International Journal of Nutrition, Pharmacology, Neurological Diseases

REVIEW ARTICLE
Year
: 2011  |  Volume : 1  |  Issue : 2  |  Page : 134--138

Process advantages and product benefits of interesterification in oils and fats


Mohammad Asif 
 Department of Pharmacy, GRD (PG) Institute of Management and Technology, -Dehradun, Uttarakhand, India

Correspondence Address:
Mohammad Asif
Department of Pharmacy, GRD (PG) Institute of Management and Technology, 214, Rajpur Road, Dehradun-248 901, Uttarakhand
India

Abstract

The physical properties of oils and fats depend on their chemical properties, such as unsaturation, saturation, chain length, and distribution of the three hydroxyl groups of glycerol in the fatty acids. These characteristics change by hydrogenation, fractionation, blending, and interesterification (IE), hence improving the spectrum for the application of the oils and fats. IE is a process where the fatty acids have been moved from one triglyceride molecule to another and it does not alter the fatty acids. IE (chemical and enzymatic) is used to deal with the problems of plastic fat products such as granular development, texture breakdown, lumpy appearance, post hardening, consistency, melting point, and rancidity and create oil more suitable for deep frying or making margarine with good taste and low content of saturated fatty acids, etc. Nutritionally, IE contributes in eliminating or reducing trans fatty acids, providing a higher essential fatty acid activity. Trans and hydrogenated fats increase the coronary heart disease risk factors.



How to cite this article:
Asif M. Process advantages and product benefits of interesterification in oils and fats.Int J Nutr Pharmacol Neurol Dis 2011;1:134-138


How to cite this URL:
Asif M. Process advantages and product benefits of interesterification in oils and fats. Int J Nutr Pharmacol Neurol Dis [serial online] 2011 [cited 2019 Jun 15 ];1:134-138
Available from: http://www.ijnpnd.com/text.asp?2011/1/2/134/84203


Full Text

 Introduction



Fats consist mainly of various triglycerides which are made up of a glycerol backbone that is esterified with three fatty acid molecules. The triglycerides contain a mixture of saturated, monounsaturated, and polyunsaturated fatty acids. Interesterification (IE) is carried out by blending the desired oils and then rearranging the fatty acids over the glycerol backbone with the help of catalysts or enzymes (e.g., lipase). The physical characteristics of oils and fats depend on their chemical properties, such as chain length, presence of double bonds, and the distribution of the three hydroxyl groups of glycerol in the fatty acids. These characteristics change by hydrogenation, fractionation, blending, and IE for improving the application of fats and oils. Saturated fats come from two primary sources, animals, in the form of animal fats, butter, cream, milk, cheeses, and other dairy products, and from plants such as coconut oil, palm oil, and cocoa butter. [1],[2],[3] These types of fat have been linked with high levels of blood cholesterol. Unsaturated fats, which are commonly found in fish oil, perilla oil, linseed oil, olive oil, etc., are considered heart healthy fats because they may help lower blood cholesterol [Table 1].{Table 1}

When exposed to air, unsaturated fats are decomposed, and give rancid, stale, or unpleasant odors. Saturated fatty acids are generally solid at room temperature and not very desirable for many applications. Rearranging these tryglycerides with oils containing unsaturated fatty acids lowers the melting point and creates fats with properties better suited for target food products. In addition, blending interesterified oils with liquid oils allows the reduction in saturated fatty acids in many trans fatty acid-free food products. The interesterified fats can be separated through controlled crystallization also called fractionation. [3],[4]

In partial hydrogenation, some of the unsaturated fatty acids, which are normally found as the cis isomer about the double bonds, are changed to a trans double bond and remain unsaturated. Trans fatty acids of the same length and weight as the original cis fatty acids still have the same number of carbons, hydrogens, and oxygens but they are now shaped in a more linear form, as opposed to the bent forms of the cis isomers [Figure 1] and [Figure 2]. These trans fatty acids tend to raise low-density lipoprotein (LDL) or bad cholesterol level and lower high-density lipoprotein (HDL) or good cholesterol level. [5],[6]{Figure 1}{Figure 2}

