How to recruit microbes for sourdough baking
Michael Gänzle, University of Alberta, Edmonton, Canada.
Humans have used microbes for production of steamed or baked leavened goods since the onset of agriculture about 14,000 years ago. Increased interest in sourdough use by industrial, artisanal and amateur bakers in the past decade also stimulated research activity to understand the assembly of microbial communities in sourdough and their impact on bread quality. Currently, detailed information on the community structure of more than 400 sourdoughs and their use in baking is available (1). Spontaneous fermentations of cereals are dominated by plant-associated bacteria, e.g. Lactiplantibacillus, Levilactobacillus or Weissella species. Long-term propagation of sourdoughs, which is done in most bakeries, recruits bacteria from intestinal communities in insect hosts (Fructilactobacillus sanfranciscensis) or animal hosts (Limosilactobacillus spp. and Lactobacillus spp.). In contrast to sourdough bacteria, sourdough yeasts show signs of domestication (2).
Wheat and rye sourdoughs that are used as sole leavening agent have a consistent composition worldwide that in a majority of sourdoughs includes F. sanfranciscensis and K. humilis. The main contribution of these microbes is production of CO2 and acids. K. humilis also produces flavor volatiles; F. sanfranciscensis accumulates glutathione which modulates gluten quality. Sourdoughs that are used industrially as baking improvers in conjunction with baker’s yeast often include a combination of Lactobacillus and Limosilactobacillus species; these sourdoughs make only a limited contribution to dough leavening but contribute taste-active amino acids and peptides, antifungal metabolites, texture-forming polysaccharides and, in specific cases, extracellular fructan degrading enzymes. Most lactobacilli grow in sourdough; the use of defined strains as inoculum can therefore recruit the entire metabolic potential of lactobacilli for improved bread quality.
Dr. Michael Gänzle is Professor and Canada Research Chair in Food Microbiology and Probiotics in the Department of Agricultural, Food and Nutritional Science of the University of Alberta, Edmonton, Canada. Prior to coming to Canada, Dr. Gänzle received his training at the University of Hohenheim, Stuttgart, Germany and the Technical University of Munich, Germany. He is co-editor of German- and English-language books on Sourdough Biotechnology, serves as Associate Editor of “Frontiers in Microbiology” and is member of the editorial board of “Food Microbiology”, “Applied and Environmental Microbiology”, and “International Journal of Food Microbiology”.
His research interests include the characterisation of lactic acid bacteria for use as starter cultures or probiotics in food and has been active in the field of sourdough for more than 20 years. His research program addresses the questions “how does bread technology impact the microbial ecology of sourdough?” and “how does microbial metabolism impact bread quality?”
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