Benders'dictionary of nutrition and food technology

283extracted into an aqueous medium: cholesterol and othersterols, squalene, carotenoids and vitamins a, d, e and k.Thesaponifiable lipids are triacylglycerols (and mono- and diacylglycerols)and phospholipids, which can be extracted into anaqueous medium after alkaline hydrolysis (saponification).lipids, plasma Total blood lipid concentration in the fasting stateis about 590 mg per 100 mL plasma: 150 mg triacylglycerols,160 mg (4 mmol) cholesterol, 200 mg phospholipids, mainly in theplasma lipoproteins. After a meal the total fat increases, as aresult of the chylomicrons containing the recently absorbeddietary fat.See also lipoproteins, plasma.lipochromes Plant pigments soluble in lipids and organic solvents,e.g. chlorophyll, carotenoids.lipodystrophy Abnormality in the metabolism or deposition offats; abnormal pattern of subcutaneous fat deposits.lipofuscin A group of pigments that accumulate in several bodytissues, particularly the myocardium, during life and are consequentlyassociated with the ageing process.lipoic acid 1,2-Dithiolane-3-valeric acid (6,8-thioctic acid),coenzyme in the oxidative decarboxylation of pyruvate, α-ketoglutarate and branched-chain keto-acids. Not a dietaryessential.lipolysis Hydrolysis of triacylglycerols to mono- and diacylglycerols,glycerol and free fatty acids, catalysed by lipase.lipolytic rancidity Spoilage of foods as a result of hydrolysis offats to free fatty acids on storage (by the action of lipase, eitherbacterial lipase or the enzyme naturally present in the food).Sincethe enzyme is inactivated by heat, occurs only in uncooked foods.See also acid number.lipoprotein [a] (Lp[a]) Complex of low-density lipoprotein inwhich an additional protein, apo-a, is bound to apo-protein B-100 by a disulphide bridge. It is genetically determined and thereis a strong association between Lp[a] and coronary arterydisease.lipoproteins, plasma Lipids, encased in protein, in the bloodplasma.Chylomicrons are assembled in the intestinal mucosa, andcontain the products of digestion of dietary fat. They areabsorbed into the lymphatic circulation, and enter the bloodstreamat the thoracic duct. Triacylglycerol is hydrolysed bylipoprotein lipase in adipose tissue and muscle, and the chylomicronremnants are cleared by the liver.Very low-density lipoproteins are secreted by the liver, containingnewly synthesised triacylglycerol and that from chylomi-