Physicochemical and rheological properties of soybean protein emulsions processed with a combined temperature/high-pressure treatment

Processing treatments such as temperature or high pressure (T/HP) can modify the structure and emulsifying properties of soybean protein isolates (SPIs). Few studies concern the processing of previously prepared oil-in-water emulsions stabilized with SPIs. Furthermore, the combined effects of T and HP were not assessed. Consequently, the aim of this study was to better understand the impact of the combined T/HP (T 20-60 degrees C/HP 0.1-600MPa) treatment on physicochemical and rheological properties of emulsions prepared with native SPIs at 7% (w/v). Our results show that the size and aggregation of oil droplets of emulsions prepared with SPI 7% (w/v) solutions are not altered by the combined T/HP treatment. Such emulsions did not flocculate or coalesce. Simultaneously, we observed a significant increase of the apparent viscosity with the intensification of pressure, which was reinforced by temperature. This phenomenon can be attributed to gelation of non-adsorbed soybean proteins facilitated by their high concentration. Furthermore, temperature seems to improve this gelation process but only until 400 MPa. For higher pressure, the combined effect of temperature and pressure conduced to dissociation of the protein aggregates, lowering gelation. This distinct behavior could be used to obtain SPI emulsions with modulated rheological properties. (C) 2007 Published by Elsevier Ltd.