Turkish fermented sausages (sucuk) were produced by replacing 15, 30 and 50% of beef fat with hazelnut oil incorporated as pre-emulsified with simplesse((R)) 100 (whey protein powder) Each treatment was formulated to contain 20% total fat and beef fat was the only fat material used in the control (C) group. After 12 days of fermentation and ripening, all sucuk samples had TBA values within acceptable limits (< 1.0). Increasing levels of hazelnut oil in sucuk formulation increased penetrometer values (softer texture) and moisture content. Hazelnut oil replacement had a significant effect on redness values of the samples. Cholesterol content decreased progressively as the percentage of hazelnut oil increased in the formulation. Replacement of 50% beef fat with 50% hazelnut oil significantly increased MUFA, PUFA and MUFA + PUFA/SFA ratios. The use of hazelnut oil resulted in significant decreases in the slice appearance, texture and taste scores. However there was no significant difference in the overall acceptability score of samples, except those in which hazelnut oil replaced 15% beef fat, which had the highest score. (c) 2007 Elsevier Ltd. All rights reserved.