The role of oil concentration on the rheological properties, microstructure, and in vitro digestion of cellulose ether emulsions

Abstract

The effect of oil concentration (from 5 to 47%) and type of cellulose ether on the rheological properties (flow and linear viscoelasticity), microstructure and oil digestion in o/w cellulose ether emulsions were investigated in the study. Three types of cellulose ethers were used: a hydroxypropyl methylcellulose (HPMC) and two methylcelluloses (MC) with different degrees of methoxyl content. All the emulsions showed shear thinning behaviour. The increase in oil concentration increase the emulsion's viscosity, the viscoelastic moduli G′ and G″, and decreases the loss tangent. The greatest viscosity and viscoelasticity was in the MC with the highest methoxyl content. Oil digestibility was determined by a titration method during in vitro digestion. Compared to a whey protein emulsion (control), the cellulose ether emulsions required a lower NaOH, which indicates lower free fatty acid generation and lower fat digestion. In the cellulose ether emulsions, this decrease in oil digestion was found at all the oil concentrations. A difference in oil digestion kinetics was found between the cellulose ether emulsion (linear) and the control (logarithmic), which was associated to a saturation in the digestive system in the whey protein emulsion. The microstructure after in vitro digestion showed practically no fat globules in the whey protein emulsion, whereas fat globules were observed in the cellulose ether emulsions, which confirms the highest oil digestion in the control emulsion. Cellulose ether emulsions with a wide variety of rheological properties can be obtained by varying cellulose type and oil concentration, with the barrier against fat digestion effective at low and high oil concentrations. • The effect of oil contentin rheology, microstructure and digestion of emulsions were studied. • Viscosity and viscoelasticity increased with oil concentration. • Cellulose ethers showed lower digestibility than a whey protein control. • Different oil digestion kinetics was found among cellulose ether and whey protein control. • Saturation occurs in the whey protein emulsion at higher oil concentration.