CIDCA   05380
CENTRO DE INVESTIGACION Y DESARROLLO EN CRIOTECNOLOGIA DE ALIMENTOS
Unidad Ejecutora - UE
capítulos de libros
Título:
Effect of freezing on stability of soy protein and sodium caseinate oil-in-water emulsions
Autor/es:
PALAZOLO, GONZALO G.; WAGNER, JORGE R.
Libro:
Functional Properties of Food Components
Editorial:
Research Signpost
Referencias:
Lugar: Kerala, India; Año: 2007; p. 33 - 56
Resumen:
Freezing is an important preservation method for maintenance microbiological and chemical stability and extending the shelf life of food products. Nevertheless, many oil-in-water emulsions are highly unstable when they are frozen and rapidly breakdown after thawing. In this article, the influence of sample concentration (0.5-2 % w/v) and frozen storage temperature (-20º and -80º C) on global stability of o/w soy protein isolate (SPI) emulsions was studied in comparison with those prepared with sodium caseinate (SC). Initial emulsions were prepared by mixing aqueous dispersions of SPI or SC and sunflower oil (f=0.25), using a two step homogenization process. The emulsions were placed in temperature-controlled freezers at -20º C or -80º C for 24 hours and then, they were thawed in a water-bath at 20º C. SPI emulsions were highly unstable after freeze-thawing, independently of subzero temperature and sample concentration, exhibiting a coagulated creamy-layer with extensive oiling off (» 30 %). The freeze-induced interfacial aggregation of soy globulins promotes emulsion destabilization due to irreversible and negative changes on integrity of interfacial film. SC emulsions were more stable probably due to their lower initial flocculation index and high electrostatic repulsion between droplets. When glucose was added in the aqueous phase (1-5 % w/w), SC emulsions were completely stable after freeze-thawing. In SPI emulsions a concomitant increase of sample concentration and cryoprotectant exerted a synergic effect on the coalescence stability, although the flocculation can not avoid, both at -20º C and a -80º C. At 0.5 % w/v of SPI, it appears that a slow cooling rate and the addition of cryoprotectant at high concentration have the best stabilizing effects.