Sourdough production: fermentation strategies, microbial ecology, and use of non-flour ingredients

Abstract

Sourdough production is an ancient method to ferment flour from cereals for the manufacturing of baked goods. This review deals with the state-of-the-art of current fermentation strategies for sourdough production and the microbial ecology of mature sourdoughs, with a particular focus on the use of non-flour ingredients. Flour fermentation processes for sourdough production are typically carried out by heterogeneous communities of lactic acid bacteria and yeasts. Acetic acid bacteria may also occur, although their presence and role in sourdough production can be criticized. Based on the inoculum used, sourdough productions can be distinguished in fermentation processes using backslopping procedures, originating from a spontaneously fermented flour-water mixture (Type 1), starter culture-initiated fermentation processes (Type 2), and starter culture-initiated fermentation processes that are followed by backslopping (Type 3). in traditional recipes for the initiation and/or propagation of Type 1 sourdough productions, non-flour ingredients are often added to the flour-water mixture. These ingredients may be the source of an additional microbial inoculum and/or serve as (co-)substrates for fermentation. An example of the former is the addition of yoghurt; an example of the latter is the use of fruit juices. The survival of microorganisms transferred from the ingredients to the fermenting flour-water mixture depends on the competitiveness toward particular strains of the microbial species present under the harsh conditions of the sourdough ecosystem. Their survival and growth is also determined by the presence of the appropriate substrates, whether or not carried over by the ingredients added.

A Review on Factors Influencing the Fermentation Process of Teff (Eragrostis teff) and Other Cereal-Based Ethiopian Injera

“…Sourdough should be considered a unique and stressful ecosystem with variable carbohydrate concentrations, an acidic environment, limited oxygen availability, and higher counts of LAB with 10 8 colony-forming units per gram (CFU/g) than yeasts (10 7 CFU/g), resulting in a LAB to yeast ratio of 10 : 1 to 100 : 1 [ 57 ]. The sourdough microbiota's metabolic influences include acidification (LAB), taste production (LAB and yeasts), and leavening (yeasts and heterofermentative LAB species).…”

Use of the β-Glucan-Producing Lactic Acid Bacteria Strains Levilactobacillus brevis and Pediococcus claussenii for Sourdough Fermentation—Chemical Characterization and Chemopreventive Potential of In Situ-Enriched Wheat and Rye Sourdoughs and Breads

“…The use of lactic acid bacteria (LAB) as starter cultures in sourdough fermentation has a long tradition in the production of baked goods such as wheat or rye breads. The main advantages of the use of sourdoughs and LAB as starters in the fermentation process are the positive effects on shelf-life and structural as well as sensory properties of the resulting breads [ 1 , 2 , 3 ]. During sourdough fermentation, the LAB form exopolysaccharides (EPS), which improve the water holding capacity and rheological properties of the doughs as well as the texture of the resulting breads [ 1 , 4 , 5 , 6 ].…”

Evaluation of the variations in chemical and microbiological properties of the sourdoughs produced with selected lactic acid bacteria strains during fermentation

“…Sourdough is a mixture of flour and water that is fermented by a microbial ecosystem mainly including lactic acid bacteria (LAB) and yeasts ( De Vuyst et al, 2021 ). Sourdough microbiota determines bread characteristics in terms of acid production, leavening and aroma ( Gänzle and Zheng, 2019 , Moroni et al, 2009 ).…”

“…Back-slopping is the addition of flour and water mixture inoculum that is fermented at a defined temperature for a certain time to begin the fermentation of a new mixture of flour and water ( Corsetti, 2013 ). Type I sourdough production process is conducted daily by back-slopping that keeps LAB and yeasts in a metabolically active state ( Arora et al, 2021 , De Vuyst et al, 2021 ). Biochemical transformations that occur during sourdough fermentation as a result of the metabolic activities of LAB and also yeasts, improve the functional properties of the dough and final bread ( Boyaci Gunduz and Erten, 2019 , Gobbetti et al, 2019 ).…”