Rheological properties of protein/polysaccharide blends as affected by time-dependent

JARA, FEDERICO L.; PILOSOF ANA M.R.

Proceedings of 11th International Congress on Engineering and Food

Cosmoware, Atenas, Grecia

Lugar: Atenas; Año: 2011; p. 1 - 6

The use of mixed protein/polysaccharide systems offers the possibility to control or improve the functional and structural properties of food products due to their synergistic interactions. Protein/polysaccharide blends tend to separate into two phases due to the phenomenon of thermodynamic incompatibility. In the present work, we studied the rheological properties of gels prepared from a mixture of whey protein concentrate (WPC) and hydroxypropylmethylcellulose (HPMC) as affected by the degree of phase separation. The phase separation kinetics of a mixed system containing 4% wt/wt HPMC and 15% wt/wt WPC was determined, measuring the change of the lower phase volume over time. Dynamic rheological tests were conducted in a controlled stress rheometer (Paar Physica MCR 300), on mixed gels with different degrees of phase separation (0, 7, 16, 34 and 70%) and single WPC and HPMC gels, determining the elastic modulus (G ´) and gelation temperature (Tgel). Tgel values for WPC and HPMC were 82.0 ± 1.0 ºC and 54.0 ± 2.0 ºC, respectively. The initial system (0% of phase separation) presented a Tgel of 76.3 ± 2.0 ºC, which tends to the average value of the Tgel of individual components affected by their concentrations (76 ºC). At low phase separation degrees (7 or 16%) the Tgel was determined by the HPMC rich-phase. When the system reaches a 70% of phase separation, it presented a Tgel of 79.4 ± 4.0 ° C, similar to that obtained for single WPC (80 ºC). On the other hand, the elastic modulus (G´) of mixed gels did not show any correlation with the degree of phase separation, although there was a synergistic effect due to concentration of the components during the separation process. Controlling the degree of phase separation before gelling a mixed WPC/HPMC system allows obtaining gels with specific gelation temperature or elastic properties.