Reference Number: 91
Sourdough bread is a traditional product with great potential. This can only be achieved if the interactions between the lactic acid bacteria and yeasts that populate the sourdough are understood. Associations of yeasts and lactic acid bacteria (LAB) are often encountered or used in the production of beverages and fermented foods. Wheat and rye sourdoughs are ecosystems where fundamental interactions between LAB and yeasts take place. Studies on sourdoughs are also helpful for understanding relationships between LAB and yeasts in foods such as kefir, cheese, wine, cider and sausages.
This review focuses on the trophic and non-trophic interactions between sourdough LAB and yeasts based on the metabolism of carbohydrates and nitrogen compounds, the production of CO2 and other volatile compounds, and on the antimicrobial activity.
Lactobacilli, obligately homofermentative and facultatively or obligately heterofermentative, are the typical sourdough LAB. Lactobacillus sanfranciscensis (synonym Lb. brevis subsp. lindneri), Lb. plantarum and Lb. brevis are the most frequently isolated lactobacilli. Some strains, initially classified as Lb. brevis, were recently allotted to the new species Lb. pontis. Leuconostoc sp. and Enterococcus sp. are occasionally found or used in sourdough processes. Several species of yeasts are found in sourdoughs; Saccharomyces cerevisiae is frequently present or is added. The amount of S. cerevisiae may be overestimated due to the lack of reliable systems for identifying and classifying yeasts from this habitat. In particular S. exiguus (imperfect state Torulopsis holmii or Candida holmii, physiologically similar to C. milleri), and C. krusei, Pichia norvegensisand Hansenula anomala are yeasts associated with LAB in sourdoughs. The LAB:yeast ratio in sourdoughs is generally 100:1.
SIGNIFICANCE OF THIS STUDY
This study describes the types, functions and optimum growth conditions of the most common bacterial and yeast species present in sourdough. The study explains how the cooperative interactions between sourdough bacteria and yeast species help in promoting the sensory, nutritional and health properties of sourdough bread.