Meyer, A. R.; Gettemans, T.; Tan, J. P.; Tucillo, F.; Viretto, C.; Angelescu, I.-R.; De Bondt, Y.; Neugebauer, M.; Zein Alabiden Tlais, A.; Cavelti, F.; De Vuyst, L.; Gobbetti, M.; Courtin, C. M.; Zamfir, M.; Coda, R.; Nystroem, L.; Weckx, S.; Bokulich, N. A.

Fermented foods are culturally significant and increasingly recognized 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 sourdough fermentation data across Europe. Over 1000 participants from 33 countries registered, with 671 samples submitted, enabling large-scale analysis of fermentation practices, motivations, and sourdough characteristics. Participants also completed standardized 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. Ingredient choices and motivations varied by country, shaped by perceived health benefits. Beyond data collection, this initiative established a microbial biobank and harmonized 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.