Abstract
The rehydration properties of original whey protein isolate (WPIC) powder and spray-dried WPI prepared from either unheated (WPIUH) or nanoparticulated WPI solutions were investigated. Nanoparticulation of whey proteins was achieved by subjecting reconstituted WPIC solutions (10% protein, w/w, pH 7.0) to heat treatment at 90 °C for 30 s with no added calcium (WPIH) or with 2.5 mM added calcium (WPIHCa). Powder surface nanostructure and elemental composition were investigated using atomic force microscopy and X-ray photoelectron spectroscopy, followed by dynamic visualisation of wetting and dissolution characteristics using environmental scanning electron microscopy. The surface of powder particles for both WPIUH and WPIC samples generally appeared smooth, while WPIH and WPIHCa displayed micro-wrinkles with more significant deposition of nitrogen and calcium elements. WPIH and WPIHCa exhibited lower wettability and solubility performance than WPIUH and WPIC during microscopic observation. This study demonstrated that heat-induced aggregation of whey proteins, in the presence or absence of added calcium, before drying increases aggregate size, alters the powder surface properties, consequently impairing their wetting characteristics. This study also developed a fundamental understanding of WPI powder obtained from nanoparticulated whey proteins, which could be applied for the development of functional whey-based ingredients in food formulations, such as nanospacers to modulate protein–protein interactions in dairy concentrates.
Highlights
Whey protein ingredients, such as whey protein isolate (WPI), have a wide range of applications in food formulations due to their diverse techno-functional and nutritional properties [1]
In an effort to study the influence of nanoparticulation on physical and rehydration properties of the WPI powders, it was important that all powders had similar composition
The nitrogen and calcium contents at the surface of WPI powders were similar in heated samples (WPIH and WPIHCa), while the contents in unheated samples (WPIC and WPI prepared from either unheated (WPIUH)) were significantly lower (p < 0.05)
Summary
Whey protein ingredients, such as whey protein isolate (WPI), have a wide range of applications in food formulations due to their diverse techno-functional and nutritional properties [1]. The functionality of whey proteins can be tailored for applications such as fat mimetics and encapsulation, through processes such as heat treatment, high-pressure processing or enzymatic treatment Applying such treatments separately or in combination to WPI solutions prior to drying leads to the development of novel WPI powders with unique functional properties, customized for specific applications [2,3]. This has aided the response to the continual demand by the food industry for ingredients with tailored functionalities [4] driven by cleaner labels, diversification into new markets and regulatory considerations [5]. Understanding the rehydration properties (i.e., wetting, swelling, sinking, dispersion and dissolution characteristics) of novel WPI powders is required to underpin their potential applications in food formulation. It is well-established that wetting is the ratelimiting step during rehydration for WPI powders and poor wetting is most often manifested as powder clump formation on the surface of water [6]
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