DYNAMICS OF GELATION AND STRUCTURE OF WHEY PROTEINS-HIDROXYPROPYLMETHYLCELLULOSE MIXTURES

PÉREZ, OSCAR E; WARGON, VICTORIA; JARA, FEDERICO LUIS; PILOSOF, ANA MR.

Holanda

Congreso; NISO 2005; 2005

National Information Standards Organization (NISO)

Hidroxypropylmethylcellulose (HPMC) is a water-soluble modified cellulose widely used in the food, pharmaceutical and cosmetic industries for its surfactant, thickening and gelling properties.It is also used in delivery systems for controlled release. HPMC solutions have the unusual property of  forming thermoreversible gels on heating. Use of mixed proteins and polysaccharides is gaining importance because of their synergistic interactions that offer the possibility for controlling or improving  the structure and properties of dairy foods and ingredients. The aim of present work was to study the behavior and structure of whey proteins – hidroxypropyl methylcellulose gels heated at temperatures within 70 and 80 ºC. Whey protein concentrate (WPC) (15 %) and HPMC (4%) of different molecular structures and gelling performance (E50, E4M, F4M, K15M) were prepared  at pH 7.0. WPC-HPMC mixtures at room temperature were incompatible and separated into two phases. The dynamics of gelation was determined in a Paar Physica controlled stress Rheometer (MCR 300). The gelation was also performed in test tubes at 90 °C and the structure analysed after cooling. DSC and optical microscopy were also used to understand the performance of the mixed systems. DSC of mixtures revealed two endothermic  peaks related to HPMC and WPC transitions in accordance to the observed phase separation. The gelation temperature and the evolution of the elastic modulus on heating revealed significant differences among the different HPMC. A great synergism between protein and HPMC was observed on elastic modulus. The addition oh HPMC to WPC, gave rise to an heterogeneous structure comprising large aggregates. The gels formed with E4M and K15M were the most firm after cooling. For E4M-WPC gels, the protein constituted the gelled phase and the polysaccharide the inner filler. F4M formed spread gels with low water holding capacity.