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Composition and structure of whey protein/gum arabic coacervates
F Weinbreck1, R H Tromp, C G de Kruif
1NIZO food research, P.O. Box 20, 6710 BA Ede, The Netherlands. fanny.weinbreck@nizo.nl
Biomacromolecules
|July 13, 2004
Summary
This study reveals how pH, mixing ratio, and ionic strength affect whey protein/gum arabic (WP/GA) complex coacervation. Optimal conditions yield the fastest phase separation and most concentrated, structured coacervates.
Area of Science:
- Food science and technology
- Colloid and interface science
- Biopolymer interactions
Background:
- Complex coacervation is a liquid-liquid phase separation process driven by electrostatic interactions between oppositely charged polymers.
- Whey protein (WP) and gum arabic (GA) are widely used biopolymers in food and pharmaceutical applications.
- Understanding the factors influencing WP/GA coacervation is crucial for controlling product texture, stability, and delivery properties.
Purpose of the Study:
- To investigate the influence of pH, initial protein to polysaccharide mixing ratio (Pr:Ps)(ini), and ionic strength on the phase separation kinetics, coacervate composition, and internal structure of WP/GA complex coacervates.
- To determine the optimal conditions for WP/GA complex coacervation.
- To elucidate the structural characteristics of the coacervate phase under varying conditions.
Main Methods:
- Complex coacervation experiments were conducted by varying pH, (Pr:Ps)(ini), and ionic strength.
- Phase separation kinetics and coacervate volume were monitored.
- Coacervate composition was analyzed after 48 hours.
- Small-angle X-ray scattering (SAXS) was employed to study the internal structure of the coacervate phase.
- Model calculations were performed to interpret SAXS data.
Main Results:
- An optimal pH (pH(opt)) was identified for each (Pr:Ps)(ini), where electrostatic interactions were strongest, leading to the fastest phase separation and largest coacervate volume.
- At pH(opt), the coacervate phase exhibited the highest concentration and a dense, structured morphology, confirmed by SAXS.
- Increasing (Pr:Ps)(ini) shifted pH(opt) to higher values due to charge compensation.
- Increasing ionic strength resulted in a less concentrated, more heterogeneous, and less structured coacervate phase due to screening of electrostatic interactions.
Conclusions:
- The study successfully mapped the influence of key parameters on WP/GA complex coacervation, providing insights into controlling the process.
- Optimal conditions (specific pH, ratio, and low ionic strength) favor the formation of concentrated and structured coacervates.
- SAXS analysis revealed distinct structural differences in coacervates formed under varying conditions, correlating with charge compensation and electrostatic screening.