Interesterification, directed

Early work showed that interesterification of milk fat resulted in an increase in the melting point of milk fat and the concentration of high melting triacylglycerols (de Man, 1961). The effect on the melting point of milk fat was greater in the case of directed interesterification compared to random interesterification. The use of solvents in the interesterification process also enhances its effects on the melting point of the modified milk fat (Weihe, 1961). 

In directed interesterification, the reaction temperature is lowered until the higher-melting and least-soluble triglyceride molecule in the mixture crystallizes. In this way, a fat can be separated into higher and lower melting fractions. 

The directed interesterification is of much industrial significance because it can be used to convert oils into more and/or less saturated fractions of original fat or oil or blend of two oils. 

In directed interesterification, the course of the reaction is shifted away from production of a population of acylglycerols with a fully random fatty acid distribution. This is achieved by a modification of reaction conditions to selectively remove from reaction some of the produced acylglycerol species as they are formed. Most... 

Directed interesterification can be employed to produce lard with an increased solids content at high temperatures, because of production of a fully saturated acylglycerol population. Such a product would be plastic over a greater range of temperature. Lard produced by nondirected interesterification requires the addition of stearin for high-temperature stability. 

Some companies are producing low-trans- or zero tranj -margarines by random (252) or directed interesterification of mixtures of unhydrogenated and fully hydrogenated soybean oils and other fats (253). To produce these products, a liquid oil and completely hydrogenated hardstock are interesteiified, so that proper plasticity can be obtained. Oils that contain considerable amounts of palmitic acid favorably influence crystallization and polymorphic form of the interesterified fat blends (254). 

Continuous interesterification processes exist but to date none have been commercialized. Interesterification is generally performed in small batches by specialty processors. An alternate method of increasing interest is directed interesterification using enzymes. The process is generally applied to palm-oil-based materials such as cocoa butter substitutes and to coconut oils. There is some concern about the effectiveness of interesterification with physical refined oils as low levels of FFA must be present or the reaction will not proceed as planned (5). Although not a hazardous process, interesterification is often included in the hydrogenation section of the refinery because of the similarity of the reactors. 

Fiq. 12-7. Calculated change in lard glyceride composition with directed interesterification. awley and Holman, J. Oil Chemists Soc., 33, 29 (1956).]... 

An alkaline catalyst, such as sodium methoxide, or metallic sodium is normally used. The fat must be dry and free of fatty acids to prevent destruction of the catalyst. When the reaction is conducted at a temperature that maintains the fat in a molten state the process leads to "random" interesterification. "Directed" interesterification takes place when a portion of the fat is in a solid state. In a typical case of random interesterification the fat is heated in a closed tank under vacuum to 135°-150°C, 0.1% of catalyst is added, and mixed thoroughly for about 0.5 hr. A sample is taken for analysis and if the reaction is not complete an additional amount of catalyst is added and mixed for another 0.5 hr. When the interesterification is complete approximately 0.05% of phosphoric acid is added with agitation to neutralize the catalyst. The batch is then washed or bleached. 

If the equilibrium is disturbed by, for example, the crystallization from the reaction mixture of high-melting-point triglycerides it is then referred to as directed interesterification. 

These changes can be further modified if the interesterification process is carried out at a lower temperature (0-40 C), so that fully saturated glycerides (S3) crystallize from the reaction mixture. This is called directed interesterification. Crystallization disturbs the equilibrium in the liquid phase so that more S3 forms and again separates producing, finally, more S3 and U3 and less of the mixed glycerides. This usually causes an increase in the melting range of the fat. Such reactions are slower and may take up to 24 hours. 

Diphosphoinositide, 29, 307 Dipalmitoylphosphatidylcholine, 549 Dipyridine haems, electronic spectra, 445 Direct extraction, 250 Directed interesterification, 478 Disorder in hydrocarbon chains, 336... 

Nugrahini, A. D. Soerawidjaja, T. H. (2015). Directed Interesterification of Coconnt Oil to Produce Structured Lipid. Agriculture and Agricultural Science Procedia, 3, 248 - 254... 

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