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Food products that contain high levels of protein can help to control food intake and to maintain a healthy body weight due to their strong satiating properties. They are also beneficial in the nutrition of elderly and commonly used in medical nutrition. Preparation of food products at high protein concentrations is difficult, mainly due to protein aggregation, occurring during processing and storage. A possible route in controlling this aggregation is using pre-fabricated protein structures, such as protein particles with controlled internal and surface properties. The aim of this thesis was to design dense protein particles and to study their properties and functionality at high protein concentrations.
Dense protein particles were prepared through two-step emulsification. The average diameter of the protein particles was in the order of a few micrometers and protein was homogeneously distributed throughout the particles. Particles were spherical when formed at pH 6.8, whereas they were irregular and had a cauliflower-like appearance when formed at pH 5.5. Particles formed at pH 5.5 had a higher internal protein concentration (~ 39% w/v), than the particles formed at pH 6.8 (~ 18.5% w/v). The rheological properties and heat stability of the particle dispersions were shown to be strongly influenced by the type of the particle. The properties of concentrated whey protein particle dispersions in different dispersing media were also addressed. The results indicated that protein particles swell during heat treatment, which considerably influences their rheological properties. It was also observed that the type and the concentration of the stabilizer present in the dispersing media alters the rheological properties, as well as the heat stability at high particle volume fractions.
Functionality of protein particles was addressed both for liquid and gelled systems. It was shown that, protein particles can considerably increase the protein concentration of (model) drinks. After heat treatment at 90 oC for 30 min, no change in the viscosity of the protein particles dispersions (particles prepared at pH 5.5) was observed at a total protein concentration of about 18% (w/w), whereas a WPI solution already gelled under the same heating conditions at protein concentrations around 11% (w/w). The gelled systems containing dense protein particles at high protein concentrations (16-22% w/w) were investigated. Incorporation of dense whey protein particles, in a whey protein gel, while keeping the total protein concentration constant, led to a lower storage modulus (G’). A total protein increase between 25 to 55% (w/w) could be obtained in the presence of whey protein particles, without significantly changing the G' of the gels. The gels were also fractured at lower strain values in the presence of protein particles compared to the WPI gels, without added particles, at the same protein concentration. These results show that protein particles can be used to improve the heat stability and as well they are promising candidates for the formation of high protein foods with improved textural properties.
In conclusion, this thesis has made significant progress in understanding the properties of protein particles at high protein concentrations and their potential for the development of high protein foods.
|Qualification||Doctor of Philosophy|
|Award date||16 Nov 2012|
|Place of Publication||[S.l.]|
|Publication status||Published - 2012|
- whey protein
- mechanical properties
- heat stability