How dried sourdough starter can enable and spread the use of sourdough bread

Sourdough production can be considered one of the oldest biotechnology processes because it has been used in bread manufacture for thousands of years. Today, sourdough baking involves the improvement of flavor, texture, and microbiological shelf-life of bread. Fermentations are based on the unique symbiosis of certain lactic acid bacteria and yeasts. Sourdough appreciation has grown worldwide, but mainly in artisanal bakeries due to the difficulties and costs of maintaining a live microbial culture (sourdough starter) in industries. To reduce the need for sourdough starter maintenance, researchers have evaluated drying techniques, such as freeze-drying and spray-drying, to preserve high fermentation capacity and cell viability after reconstitution. The main idea of the present review is to identify how drying processes can help to obtain a shelf-stable sourdough starter whose microorganisms are in an inactive state but could be reactivated at fermentation time. As drying technologies can strongly influence microbial viability, the flavor, and the shelf life of the final product, distinct specifications are required in each technique. Freeze-drying, for example, requires the presence of a cryoprotectant to prevent cell damage during the freezing moments. In spray-drying, the inlet and outlet temperatures are critical parameters that affect microorganism survival. The conditions and solvents used for dried powder rehydration are an important step to recover dried cells of the sourdough starter, as well as the starter activation before fermentation. Freeze-drying and spray-drying show great potential to increase the widespread use of sourdough on an industrial scale.