Microbiological and Fermentative Properties of Baker's Yeast Starter Used in Breadmaking

Abstract

This study assessed the levels of microbial contaminants in liquid, compressed and dry commercial baker's yeasts used as starters in breadmaking. Eumycetes, Enterobacteriaceae, total and fecal coliforms, Bacillus spp., and lactic acid bacteria (LAB), in particular enterococci, were quantified. Results obtained in this study highlighted that baker's yeast could represent a potential vehicle of spoilage and undesirable microorganisms into the baking environment, even if these do not influence the leavening activity in the dough, as ascertained by rheofermentometer analysis. Different microbial groups, such as spore-forming bacteria and moulds, were found in baker's yeast starters. Moreover, different species of LAB, which are considered the main contaminants in large-scale yeast fermentations, were isolated and identified by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rDNA sequencing. The most recurrent species were Lactobacillus plantarum, Enterococcus faecalis, and Enterococcus durans, isolated from both compressed and dry starters, whereas strains belonging to Leuconostoc and Pediococcus genera were found only in dry ones. Nested-Polymerase Chain Reaction (Nested-PCR) and Randomly Amplified Polymorphic DNA-PCR (RAPD-PCR) were also used to highlight the biodiversity of the different commercial yeast strains, and to ascertain the culture purity.

Sourdough microbial community dynamics: An analysis during French organic bread-making processes

“…Finally, the microbial composition of the community may affect the microbial counts, as suggested by the low counts of yeasts in presence of T. delbrueckii observed for Bakery 1 and also in a Belgium sourdough (Scheirlinck et al, 2007). The consequences of a low count are not well documented, but may not be a low leavening ability (Reale et al, 2013). We also found count variations during the bread-making process but this variations were ten times lower than between breadmaking runs.…”

Sub-optimal pH Preadaptation Improves the Survival of Lactobacillus plantarum Strains and the Malic Acid Consumption in Wine-Like Medium

“…However, other LAB species, mainly Lactobacillus plantarum , are frequently found in wine (Cañas et al, 2009; Ruiz et al, 2010; Iorizzo et al, 2016). Strains belonging to this species are widely diffused and often isolated from different environmental niches such as grape, must, wine, dairy, bakery, and probiotic products (Beneduce et al, 2004; Ribéreau-Gayon et al, 2006; Cañas et al, 2009; Ruiz et al, 2010; Reale et al, 2011, 2013; Ricciardi et al, 2014; Succi et al, 2014; Testa et al, 2014). In wine, apart from the aptitude to cope with stress conditions, mainly represented by high alcohol concentration and low pH (Spano and Massa, 2006; López et al, 2008; Miller et al, 2011), some Lb.…”

Metabolite Analysis Allows Insight into the Differences in Functionality of 25 Saccharomyces cerevisiae Strains in Bread Dough Fermentation

“…Several parameters are mentioned as favorable characteristics for baker's yeast, namely, 1) high biomass yield (for propagation in molasses), 2) short lag phase before starting the fermentation, 3) fast fermentation, 4) contribution to the favorable aroma of the end product, 5) ability to ferment several disaccharides such as melibiose (propagation in molasses), sucrose, and maltose (fermentation in dough), 6) ability to tolerate the stress conditions in fermenting dough such as low water activity, salt, and osmotic stress, 7) freezing, drying, and rehydration tolerance, and 8) organic acid resistance (Oda and Ouchi 1989;Benitez et al 1996;Walker 1998;Dequin 2001;Giannone et al 2010;Reale et al 2013).…”