Two-stage dry fractionation of sheep tail and ostrich fats and evaluation of physicochemical properties of their fractions

In Iran, there is a large capacity for animal fat production, which is less used in food products. In this study, the fat obtained from sheep tail and ostrich abdominal tissue were investigated as waste from the slaughterhouse. For this purpose, in the first step, fats were extracted by wet rendering method and their chemical compositions were analyzed. In the second step, the fat was separated into two parts, stearin and olein, by dry fractionation. Then, the olein fraction was divided into two parts, soft stearin and superolein, and their fatty acid composition and physicochemical properties were measured. The sheep tail and ostrich tissues contained 10.66% and 5.18% moisture, 4.10% and 4.29% protein, 0.26% and 0.62% ash, and 84.93% and 88.35% fat, respectively, and the extraction yield were obtained 37.42% and 62.56%, respectively. The gas chromatography results showed that oleic acid, palmitic acid and stearic acid were the main fatty acids in sheep tail fat and oleic acid, palmitic acid, palmitoleic acid and linoleic acid were dominant in the fatty acid profile of ostrich fat. After fractionation, an increase in oleic content of olein and superolein in both fats increased iodine value and refractive index followed by decreasing melting point and L*. Peroxide value of sheep tail fat was 1.54 meqO2/ kg and the fractionation process had no significant effect on it, however, the peroxide value of ostrich fat increased significantly after the separation (p<0.05), which could be due to the presence of a considerable portion of linoleic in this fat. Therefore, it can be concluded that the fat extracted by wet rendering from sheep tail and ostrich tissues has an acceptable quality for edible use, and their stearin and soft stearin fractions can be used as an alternative to the hydrogenation process to produce semi-solid fat in food products.