CONICET | Buscador de Institutos y Recursos Humanos

Hydroxypropylmethylcellulose (HPMC) is a water-soluble modified cellulose widely used in food, pharmaceutical and cosmetic industries for its surfactant, thickening, and gelling properties. It 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 the present work was to study the behaviour and structure of whey proteins hydroxypropylmethylcellulose 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 mixed at pH 7.0. The 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 80 ºC and 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 HPÑC and WPC transitions in accordance to 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 of HPMC to WPC, gave rise to an heterogeneous structure with large protein 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.

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