Influence of oat components on lipid digestion using an in vitro model: Impact of viscosity and depletion flocculation mechanism. (October 2018)

• Record Type: Journal Article
• Authors: Grundy, Myriam M.L.; McClements, David J.; Ballance, Simon; Wilde, Peter J.
• Is Part Of: Food hydrocolloids. Volume 83(2018)
• Page Start: 253
• Page End: 264
• Publication Date: 2018-10
• Subjects: Oat β-glucan -- Flocculation -- Viscosity -- Molecular weight -- Lipolysis; BG1 oat β-glucan of high Mw -- BG2 oat β-glucan of medium Mw -- BG3 oat β-glucan of low Mw -- CFC critical flocculation concentration -- CVC critical viscosity concentration -- FFA free fatty acids -- Mw weight-average molecular weight -- Rh weight-average hydrodynamic radius -- WPI whey protein isolate; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2018.05.018
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: Depletion flocculation is a well-known instability mechanism that can occur in oil-in-water emulsions when the concentration of non-adsorbed polysaccharide exceeds a certain level. This critical flocculation concentration depends on the molecular characteristics of the polysaccharide molecules, such as their molecular weight and hydrodynamic radius. In this study, a range of analytical methods (dynamic shear rheology, optical microscopy, and static light-scattering) were used to investigate the interaction between lipid droplets and polysaccharides (guar gum and β-glucans) of varying weight-average molecular weight and hydrodynamic radius, and concentration. The aim of this work was to see if the health benefits of soluble fibers like β-glucans could be explained by their influence on the structure and digestibility of lipid emulsions. The apparent viscosity of the emulsions increased with increasing polysaccharide concentration, molecular weight, and hydrodynamic radius. Droplet flocculation was observed in the emulsions only at certain polysaccharide concentrations, which was attributed to a depletion effect. In addition, the water-soluble components in oat flakes, flour, and bran were extracted using aqueous solutions, to examine their impact on emulsion stability and properties. Then, the rate and extent of lipolysis of a sunflower oil-in-water emulsion in the presence of these oat extracts were monitored using the pH-stat method. However, the inhibition of lipolysis was not linearly related to the viscosity of the oat solutions. The water-soluble extracts of β-glucan collected from oat flakes had a significant inhibitory effect on lipolysis. The results of this study increase our understanding of the possible mechanisms influencing the impact of oat constituents on lipid digestion. This work also highlights the importance of considering the molecular properties of polysaccharides, and not just their impact on solution viscosity. Graphical abstract: The effect of oat and β-glucan on lipid digestion relies on complex mechanisms. Image 1 Highlights: Smaller β-glucans induce depletion flocculation over wider concentration range. β-glucan molecules occupied the bulk solution around the droplets and drove them together. Viscosity is not the only factor affecting depletion flocculation. Compounds released from oat flakes caused the greatest depletion flocculation. Lipolysis was reduced in the presence of oat flake extract solutions.