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Food Lipids: Chemistry, Nutrition, and Biotechnology

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also found to decrease the crystallization temperature <strong>and</strong> lower the melting range<br />

of the milk lipids.<br />

Along with the enrichment of oils, acidolysis using EPA <strong>and</strong> DHA has also<br />

been useful in the synthesis of structured lipids. Structured lipids are composed of<br />

medium chain <strong>and</strong> long chain fatty acids, which meet the nutritional needs of hospital<br />

patients <strong>and</strong> those with special dietary needs. When consumed, medium chain fatty<br />

acids, such as capric <strong>and</strong> caproic acid, are not incorporated into chylomicrons <strong>and</strong><br />

are therefore not likely to be stored, but will be used for energy. They are readily<br />

oxidized in the liver <strong>and</strong> constitute a highly concentrated source of energy for premature<br />

babies <strong>and</strong> patients with fat malabsorption disease. Medium chain fatty acids<br />

also possess a nutritional advantage compared with other fatty acids in that they are<br />

non-tumor-producing forms of fat (27). Long chain fatty acids are also required by<br />

the body, especially in the form of PUFAs in the form of omega-3 <strong>and</strong> omega-6 fatty<br />

acids, which have been associated with reduced risk of platelet aggregation <strong>and</strong><br />

cardiovascular disease, <strong>and</strong> the lowering of cholesterol (27,28). When polyunsaturated<br />

fatty acids are present in the sn-2 position <strong>and</strong> medium chain fatty acids are<br />

present in the sn-1,3 positions, they are rapidly hydrolyzed by pancreatic lipase,<br />

absorbed <strong>and</strong> oxidized for energy, whereas essential PUFAs are absorbed as 2-monoacyglycerols.<br />

Therefore, structuring triacylglycerols with medium chain fatty acids<br />

<strong>and</strong> PUFAs can dramatically improve the nutritional properties of triacylglycerols<br />

(29). Producing a triacylglycerol rich in EPA or DHA at the sn-2 position, with<br />

medium chain fatty acids in the sn-1 or sn-3 positions, would provide maximal<br />

benefit, especially for intravenous use in hospitals (30). Structured lipids that are<br />

reduced in caloric content have also been developed by esterifying long chain monoacylglycerols<br />

containing behenic acid with capric acid. The produced triacylglycerols<br />

contain half the calories relative to natural triacylglycerols due to the incomplete<br />

absorption of behenic acid during digestion (31).<br />

Acidolysis is also a common method for production of cocoa butter substitutes.<br />

The most common method is acidolysis of palm oil midfraction, which contains<br />

predominantly 1,3-dipalmitoyl-oleoyl-glycerol with stearic acid to increase the level<br />

of stearate in the lipid (32). Chong et al. (33) also incorporated stearic acid into<br />

palmolein to produce 25% cocoa butter-like triacylglycerols.<br />

C. Alcoholysis<br />

As previously mentioned, alcoholysis is the esterification reaction between an alcohol<br />

<strong>and</strong> an ester (Fig. 4). Alcoholysis has been used in the production of methyl esters<br />

from esterification of triacylglycerols <strong>and</strong> methanol with yields of up to 53% (34).<br />

During alcoholysis, hydrolysis of triacylglycerols to produce diacylglycerols <strong>and</strong><br />

monoacylglycerols can occur, in some cases reaching levels as high as 11%, although<br />

the presence of small amounts of alcohol can inhibit hydrolysis. The main use of<br />

alcoholysis is in the performance of glycerolysis reactions.<br />

Figure 4 Lipase-catalyzed alcoholysis reaction between an acylglycerol <strong>and</strong> an alcohol.<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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