ELSEVIER Int. Dairy zyxwvutsrqponmlkjihgf Journal 6 (1996) 645-658 Copyright 0 1996 Elsevier Science Limited Printed in Ireland. All rights reserved 0958-6946/96/$15.00 + 0.00 0958-6946(95)00054-2 Stability and Rheological Properties of Salad Dressing Containing Peptidic Fractions of Whey Proteins Sylvie L. Turgeorf, Christian Sanchezb, Sylvie F. Gauthie?* & Paul Paquinb %ervice des Technologies Alimentaires, Direction de la Recherche et du Developpement, Minis&e de l’Agriculture, des Pecheries et de 1’Alimentation du Quebec, 3600 Bd Casavant Ouest, Saint-Hyacinthe, Quebec, Canada, J2S 8E3 ‘Centre de Recherche STELA, Departement de Sciences et Technologie des Aliments, Pavillon Paul-Comtois, Universite Laval, Ste-Foy, Quebec, Canada, GlK 7P4 (Received 12 April 1995; revised version accepted 20 July 1995) ABSTRACT A whey protein concentrate (WPC), a heat-treated WPC (9O”C, pH 2.5, IO min) and peptidic fractions obtained by ultrafiltration of their tryptic and chymotryptic hydrolysates were incorporated in a salad dressing jbrmulation at 0.5, 1.0 or 1.5% (w/w) protein. Emulsion stability was evaluated at 25 and 4°C during a h-month storage period and rheological properties were measured by dynamic oscillatory shear experiments. Peptidic fractions obtained from tryptic hydrolysates produced the most stable salad dressings (over 6 months at the 1.0% and 1.5% protein level) with rheological properties similar to a commercial mayonnaise. The most impor- tant ,fizctors for emulsion stability were the incorporation level and the nature of peptides. Copyright 0 1996 Elsevier Science Limited INTRODUCTION Many food products, such as salad dressing and mayonnaise, are oil-in-water emulsions which may be stabilized by emulsifiers and stabilizers. Emulsifiers act generally by one or more mechanisms, including reduction of the interfacial tension between oil and water phases, or covering fat globules with a charged layer to create a physical barrier preventing flocculation (Walstra, 1986 and others). Stabilizers, mainly polysaccharides, usually stabilize emulsions by increasing the viscosity of the aqueous phase. Proteins are among the most widely * To whom correspondence should be addressed. 645