Biochemical characteristics and breadmaking performance of freeze-dried wheat sour dough starters

Four mixtures (I–IV) of pure yeasts (Sacharomyces cerevisiae, S.fructuum andCandida boidinii) and/or lactobacilli (Lactobacillus brevis andL.plantarum) were inoculated into wheat sourdoughs, which after 18 h fermentation time were freeze-dried and used as starters (DS). Before their addition to wheat doughs they were rehydrated and reactivated. Besides DS (20% flour basis), bread dough contained instant active dry yeast (0.6%). Biochemical characteristics (production of organic acids, evolution of sugars and headspace composition), and breadmaking performance (fermentative and rheological properties and bread quality) of these doughs were investigated and compared with control doughs (C) without DS. Doughs with DS showed lower gassing power, and pH, and higher total titratable acidity (TTA) than C. The dough level in the maturogram reached maximum values for C and DS (IV) with only lactic acid bacteria. Doughs with DS (IV) also led to lower values for extensibility, and higher resistance to extension in the extensigram. The dynamics of glucose and fructose were faster during fermentation of doughs with DS than for C. The lactic and acetic acid levels were higher in DS-containing doughs, but ethanol and ethyl acetate contents were greater for C. Some bread characteristics (volume, density, pH, TTA, organic acids and sugar contents) were similar for all DS samples, and, except for sugars, significantly differed from those of C. Generally, sensory bread scores were higher for DS breads than for C, mainly for loaf shape, volume, edibility and overall acceptance. Starters I and IV, with the same composition of lactobacilli, showed a similar performance over starters II, III, and C.