ABSTRACT Clean‐label demands are shifting bread preservation from chemical additives to biological approaches. Our prior work showed that a co‐fermented F. sanfranciscensis (LAB)– Propionibacterium freudenreichii (PAB) sourdough improves shelf life and quality at low inclusion level; however, longer distribution may require higher additions whose impacts are not well defined. Accordingly, we tested 5%–50% inclusion level to map dose–response relationships linking organic acids, fermentation quotient (FQ), and pH to processing performance, loaf structure, texture, storage‐related staling, and antifungal outcomes. Organic acids increased monotonically with inclusion level (e.g., lactic increased by 95% and propionic by 69% at 50% relative to 5%); FQ rose from 2.5 (5%) to 3.6 (50%), whereas pH declined from 4.6 (5%) to 3.0 (50%). Loaf structure exhibited a clear optimum at 20%: Specific volume was 17% higher than at 5%, the height‐to‐diameter ratio was 13% higher, and baking loss was lowest at ≤20% but increased at higher levels. During refrigerated storage at 4°C, 10%–20% inclusion level best preserved moisture, slowed staling (smaller hardness increase), and yielded a lower Day‐7 retrogradation enthalpy (Δ H 2.6 vs. 3.2 J g −1 at 50%). Antifungal protection strengthened with inclusion level: at a 150 CFU g −1 threshold, visible mold appeared on Day 5 (5%), Day 7 (10%–15%), Day 9 (20%), Day 11 (25%–30%), Day 13 (35%–45%), and Day 15 (50%). Overall, an inclusion level near 20% provides a practical operating window that balances preservation with processability and key instrumental quality attributes, whereas higher doses extend mold control further but may require mitigation (e.g., acid‐tolerant yeast and buffering) to limit quality losses associated with excessive acidification.
Wu et al. (2026) studied this question.