Response of wheat sourdough parameters to temperature, NaCl and sucrose variations Original Research Article

Fermentation temperature, NaCl level and sucrose level of a wheat sourdough were varied according to a Box–Behnken response surface design. The effect on yeast increase, lactic acid bacteria (LAB) increase and sourdough acidity was investigated. Yeast and LAB growth increased with temperature in the range from 15°C to 27°C. Optimum growth temperature of two Candida milleri strains, isolated earlier from the same sourdough as used in this study, was between 26°C and 28°C in pure culture. Decreasing temperature affected yeast growth to largely the same extent as LAB. Increasing NaCl addition had a negative effect on yeast growth throughout the range (0–3.2%). A low level of NaCl (up to 0.7%) stimulated LAB growth but higher levels decreased LAB growth drastically, and to a much greater degree than yeast growth. Sucrose addition had a stimulatory effect on both yeast and LAB growth. Sourdough TTA increased with sucrose addition throughout the range (0–6%) and was largely due to the increase in acetic acid accumulation.