Citrus lipids

From a dietary standpoint, the contribution of citrus lipids is insignificant and only between. 06 and. 09 percent has been found in oranges (37J. They are, however, of importance because of their effects on the development of off-flavors (12J, thus lowering the palatability of these products. The near absence of lipids in citrus makes it a desirable food for those on a limited fat diet. 

After the extraction of lipid and nonlipid components from the leaves of mandarin orange Citrus reticulata, the lipid fraction was further separated by PTLC to determine different lipid classes that affect the chemical deterrence of C. reticulata to the leaf cutting ecat Acromyrmex octopinosus. These lipids seem to be less attractive to the ants [81a]. The metabolism of palmitate in the peripheral nerves of normal and Trembler mice was studied, and the polar lipid fraction purified by PTLC was used to determine the fatty acid composition. It was found that the fatty acid composition of the polar fraction was abnormal, correlating with the decreased overall palmitate elongation and severely decreased synthesis of saturated long-chain fatty acids (in mutant nerves) [81b]. 

Alpha hydroxy acids (AHAs) are water-soluble substances and thereby penetrate the outermost epidermal skin layers. In contrast, beta hydroxy acids (BHAs) are lipid (fat) soluble and are capable of penetrating to the underlying layers of skin (the dermis) located 1-5 mm below the surface of the skinJ2 Most AHAs are derived from plant materials and marine sources. Commonly used AHAs include malic acid (found in apples), ascorbic acid (a common ingredient in numerous fruits), glycolic acid (a constituent of sugar cane), lactic acid (a component of milk), citric acid (naturally abundant in citrus fruits), and tartatic acid (found in red wine). A common BHA is salicylic acid (an ingredient in aspirin). 

Botanically speaking, citrus is a hesperidium, a berry with a leathery aromatic rind and a fleshy interior divided into sections. As shown by the cross section shown in Fig. 6.1, the exo carp or peel consists of an outer layer called the flavedo which contains oil glands and pigments and a white spongy inner layer called the albedo. The fleshy interior or endocarp of the fruit consists of wedge-shaped sections (segments) filled with multiple fluid-filled sacs or vesicles. These juice sacs constitute the edible portion of a citrus fruit. The cytoplasm contents provide the primary source of the citrus juice. The juice consists primarily of water, sugars, pectins, lipids, terpenes, amino acids, phenolics, carotenoids and minerals. 

Thiobarbituric acid (TBA) assays detection in lipids, 547-564 Malondialdehyde. see Malonaldehyde Malt, (3-glucan quantitation, 751 Mandarin orange oil. see Citrus oils Orange... 

Certain bioflavonoids may play a preventive role against cardiovascular diseases. Some citrus and other bioflavonoids have been demonstrated to reduce serum cholesterol levels and to affect fatty acid metabolism (70,71,72). The strong antiadhesive action on red cells and platelets of highly methoxylated flavones such as nobiletin, which also demonstrates antithrombogenic activity (73), indicates an important role in blood rheology and tissue perfusion. The antiadhesive action may indicate a preventive role in atherosclerosis since there is evidence that reduced perfusion of the vascular wall may interact with serum lipids to promote atherogenesis (74). 

The bright orange and yellow colors of citrus peel are due to the lipid soluble carotenoids. The more common ones in peel and juice are shown in Figure 1. Some of the first studies on citrus carotenoids were by the European workers, Zechmeister and Tuzson, in 1931 (26, 2 7, 28). They isolated p-carotene, cryptoxanthin, lutein, zeaxanthin, p-citraurin, and probably violaxanthin. In 1952, Natarajan and MacKinney (29) found phytofluene and a, p, and zeta carotenes. These studies were followed by those of Curl, who between 1953 and 1967 reported the presence of some 74 carotenoids in several citrus cultivars. 

Versteeg (8) speculated on the function of PE in vivo. He noted the high activity of PE in citrus fruit compared to the amount of available pectin. The fruit contain sufficient activity to deesterify the pectin to low methoxy pectin in 10 min at optimum pH. He suggested that the methyl transferase found by Kauss and Hassid (39) to esterify pectic acid to pectin in mung bean shoots and to be located in a lipid-membrane complex (31) functioned as pectinesterase after the lipid membranes were destroyed and the environment changed. However, no definitive experiments to establish the role of PE in fruits were reported. 

