Some Functional Properties of Rapeseed Protein Isolates and Concentrates

Abstract

Protein isolates and concentrates obtained from rapeseed flour by a successive water, HCl, and NaOH extraction process were subjected to baking, emulsification, and whipping tests.In baking, a 5% replacement of wheat flour with rapeseed protein isolates and concentrates decreased loaf volume by 10 to 15% and 20%, respectively. Addition of .5% emulsifier (Atmul 124) restored loaf volume to most breads: 10 to 15% larger loaf volume for the water and HCl extracted isolate breads than the all-wheat control; 8% inferior loaf volume for the protein concentrate breads except for the NaOH extracted concentrate (12% larger loaf volume).Whipping tests with 3% replacement of egg white protein by isolates or concentrates generally resulted in a decreased specific volume compared to the all-egg white control. An exception was the HCl extracted isolate with a 10% larger specific volume than the control. All fractions improved foam stability; particularly, meringues containing the water extracted isolate showed no sign of drip for 1.5 h.The water extracts displayed highest emulsification capacity; 45ml of corn oil per 100mg of protein in the isolate compared to approximately 35ml for other fractions. Emulsions containing the HCl extract showed remarkable stability: 200 min compared to 3 min for the control.No significant correlation was observed between the solubility of rapeseed protein products and their functional properties.