Transesterification interesterification

RandomiZation/Interesterification. Transesterification occurs when a carboxyUc acid (acidolysis) or alcohol (alcoholysis) reacts with an ester to produce a different ester (20). Ester—ester interchange is also a form of transesterification. If completely unsaturated triglyceride oil (UUU) reacts with a totally saturated fat (SSS) in the presence of an active catalyst such as sodium, potassium, or sodium alkoxide, triglycerides of intermediate composition may be formed. 

Interesterification (INES) is the exchange of acyl radicals between an ester and an acid (aci-dolysis), an ester and an alcohol (alcoholysis), or an ester and an ester (transesterification), and can be random, directed, or enzymatic. The process has been called intraesterification if an exchange of positions occurs within the same molecule, and randomization if exchange occurs between molecules.44,48 The principles can be used to position fatty acids on mole-... 

Interesterification > Acidolysis (triglyceride + fatty acid) Transesterification (e.g. triglyceride + triglyceride), Reaction with the fatty acids in the 1,3-positions only Reaction with the fatty acids in all three positions... 

In the interesterification of fats, 1,3-positional specific lipases catalyze reactions in which only the fatty acids in the a-positions of the triglycerides take part, whereas positional nonspecific lipases are able to catalyze reactions in which the fatty acids from both the a- and / -positions take part. In transesterification between two types of fat, the positional non-specific lipase is therefore able to randomize the fatty acids, resulting in the same fatty acid composition in the triglycerides as obtained in the commercially important chemical randomization process. In ester synthesis, positional non-specific lipases catalyze the reaction with both primary and secondary alcohols whereas positional specific lipases are more or less specific for primary alcohols. 

Enzymatic reactions in organic media have been a major issue in the field of biocatalysis over the last two decades. Carboxylesterases (mostly lipases) have been used in monophasic organic solution under controlled values of water activity (ajj for catalyzing ester formation the reaction equilibrium can be shifted towards ester formation by interesterification or transesterification [1]. Direct esterification is often hampered by water formation, which may increase o , thus negatively influencing the equihbrium. 

Under almost anhydrous conditions in organic medium, lipases can be used in the reverse mode for direct ester synthesis from carboxylic acids and alcohols, as well as transesterifications (acyl transfer reactions) which can be divided into alcoholysis (ester and alcohol), acidolysis (ester and acid), and interesterification (ester-ester interchange). The direct esterification and alcoholysis in particular have been most frequently used in asymmetric transformations involving lipases. The parameters that influence enzymatic catalysis in organic solvents have been intensively studied and discussed. ... 

Modification of the Properties of Fats and Oiis Transesterification reactions (interesterification and acidolysis) of triacylglycerols have been an important tool in fats and oils processing for the modification of their physical and rheological properties by changing the composition and distribution of their fatty acids. 

Many carbohydrate-based fat substitutes are mixtures of sucrose esters formed by chemical transesterification or interesterification of sucrose with one to eight FAs. The class with six to eight FAs are called sucrose FA polyesters. These molecules are too large to be broken down by intestinal lipase enzymes and, for that reason, do not show any caloric value (Voragen, 1998). 

Interesterification is a term used to describe reactions in which fatty acid esters react with free fatty acids (acidolysis), alcohols (alcoholysis), or with other fatty acid esters (transesterification). In food application, interesterification often refers to the reaction between different oils or fats with their fatty acyl groups rearranging among the molecules. 

This distribution of fatty acids is also of some interest to nutritionists as the effects of fatty acids in rats can be modified by redistributing the fats by interesterification (Mukherjee and Sengupta, 1981). As much as 40% of the dietary fat consumed in the Federal German Republic in recent years has been subjected to transesterification processes such as described by Perron and Broncy (1978) and Monseigny eta/. (1979). This makes surveys of composition of edible fats rather difficult in terms of fatty acids (Heckers and Melcher, 1978), and enforces the examination of unsaponifiable materials to discover the original oil composition (Strocchi, 1981). 

The uses cited by Coleman and Macrae (1980) for the lipase catalysed reaction are examples of acidolysis and transesterification. Acidolysis is illustrated by the increase in l(3)-palmitoyl-3(l)-stearoyl-2-olein (POSt) resulting from the reaction of palm oil mid-fraction with stearic acid in the presence of a 1,3-specific enzyme, and by the increase in the content of linoleic acid in olive oil when that oil is reacted with linoleic acid in the presence of an enzyme with fatty acid specificity. An example of transesterification is shown by the increase in POSt triglycerides when a 1,3-specific enzyme is used to catalyse the interesterification of shea butter and palm oil mid-fraction. 

Production of TAG enriched with polyunsaturated fatty acids (PUFA) via lipase catalysis in codliver oil has also been described (Haraldsson et ah, 1989). Preparation of y-linolenic acid enriched TAG via rapeseed lipases (Syed Rahmatullah et aL, 1994 Jachmanian and Mukerjee, 1996) and microbial lipases (Akoh et aL, 1995, 1996) has also been reported. Incorporation of eicosapentaenoic and docosahexaenoic acids into peanut oil via transesterification catalysed by microbial lipases has been reported by Sridhar and Lakshminarayana (1992). According to Wada and Koizumi (1986) and Kimoto et aL (1994) interesterification of fish oils to form TAG containing PUFA in the 2-position rather than the 1,3-positions increases the oxidative stability of the modified oil as compared to its original counterpart. 

Sometimes, the term transesterification is used instead of alcoholysis, particularly instead of methanolysis. It is also possible to come across the term re-esterification, which is also used in several senses. Oleochemistry uses this term for interesterification and esterification of fatty acids with glycerol. 

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