Relationships between physico-chemical properties and colonic fermentation in pea fibre and protein

Doktorsavhandling, 2025

Heightened consumption and production of plant-based foods increases the amount of dietary protein reaching the colon. Excessive colonic fermentation of protein by the gut microbiota produces toxic metabolites. The demand for plant proteins results in larger amount of side-streams. One such side stream is pea hull fibres, which are generated during the extraction of pea proteins. Pea hull fibres need to be modified to improve their physico-chemical properties and their utilisation as food components. Modifications of pea hull fibres and pea protein can also affect how they are fermented in the colon.
The aim of this thesis is to explore how modifications of pea hull fibre and pea protein can prompt changes in their physico-chemical properties and in vitro colonic fermentation. Thermal and enzymatic treatments were applied to pea hull fibres and pea protein. The effect of these processes was studied through compositional, physical and rheological changes. Subsequently, colonic fermentation of modified fibre and protein was investigated using in vitro batch fermentation, and evaluated through the microbial and metabolic responses.
Enzymatic treatment of pea hull fibre by pectate lyase induced differences in cell wall structure and rheological properties. The rheological behaviour of the pea hull fibres could be predicted using soft particle models. Modifications to pea hull fibres did not alter the metabolite production during in vitro colonic fermentation. However, changing the pea protein degree of hydrolysis induced changes in the metabolic response and clear differences in the microbial community. Higher degree of hydrolysis of the pea protein resulted in a microbiota similar to those found during pea hull fibre fermentation. Combined fibre and protein fermentation gave higher fraction of healthy metabolites compared to pure protein fermentation, but also increased proteolytic fermentation products. Overall, changes in physico-chemical properties can be related to differences in colonic fermentation outcome, but is dependent on substrate and treatment.