Characterization of whey protein isolate-ascorbic acid stabilized oil in water pickering emulsions

Abstract

This study explores the physicochemical characteristics of conjugated whey protein isolate (WPI) with ascorbic acid (AA) particles and their ability to form stable Pickering emulsions (PEs). Conjugation was studied with WPI: AA in the ratio of 10:1 mg/mL under different treatments, including heat treatment at 60 °C, and alkaline conditions (pH = 9). Conjugation in the heat-treated WPI-AA under alkaline conditions (HWPI-AA-pH) sample was confirmed by a reduction in free amino groups (27.95 %), quenching of fluorescence intensity at 320 nm, and reduction of amide I and II band intensities in FT-IR analysis, indicating the severity of the Maillard reaction under thermal treatment and alkaline conditions. The HWPI-AA-pH particles exhibited an average size of 105 nm, a zeta potential of −36 mV, and a three-phase contact angle of 80°, and were able to significantly reduce the interfacial tension. The physical and oxidative stability of the prepared emulsion with variously treated WPI-AA as the aqueous phase at the ratio of 50:50 water-to-oil was evaluated over 40 days. Among treatments, HWPI-AA-pH provided the highest physical stability, as observed by the creaming index, confirming the formation of PEs. The mentioned emulsions also demonstrated superior oxidative stability, with lower peroxide values and thiobarbituric acid reactive substances. The findings highlight the potential of WPI-AA conjugates as innovative stabilizers for high-oil emulsions, offering practical applications as fat replacers in low-calorie food formulations. The use of AA for protein modification underlines a novel approach in food science, with promising implications for improving the functionality of emulsion-based products.

Keywords

• WPI
• Pickering emulsions
• Solid particle
• Reducing agent
• Maillard reaction