The influence of processing on the bio-accessibility of Ferulic acid from cereal dietary fibre

Ferulic acid (FA) is the predominant phenolic acid in cereal grains and is mainly present in a covalently bound form within the cell wall matrix, which severely limits its release, bioaccessibility and subsequent bioavailability. This thesis aimed to develop processing strategies to enhance the liberation of FA from cereal dietary fibre, to characterise its behaviour during gastrointestinal digestion and transepithelial transport, and to investigate the downstream effects of FA-rich cereal products on the gut microbiota and short-chain fatty acid (SCFA) production.
A systematic review of the literature identified bioprocessing as the most effective single strategy for enhancing FA release and highlighted the potential of combining thermal and enzymatic treatments. Guided by these insights, a series of cereal-based biscuit formulations were developed using thermal pretreatment and commercial enzyme, and their FA content and matrix structure were characterised. The fate of FA during digestion was then assessed using a standardized semi-dynamic in vitro digestion model, coupled with an ex vivo Ussing chamber system to examine transepithelial transport across intestinal tissue. Finally, upper intestinal digesta were subjected to in vitro faecal batch-culture fermentation to evaluate colonic metabolism, microbiota composition (16S rRNA sequencing) and SCFA profiles.
The combined thermal and enzymatic treatments substantially increased FA release from the cereal matrix and improved its bioaccessibility in the upper intestinal phase, with evidence for enhanced transepithelial transport. However, partial depolymerisation of the fibre matrix in enzyme-treated biscuits altered fermentation patterns and resulted in distinct microbiota and SCFA profiles compared with control biscuits containing more intact cereal fibre. Together, these findings demonstrate that targeted processing can effectively enhance FA availability from cereal foods but also modulates the functional properties of the residual fibre. The work provides a mechanistic basis and practical framework for designing cereal-based products that optimise FA delivery while maintaining beneficial fibre–microbiota interactions and lays the groundwork for future mechanistic and clinical studies in human populations.