80-4 |
Effect of ultra high pressure homogenization (350 MPa) on the texture of soy protein emulsions |
J. FLOURY, GEPEA-ENITIAA, La Geraudiere BP82225, Cedex 3, Nantes, 44322, France, A. Desrumaux, GEPEA - ENITIAA, La Géraudière BP82225, Nantes cx 3, 44322, France, and J. Legrand, GEPEA-UMR MA100, Université de Nantes - IUT Saint-Nazaire, CRTT - BP 406, SAINT-NAZAIRE Cedex, 44602, France. A ultra high pressure homogenizer (STANSTED, UK, 1997) going up to 350 MPa was used to realize very fine food emulsions stabilized by soy proteins. The effect of homogenizing pressure (from 20 to 350 MPa) was studied on model oil-in-water emulsions stabilized by 11S globulins at neutral pH. The structure and rheology of emulsions were characterized by laser-light scattering for droplet size measurements and with a coaxial cylinder rheometer. Mean droplet sizes of emulsions were greatly reduced with high pressure homogenization as predicted by literature (Walstra, 1983). Unlike Floury et al. (2000) who observed a strong decrease of the viscosity of whey protein stabilized emulsions obtained by high pressure homogenization, the liquid-like soy protein emulsions were converted into creamy-like emulsions by homogenization at pressures above 250 MPa. The effect of the high pressure treatment on the conformation of 11S soy globulin was then investigated by microcalorimetry and size exclusion chromatography to explain the rheology of those structured food emulsions. It was found that high pressure homogenization caused denaturation of 11S proteins due to strong mechanical forces and high temperatures encountered in the homogenizing valve at very high pressures. High pressure treatment induced significant level of flocculation in emulsions. Hydrophobic interactions between the 11S proteins were supposed to predominantly contribute to cause the formation of these aggregated particle networks responsible of the gel-like network structure of ultra high pressure homogenized emulsions.
Session 80, Ultra high pressure: Molecular changes in foods
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