Food Lipids: Chemistry, Nutrition, and Biotechnology

5
Extraction and Analysis of Lipids
FEREIDOON SHAHIDI
Memorial University of Newfoundland, St. John’s, Newfoundland, Canada
P. K. J. P. D. WANASUNDARA
University of Saskatchewan, Saskatoon, Saskatchewan, Canada
I. INTRODUCTION
Lipids are among the major components of food of plant and animal origin. There
is no precise definition available for the term lipid; however, it usually includes a
broad category of compounds that have some common properties and compositional
similarities. Lipids are materials that are sparingly soluble or insoluble in water, but
soluble in selected organic solvents such as benzene, chloroform, diethyl ether, hexane,
and methanol. Together with carbohydrates and proteins, lipids constitute the
principal structural components of tissues. However, the common and unique features
of lipids relate to their solubility rather than their structural characteristics [1]. Many
classification systems have been proposed for lipids. From the nutrition point of view,
according to the National Academy of Sciences’ report on nutrition labeling, fats and
oils are defined as the complex organic molecules that are formed by combining
three fatty acid molecules with one molecule of glycerol [2]. As indicated in Table
1 [3–5], lipids are generally classified as simple and compound (complex) or derived
lipids according to the Bloor [3] classification.
Foods contain any or all of these lipid compounds; however, triacylglycerols
(TAGs) and phospholipids (PLs) are the most abundant and important ones. Liquid
TAGs at room temperature are referred to as oils, and are generally of plant or marine
origin (e.g., vegetable and marine oils). Solid TAG at room temperature are termed
fats, which are generally of animal origin (e.g., lard and tallow).
Accurate and precise analysis of lipids in foods is important for determining
constituting components and nutritive value, standardizing identity and uniformity,
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.