Interesterification Of Fats And Oils-a Review 232e2m

PAK. J. FOOD SCI., 22(3), 2012: 143-153 ISSN: 2226-5899

Interesterification of fats and oils-A Review Rai Muhammad Amir1, Muhammad Asim Shabbir1, Moazzam Rafiq Khan1, Shahzad Hussain2, 1

National Institute of Food Science and Technology, University of Agriculture, Faisalabad, Pakistan

2

Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia Corresponding Author: [email protected]

ABSTRACT Interesterification is a process used to amend the physico-chemical characteristics of oils and fats. There are numerous frightful health problems are associated with trans fats due to this the food industry has been effectively perfecting another 'man-made' replacement to ensure that sales and profits of company are remained at a high level. This new solution is called interesterification, a technique for making butter-like products from liquid vegetable oils. It can be used to make margarines, shortenings, baked goods and confectionary that require the texture, mouth feel and smoothness similar to saturated fats. Interesterification involves an exchange of acyl group among triglycerides. Acyl groups may exchange positions within a triglyceride or among triglyceride molecules. This review is about interesterification of fats and oils. Keywords: Interesterification, Chemical Interesterification, Enzymatic interesterification Introduction Interesterification is one of the processes used to modify the physico-chemical characteristics of oils and fats. Interesterification is an acyl-rearrangement reaction on the glycerol molecule. On the other hand, hydrogenation involves addition of hydrogen to the double bonds of unsaturated fatty acids. Due to health implications of trans fatty acids, which are formed during hydrogenation, the industry needs to find alternatives to hydrogenated fats. So interesterified fats, with particular reference to interesterified palm products, as alternatives to hydrogenation can be used for health conscious people (Nor and Noor, 2005). Two types of interesterification are available, i.e. chemical and enzymatic. Interesterification produces a complete positional randomization of acyl groups in triacylglycerol, by using chemical catalysts. Enzymatic interesterification uses lipases as catalyst. Each type of interesterification possesses advantages and disadvantages. The random or chemical interesterification is the most applied interesterification modification process of oils and fats as it is simpler, cheaper and easier to carry out compared to directed or enzymatic interesterification (Sreenivasan, 1976). Enzymatic interesterification Cocoa butter-like fats were prepared from refined, bleached, and deodorized palm oil (RBD-PO) and fully hydrogenated soybean oil (HSO) by enzymatic interesterification at various weight ratios of substrates. The cocoa butter-like fats were isolated from the crude interesterification mixture by fractional crystallization from acetone. Analysis of these fat products by RP-HPLC in combination with ELSD or MS detection showed that their TAG distributions were similar to that of cocoa

butter but that they also contained MAC and DAG, which were removed by silica chromatography. The optimal weight ratio of RBD-PO to HSO found to produce a fat product containing the major TAG component of cocoa butter, namely, 1(3)-palmitoyl-3(1)-stearoyl-2-monoolein (POS), was 1.6:1. The M.P. of this purified product as determined by DSC was comparable to the M.P. of cocoa butter, and its yield was 45% based on the weight of the original substrates (Abigor et al., 2003). Immobilized PS-C 'Amano' II lipase was used to catalyze the interesterification of palm olein (PO) with 30, 50, and 70% stearic acid in n-hexane at 60ºC. The catalytic performance of the immobilized lipase was evaluated by determining the composition change of fatty acyl groups and triacylglycerol (TAG) by gas liquid chromatography and high-performance liquid chromatography, respectively. The interesterification process resulted in the formation of new TAGs, mainly tripalmitin and dipalmitostearin, both of which were absent in the original oil. These changes in TAG composition resulted in an increase in slip melting point, from the original 25.5ºC to 36.3, 37.0, and 40.0ºC in the modified PO with 30, 50, and 70% stearic acid, respectively. All the reactions attained steady state in about 6 h. This type of work will find great applications in food industries, such as confectionery (Yassin et al., 2003). The interesterification of palm stearin with soybean oil, catalysed by a commercial immobilised lipase from Candida antarctica, in a continuous fluidised-bed reactor. The interesterification was indirectly followed by the decrease in the solid fat content at 35ºC (SFC). The best reaction conditions were previously established batch wise via response surface methodology as a function of temperature and medium

