Exploring the effects of heat, ultrasound, and high hydrostatic pressure on the structural, functional, and rheological properties of whey protein isolate

Keshvari Khojasteh, Sara; Kadkhodaee, Rassoul; Ritzoulis, Christos; Shokrollahi Yancheshmeh, Behdad; Mohammadifar, Mohammadamin; Emam-Djomeh, Zahra; Emadzadeh, Bahareh

doi:10.22104/ift.2026.8142.2275

Exploring the effects of heat, ultrasound, and high hydrostatic pressure on the structural, functional, and rheological properties of whey protein isolate

Articles in Press

Document Type : Research Article

Authors

¹ Department of Food Nanotechnology Research Institute of Food Science and Technology Km12, Mashhad-Quchan Highway PO Box 91895/157/356 Mashhad, Iran

² Department of Food Physics, Research Institute of Food Science and Technology (RIFST), Km 12 Mashhad- Iran.

³ rofessor of of Food Chemistry, Department of Food Science and Technology, International Hellenic University, Thessaloniki, Greece.

⁴ ,National Food Institute Research Group for Food Production Engineering

⁵ Research Group for Food Production Engineering Associate Professor, Head of Research Group, National Food Institute Research Group for Food Production Engineering

⁶ Professor Campus of Agriculture and Natural Resources / agri / Science and engineering of food industry

⁷ Associate Professor at Research Institute of Food Science and Technology

10.22104/ift.2026.8142.2275

Abstract

This study aimed to investigate the effects of heat (HE), ultrasound (US), and high hydrostatic pressure (HHP) on the structural and functional properties of whey protein isolate (WPI). The structural modifications were characterized by determining surface hydrophobicity, scanning electron microscopy (SEM), circular dichroism (CD) spectroscopy, and steady shear rheological measurements. The functional performance was evaluated by studying adsorption kinetics, interfacial dilatational rheology, emulsifying activity index (EAI), and emulsion stability index (ESI). The results showed that all treatments increased surface hydrophobicity, with HE having the greatest impact (529.78 ± 11.81) , followed by HHP (402.35 ± 10.44) and US (245.48 ± 2.55). Each treatment also resulted in distinct changes in conformation and functionality. Specifically, US decreased viscosity, increased molecular flexibility (as evidenced by an increase in α-helix content to 20.9%), and resulted in the formation of an elastic interfacial film. It also accelerated both interfacial adsorption and rearrangement, yielding the highest EAI (1.22 ± 0.11 m²/g) and ESI (257.33 ± 13.49 min). HE treatment caused protein unfolding and aggregation into larger, more viscous structures, resulting in mobile interfacial films and moderate improvement in emulsification. HHP led to mild unfolding without altering viscosity, but reduced adsorption dynamics and relatively enhanced interfacial elasticity, ending up in diminished emulsifying performance (0.75 ± 0.12 m²/g). These findings provide a deep understanding of how different physical treatments affect the structure and function of WPI and can be used to tailor protein functionality for food emulsification applications.

Keywords