Evaluation of mono or mixed cultures of lactic acid bacteria in type II sourdough system

Various cold storage-backslopping cycles show the robustness of Limosilactobacillus fermentum IMDO 130101 as starter culture for Type 3 sourdough production

Type 3 sourdoughs, which are starter culture-initiated and subsequently backslopped, are less studied than other sourdough types. Yet, they can serve as a model to assess how competitive starter culture strains for sourdough production are and how the microbial composition of such sourdoughs may evolve over time. In the present study, Limosilactobacillus fermentum IMDO 130101 was used to produce Type 3 sourdoughs, prepared from wheat and wholemeal wheat flours. Therefore, an initial fermentation of the flour-water mixture was performed at 30 °C for 48 h. This was followed by cold storage-backslopping cycles, consisting of refreshments (50 %, v/v), fermentation steps of 16 h, and storage at 4 °C each week, every three weeks, and every six weeks. The microbial dynamics (culture-dependent and -independent approaches) and metabolite dynamics were measured. In all sourdoughs produced, starter culture strain monitoring, following an amplicon sequence variant approach, showed that Liml. fermentum IMDO 130101 prevailed during one month when the sourdoughs were refreshed each week, during 24 weeks when the sourdoughs were refreshed every three weeks, and during 12 weeks when the sourdoughs were refreshed every six weeks. This suggested the competitiveness and robustness of Liml. fermentum IMDO 130101 for a considerable duration but also showed that the strain is prone to microbial interference. For instance, Levilactobacillus brevis and Pediococcus spp. prevailed upon further cold storage and backslopping. Also, although no yeasts were inoculated into the flour-water mixtures, Kazachstania unispora, Torulaspora delbrueckii, and Wickerhamomyces anomalus were the main yeast species found. They appeared after several weeks of storage and backslopping, which however indicated the importance of an interplay between LAB and yeast species in sourdoughs. The main differences among the mature sourdoughs obtained could be explained by the different flours used, the refreshment conditions applied, and the sampling time (before and after backslopping). Finally, the metabolite quantifications revealed continued metabolite production during the cold storage periods, which may impact the sourdough properties and those of the breads made thereof.

Effect of selected strains on physical and organoleptic properties of breads

The use of selected Saccharomyces cerevisiae PS7314, Lactobacillus rossiae NOS7307, Lactobacillus brevis NOS7311, and Lactobacillus plantarum NOS7315 as mono-culture or co-culture for production of sourdoughs, their breads showed different physical and organoleptic properties. The pH of breads fermented with sourdoughs incubated with mono-culture or co-culture all decreased. An opposite trend was found for TTA. The use of single lactobacillus for the dough fermentation decreased the specific volume of bread, which was 4.15-19.10% lower than that of control bread (CB). However, the synergetic fermentation helped the improvement of bread quality. Compared to CB, the mixed culture 4 sourdough remarkably decreased the hardness by 52.08%, increased the specific volume by 5.29%, improved porosity of final product by 24.90%, and gave a preferable sensory characteristic to bread. Thus, the MC4 could be recommended for replacing spontaneous sourdough for improving the quality of bread.