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composition. The reactor operated continuously for 21 days. During the first 16 days, no significant decrease in the initial activity was observed and a reduction of 3040% in the SFC was achieved. Subsequently, a progressive decrease in the activity was detected, and a reduction of only 5% in the SFC was obtained after 21 days of operation. The biocatalyst could be partially reactivated and was reused, under the same conditions, for a further period of 21 days. A similar inactivation profile, described by a series-type inactivation kinetics model, was observed. The estimated values for the halflife and the deactivation coefficient were the same for the fresh and reactivated biocatalyst (17 days and 0.0035, respectively). The free fatty acid content of the interesterified fat in the continuous reactor (0.7-1.2%) was lower than that of the fat obtained batch wise (2-6%) (Osorio et al., 2005). Lipase-catalyzed interesterified solid fat was produced with fully hydrogenated soybean oil (FHSBO), and rapeseed oil (RSO) and palm stearin (PS) in a weight ratio of 15:20:65, 15:40:45 and 15:50:35. The interesterified fats contained palmitic (27.8–44.6%), stearic (15.6–16.2%), oleic (27.5–36.5%) and linoleic acids (8.0–13.5%). After interesterification of the blends, the physical properties of the products changed and showed lower melting points and solid fat contents, different melting and crystallization behaviors as well as the formation of more stable crystals. The produced interesterified fats (FHSBO:RSO:PS 15:20:65, 15:40:45 and 15:50:35 blends) contained desirable crystal polymorphism (β’ form) as determined by X-ray diffraction spectroscopy, a long plastic range with solid fat content of 51–63% at 10°C to 4–12% at 40°C, and melting points of 39 (15:50:35), 42 (15:50:45) and 45°C (15:20:65). However, a reduction in tocopherols (α and γ) content and a reduced oxidative stability were observed in the interesterified fats. The physical properties of the interesterifed fats were influenced by the amount of PS, resulting in more hardness and higher solid fat contents for 15:20:65 than 15:40:45 and 15:50:35 blends. The present study suggested that the produced interesterified fats containing trans-free fatty acids could be used as alternatives to hydrogenated types of bakery shortenings (Jeung et al., 2008). Palm stearin (PS) and rice bran oil (RBO) blends of varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3 specific immobilized lipase. The interesterified blends were evaluated for their physicochemical characteristics and bioactive phytochemical contents using differential scanning calorimeter (DSC), X-ray diffraction (XRD), gas chromatography (GC) and high performance liquid chromatography (HPLC). The blends of PS and RBO in different proportions (40:60, 50:50, 60:40 and 70:30) had saturated fatty acid content and unsaturated fatty acid content in the range of 37.6–52.0% and 48.0–62.4%, respectively. The blends 40:60, 50:50 and 60:40 showed

