29B-37 |
Viscosity enhancement and depletion flocculation by biopolymers in model beverage emulsions |
R. CHANAMAI1, G. R. Horn1, R. Hammond1, and D. J. McClements2. (1) WILD Flavors, Inc., 1261 Pacific Ave., Erlanger, KY 41018-1260, (2) Dept. of Food Science, Univ. of Massachusetts, Amherst, 238 Chenoweth Lab., Box 31410, Amherst, MA 01003-1410 Beverage emulsions often contain biopolymers to improve stability and modify texture. However, many biopolymers induce droplet flocculation through a depletion mechanism, which adversely affects beverage stability. Knowledge of the relationship between biopolymer properties and emulsion stability is therefore important for producing beverage emulsions with desired physical characteristics. Our objective was to examine the influence of biopolymer type and concentration on the flocculation of model beverage emulsions containing monodisperse droplets to facilitate data interpretation. Monodisperse soybean oil-in-water emulsions stabilized with Tween 20 were fractionated from polydisperse emulsions. Depletion flocculation was induced in the emulsions by addition of different types (pectin, locust bean gum, and xanthan gum) and concentrations (0.01 to 4 wt% of the aqueous phase) of biopolymer. Creaming rates of emulsions with different droplet radii (0.50, 0.25 and 0.15 micron) and biopolymer concentrations (0-4 wt%) were monitored at 25°C by measuring back-scattered light from emulsions as a function of their height. The viscosity of biopolymer solutions was measured using a dynamic shear rheometer. When the aqueous phase biopolymer concentration exceeded the critical flocculation concentration (CFC), depletion flocculation was observed which led to rapid creaming. When the biopolymer concentration reached the critical viscosity concentration (CVC), creaming was inhibited due to the high viscosity of biopolymer solutions. For the same biopolymer, CFC increased when droplet radii decreased, because the magnitude of the depletion attraction increases with droplet size. The viscosity of the aqueous phases and the value of the CVC increased in the following order: pectin < locust bean gum < xanthan, due to differences in biopolymer molecular weight and structure. This study gave valuable insights into the influence of biopolymer characteristics on creaming stability of beverage emulsions, which have important implications for the formulation of beverage emulsions.
Session 29B, Food Chemistry: Lipids, antioxidants and emulsifiers
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