Changes in Turbidity, Zeta Potential and Precipitation Yield Induced by Persian Gum-Whey Protein Isolate Interactions During Acidification

Abstract

To measure the molecular parameters of Persian gum (PG) (gathered from Kazeroon plains/Iran) by gel permeation chromatography-multiangle laser light scattering (GPC-MALLS), water-insoluble part of gum was removed using filtration method. In the following, acidification of whey protein isolate/PG mixture solutions (pH ∼ 7.00–2.00) at different biopolymer mixing ratio (r = 0.1–10) was induced by HCl, allowing turbidity, zeta potential and precipitation yield determinations. Contrary to previous studies, it was demonstrated that more than 93% of gum is composed of large water-insoluble particles and water-soluble part contains heavy and heterogeneous compounds with high weight-average molecular mass (up to 5.11 × 106 g/mol) and high dispersity index (∼2.54–6.64). Acid titration of the mixtures displayed that the net neutrality shifts to the higher pHs by increasing the mixing ratio, and the charge neutralization occurs at pHs near pHopt as well. Generally, the maximum interaction was found for a 1:1 WPI/PG mixture with the highest liquid precipitate yield achieved at pH 3.4. Practical Application Persian gum exudes from the wild almond tree (Amygdalus scoparia), growing in the Middle East countries. The characteristics of this hydrocolloid highly depend on the color of exudate and region of the tree. As a mixture with gum Arabic, it has wide industrial and pharmaceutical applications due to economic reasons and high functionality. However, very few scientific information about this gum has been already published. Some researchers have displayed the emulsifier, stabilizer and fat replacer ability of this gum. The interaction of PG with other biopolymers such as proteins would be beneficial in food and pharmaceutical applications in the form of gels, microcapsules, etc. In this study, we have measured the water-soluble and insoluble fractions and molecular parameters of PG gathered from Kazeroon plains. To have a basic knowledge for our future investigations on encapsulation ability of PG-WPI complexes, titration method was applied for different PG-WPI admixtures.