IE fat is a type of oil where the fatty acids have been moved from one triglyceride molecule to another. IE does not alter the fatty acids. This is unlike partial hydrogenation which produces trans fatty acids. IE modifies the physical properties of an oil or fat blend by rearranging the fatty acid groups within and between different triglycerides. This is generally done in order to modify the melting and crystallization properties, slow rancidification, and create oil more suitable for deep frying with a good taste and low content of saturated fatty acids. Interesterified fats are used primarily in coating fats, margarines, sweets, shortening, pastry, and other confectionary products. IE is used to deal with the problems of plastic fat products such as granular development, texture breakdown, lumpy appearance, posthardening, consistency, etc. Nutritionally, IE contributes in many ways; apart from eliminating or reducing trans fatty acids, it provides a higher essential fatty acid activity. [3],[7],[8]

 Modification of Fats and Oils



Hydrogenation

Hydrogenation is carried out with hydrogen at high temperature and pressure, catalyzed by a nickel catalyst that changes the unsaturated fat to a saturated fat. The hydrogenation process increases the melting point of the fat, which changes liquid oil into solid shortening. This process stops the decomposition or rancidity of unsaturated fats. By controlling the degree of hydrogenation, it is possible to control the melting profile of the fats. After the reaction, the addition of citric acid is required to eliminate nickel soaps, filtration, bleaching, and deodorizing. Food products containing hydrogenated fats have an improved shelf-life and flavor stability compared to unsaturated fats. But fully hydrogenated fats are too waxy or solid to use as food additives, so manufacturers use partially hydrogenated oils instead. In terms of food safety, the possibility of having trace metal residues in IE fats, as is the case with hydrogenation, can be totally eliminated. [8],[9]

Production of trans fats

During the process of partial hydrogenation, some of the double bonds are rearranged, which alters cis/trans configurations, thereby producing trans fatty acids [Figure 3]. The cis configuration is very common in any unsaturated fat that has not been subjected to the partial hydrogenation process, which allows the fat molecules to lie close together and become solid rather than liquid.{Figure 3}

This process includes the use of hydrogen, chemical catalyst (nickel), and the formation of trans fatty acids (partial hydrogenation). Trans fatty acids have a negative impact on health when consumed in large amounts. Trans fatty acids are artery cloggers, and they have been shown to decrease the levels of HDL or good cholesterol, and increase the blood levels of LDL or bad cholesterol. Elevated levels of LDL cholesterol increase the risk of developing coronary heart disease (FDA, 2006). The majority of trans fats in the diet comes from partially hydrogenated unsaturated fats which are used in the making of many prepared foods like french fries, cookies, etc. because they increase the shelf-life and add flavor. There is an overall trend to reduce/eliminate trans fats from diet and replace trans fats with low or zero trans fat alternatives. [6],[7],[9]

Fully hydrogenated fats do not contain trans fatty acids, because all the double bonds in the fat molecules have been eliminated. One way to achieve a more suitable melting profile without producing trans fatty acids is to mix a fully hydrogenated fat with a naturally liquid oil or to interesterify the mix to get the specific melting profile of the end-product.

To address this growing concern about trans fats, alternative methods of fat modification technology are used, particularly IE. The method of IE is chemical as well as enzymatic. The chemical method is not perfect, and the enzymatic IE seems to be the perfect solution to the problem. [3],[9],[11]

 Interesterification



IE was introduced in the 1940s and commercialized in the 1950s. [12] Since then, its applications in food have more or less been established. IE is one of the three main fat modification techniques; other two techniques are fractionation and hydrogenation. The hydrogenation process is complicated, and requires multiple steps.

IE or ester-ester exchange is a process during which the fatty acids of triglycerides exchange positions from one glyceride to another, thereby altering the chemical composition as well as physical properties of the fats. IE is thus an efficient way for changing and controlling the melting properties of oils and fats. IE is applied directly to naturally derived oils or fats, or to hydrogenated or fractionated oils. This process is accomplished by catalytic methods (chemical or enzymatic). IE is a rearrangement process which does not change the degree of unsaturation or the isomeric state of the fatty acids as they transfer in their entirety from one position to another. Under some conditions, the fatty acids are distributed in a more random manner than they were present originally.

