Modelling of the activity of selected starters during sourdough fermentation

In this paper, a central composite design has been applied to evaluate, by means of empirical modelling of the data, the importance of dough yield, NaCl, type of wheat flour, as well as fructose and citrate addition, on the growth and fermentative activity of mixed sourdough starters made by selected lactic acid bacteria and yeast. The dough yield variable was important in increasing yeast and lactic acid bacteria growth. The stimulating effect of NaCl on yeasts can be indirectly attributed to a reduction in competition with lactic acid bacteria for the available sugar. The latter were in turn inhibited by NaCl above a certain threshold level. Citrate and fructose modification can be used to optimize the relative ratios of acetic and lactic acids. This preliminary work considered neither microstructural rheological features of the dough, nor bread organoleptic properties. However, the results confirmed the key role of some ingredients in the interaction among the sourdough starters and in the regulation of their metabolism. (C) 1997 Academic Press Limited.