The Influence of Guar Gum on Lipid Emulsion Digestion and Beta-Carotene Bioaccessibility
A better understanding of how dietary fibres impact the bioavailability of fat-soluble nutrients and nutraceuticals is required. The purpose of this research was to determine the influence of guar gum (GG) on the transfer processes impacting beta-carotene (BC) bioaccessibility (transfer to the aqueous phase) from an oil-in-water emulsion using an in vitro model simulating gastric and duodenal digestion. Canola oil emulsions (1.5 % soy protein isolate, 10 % canola oil and 0.1 % all trans BC, D4,3~160 nm) were prepared by microfluidization (40 MPa, 4 passes) and exposed, in the presence of 0.0, 1.0, 1.5, 2.0, or 4.0 % GG, to conditions representative of the stomach and duodenum in the fed state. Lipolysis, BC bioaccessibility, digestate apparent viscosities, droplet size, and bile acid (BA) binding were studied. With increasing concentration of GG, digestate viscosity was increased and lipolysis and bioaccessibility were decreased (P<0.05). Peak lipolysis was 56.2% vs. 21.6% for emulsions containing 0.0 % vs. 4.0 % GG, respectively. BC bioaccessibility was also lower in the presence of GG (i.e. 29.7 vs. 6.98 % for 0.0 vs. 4.0 % GG respectively). Thus, the presence of GG impacted digestive processes central to BC absorption. The impact of GG may be related to increased digestate viscosity entrapping mixed micelles or BAs and decreasing diffusion leading to decreased lipolysis and BC bioaccessibility.