Chemical and enzymatic interesterification

The IE process works through the use of a variety of chemicals as the catalyst. This process is known as chemical interesterification (CIE). The most recent advancement in this field has been the development of a new method of IE which uses a biologically derived enzyme as the catalyst. This process is known as enzymatic interesterification (EIE). IE adjusts the melting profile of a blend of saturated and unsaturated fats. [12],[13],[14],[15]

Chemical interesterification

There is no possibility of a partial reaction in CIE which is contrast to hydrogenation and EIE. This is because the CIE occurs very rapidly once started, and equilibrium is reached within minutes. The reaction will therefore be completed and the properties of the interesterified product can only be controlled by the composition of the fat ingredients. Although the reaction time is short, washing, bleaching, and deodorization are required after CIE. The most common chemical catalysts are sodium methylate (methoxide) or sodium ethylate (ethoxylate). The catalyst shifts the fatty acids of the triglycerides around randomly. No trans fatty acids are produced, but the catalyst requires thorough purification downstream after the IE to give the required quality.

The drawback of CIE is that the catalysts are very reactive and must be handled with extreme care to prevent contact with the skin or eyes. The level of CIE cannot be controlled. In contact with water, the catalysts may explode. The process is carried out under harsh conditions and by-products are formed. These by-products are removed by bleaching and washing. In CIE, all three positions of the triglycerides are shifted randomly, which creates a less natural fat compared to the EIE method. The process produces waste water, and oil loss due to the posttreatments.

Enzymatic interesterification

EIE has been used by biological compounds or enzyme. The lipase immobilization technology was obtained with the development of the granulation technology and novozymes to develop a low-cost silica granulated lipase product for bulk fat modification. This granulated lipase product enables lipases to be used for the production of bulk fats such as margarine, shortenings, and vanaspati by EIE.

The enzymatic process is much simpler than the chemical and there is no requirement for any posttreatment of the interesterified oil afterward. The benefits of EIE are low investment costs, no trans fats formed, simple and easy continuous process, more natural fat produced, production of a large variety of end-products, environment friendly production, and no use of chemicals or solvents. The use of CIE is not feasible. Instead, EIE can be used to produce IE fats of specific triglycerides.

Basic chemistry of interesterification

IE is the random exchange of acyl groups within a triglyceride or between more than one triglyceride. Interesterification within triglyceride molecules i.e. rearrangement of fatty acids chains (R1, R2, and R3). The final product of Interesterification formed by interchange the position of glycerides. IE can occur at high temperatures, or it can be induced at low temperatures with the use of a catalyst [Figure 4] and [Figure 5]. [1],[2],[3],[4]{Figure 4}{Figure 5}

 Applications of Interesterification in Fats/Oils



The major development by IE has been in the improvement of processing technology with higher efficiency through lower utility consumption and minimal oil loss, and as such, is a feasible option to hydrogenation in solid fat production. IE helps stabilize and increase the amounts of crystals which are needed for a smooth texture and functional properties, and products are free from trans fatty acids. A softer product with a lower melting point and without phase separation can be produced by IE. IE is used to modify fats in the following ways:

Change the overall melting profileImprove the compatibility of the triglycerides in the solid stateImprove the plasticity of the resulting solid by changing the crystallization propertiesCombine the properties of mixed oils and fatsIE can also be used to produce a waxy translucent for coating purposesIE blends soft oils with hard fats to a desired functionality and consistencyBy combining IE and other modification processes, many products such as shortenings, margarines, and vegetable ghee with low trans fat or no trans fat at all can be formulatedInteresterifying oil improves its melting propertiesSatisfactory quality of confectionery fats can be produced.

The health effects of IE concluded that both the IE blend and the partially hydrogenated fat blend increase the fasting LDL/HDLcholesterol ratio, indicating an adverse effect on CVD risk and also found that fasting plasma glucose levels were higher after few weeks on the interesterified fat than after other diets. This study found no effects of IE on fasting levels of blood lipids, glucose, and insulin. Christophe et al. have studied the effect of IE where it lowers the blood total cholesterol level. [15],[16],[17],[18],[19],[20]

 Conclusions



In conclusion, there are many reasons for changing the melting properties of fats and oils. Basically, five different methods of changing the melting property profiles of fats and oils exist: blending, fractionation, chemical interesterification, enzymatic interesterification, and hydrogenation. In this article, we have only discussed the last three methods which have one thing in common: they all change the composition of the fat molecules during the process. IE is an alternative process to hydrogenation. With the advanced technology, cheap raw materials such as stearin can be optimized in fat product formulations. The IE process is much more flexible in modifying oils and fats and time saving and environment friendly as well. EIE of fats and oils provides a safe, easy and cost-efficient alternative to CIE and hydrogenation. The process gives a more natural product, free of trans fatty acids.

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