A deeper insight into the characteristics of double-layer oil-in-water emulsions stabilized by Persian gum and whey protein isolate

Abstract

Whey protein isolate (WPI) is an excellent emulsifier. However, WPI-stabilized emulsions tend to flocculate at pH values close to their isoelectric point. In this work, a layer by layer (LBL) technique was used to develop double layer oil in water emulsions using a mixture of WPI and water-soluble fraction of Persian gum (WSPG). Polysaccharide concentration and pH were found to have a major impact on the stability of the final system. At a constant total biopolymer concentration, increasing the amount of WSPG significantly (p < 0.05) improved the emulsion physical stability. An appropriate stability was obtained at 0.5 wt% WPI, 1 wt% WSPG, and pH 5.0. At high ionic strength, the emulsions became unstable with a higher sensitivity to CaCl₂ than NaCl. Confocal laser scanning microscopy and zeta-potential measurements confirmed the electrostatic adsorption of WSPG onto the WPI-stabilized oil droplets. The results of interfacial tension and dilatational rheology measurements revealed a slight decrease in the interfacial tension after the adsorption of WSPG as the second layer and a predominantly elastic behavior (E′ > E″), at the interface especially at pH 5.0. The results showed that WSPG is an appropriate candidate for improving the physical stability of WPI-stabilized emulsions at pH values close to isoelectric point.

Graphical Abstract

KEYWORDS:

• Multilayer emulsion
• Persian gum
• whey protein isolate
• electrostatic deposition
• dilatational rheology

Disclosure statement

The authors declare that they have no competing interests.

Availability of data and material

All data are available.

Code availability

Not applicable.

Authors’ contributions

Mohammad Hadian was responsible for the experiment part and writing the manuscript. All authors contributed to the study conception and design. All authors read and approved the final manuscript.

Additional information

Funding

This work was financially supported by University of Tehran (grant no. 5100588).