Abstract
Sourdough fermentation, one of the oldest biotechnological processes in food production, has reemerged as a valuable tool to improve the nutritional, functional, and sensory quality of cereal based baked goods while contributing to sustainability. Through the metabolic activity of lactic acid bacteria and yeasts, sourdough fermentation enhances dough rheology, aroma complexity, and the bioavailability of bioactive compounds. However, limited information exists on the exploitation of probiotic starter cultures and the use of emerging cereals such as Tritordeum to improve the functional and physiological relevance of bread. The first part of this PhD research focused on developing a next-generation probiotic sourdough using a defined LAB consortium composed of Lactiplantibacillus plantarum DSM33363 and DSM33364 Lacticaseibacillus paracasei DSM33373, and Limosilactobacillus reuteri DSM33374 in Type IV sourdough fermentation, this consortium produced breads with significantly higher in vitro protein digestibility (IVPD) (up to 77.4%) and a lower predicted glycaemic index (pGI) (as low as 64.5%) than baker’s yeast control bread. Importantly, the nutritional indices, including essential amino acid index, biological value, protein efficiency ratio, and nutritional index were comparable to those of Type II sourdough breads prepared with traditional starters, and higher than baker’s yeast bread. Fermentation with the probiotic consortium also generated a more diversified volatile profile, highlighting its potential to improve both functionality and aroma. To extend the scope of sourdough biotechnology beyond probiotic starter suitability, the second study addressed the nutritional and microbiological impact of sourdough fermentation in Tritordeum-bran composites. Compared to baker’s yeast Tritordeum bread, the bran-enriched sourdough bread showed higher levels of total dietary fiber including soluble and insoluble fiber, total phenolic compounds, radical scavenging activity, β-glucans, arabinoxylans, and free amino acids, together with improved IVPD and reduced pGI. Targeted phenolic profiling further revealed increased concentrations of protocatechuic, ferulic, and vanillic acids, confirming the contribution of bran and sourdough fermentation to enhanced phenolic bioavailability. Further, the impact of Tritordeum sourdough breads with or without bran on colonic microbiota was evaluated in vitro using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®). Application of sourdough bread digesta in the SHIME® model enhanced short-chain fatty acid production, with bran-based sourdough bread sustaining higher butyrate level, while sourdough bread without bran and Tritordeum baker’s yeast bread favored acetate- and propionate accompanied by bifidogenic shifts in microbial composition and diversity. Finally, the third study investigated the technological implications of Tritordeum bran addition. Starter-assisted sourdough fermentation markedly improved dough stability, viscosity, and extensibility, yielding bread with higher loaf volume, softer crumb, and delayed staling. These improvements confirm the dual role of sourdough fermentation in conferring both functional and technological advantages to breadmaking. Altogether, the findings of this thesis demonstrate that the integration of functional probiotic starters, Tritordeum flour, and bran valorization within sourdough biotechnology leads to the bread making with enhanced nutritional and functional value while selectively altering the gut microbiota, establishing sourdough fermentation as a promising and sustainable approach for developing next-generation functional foods.