Comparison of biopolymer emulsifier performance in formation and stabilization of orange oil-in-water emulsions.

摘要

The effectiveness of various biopolymer emulsifiers at forming and stabilizing model beverage emulsions was examined: beta-lactoglobulin (BLG); gum arabic (GA); conventional modified starch (MS-old); new modified starch (MS-new). Orange oil-in-water emulsions (5% oil) were prepared using high pressure homogenization. For BLG, MS-new, MS-old and GA, the minimum droplet diameters produced were 171, 254, 222 and 497 nm, while the minimum mass ratio of emulsifier-to-oil required to produce small droplets were 0.5:5, 1:5, 3:5 and 5:5, respectively. The influence of pH (3-8), ionic strength (0-500mM NaCl, 0-50mM CaCl₂) and thermal treatment (30-90 degrees C) on the stability of the emulsions was examined. Extensive droplet aggregation occurred in BLG-stabilized emulsions around their isoelectric point (pH 5), at high salt concentrations (>=300mM NaCl, >=10mM CaCl₂, pH 7) and at high temperatures (>70 degrees C, 200mM NaCl, pH 7) due to changes in electrostatic and hydrophobic interactions. There was little effect of pH, ionic strength and temperature on emulsions stabilized by GA or MS due to strong steric (rather than electrostatic) stabilization. The new type of modified starch used in this study was capable of forming stable emulsions with small droplet sizes at low concentrations.