Properties Of Whey Protein Gels Research Articles

High-Protein Foods for Dysphagia: Manipulation of Mechanical and Microstructural Properties of Whey Protein Gels Using De-Structured Starch and Salts.

This study focuses on understanding the effect of ionic strength on the mechanical and microstructural properties of novel composite gels containing 13% whey protein isolate (WPI) and 4% de-structured waxy potato starch (DWPS). The DWPS is a physically modified waxy potato starch treated at 140 °C for 30 min under constant shear. Thermodynamic incompatibility between WPI and DWPS was observed upon the addition of NaCl (~75 mM) or CaCl2 (10–75 mM). The combined effects of such thermodynamic incompatibility with the changes in protein connectivity induced by varied ionic strength led to the formation of distinctive gel structures (inhomogeneous self-supporting gels with a liquid centre and weak gels with paste-like consistency) that were different from thermodynamic compatible homogeneous self-supporting gels (pure WPI and WPI + maltodextrin gels). At ≥ 250 mM NaCl, instead of a paste-like texture, a recovered soft and creamy self-supporting gel structure was observed when using DWPS. The ability to generate a range of textures in WPI gelation-based foods by using DWPS under different ionic conditions, is a feasible strategy for formulating high-protein foods for dysphagia—aimed to be either thickened fluids or soft solids. Additionally, this acquired knowledge is also relevant when formulating food gels for 3-D printing.

In vivo oral breakdown properties of whey protein gels containing OSA-modified-starch-stabilized emulsions: Impact of gel structure

This study investigated the effects of gel structure on the in vivo oral breakdown properties of whey protein gels containing emulsion droplets stabilized by octenyl succinic anhydride (OSA)-modified starches. The gel structure was manipulated by the degree of substitution (DS) of the OSA-modified starch and the salt concentration. Rheological measurements showed that, when the DS or the NaCl concentration increased, the storage modulus, hardness and Young's modulus of the gels increased. Hard gels (100 mM NaCl) required more chewing cycles than soft gels (10 mM NaCl), which led to smaller mean particle size (d50) of the bolus. Correlation analysis showed that d50 had an excellent power-law relationship with hardness and Young's modulus, whereas it had a positive linear relationship with fracture force and fracture strain. This indicated that the physical/mechanical properties of the gel were the critical factors that determined the bolus particle size. During oral processing, there were no significant changes in the microstructures of the gels and only very few oil droplets were released from the protein matrix, suggesting that the OSA-modified-starch-stabilized emulsion droplets remained bound within the whey protein gel matrix.

Whey protein gel — mechanical cleaning capability through modelling and experimental testing including compression and wire cutting investigation

Abstract Whey protein has been used extensively to investigate the efficiency of procedures for cleaning dairy production equipment owing to the chemical reaction it undergoes at high temperature, similar to the formation of fouling deposits during heat treatment. In addition to the chemical and thermal aspects, a detailed understanding of the fundamental mechanical and fracture mechanisms that significantly influence the success of the cleaning procedure is indispensable. Consequently, to determine the basis for the mechanical detachment of whey protein isolate, in the present study, the mechanical characteristics and fracture properties of whey protein gels (WPGs) with a protein content of 15% and a treatment temperature of 80 °C were determined. For purely mechanical characterisation, axial compression and compression relaxation experiments were performed. The results suggest a non-linear stress–stretch behaviour combined with time-dependent mechanical characteristics. To characterise the fracture properties of WPGs, wire cutting experiments were performed. Based on a viscoelastic numerical model and the corresponding parameters identified from the experimental investigations, the cutting procedure of WPGs was simulated by assigning a fracture criterion, and the critical stress was determined based on the measured cutting forces.

Surface Properties of Whey Protein Gels

Surface properties of whey protein gels are reviewed based on traditional microscopic techniques and new methods, as optical profilometer and contact angle measurements. Optical profilometer is an instrument allowing measurement of surface roughness and contact angle measurements to determine the surface wettability behavior (hydrophobicity/hydrophilicity) of the gels. Investigation of surface properties of whey protein gels is very important, as it can transform this product to a new level of application. It could be used as a matrix for an active ingredient release, material for tissue engineering, e.g. scaffolds, i.e. temporally structures biodegraded in the human organism.

Development of iron-rich whey protein hydrogels following application of ohmic heating – Effects of moderate electric fields

The influence that ohmic heating technology and its associated moderate electric fields (MEF) have upon production of whey protein isolate cold-set gels mediated by iron addition was investigated. Results have shown that combining heating treatments (90°C, 5min) with different MEF intensities let hydrogels with distinctive micro and macro properties – i.e. particle size distribution, physical stability, rheological behavior and microstructure. Resulting hydrogels were characterized (at nano-scale) by an intensity-weighted mean particle diameter of 145nm, a volume mean of 240nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3V∙cm−1 was combined with a cold gelation step using 33mmol∙L−1 of Fe2+. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10V∙cm−1. According to transmission electron microscopy, ohmic heating gave rise to a more homogenous and compact fine-stranded whey protein-iron microstructure. Ohmic heating appears to be a promising technique, suitable to tailor properties of whey protein gels and with potential for development of innovative functional foods.

