Shear-induced structuring of particulate whey protein gels

Characterisation of heat-induced protein aggregation in whey protein isolate and the influence of aggregation on the availability of amino groups as measured by the ortho-phthaldialdehyde (OPA) and trinitrobenzenesulfonic acid (TNBS) methods

Whey protein isolate (WPI) solutions, with different levels of aggregated protein, were prepared by heating (5% protein, pH 7, 90°C for 30min) WPI solutions with either 20mM added NaCl (WPI+NaCl), 5mM N-ethylmaleimide (WPI+NEM) or 20mM added NaCl and 5mM NEM (WPI+NaCl+NEM). Gel electrophoresis demonstrated that the heated WPI and WPI+NaCl solutions had higher levels of aggregated protein, due to more covalent interactions between proteins, than the heated WPI+NEM and WPI+NaCl+NEM solutions. There were marked differences in the levels of amino groups between all heated WPI solutions when measured by the OPA and TNBS methods, with lower levels being measured by the TNBS method than by the OPA method. These results demonstrate that the measurement of available amino groups by the OPA method is less impacted than by the TNBS method after heat-induced structural changes, arising from disulfide or sulfhydryl-disulfide bond-mediated aggregation of whey protein molecules.

Preparation and rheological properties of whey protein emulsion fluid gels

The research uses a novel approach to tackle structuring in liquids through shear-gel technology, resulting in advanced material properties.

Extrusion texturized dairy proteins: processing and application

The primary proteins in milk, casein and the whey proteins α-lactalbumin and β-lactoglobulin, have a number of health benefits and desirable functional properties. In a twin-screw extruder, mechanical shear forces, heat, and pressure cause considerable changes in the molecular structures of the dairy proteins, a process known as texturization. These changes further impart unique functional properties to dairy proteins, resulting in new protein-based food ingredients. The new functional behavior depends on the extent of texturization and the degree of structural change imparted and is controlled by adjusting parameters such as extrusion temperature and moisture level. Such texturized proteins can be used to produce puffed high-protein snacks. Softer gels and expanded structures can be made using supercritical fluid extrusion and cold extrusion, techniques that avoid elevated temperatures, minimizing possible damage to the nutritive components and functionality of the texturized dairy proteins. The uses of the texturized dairy ingredient in food products with improved functionality and enhanced nutritive profiles are presented.

Continuous flow structuring of anisotropic biopolymer particles

We review concepts and provide examples for the controlled structuring of biopolymer particles in hydrodynamic flow fields. The structuring concepts are grouped by the physical mechanisms governing drop deformation and shaping: (i) capillary structuring, (ii) shear and elongational structuring and (iii) confined flow methods. Non-spherical drops can be permanently structured if a solidification process, such as gelation or glass formation in the bulk or at the interface, is superimposed to the flow field. The physical and engineering properties of these processes critically depend on an elaborate balance between capillary phenomena, rheology, gel or glass formation kinetics, and bulk heat, mass and momentum transfer in multiphase fluids. This overview is motivated by the potential of non-spherical suspension particles, in particular those formed from 'natural' and 'sustainable' biopolymers, as rheology modifiers in food materials, consumer products, cosmetics or pharmaceuticals.

Double emulsions stabilized with hybrids of natural polymers for entrapment and slow release of active matters

The main focus and efforts for the next few years in the area of emulsion technology will be to improve stability and control the release of active matter in double emulsions (3rd World Congress on Emulsions, Lyon, France, September 2002). Almost any possible blends of low-molecular weight emulsifiers, oils, cosolvents and coemulsifiers have been already tested. Biopolymers, synthetic graft and comb co-polymers and polymerizable emulsifiers that impart steric or mechanical stabilization with improved stability and better controlled release were explored. Amphiphilic macromolecules, natural occurring or synthetic, that increase the viscosity of each of the phases, complex with the oil or the emulsifiers and form systems that will behave much like microcapsules, microspheres and/or mesophasic liquid crystals have been mentioned as possible new technologies for improved stability. This review will concentrate only on the most recent findings that can enhance stability of the double emulsions and/or will reduce droplets sizes for potential food applications. The attempts and achievements include: selection of food-grade blends of emulsifiers to enhance emulsion stability at both inner and outer interfaces and use of new polymeric amphiphiles (carriers, complexing agents, natural polymeric emulsifiers) to control and reduce the reverse micellar transport phenomena and to control the addenda transport.

Viscous properties of microparticulated dairy proteins and sucrose

Slurries of whey protein concentrate (WPC) or sodium caseinate (Na-CN) mixed with sucrose (36% T.S.) were subjected to microparticulation by a high shear homogenizer operated at 27,000 rpm for 2, 4, and 6 min to facilitate gel formation. After microparticulation treatment, the milk protein and sucrose slurries were evaporated at 85 degrees C for 60 min under a partial vacuum (20 to 45 mm of Hg) to form composite gels. Particle sizes and viscoelastic properties were determined before microparticulation treatment. Microparticulation reduced the particle size of WPC-sucrose slurries from an average size of 330 to 188 nm after 4 min and NaCN-sucrose slurries from 270 to 35 nm after 2 min. The WPC-sucrose composites were gel-like, but NaCN-sucrose composites did not gel. Viscoelastic properties of heated WPC-sucrose composites were liquid-like, exhibiting significant reduction in storage modulus and complex viscosity. Microparticulation reduced particle sizes, which resulted in softer gels as time of shearing increased.