Designing antioxidant-rich functional breads: The role of fruit and vegetable fortification and sourdough...

Bread fortification with fruit- and vegetable-derived ingredients has emerged as a promising strategy to enhance the antioxidant potential of a widely consumed staple food. However, increases in total phenolic content (TPC) and in vitro radical-scavenging activity do not necessarily indicate improved physiological antioxidant delivery. This review examines fruit- and vegetable-fortified breads as carriers of antioxidants, with emphasis on bioaccessibility, processing-induced transformations, and the role of sourdough fermentation as a modulatory bioprocess. Current evidence on how ingredient form (e.g., juice, powder, pomace, peel), cereal matrix interactions, fermentation conditions, and baking parameters influence the release, transformation, stability, and gastrointestinal accessibility of phytochemicals are addressed. Particular attention is given to the distinction between antioxidant content, extractability, bioaccessibility, and bioefficacy, as well as to methodological limitations associated with common spectrophotometric assays. Sourdough fermentation is discussed as an enabling factor that can enhance antioxidant delivery through acidification, enzymatic hydrolysis, structural modification of cereal polymers, and microbial biotransformation of phytochemicals, while also interacting with technological and sensory quality. Finally, key research gaps are identified, including the need for harmonized analytical protocols, compound-specific tracking after digestion, and translational/clinical validation of functional claims. This review proposes an integrated framework for the development and evaluation of antioxidant-enriched breads with improved functional relevance.