Estela M. Alvarez

Acid-Induced Aggregation and Gelation of Bovine Sodium Caseinate-Carboxymethylcellulose Mixtures

Maria Eugenia Hidalgo1, Bibiana D. Riquelme1,2, Estela M. Alvarez1, Jorge R. Wagner3 and Patricia H. Risso1,2,4 1Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario 2Instituto de Fisica Rosario (IFIR), CONICET-UNR, (2000), Rosario, 3Departamento de Ciencia y Tecnologia, 4Facultad de Ciencias Veterinarias,Universidad Nacional de Rosario, Rosario Universidad Nacional de Quilmes, Buenos Aires, Argentina

Physicochemical study of mixed systems composed by bovine caseinate and the galactomannan from Gleditsia amorphoides

Model systems formed by sodium caseinate (NaCAS) and espina corona gum (ECG) were studied. There was no evidence of attractive interactions between NaCAS and ECG macromolecules. Aqueous mixtures of NaCAS and ECG phase-separate segregatively over a wide range of concentrations. According to the images obtained by confocal laser scanning microscopy, NaCAS particles form larger protein aggregates when ECG is present in the system. An increase in the hydrodynamic diameter of NaCAS particles, as a result of ECG addition, was also observed by light scattering in diluted systems. A depletion-flocculation phenomenon, in which ECG is excluded from NaCAS surface, is proposed to occur in the concentrated mixed systems, resulting in NaCAS aggregation. ECG raises the viscosity of NaCAS dispersions without affecting the Newtonian flow behaviour of NaCAS. These results contribute to improve the knowledge of a barely-studied hydrocolloid which may be useful in the development of innovative food systems.

Microstructural and textural properties of rennet-induced milk protein gel: Effect of guar gum

ABSTRACT The knowledge of the effect of polysaccharide addition on the textural properties of milk protein gels is important for foodstuff engineering design. Therefore, the microstructure, texture, and water-holding capacity of rennet-induced milk protein gel with and without the addition of different concentrations of guar gum (GG) were determined. It was found that the presence of GG changed the microstructure of rennet-induced milk gel. The addition of a GG concentration higher than 0.075% w/v led to a discontinuous protein network. Changes in the structure of the gel samples are reflected in the texture perception and their capability of water retention. When a limit GG concentration of 0.15% w/v was exceeded, a very weak gel sample was obtained. The results demonstrated that different milk protein gel microstructures can be created by the addition of different concentrations of GG.