Rising together: exploring sourdough fermentation diversity through co-design in the HealthFerm citizen science initiative

Fermented foods are culturally significant and increasingly recognised for their potential health benefits, yet scientific data on household fermentation practices remain limited. We launched a co-designed citizen science (CS) initiative within the HealthFerm project to collect information about the diversity of sourdough fermentation practices implemented at the household level across Europe, how these practices vary by location and baker demographics, and their relationship with baking motivations and attitudes. This manuscript describes the citizen science survey results, as a resource for evaluating sourdough baking practices and motivations across Europe. Over 1000 participants from 33 countries registered, with 671 samples submitted. Participants also completed standardised at-home experiments and sensory evaluations, generating a dataset linking baking habits with physicochemical and sensory profiles. Distinct patterns emerged: professional bakers used older, more frequently refreshed starters and fermented at higher temperatures than household bakers. Ingredient choices and motivations varied by country, shaped by perceived health benefits. Beyond fermentation practice data collection, this initiative established a microbial biobank and harmonised metadata resource, while offering practical insights into co-design, logistics, and public engagement. The resulting framework provides a transferable model for participatory research in microbiology and food systems science.