Characterization of the Lipid Fraction in Lamb Meat: Comparison of Different Lipid Extraction Methods
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Characterization of the Lipid Fraction in Lamb Meat: Comparison of Different Lipid Extraction Methods Myriam Fiori & Maria Francesca Scintu & Margherita Addis
Received: 10 October 2012 / Accepted: 20 February 2013 # Springer Science+Business Media New York 2013
Abstract The aim of this study was to evaluate the performance of four different extraction methods commonly used to quantify the intramuscular lipid content in meat: the Association of Analytical Chemists (AOAC) method (reference method) and methods based on the use of a solvent mixture with different polarities, such as chloroform–methanol described by Folch et al. (J Biol Chem 226:497, 1957) and Christie (1989) or hexane–isopropanol described by Hara and Radin (Anal Biochem 90:420, 1978). The following parameters were taken into account: lipid content; relative proportions of neutral and polar lipids; fatty acid composition of total, neutral, and polar lipid fractions; and phospholipid composition. The use of a combination of solvents with different polarities (Hara–Radin, Folch, and modified Folch methods) was more effective in extracting intramuscular lipids than the use of a single solvent (AOAC, reference method). The Hara– Radin method provided a cleaner lipid extract with a significantly higher content of total fatty acids than that obtained with the Folch and modified Folch methods. The lower polarity of the hexane–isopropanol mixture allowed us to obtain an extract richer in neutral lipids (triglycerides and diglycerides) and thus in saturated and monounsaturated fatty acids. The percentage distribution of individual fatty acids in the neutral lipid fraction was generally not affected by the extraction method adopted, while lipid obtained with both the Hara– Radin and Folch methods had a polar fraction with a higher percentage of polyunsaturated fatty acids. The use of the Hara–Radin method provided a polar fraction with less nonlipid material and lower phospholipid degradation. M. Fiori : M. F. Scintu : M. Addis (*) Dipartimento per la Ricerca nelle Produzioni Animali, AGRIS Sardegna, 07040 Loc. Bonassai, S.S. 291 Sassari-Fertilia Km. 18,600, Olmedo, Sassari, Italy e-mail: [email protected]
Keywords Lipid extraction . Lipid composition . Fatty acids . Phospholipids . Lamb meat
Introduction Lipids in meat are a mixture of nonpolar compounds (mainly triglycerides, diglycerides, monoglycerides, and cholesterol), free fatty acids, and several polar compounds such as phospholipids and sphingolipids (Ruiz et al. 2004). They are linked to other cellular components (carbohydrates and proteins) by weak hydrophobic forces, van der Waals interactions, or ionic or hydrogen bonds. In general, the characterization of lipids in food requires their solvent extraction as the initial step. The results of the subsequent analysis, aimed at further characterizing the extracted lipid matrix, depend on the choice of extraction procedure. Solvents used to extract fat should have high solubility for all lipid compounds and should be sufficiently polar (Smedes an
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