Emulsifying activity of commercial sugar beet pectins with aromatic and aliphatic oils

Abstract

Commercial sugar beet pectin (SBP), 1.5% (w/v), was emulsified with three structurally different oils at 15% (w/v), aromatic limonene, aliphatic medium chain triglycerides (MCT), and aliphatic rice bran oil (RBO). Stability of RBO emulsified with four commercial pectins was determined. Emulsions had volume-based diameter, (D_4,3 values) ≤ 2 μm at day 0. Emulsions made with limonene showed the largest particle size increase from day 0 to day 1 (≤3.34 μm) and reached 10 μm by day 9. Emulsions made with MCT had similar (p>0.05) particle sizes between day 1 and day 30 (≤3.83 μm); emulsions made with RBO had similar (p>0.05) particle sizes throughout the entire study (≤3.77 μm). Light microscopy images reflected similar trends as particle size data. Emulsions prepared with RBO were fitted following the Power-Law model and displayed shear-thinning behavior with a flow behavior index of 0.940 or 0.894 at day 0 and 30, respectively. Emulsions prepared with four commercial pectins and RBO had similar particle size and light microscopy, but consistency index was higher and more shear thinning after 30 days in two pectins. Commercial beet pectins had similar protein content, degree of esterification, molecular weight and surface hydrophobicity. Galacturonic acid content and neutral sugar content varied between pectins. Particle size, light microscopy and rheological parameters show variability in SBP emulsion stability with aromatic and different aliphatic oils. For emulsions prepared with a single oil, RBO, emulsion stability varies between different lots of pectin that is not predicted by typical specifications of commercial SBP.