Combined microscopic and dynamic rheological methods for studying the structural breakdown properties of whey protein gels and emulsion filled gels

The microstructural and large deformation rheological properties of model food gels were studied by performing notch propagation tensile testing on the gels using a tensile stage and observing changes in the microstructure of the gels during tensile testing using confocal laser scanning microscopy (CLSM). Heat-set whey protein (WP) gels containing either added sodium caseinate (NaCN) or sunflower oil droplets emulsified with WP or NaCN as the emulsifier protein were prepared in 0 or 50 mM NaCl. The WP gel structure strengthened in the presence of added NaCl and NaCN. The rheological properties of WP gels containing sunflower oil droplets emulsified with WP or NaCN were influenced by the NaCl concentration, oil concentration and extent of oil droplet aggregation in the gel or by the type of emulsifier protein used. During tensile testing, the notch length in all gels increased above a certain critical stress, leading to fracture of the gels through the notch. Also, the microstructural changes in the oil phase of emulsion filled gels subjected to tensile testing were influenced by the structural properties of the WP gel matrix and the proximity of the oil droplet to the fracture path.

Using whey protein gel as a model food to study dielectric heating properties of salmon (Oncorhynchus gorbuscha) fillets

It is desirable to develop rapid commercial microwave and radio frequency sterilization processes to produce high quality shelf stable muscle foods, particularly aquatic foods. Whey protein gels containing D-ribose and salt were studied as a model food to determine heating patterns in salmon fillets during high temperature microwave sterilization processes. Dielectric constant (3 0) and loss factor (300) of whey protein gels with D-ribose (0.5 g/100 g, 1 g/100 g, and 1.5 g/100 g) at different salt contents (0, 0.1 g/100 g, 0.2 g/100 g, 0.3 g/100 g, 0.4 g/100 g, and 0.5 g/100 g) and frozen and thawed pink salmon (Oncorhynchus gorbuscha) fillets were determined over the frequency range of 27–1800 MHz at temperatures ranging from 20 to 120 � C. The dielectric properties of whey protein gels containing 1 g/100 g D-ribose and 0.2 g/ 100 g or 0.3 g/100 g salt closely matched the dielectric behavior of salmon fillets in both radio frequency (RF, 27 MHz) and microwave (MW, 915–1800 MHz) ranges. Altering the salt content had a greater impact on dielectric constant and loss factors at lower frequencies. These results suggest that whey protein gel may be a good model food for microwave sterilization process development, particularly for determining the locations of cold and hot spots in complex muscle foods.

Influence of glycerol on optical properties and large-strain rheology of heat-induced whey protein isolate gels

The influence of glycerol (0–50 wt%) on the properties of gels formed by heating 10 wt% whey protein isolate (WPI) solutions (pH 7.0, 100 mM NaCl) at 90 °C has been studied. The elastic modulus, breaking stress and breaking strain of the gels were measured using uniaxial compression. The optical properties of protein solutions were characterized by turbidity or colorimetry measurements. The onset of gelation at 90 °C was delayed in the presence of glycerol, presumably because the cosolvent increased the thermal stability of the globular proteins and reduced the protein–protein collision frequency. On the other hand, the elastic modulus, breaking stress and breaking strain of gels heated at 90 °C for 60 min increased with glycerol concentration, presumably because the glycerol increased the strength of the intermolecular attraction between fully denatured proteins. Glycerol decreased the lightness of the gels because it reduced the scattering efficiency of the protein aggregates. This study shows that glycerol can be used to modulate the physicochemical properties of whey protein gels.

Properties of Acidic Whey Protein Gels Containing Emulsified Butterfat

ABSTRACTChanges in physical properties of whey protein gels following addition of emulsified fat were investigated. Gels were made by heating mixtures of dialyzed whey protein isolate at pH 4.60 with and without emulsified fat droplets. Addition of emulsified fat improved the gel‐like qualities of these systems. Gel strength progressively increased upon addition of emulsified fat up to 30.00% by weight. Mean droplet size 1.85 km produced the greatest reinforcement of gel strength. Gels made with intermediate concentrations of protein were most sensitive to the effect. The elastic moduli and viscosities of whey protein gels at pH 4.60 increased with fat content, whereas syneresis decreased upon addition of fat.

Enhanced Heat-induced Gelation ofβ-Lactoglobulin byα-Lactalbumin

Heat-induced gelation in a mixed system of α-lactalbumin (La) and β-lactoglobulin (Lg) was studied to elucidate the gelling properties of whey protein. An Lg concentration of 4% (w/v) was required for the formation of a self-supporting gel following heating at 80°C for 30 min in a 100 mM potassium phosphate buffer (pH 6.8). Solutions of La, even up to a protein concentration of 8% (w/v), did not gel under the same conditions. The addition of 6% La to 2% Lg caused a significant increase in the gel hardness, although each protein did not individually form a gel at these concentrations. By adding La to Lg, firmer gels were formed at a lower heating temperature, compared to that from Lg alone. La and Lg interacted to form a soluble aggregate through a thiol-disulfide interchange reaction during gel formation, and such an interaction was critical in the formation and stabilization of the gel network structure. We conclude that the enhancing effect of La on the gel hardness of Lg was due to the formation of a specific soluble aggregate, and that such an interaction between these proteins contributes to the properties of whey protein gels.

LITERATURE ABSTRACTS

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Viscoelastic Properties of Whey Protein Gels: Mechanical Model and Effects of Protein Concentration on Creep

ABSTRACTThe creep behavior of gels made using different concentrations of whey protein isolate (WPI, >95% protein) was systematically determined. The creep curves of these gels conformed to a six element mechanical model consisting of one Hookean, two Voigt and one Newtonian component. The concentration and temperature dependence of each viscoelastic constant were examined and the data are discussed in terms of mechanisms involved in gel network structure.