In the

food industry The food industry is a complex, global network of diverse businesses that supplies most of the food consumed by the world's population. The food industry today has become highly diversified, with manufacturing ranging from small, traditional, ...

and

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology ...

, interesterification (IE) is a process that rearranges the

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

s of a fat product, typically a mixture of

triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and '' glyceride''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as ...

. The process implies breaking and reforming the ester bonds C–O–C that connect the fatty acid chains to the

glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids know ...

hubs of the fat molecules. These reactions are performed by inorganic catalysts, yielding what is called chemical interesterification (CIE) in the industry; or by

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

s, in the so-called enzymatic interesterification (EIE). This process is typically used to adjust the physical characteristics of the fat, such as

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

and plasticity, for specific uses. It can be used, for instance, to turn oils into solid or semisolid products by combining them with other solid fats. It can also be used to prevent separation of solid fractions in

palm oil Palm oil is an edible vegetable oil derived from the mesocarp (reddish pulp) of the fruit of the oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 33% of global oils produced fr ...

and lauric fats, slow rancidification, or create oils more suitable for

deep frying Deep frying (also referred to as deep fat frying) is a cooking method in which food is submerged in hot fat, traditionally lard but today most commonly oil, as opposed to the shallow oil used in conventional frying done in a frying pan. No ...

. Compared to other processes that are used for the same purpose, such as

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate org ...

, interesterification generally preserves the original distribution of fatty acids in the product and hence is expected to preserve its nutritional and health attributes. However, those other techniques may still be applied to the starting fats or to the products of IE, and the latter may be blended with other fats. Also, some of the new triglycerides produced by IE may be fractionated (separated) through controlled

crystallization Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely de ...

. Interesterified fats are used in many industrial food products, including

cookie A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chips, ...

s, crackers, biscuits, cakes and icings, dairy fat replacers, pie crust,

popcorn Popcorn (also called popped corn, popcorns or pop-corn) is a variety of corn kernel which expands and puffs up when heated; the same names also refer to the foodstuff produced by the expansion. A popcorn kernel's strong hull contains the se ...

flatbread A flatbread is a bread made with flour; water, milk, yogurt, or other liquid; and salt, and then thoroughly rolled into flattened dough. Many flatbreads are unleavened, although some are leavened, such as pizza and pita bread. Flatbreads r ...

and

tortilla A tortilla (, ) is a thin, circular unleavened flatbread originally made from maize hominy meal, and now also from wheat flour. The Aztecs and other Nahuatl speakers called tortillas ''tlaxcalli'' (). First made by the indigenous peoples of M ...

Feedstock

Typically the feedstock (starting product) is a mixture of two or more oils. In particular, unsaturated vegetable oil can be interesterified with a fully hydrogenated version thereof, as in the illustration to the right. This procedure yields less saturated fat without creating the '' trans'' fat that would be produced by partial hydrogenation. The reaction does not go to completion, and the product will be a mixture of triglycerides with different amounts of saturation.

Process

Chemistry

In principle, when interesterification is applied to two pure triglycerides, each with three identical fatty acids (AAA and BBB), the result could contain six different triglycerides (AAA, AAB, ABA, ABB, BAB, and BBB). The number is 6, rather than 2³ = 8, because of the symmetry of the glycerol backbone. The number is much greater if the feedstock has three or more distinct fatty acids.

"Chemical" interesterification

In the so-called "chemical" interesterification, the catalyst is an inorganic compound such as

sodium methoxide Sodium methoxide is the simplest sodium alkoxide. With the formula , it is a white solid, which is formed by the deprotonation of methanol. Itis a widely used reagent in industry and the laboratory. It is also a dangerously caustic base. ...

. The reaction is carried out at high temperatures and creates three

by-product A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be consid ...

s — sodium

soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are used ...

s, fatty methyl esters, and

monoglyceride Monoglycerides (also: acylglycerols or monoacylglycerols) are a class of glycerides which are composed of a molecule of glycerol linked to a fatty acid via an ester bond. As glycerol contains both primary and secondary alcohol groups two differe ...

s) in addition to the interesterified fats.

Enzymatic interesterification

Enzymatic interesterification (IE) uses an

to break and reform the ester bonds. Enzymes most suitable for this process are

esterase An esterase is a hydrolase enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis. A wide range of different esterases exist that differ in their substrate specificity, their protein structure ...

