Sourdoughs as a function of their species diversity and process conditions, a meta-analysis

Background: Sourdough is a cereal flour-water mixture that is fermented by communities of yeasts and lactic acid bacteria (LAB) and that is used for the production of baked goods. Its use has been subject to a renewed interest in the past years. The classical classification concept of sourdoughs distinguishes two major types (I and II), based on the process conditions applied for their production. Scope and approach: In this study, both species diversity (LAB and yeasts) and processing conditions of sourdoughs were taken into account for the classification of sourdoughs. Therefore, a meta-analysis of such literature data on hundreds of backslopped sourdoughs is described. Key findings and conclusions: The meta-analysis agreed with the subdivision into Type I and Type II sourdoughs. In general, the number of prevalent yeast species in a given sourdough was lower than the number of prevalent LAB species. Also, a lower number of prevalent LAB and yeast species characterized the microbial species diversity of Type I sourdoughs compared to Type II ones. This could be attributed to the prevalence of Lactobacillus sanfranciscensis in sourdoughs of the former type. The process conditions impacted the yeast species diversity, as differences were found for the fermentation temperature, dough yield, and fermentation time between sourdoughs. No influence could be found concerning the region of origin, albeit that literature data reflected regionally important sourdoughs. (C) 2017 Elsevier Ltd. All rights reserved.