Influence of Tribomechanical Micronisation on the Rheological Properties of Whey Proteins
Zoran Herceg1*, Vesna Lelas1 and Mirjana Škreblin2
1Department of Food Engineering, Faculty of Food Technology and Biotechnology University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
2»Pliva« d.d., Baruna Filipovića 79, HR-Zagreb, Croatia
Article history:
Received: May 3, 2001
Accepted: February 21, 2002
Key words:
tribomechanical micronisation, rheological properties, hydrocolloids, whey protein concentrate
Summary:
Investigations with powdered whey protein concentrates containing 60 % (WPC-60) or 80 % (WPC-80) of proteins were carried out. In this work proteins were treated using the laboratory equipment for tribomechanical micronisation with three different rotor speeds. Before and after the tribomechanical treatment, the analyses of the particle size and particle distribution as well as the specific area and scanning microscopy were carried out. The influence of tribomechanical treatment as well as hydrocolloid addition on the rheological properties of model systems of whey protein concentrate (10 % of total solid) was studied. Rheological parameters, flow behavior index (n) and consistency coefficient (k) were determined by the power-law model. The results obtained showed that the tribomechanical treatment involves a significant decrease in particle size, a change in particle distribution and an increase in specific area of powdered whey proteins. Systems without hydrocolloid addition were Newtonian, but those with hydrocolloid addition exhibited pseudoplastic properties. The viscosity of model systems containing tribomechanically treated whey protein concentrates (TWPC) was greater in comparison with the same systems prepared with untreated WPC. Systems with greater amount of proteins (WPC-80) had higher viscosity than the same systems containing lower amount of proteins. Hydrocolloid addition affected an increase of viscosity of model systems prepared with untreated WPC. The most significant increase of consistency coefficient (k) was observed in systems with carboxymethylcellulose (CMC) and addition of a special type of carboxymethylcellulose (CMC E466) known as DIKO, icecream binder 0911-E. In systems containing tribomechanically treated TWPC hydrocolloids had various effects. In systems with guar gum, carragenan, inulin, pectin or amid pectin, viscosity increased in comparison with those prepared with untreated WPC. CMC and DIKO affected a significant viscosity decrease of TWPC model systems, which is the consequence of the interaction between proteins and (CMC) hydrocolloids. The found effects were pronounced more strongly as the rotor speed of TMA equipment was greater.
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