour doughs gave more complete volatile profiles. Flour ash con tent from 0.55-1% positively influenced the total amount of volatiles and lactic and acetic acid productions. While at 3 h the sour dough wa s mainly characterized by iso-alcohols, an increase of leavening time up to 9 h gave a total amount of volatiles about three times higher th an that at 5 h and strengthened the LAB contribution. The additions of fructose and citrate to the dough enhanced the acetic acid and volati le synthesis by LAB, respectively. After baking, the ethanol disappear ed, 2-methyl-1-propanal was synthetized, lactic and acetic acids remai ned constant, the total amount of volatiles was reduced to a level < 1 2.5% of the initial and an increase in the relative percentage of iso- alcohols and aldehydes was detected. The differences attributed to the two mixed starters were maintained after baking. A comparison between amino acid and volatile profiles before and after baking showed the i nfluence of amino acids on the formation of volatiles during baking. ( C) 1995 Academic Press Limited