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Food Lipids: Chemistry, Nutrition, and Biotechnology

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are 1-palmitoyl-2-oleoyl-3-stearoylglycerol (POS), 1,3-dipalmitoyl-2-oleoylglycerol<br />

(POP), <strong>and</strong> 1,3-distearoyl-2-oleoylglycerol (SOS) with levels of 41–52%, 16%, <strong>and</strong><br />

18–27%, respectively (8,17). The main disadvantage of using cocoa butter in chocolate<br />

<strong>and</strong> confections is its high cost. A cocoa butter equivalent can be made from<br />

inexpensive fats <strong>and</strong> oils by interesterification. By transesterifying fully hydrogenated<br />

cottonseed <strong>and</strong> olive oil, Chang et al. (17) were able to produce a cocoa butter<br />

substitute with similar POS levels <strong>and</strong> slightly higher SOS levels than those found<br />

in cocoa butter. The melting range of the transesterified product was 29–49�C, compared<br />

with 29–43�C for cocoa butter. In order to remove the desired triacylglycerol<br />

product from the other triacylglycerols, trisaturated triacylglycerols were removed<br />

by crystallization in acetone. High-oleic sunflower oil <strong>and</strong> palm oil fraction have<br />

also been transesterified to obtain cocoa butter substitutes (5).<br />

B. Acidolysis<br />

Acidolysis, the transfer of an acyl group between an acid <strong>and</strong> an ester, is an effective<br />

means of incorporating novel free fatty acids into triacylglycerols (Fig. 3). Acidolysis<br />

has been used to incorporate free acid or ethyl ester forms of eicosapentaenoic acid<br />

(EPA) <strong>and</strong> docosahexaenoic acid (DHA) into vegetable <strong>and</strong> fish oils to improve their<br />

nutritional properties. The nutritional benefits of consuming polyunsaturated fatty<br />

acids, such as EPA <strong>and</strong> DHA, derived from fish oils have been proven. When consumed,<br />

EPA reduces the risk of cardiovascular disease by reducing the tendency to<br />

form blood clots, whereas DHA consumption is required for proper nervous system<br />

<strong>and</strong> visual functions, due to its accumulation in the brain <strong>and</strong> retina (20,21). Concentrations<br />

of EPA <strong>and</strong> DHA in fish oils to levels approaching 30% can be achieved<br />

using molecular distillation, winterization, <strong>and</strong> solvent crystallization. However, performing<br />

an acidolysis reaction between cod liver oil <strong>and</strong> free EPA <strong>and</strong> DHA, Yamane<br />

et al. (22) were able to increase the EPA content in the oil from 8.6% to 25% <strong>and</strong><br />

the DHA content from 12.7% to 40% using immobilized lipase from Mucor miehei.<br />

Using ethyl esters of EPA, fish oil has been enriched by interesterification to contain<br />

40% EPA <strong>and</strong> 25% DHA (wt%) (23). During acidolysis in a fixed bed reactor, Yamane<br />

et al. (24) increased the polyunsaturated fatty acid (PUFA) content of cod liver<br />

oil by reducing the temperature to between �10�C <strong>and</strong> �20�C in the product reservoir.<br />

This led to crystallization <strong>and</strong> removal of more saturated fatty acids present<br />

in the fish oil. Lipases with strong specificities against EPA or DHA have also been<br />

used to enrich their content in fish oils (25). Future developments in lipase-catalyzed<br />

interesterification using EPA <strong>and</strong> DHA is directed to improving the nutritional quality<br />

of vegetable oils by enrichment with these fish oil–derived fatty acids. Acidolysis<br />

has also been used by Oba <strong>and</strong> Witholt (26) to incorporate oleic acid into milk fat.<br />

This process led to an increase in the level of unsaturated fatty acids in butter without<br />

losses in the characteristic flavor of butter. Acidolysis of milk fat with oleic acid was<br />

Figure 3 Lipase-catalyzed acidolysis reaction between an acylglycerol <strong>and</strong> an acid.<br />

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

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