;

lipase Lipase ( ) is a family of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually tr ...

; acylase; those enzymes that facilitate acidolysis reactions, transesterification reactions,

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors **Organic synthesis, the chemical synthesis of organi ...

or ester interchange reactions; enzymes having

phospholipase A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. Acids trigger the release of bound calcium from cellular stores and the consequent increase in free cytosolic Ca2+, an essential step i ...

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the form ...

activity, including thermostable and thermotolerant

hydrolase Hydrolase is a class of enzyme that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are es ...

activity; and polynucleotides. Some enzymes will break and reform ester bonds only at positions 1 and 3 (sp1 and sp3) of the glycerol hub, leaving the acids in position 2 (sp2) fixed. The most common industrial EIE process forces the liquid fat feedstock through a fixed-bed reactor, that typically contains an oil purification bed followed by an enzyme bed. The latter has the enzyme fixed on some inert granular substrate. The first bed removes impurities from the oil blend that could inactivate the enzyme or affect its performance. The enzyme activity decreases over time, so flow must be carefully monitored and adjusted over time to maintain conversion. Two or more reactors may be used in tandem, where the first reactor has the lowest enzyme activity and absorbs most of the impurities and harmful compounds. This sequencing protects the most active enzymes, which are in the last reactors. IE has been replacing CIE because it has fewer processing steps, can be carried out at lower temperatures, produces no by-products, and has lower production costs.

Advantages

Compared to simple blends, interesterified fats have a wider plasticity range, meaning that they retain their physical properties over a wider temperature range, without separation of their components. IE can also use a wider variety of feedstocks, such as soybean oil, they provide a better risk management profile than globally produced palm oil.

History

The earliest record of enzymatic Interesterification was in 1844, when Théophile-Jules Pelouze published a study on the synthesis of a triglyceride through the esterification of glycerol by

butyric acid Butyric acid (; from grc, βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, is a straight-chain alkyl carboxylic acid with the chemical formula CH3CH2CH2CO2H. It is an oily, colorless liquid with an unpl ...

. In 1920, Wilhelm Normann, who also patented the catalytic hydrogenation of fatty acids, was granted a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling disclo ...

for the chemical interesterification of edible lipids. This process became a viable option for the food industry as it improved the spreadability and baking properties of the common shortening

lard Lard is a semi-solid white fat product obtained by rendering the fatty tissue of a pig.Lard
entry in the ...

. Enzymatic interesterification was developed in the 1970s by the team at the Unilever Research Center at Colworth House in England. Their work proved that the use of a specific enzyme predictably rearranged the fatty acids on the glycerol backbone of a triglyceride at positions 1 and 3. This provided an expanded range of available triglyceride types. Still, EIE remained largely confined to research laboratories due to high enzyme prices. It was only in the 2000s that general concerns about the health effects of ''trans'' fats drove the industry to adopt interesterification as a replacement for partial hydrogenation (which had been the oil hardening method of choice, due to its lower cost)."Legal and Policy Resources on Public Health 'Winnable Battles'"
www.cdc.gov. Retrieved October 20, 2010. Adoption was greatly facilitated by the development of enzymes bound to inert solid substrates like

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is o ...

, by Novozymes and other companies.

References

T. L. Husum, L. S. Pedersen, P. M. Nielsen, M. W. Christensen, D. Kristensen, and H. C. Holm (2003):
Enzymatic interesterification: Process advantages and product benefits.
. Palm Oil Information Online Service. Retrieved 2010-10-20. W. Hamm and R. Hamilton, editors (2000): ''Edible Oil Processing''. Rousseau, D. (2002): "The Effects of Interesterification on the Physical Properties of Fats". Chapter 13 of ''Physical Properties of Lipids''. CRC Press. “Chemical vs. Enzymatic Interesterification.”
De Greyt, Wim. IUPAC-AOCS Workshop on Fats, Oils & Oilseeds Analyses & Production, 6 Dec. 2004. Retrieved October 20, 2010 {{Cite web , url=http://www.soci.org/-/media/Files/Lecture-Series/pb82.ashx/ , title=Interesterification Process Conditions , last=Kellens , first=Marc , year=2000 , access-date=2007-01-29

External links

Novozymes
Lipids Triglycerides