Contents lists available at ScienceDirect Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa Heat stable whey protein stabilised O/W emulsions: Optimisation of the whey protein concentrate dry heat incubation conditions Qurrotul A’yun a,b, *, Istna Naf Azzahrani a , Arne Huyst a , Lorenz de Neve a , José C. Martins c , Marleen van Troys d , Chusnul Hidayat b , Paul Van der Meeren a a Particle and Interfacial Technology Group, Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium b Department of Food and Agricultural Product Technology, Universitas Gadjah Mada, Jalan Flora No. 1, 55281, Yogyakarta, Indonesia c NMR-STRUCT Group, Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281, 9000, Ghent, Belgium d Department of Biomolecular Medicine, Faculty of Medicine and Health Science, Ghent University, Albert Baertsoenkaai 3, 9000, Ghent, Belgium GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Whey protein concentrate Lactose Conjugation Emulsion Heat stability PFG-NMR Maillard reaction ABSTRACT The industrial application of whey proteins as a food emulsifer is still limited due to its susceptibility towards heating. In this study, dry heat conjugation of whey protein and lactose was investigated to improve the heat stability of WPC-stabilised oil in water (O/W) emulsions. A commercially available whey protein concentrate (WPC), containing 80 % protein and 12 % lactose, was dry heat incubated. Hereby, the efect of incubation temperature (60, 70, and 80 °C), relative humidity (64, 74, and 79 %), and preconditioning pH (4, 6, 8, 10) were determined. Temperature variation showed a pronounced efect on the required duration to obtain conjugates with excellent emulsion heat stabilising capacity. Four hours of incubation at 80 °C was sufcient to retain the original particle size and consistency after heating the emulsions at 80 °C for 20 min. Whereas circular dichroism spectroscopy revealed that this dry heat incubation condition (80 °C, 4 h) maintained the secondary structure of WPC, pulsed-feld gradient NMR revealed that about 40 % of the lactose present should become protein-bound to generate conjugates with the desired functionality. The results indicated that a heat stable WPC with about 40 % of bound lactose could be obtained by some hours of dry heat treatment at 80 °C. https://doi.org/10.1016/j.colsurfa.2020.125192 Received 31 March 2020; Received in revised form 9 June 2020; Accepted 17 June 2020 ⁎ Corresponding author at: Particle and Interfacial Technology Group, Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium. E-mail address: Qurrotul.Ayun@UGent.be (Q. A’yun). Colloids and Surfaces A 603 (2020) 125192 Available online 30 June 2020 0927-7757/ © 2020 Elsevier B.V. All rights reserved. T