The contribution of lipid oxidative products to off-flavor development has been studied by many workers, and a review of these studies has been presented by Nagy (38). It is generally agreed that the contribution of the lipid oxidative products to the flavor deterioration of processed citrus products is relatively minor when compared to the contributions by the products formed by the acid-catalyzed hydrolysis of flavoring oils and the products of Maillard browning (39,40). 

Phenolics. The phenolics of citrus represent a varied and widely studied class of compounds. They range from the lipid-soluble methoxylated coumarins and psoralens to the water-soluble glycosides of the flavanones and flavones. They include the intensely bitter naringin and the highly insoluble hesperidin. Different classes within the group have characteristic UV spectra which have been used to detect adulterations in juices and oils. 

Riederer (1990) published a more complex method based on two lipid-like compartments, an acylglycerol lipid compartment and a cuticle compartment. The acylglycerol-air partition coefficient was assumed to equal Kow/Kaw, while measured values of the cuticle-water partition coefficient were employed for the cuticle compartment. Riederer (1995) later modified this model to include a predictive equation for the cuticle-water partition coefficient, based on Kerler and Schonherr s measurements (1988) of eight chemicals with log KqW values ranging from 1.92 to 7.86. They used isolated citrus and rubber plant leaf cuticles as well as tomato and green pepper fruit cuticles. The resulting equation is... 

Lipid constituents. Early studies on off-flavor development in citrus products suggested that off-flavors might be related to the degradation of lipids (12-14). Curl (15) compared the flavors before and after storage of whole tangerine juice and tangerine... 

Riederer, M. and Schneider, G. (1990). The effect of the environment on the permeability and composition of Citrus leaf cuticles. 2. Composition of soluble cuticular lipids and correlation with transport properties. Planta, 180, 154-165. 

Borradaile, N.M., Carroll, K.K., and Kurowska, E.M. 1999. Regulation of Hep G2 cell apolipoprotein B metabolism by the citrus flavanones hesperetin and naringenin. Lipids 34, 591-598. 

Ying Zhong Memorial University of Newfoundland, St. John s, Newfoundland, Canada, Antioxidants Regulatory Status , Citrus Oils and Essences , Lipid Oxidation Measurement Methods , Marine Mammal Oils. 

Crude citrus seed oils need to be refined before use as edible oils. Only triacylglycerols, diacylglycerols, and polar lipids remain after degumming, refining, bleaching, and deodorization. However, trace amounts of phosphatides (lecithin) and plant sterols may also remain in the oil (37). 

Colker CM, Kalman DS, Torina GC, Perlis T, Street C. Effects of Citrus aurantium extract, caffeine, and St. John s wort on body fat loss, lipid levels, and mood states in overweight healthy adults. Curr Ther Res 1999 60 145-153. 

Vitamin C is used to metabolize carbohydrates, for tissue repair and capillary endothelium, and for synthesis of protein, lipids, and collagen. Vitamin C is also needed for absorption of iron and folic acid metabolism. Vitamin C is found in citrus fruits, tomatoes, leafy green vegetables, and potatoes. Excess serum levels of vitamin C are excreted without any negative effects. Vitamin C is commercially available as Ascorbicap, Cecon, Cevalin, and SoluCap C. 

Kay, R.M. and Truswell, A.S. 1977. Effect of citrus pectin on blood lipids and fecal steroid excretion in man, Am. J. Clin. Nutr., 30 171-175. 

Fresh samples of the essential oils from lemon (Citrus limori) ( R.C.TREATT , the United Kingdom), pink grapefruit (iCitrus paradisi) ( Frutarom , Israel), coriander Coriandrum sativum L.) and clove buds (Caryophyllus aromaticus L.) ( Plant Lipids Ltd. , India), and the mixtures of lemon and clove (1 1), lemon and coriander (1 1), lemon, coriander and clove (1 1 1) oils were investigated. 

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