Exploring Physico-Chemical Properties and Colonic Fermentation of Pea Hull Fibre and Pea Protein Blends

Licentiatavhandling, 2023

Yellow pea (Pisum sativum L.) is a legume with high protein and dietary fibre content commonly used for human consumption. Yellow pea is consumed as it is but also used as part of food products, in form of protein concentrate, protein isolate, dietary fibre etc. The digestion and colon fermentation of ingested foods are dependent on factors, such as composition and interaction of macromolecules. Knowledge about how more complex mixtures of plant-based nutrients changes due to processing and how it affects colon fermentation are lacking. The aim of this thesis is to study pea hull fibre and pea protein blends and determine the effect of compositional differences and thermal treatment to in vitro colonic fermentation.

Rheology, microscopy, and zeta potential measurements were used to study technical function of pea hull fibre and pea protein blends. The fermentation products of the pea hull fibre and protein were studied using in vitro colonic fermentation, with determination of pH reduction, gas production and short chain fatty acid formation. Chemical characterisation of the pea fibres was determined using high performance anion exchange chromatography and uronic acid assay. Variables used in the study was ratio of fibre and protein, thermal exposure, and pH.  

Pea hull fibre content was dominated by glucose and uronic acid, believed to originate from cellulose and pectin like polysaccharides. Pea hull fibres and pea protein were largely insoluble, and the fibre particles were observed to be larger in size (98.4 μm) than the protein particles (19.2 μm). Thermal treatment (exposure at 95 ˚C for 30 minutes) of fibre and protein blends increased the storage modulus of the single components as well as their blends. The increase in storage modulus is attributed to swelling of particles, and not release of solubilised polysaccharides.  The in vitro colonic fermentation experiment showed that the products formed from the fibre and protein blends were affected by the ratio of fibre and protein. Treatment with heating only lead to small differences in the fermentation outcome. The results show that fibre and protein composition did affect rheological and in vitro fermentation outcome, but also highlights that changes can be observed due to thermal treatment.