MIXED-CULTURE PRE-FERMENTS OF LACTIC AND PROPIONIC-ACID BACTERIA FOR IMPROVED WHEAT BREAD SHELF-LIFE

The mould-free shelf-life of wheat bread was prolonged by natural propionic acid fermentation in pre-ferments. The effects of pre-fermentation temperature and time, the type of flour and the combination of lactic and propionic acid bacteria on acid formation and wheat bread properties were investigated. Further, the effects of both acids in pre-ferments on the function of yeast in dough, as measured by leavening capacity, were studied. The acids formed during pre-fermentation typically decreased yeast-leavening capacity, especially in the early stages of leavening. The baking procedure with the pre-ferment resulted in a slightly sour wheat bread, with a pH of about 5·4 to 6·0, a titratable acidity value of about 3·9 to 5·6 and an acceptable lactic to acetic acid ratio for sour bread baking. Bread mould-free time was increased up to 10 days. © 1993 Academic Press. All rights reserved.