Abstract #M14

# M14
Improving emulsification properties of whey protein isolate by heating with pectin at near neutral pH.
Y. Wang*1, B. Vardhanabhuti1, 1Food Science Department, University of Missouri, Columbia, MO.

Interactions between protein and polysaccharides could lead to improved protein functional properties including emulsification properties. Most studies focus on complex coacervates which are formed at pH < pI. Much less attention has been given to interactions at pH > pI, especially when the mixtures are heated. The objective of this study was to investigate the emulsification properties of heated whey protein isolate (WPI) and pectin complexes formed at near neutral pH. The effect of heating pH and pectin concentration were studied. Heated WPI-pectin complexes (CPX) were formed by heating mixed WPI (3% protein) and pectin (0 to 0.6%) at pH 6, 6.5, or 7 at 85°C for 30 min. Emulsions (5% oil and 0.5% protein) were obtained by homogenizing oil and aqueous solution, followed by ultrasonic processing. The emulsions were slowly acidified to pH 5.5. Droplet size, zeta-potential, and rheological properties of emulsions were measured. Stability against creaming was determined for 14 d. Unheated or heated WPI-stabilized emulsions were unstable and separated into 2 layers within a few hours. Regardless of heating pH, all CPX formed more stable emulsions with significantly smaller droplet size and higher negative charge (P < 0.05). At similar pectin concentration, emulsions stabilized by CPX formed at pH 7 were the most stable. At optimum heating pH (pH 7), increasing pectin concentration up to 0.3% led to a decrease in mean droplet size from 2.6 µm to 491 nm and an increase in negative charge from −24 to −31.7 mV. Increasing pectin concentration above 0.3% did not affect mean droplet sizes or zeta potential (P > 0.05); however, the emulsions were more stable. Maximum stability (>30 d) was achieved with emulsion stabilized by CPX formed with 0.6% pectin at pH 7. Rheological results suggest that, in addition to increased charge potential, an increase in viscosity could also contribute to improve stability. This study demonstrates that heat complexation of whey protein with pectin at near neutral pH could improve emulsification properties at pH near pI of the protein. Heated WPI-pectin complexes could be utilized as clean-label ingredients in foods and beverages.

Key Words: whey protein, complex, emulsification properties