a considerable reduction in their highest melt peak temperature (TP) and solid fat content (SFC) on EIE. The interesterified blends retained bioactive phytochemicals like tocols (839–1172 ppm), sterols (4318–9647 ppm), oryzanols (3000–6800 ppm) and carotene (121–180 ppm). XRD studies demonstrated that the interesterified blends contained β and β′ polymorphic forms (Reshma et al., 2008). Interesterification of a 60:40 (wt/wt) mixture of olive oil and fully hydrogenated canola oil was carried out in a batch reactor using a commercial immobilized lipase from Thermomyces lanuginose as a biocatalyst. The effects of a stepwise change of temperature on the degree of conversion, the solid fat content (SFC) of the products, and the residual activity of the enzyme were investigated. As a reference condition, an interesterification trial was conducted at a constant temperature of 70°C for 48 h. For trials in which a temperature of 70°C was used for the first 4 h of reaction and a temperature of 60°C was employed for the following 44 h, there were no significant differences (p < 0.05) in the overall degree of conversion relative to the reference condition. Oils interesterified for only 1 or 2 h at 70°C had melting points higher than 60°C, whereas an oil produced by interesterification at 70°C for only 4 h had a melting point of 58°C. There was little difference (p < 0.05) between the SFC profiles of the interesterification products prepared by two different temperature protocols (70°C for 24 h; 70°C for 4 h followed by 60°C for 20 h). Use of the protocol involving a step decrease in temperature significantly decreased catalyst deactivation effects, thereby increasing the residual activity of the immobilized lipase (Kim et al., 2008). Structured lipids containing conjugated linoleic acid as a functional ingredient were blended with palm stearin in the ratios of 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 (wt/wt). The blends were subjected to enzymatic interesterification by Candida antarctica lipase. After interesterification of the blends, changes in the physical properties of the products, including lower melting points and solid fat contents along with different melting behaviors, were evidenced. Analysis of triacylglycerols (TAG) of the interesterified blends showed a decrease in the concentration of high-melting TAG. X-ray diffraction analysis revealed, that all the reacted blends were predominantly in the beta' crystal form. The mixture could be used for the formulation of margarines or other, similar products (Goli et al., 2008). Blends of high-oleic sunflower oil and fully hydrogenated canola oil were subjected to enzymatic and chemical interesterification using Candida antarctica lipase (5%) and sodium methoxide (0.3%), respectively. The effect of each interesterification process was determined by comparing the triacylglycerol (TAG) composition, solid fat content (SFC) profiles and thermal properties of the blends before and after interesterification. Interesterification resulted in a

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decrease in the concentration of triunsaturated and trisaturated TAG and an increase in the proportion of mono- and disaturated TAG. These alterations in TAG composition and the presence of a greater variety of TAG species upon interesterification was correlated with a broader melting transition by differential scanning calorimetry and, ultimately, a lower melting point for the interesterified blends. Much broader ranges in plasticity were observed for the interesterified blends (chemically and enzymatically) compared to the physical blends. Even though ideal solubility of stearin in oil was observed, the value predicted by the Hildebrand model was higher than the actual amount. Crystallization kinetic parameters (Avrami index and rate constant) were similar for the non-interesterified, enzymatically interesterified and chemically interesterified blends when compared as a function of SFC. Results from this work will aid in the formulation of more healthy fat and oil products and address a critical industrial demand in of formulation options for spreads, margarines and shortenings (Ahmadi et al., 2008). Chemical interesterification The random or chemical interesterification is the most applied interesterification modification process of oils and fats as it is simpler, cheaper and easier to carry out compared to directed or enzymatic interesterification. However, the drawbacks are their widely varied quality, the need for an induction period before the reaction starts and the loss of oil due to formation of soap and methyl esters upon removal of the catalyst by washing with water (Sreenivasan, 1976). Though the loss of oil can be minimized by introducing carbon dioxide along with water during deactivation of the catalyst, the system will only work efficiently if there is a time lag between the catalyst neutralization and centrifuge separation of the fat and water phases (Going, 1967). The interesterification of tallow: rapeseed oil 4:6 w/w oil have displayed that reduction in melting point temperature and in solid fat contents compared with blends before interesterification. The aim of study was a comparison of the oxidative stability of the products before and after chemical interesterification. Interestrerification reduces the resistance of products on thermo-oxidation (Ledochowska and Wilczynska , 1998) Fat blends, formulated by mixing a highly saturated fat (palm stearin or fully hydrogenated soybean oil) with a native vegetable oil (soybean oil) in different ratios from 10:90 to 75:25 (wt %), were subjected to chemical interesterification reactions on laboratory scale (0.2% sodium methoxide catalyst, time = 90 min, temperature = 90°C). Starting and interesterified blends were investigated for triglyceride composition, solid fat content, free fatty acid content, and trans fatty acid (TFA) levels. Obtained values were compared to those of lowand high-trans commercial food fats. The interesterified

