Document Type : Research Article
Authors
1
Department of Food Science and Technology, Mashhad Branch, Islamic Azad University, Mashhad, Iran
2
Department of Food Science and Technology, ToH.C., Islamic Azad University, Torbat Heydarieh, Iran
Abstract
Introduction
Whey proteins are among the most valuable functional ingredients derived from dairy industry. Whey proteins possess high nutritional quality, rapid digestibility, and multifunctional techno-functional properties such as solubility, emulsifying capacity, foaming ability, and fat-binding potential. The major whey protein fractions, including β-lactoglobulin, α-lactalbumin, immunoglobulins, lactoferrin, and bovine serum albumin, play a crucial role in improving texture, stability, and sensory quality of food formulations. Consequently, whey protein powders are extensively utilized in dairy products, functional foods, beverages, sports nutrition, and pharmaceutical formulations. Drying is a critical step in whey protein powder production, directly influencing product quality and functionality. Spray drying is the most widely used industrial method due to its cost-effectiveness and scalability; however, thermal stress during the process may induce protein denaturation, aggregation, reduced solubility, and wall deposition, ultimately decreasing powder yield and functional performance. Freeze drying, although effective in preserving protein structure, is limited by high energy consumption, long processing time, and low economic feasibility. Therefore, improving spray drying efficiency while maintaining or enhancing whey protein functionality remains a major industrial challenge. In recent years, ultrasound has gained attention as a non-thermal and environmentally friendly processing technology capable of modifying protein structures through cavitation-induced mechanical effects. High-intensity ultrasound can disrupt protein aggregates, alter secondary and tertiary structures, reduce particle size, and improve dispersion stability. Despite numerous studies reporting the positive effects of ultrasound on dairy proteins, comprehensive investigations on the combined effects of ultrasound pretreatment and drying methods on whey protein powder characteristics are still limited. Accordingly, the present study aimed to evaluate the influence of ultrasound pretreatment and to compare its effects with conventional spray drying and freeze drying on the physicochemical, structural, and functional properties of whey protein powder.
Materials and Methods
Pasteurized low-fat milk (1.5% fat) was used for whey protein extraction using an acid precipitation method. The obtained whey was subjected to ultrasound pretreatment using an ultrasonic bath operating at 20 kHz. Treatments were applied at power levels of 100, 200, and 300 W for durations of 5, 15, and 25 min. The treatment temperature was maintained below 30 °C using an ice-water bath to prevent thermal denaturation. Ultrasound-treated samples were dried using a spray dryer under controlled conditions (inlet temperature 170 °C, outlet temperature 70 °C, feed solids 20%). Control samples were produced without ultrasound pretreatment and dried either by spray drying or freeze drying. Freeze drying was performed at −80 °C followed by sublimation under vacuum (0.01 mbar). Powder yield, protein solubility, fat absorption capacity, emulsifying activity index, and foaming capacity were determined using standard methods. Structural and physicochemical properties were analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, and zeta potential measurements. All experiments were conducted in triplicate. Statistical analysis was performed using ANOVA, and optimization of ultrasound conditions was carried out using response surface methodology.
Results and Discussion
Ultrasound pretreatment significantly improved spray drying performance and functional properties of whey protein powder (p < 0.05). Powder yield increased from 46.29% in the control spray-dried sample to a maximum of 72.27% in ultrasound-treated samples, primarily due to improved atomization, reduced feed viscosity, and decreased wall deposition. Protein solubility showed a substantial increase, reaching up to 98.11% after ultrasound pretreatment, which was attributed to protein unfolding, exposure of hydrophilic groups, and reduced aggregation. Although fat absorption capacity decreased in ultrasound-treated samples compared to freeze-dried controls, extended ultrasound treatment partially restored this property, indicating a balance between structural unfolding and reorganization. Emulsifying activity and foaming capacity were markedly enhanced in the optimized ultrasound-assisted spray-dried sample, correlating with reduced particle size, higher surface charge, and improved colloidal stability. FTIR analysis revealed changes in amide I and II bands, suggesting alterations in secondary protein structure without affecting the primary structure. XRD patterns indicated an amorphous structure for all samples, with ultrasound-treated powders exhibiting a more compact amorphous arrangement. SEM images confirmed that ultrasound-assisted spray drying produced smoother, more uniform particles with fewer surface irregularities. Optimization results identified ultrasound treatment at approximately 273.5 W for 25 min as the optimal condition for maximizing yield and functional performance.
Conclusion
This study demonstrates that ultrasound pretreatment prior to spray drying is an effective and practical strategy for enhancing the quality and functionality of whey protein powder. The synergistic combination of ultrasound and spray drying significantly improved powder yield, solubility, emulsifying activity, and foaming capacity while promoting favorable structural modifications such as reduced particle size, improved surface uniformity, and increased colloidal stability. Compared to conventional spray drying and freeze drying, ultrasound-assisted spray drying offered superior overall performance with higher industrial feasibility. From an application perspective, this approach provides a cost-effective, non-thermal, and environmentally friendly solution for producing high-quality whey protein powders suitable for use in functional foods, beverages, and protein-enriched formulations. The findings support the industrial potential of ultrasound technology as pretreatment step for optimizing whey protein powder production.
Keywords
Subjects
