Effects of biopolymer ratio and heat treatment on the complex formation between whey protein isolate and soluble fraction of Persian gum

ABSTRACT

Proteins and polysaccharides are the two most important natural ingredients with unique functional properties. Their interactions can be considered as a route to produce new materials of various technological applications. In this study, the effect of pH (3–7) as well as the mixing ratio of whey protein isolate (WPI)/soluble part of Persian gum (PG) (1:3, 1:1, 3:1, 6:1, and 9:1% w/w WPI/PG) on the complex formation behavior of the two polymers were studied using spectrophotometric and dynamic light scattering techniques, soluble protein measurement, and microscopic observations. Investigating the curves of turbidity versus pH showed that pHc and pH_ϕ1, which are associated with the formation of soluble and insoluble complexes, moved toward higher pH values by increasing WPI:PG ratio. Increased solubility was observed at pHc > pH > pH_ϕ1 for all biopolymers mixtures. In addition, lowering the pH toward pH_ϕ1 resulted in a decrease in the size of complexes, while further decrease of pH beyond this point led to larger particles. No significant difference was noticed between pH_c and pH_ϕ1 of heated and unheated WPI/PG mixtures, although the turbidity of heated samples increased due to the formation of larger aggregates.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electrical equivalence pH
• Persian gum
• protein–polysaccharide complex
• WPI

Acknowledgments

The authors gratefully acknowledge “Center for International Scientific Studies and Collaboration” for partial support of this research.