The relationship between structural lipids of sheep wool with its individual macrostructural components, chemical composition and physical indicators

Abstract

The data on the peculiarities of the structural organization, chemical composition and physical parameters of sheep wool of different breeds depending on the type of their hair are presented. It has been found that the down fibers of ewes of the Ukrainian Carpathian Mountain breed possess the lowest content of β-keratosis (10.2%) and the highest content of α-keratosis (64.4%). In the fine wool of Ascanian ewes and Prekos ewes, the content of β-keratosis is 12.9 and 11.5%, respectively, and the highest content of it (15.1%) is contained in the guard fibers of the Carpathian Mountain ewes. However, in the down fibers of these ewes and the Prekos breed ewes, there is the highest content of γ-keratosis ― 28.4 and 28.7%, the total sulfur and cystine (2.9 and 2.9 and 11.2 and 11.5%), respectively. Besides that, the guard fibers contain the lowest content of both γ-keratosis (58.2%) and sulfur and cystine (2.7 and 9.0%), respectively. It has been established that different categories of fibers contain different amounts of total lipids. The smallest amounts of free lipids are found in the thin down of the Carpathian Mountain ewes (0.75%), the thin wool of the Prekos ewes (0.71%) and Ascanian ewes (0.83%), and the largest number of them is found in the semi-coarse guard fibers of the Carpathian Mountain sheep (1.39%). For bound lipids, a diametrically opposite difference was established: the largest amount of lipids was found in the thin down (1.85%), and the smallest amount — in the semi-coarse guard fibers (1.47%). In the guard fibers, the biggest amount of free lipids is accounted for the fraction of non-esterified cholesterol (64.9% versus 56.5% in the down, 57.7 in the wool of Ascanian ewes and 63.3% in the Prekos ewes), and the least of all they contain the fraction of non-esterified fatty acids (9.6%), and another sterol fraction (9.2%). The fibers of the Prekos breed sheep are noted with the lowest content of esterified cholesterol (8.9%) and the highest content of non-esterified fatty acids. But the fraction of polar lipids consists of almost 50% of ceramides and sulfolipids (more than 20%). At the same time, ceramides account for no more than 40% in the fraction of bound lipids. Physical indicators of wool to some extent reflect the peculiarities of its structure and chemical composition. Thus, the guard fibers have the highest strength (9.1 cN/tex) and fineness (48.8 μm), which is natural, because the guard has the highest content of β-keratose, i.e. cuticle, and the highest amount of lipids. Instead, the thinnest fibers are down fibers (16.9 μm) and they are the weakest (7.0 cN/tex) and these fibers contain the least β-keratose. Thus, there is a direct relationship between the content of the free lipid fraction and the fiber diameter (r = 0.996; 0.887; 0746 for down, fine and semi-coarse, respectively), and between the content of bound lipids — inverse (r = –0.993;–0.995; –0.694).