Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
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 containingn 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.U ovom su radu istraživanja provedena s praškastim koncentratima proteina sirutke koji su sadržavali 60 % (WPC-60) ili 80 % (WPC-80) proteina. Uzorci su obrađeni u laboratorijskom uređaju za tribomehaničku mikronizaciju i aktivaciju pri trima različitim brzinama okretaja rotora. Prije i nakon tribomehaničke obradbe određena im je veličina i razdioba veličine čestica, te specifična površina, a provedena je i pretražna mikroskopija. Utjecaj tribomehaničke obradbe te dodatka hidrokoloida na reološka svojstva koncentrata proteina sirutke ispitivan je na modelnim sustavima koji su sadržavali 10 % suhe tvari. Reološki parametri, indeks tečenja (n) i koeficijent konzistencije (k), određeni su pomo}u modela potencijalne funkcije. Dobiveni su rezultati pokazali da se tribomehaničkom obradbom bitno smanjuje veličina čestica, mijenja njihova razdioba, te povećava slobodna površina praškastih koncentrata proteina sirutke. Sustavi bez dodatka hidrokoloida imali su newtonski karakter, a oni s dodanim hidrokoloidima uglavnom pseudoplastična svojstva. Utvrđeno je da je viskoznost modelnih sustava s dodatkom tribomehanički obra|enih WPC (TWPC) veća nego istih sustava s dodatkom neobrađenih WPC. Sustavi istog udjela suhe tvari, ali s većim udjelom proteina (WPC-80), imali su veću viskoznost od istih sustava s manjim udjelom proteina (WPC-60). Dodatak hidrokoloida utjecao je na povećanje viskoznosti modelnih sustava pripremljenih s neobrađenim WPC, pri čemu je najznačajnije povećanje viskoznosti izraženo koeficijentom konzistencije (k) utvrđeno u sustavu s dodatkom karboksimetilceluloze (CMC) i dodatka specijalnog tipa karboksimetilceluloze (CMC E466, poznate kao DIKO, vezivo za sladoled). U sustavu s tribomehanički obrađenim proteinima sirutke (TWPC) dodatak je hidrokoloida različito utjecao. U onima s guar gumom, karagenom, inulinom, pektinom i amidiranim pektinom viskoznost se pove}ala u usporedbi sa sustavima s neobrađenim WPC, a u onima s CMC i DIKO viskoznost se smanjila, što je posljedica međudjelovanja između proteina i hidrokoloida. Utvrđeni utjecaji bili su to jače izraženi što je bila veća brzina okretaja rotora pri obradbi WPC-a
