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

## TL;DR

This paper explores sourdough fermentation practices across Europe through a citizen science project, revealing how baking habits and motivations vary by location and baker type.

## Contribution

The study introduces a co-designed citizen science framework for collecting sourdough fermentation data and motivations across Europe.

## Key findings

- Professional bakers use older, more frequently refreshed starters and higher fermentation temperatures than household bakers.
- Baking motivations and ingredient choices vary by country, influenced by perceived health benefits.
- The initiative created a microbial biobank and harmonized metadata resource for future research.

## Abstract

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.