Wet−dry heating−induced Maillard conjugation of whey protein isolate and maltodextrin: enhancing thermal stability and emulsion properties

Wet−dry heating is a combined process for controlling drying and the Maillard reaction simultaneously, enabling accelerated protein−carbohydrate conjugation. This study aims to develop a protein−carbohydrate conjugate via wet−dry heating to improve the physicochemical properties of emulsion. Whey protein isolate (WPI) was conjugated with maltodextrin DE 18 (MD18) in a cabinet dryer, and the resulting conjugate (CJ) was compared with native WPI and simple mixing (SM) in terms of physicochemical properties. The results showed that conjugation was achieved after 4.5 h at 60 °C. FTIR analysis of CJ displayed a new absorption band at 1658–1660 cm− 1, confirming C = N (imine) formation and successful conjugation via Maillard reaction. CJ had a glycation degree of 18.45 ± 0.84 and a 2.3−fold lower surface hydrophobicity than that of WPI. It had a much lower ΔH value (138.60 ± 0.31 J/g) but a higher denaturation temperature (102.06 ± 0.04 °C) than that of SM, as determined by DSC analysis. Furthermore, the CJ−stabilized emulsion had a smaller particle size (116.5 ± 2.42 nm), the lowest PDI (0.21 ± 0.01), the highest zeta potential (37.3 ± 0.45 mV), and an emulsion stability index of 30.64 ± 0.56 h. The emulsion only showed slight droplet aggregation after heating. In summary, these phenomena indicate that MD18 attachment to WPI via the wet−dry heating improves the functional properties and thermal stability of emulsion. It highlights the great potential of this method for producing conjugate products that enhance emulsion systems. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.