Oxidative Stability and Determination of Fatty Acid Composition of Sheep Tail-Fat of Ethiopian Black Head Somali Sheep Reared at Different Feeding System

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Addis Ababa University


Animals are slaughtered to produce their by-products which can be well utilized for various applications in day to day human life, thus, contributing to the value of animals. Understanding its chemical composition as well as its stability is very important for its proper utilization and also for its technological application. The Black Head Somali Sheep's tail-fat, obtained from pasture sites (Borena & Gode) consisting of three sheep each, and non pasture sites ( Alfoz and cooperate) also consisting of three sheep each, were collected in Ethiopia from different actual feeding areas comprising of a total of twelve (n=12) intact male sheep were investigated. In addition to the fat content of the sheep tail, the fatty acid composition and oxidative stability of the tail-fat were determined by GC-MS and professional rancimat method respectively and the quality control parameters including peroxide value, acid value, saponification value, moisture content and refractive index were evaluated. The fat content of tail tissue from Borena (B) site amounted 75.50%, whereas that of Gode, Alfoz (AF) and Cooperate(C) were found to be 78.50, 73.66 and 75.48%, respectively. The determined fatty acids composition of sheep tail-fat were comprising of a number of fatty acids which involves Myristc acid (C14:0), palmitic acid, stearic acid (C18:0), oleic acid (C18:1), Elaidic acid (C18:1n-9t), linoleic acid (C18:2),linolenic acid (C18:3). The oxidative stability of the oils, as measured by the Rancimat test at 110OC and 120OC, and extrapolated to real shelf life of tail- fat were 1.67yr,1.58yr,2.01yr and 1.92yr for the sheep's tail- fat obtained from B, G, AF & C sites respectively. In conclusion, there are differences between study group for the their fatty acids composition. The sheep tail fat from Pasture sites had better attributes of fatty acid composition with higher PUFA, UFA/SFA ratio, EFA and total n-3 PUFA. Also sheep tail fat from Pasture sites have lower oxidative stability and lower initial quality in terms of its PV and AV in general terms due to its fatty acid composition compared to non pasture sites.



Black Head Somali (BHS) Sheep, Fatty Acids, Oxidative Stability, Rancimat, Tail-fat