ABSTRACT A MCR301 rheometer from Anton Paar, fitted with a PP50 plate/plate system was used to investigate the rheological properties of some full- and low-fat mayonnaises. The test conditions were relevant for the use of mayonnaise in the preparation of typical food dishes. A hysteresis test was run to investigate the thixotropic nature of the mayonnaise at +4 ○ C. A strain controlled amplitude sweep was run at 4, 14 and 24 ○ C. The samples were then cooled to -15 ○ C at a rate of 0.5 ○ C/min in rotation at 50 1/s to detect the freezing temperature of the different products. A Malvern Mastersizer 3000 was used to measure particle sizes in a selection of the mayonnaises investigated. pH in the mayonnaise was measured directly at 20 o C. Commercially produced low fat mayonnaise did not behave very different from commercially full fat mayonnaise. The results did not show significant differences between the investigated mayonnaises on all the measured parameters, except for the particle size of the emulsion. INTRODUCTION Mayonnaise, which is one of the oldest sauces in the world, is still widely used. It belongs to the most important traditional food emulsions. Contrary to butter and margarine, which are water-in-oil emulsions, mayonnaise is an oil-in-water emulsion, similar as salad dressings or cream. The rheology of mayonnaise has been intensively studied as it influences the consumers’ attitude, not only regarding texture and flavor. It also affects functional properties, such as an application on salads, decoration on sandwiches, French fries and as a flavor enhancer in various dishes 1,2 . The mayonnaise emulsion is conventionally prepared by carefully mixing of egg yolk, vinegar, oil, spices and some optional ingredients such as sugar, salt or sweeteners. Carefully mixing of mayonnaise retain closely packed foam of oil droplets, which contribute to its viscoelastic properties. Mayonnaise has time dependent characteristic, pseudo plastic-, and thixotropic behavior 3 . According to Codex Alimentarius Commission specifications 4 , traditional mayonnaise must contain at least 78.5% total fat and 6% pure egg yolk. This is usually called full fat mayonnaise. Egg yolk is often used in mayonnaise as an emulsifier because it imparts desirable flavor, mouthfeel, and color. The emulsifying capacity of egg yolk is mainly due to presence of phospholipids, high density- and low density- lipoproteins (HDL and LDL). Non-associated proteins (livetin and phosvitin) along with LDL being the most important contributor to these emulsifying properties. The good emulsifying properties of egg yolk lipoproteins are attributed to their highly flexible structures, allowing great affinity and adsorption at oil–water interfaces. Vinegar, salt, sugar and mustard are mostly added to mayonnaise as flavoring ingredients. But these ingredients also seem to play an important role for the physical stability of emulsions 5 . Usually a vinegar with a strength of 5- 10% is used. This helps to give a vinegar Rheological properties of different types of mayonnaise Elling-Olav Rukke and Reidar Barfod Schüller Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O.Box 5003, N-1433 Ås, Norway ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 27, 2019 165