Properties of whey protein–maltodextrin conjugates as impacted by powder acidity during the Maillard reaction

• Protein solutions were adjusted to pH 4.0–7.0 (m-pH) before spray-drying for glycation.
• The highest degree of glycation occurred for the powder produced at m-pH 6.0.
• The m-pH 6 conjugate had the lowest surface hydrophobicity and lowest isoelectric point.
• The m-pH 6 conjugate had the highest denaturation temperature and was most heat stable.
• The glycated protein after UHT processing was completely digested at simulated conditions.

Heating the powder of whey protein isolate (WPI)-maltodextrin (MD) mixture, the Maillard reaction, improves thermal stability of WPI, but the effects of powder acidity have not been studied. In this work, solutions with WPI and MD were adjusted to pH 4–7 (m-pH) to obtain spray-dried powder that was glycated at 80 °C and 65% relative humidity for 1–4 h. The conjugates were evaluated for physicochemical properties. A higher m-pH and a longer glycation resulted in a darker color. The m-pH 6 treatment had the highest degree of glycation, lowest surface hydrophobicity, lowest isoelectric point, and highest denaturation temperature, which contributed to the best heat stability evaluated at 5% protein, pH 4–7 and 0–150 mM NaCl by heating at 138 °C for 1 min. The results indicate that adjusting WPI-MD mixture solution to pH 6.0 to prepare powder for glycation can reduce the color of protein ingredients while providing heat stability for transparent beverage applications.

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