blends with 30–50% of hard stock had plasticity curves in the range of commercial shortenings and stick-type margarines, while interesterified blends with 20% hard stock were suitable for use in soft tub type margarines. Confectionery fat base stocks could be prepared from interesterified fat blends with 40% palm stearin or 25% fully hydrogenated soybean oil. TFA levels of interesterified blends were low (0.1%) compared to 1.3– 12.1% in commercial food fats (Petrauskaite et al., 1998). The effects of blending palm oil (PO) with soybean oil (SBO) and lard with canola oil, and subsequent chemical interesterification (CIE), on their melting and crystallization behavior. Lard underwent larger CIE-induced changes in triacylglycerol (TAG) composition than palm oil. Within 30 min to 1 h of CIE, changes in TAG profile appeared complete for both lard and PO. Palm oil had a solid fat content (SFC) of ~68% at 0°C, which diminished by ~30% between 10 and 20°C. Diluation with SBO gradually lowered the initial SFC. Chemical interesterification linearized the melting profile of all palm oil-soybean oil (POSBO) blends between 5 and 40°C. Lard SFC followed an entirely different trend. The melting behavior of lard and lard-canola oil (LCO) blends in the 0-40°C range was linear. Chemical interesterification led to more abrupt melting for all LCO blends (Marangoni and Rousseau, 1998) Chemical interesterification has long been used to modify oils and fats into functional products. Many chemical compounds can be used as the catalysts, such as sodium metal and sodium methoxide. With addition of the catalyst, the oil turns a well documented distinctive reddish brown. Many believe that this color compound may be the real catalyst in interesterification. The spectral changes of an oil undergoing interesterification were examined in the visible and ultraviolet wavelength ranges. An absorbance peak was found from 320-450 nm. Because this range is the wavelength of blue light, this absorption gives the oil a reddish brown color, the compensated color of blue light. The peak increases as the amount of sodium methoxide increases. To initiate and complete interesterification, the oil absorbance must reach levels of 0.4 and 1.0 at 374 nm, respectively. Controlled partial interesterification is now also possible by controlling the absorbance between 0.4 and 1.0. A novel patent-pending technology, based on this observation, was developed to monitor the progress of interesterification on-line using fiber optic technology. The reaction time and the dosage of sodium methoxide used for randomization have been significantly reduced on bench-scale when using this new tool. Furthermore, the oils interesterified with monitoring have higher oxidative stability and tocopherol contents compared to those by conventional randomization (Linsen and Lampert, 1999) Chemical interesterification (CIE) and 1, 3specific enzymic interesterification (EIE) of butterfat lead to decreases in the 32-42 carbon number triglycerides

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(TAGs) and increases in the 44-54 TAGs. The solid-fatcontent (SFC) of butterfat and the 80% blend dropped upon EIE at all temps. The SFC for CIE butterfat dropped 2-3% below 15° and increased ~5% above 20°, while for the 80% blend; SFC dropped ~5% only below 15°. The hardness index (HI) and storage modulus (G') of butterfat and blends above 70% butterfat decreased upon interesterification. The dropping point (DP) of butterfat increased by 3° upon CIE. The DP of blends above 60% butterfat did not change significantly upon CIE. The DP of EIE butterfat and blends above 60% decreased 2-5°. The relative proportion of the polymorph decreased slightly upon CIE and EIE and blending with canola oil. CIE of butterfat led, however, to a complete conversion to the polymorph. Sensory evaluation of spreads made using these modified fats showed that interesterification improved spread ability significantly, however, at the expense of some of the butter-like flavor (Marangoni and Rousseau, 1999). Chemical interesterification lacks specificity and several triacylglycerol products which may not be desired are produced in the blend. It is possible to direct interesterification reaction somewhat, by removing desired, high melting point fractions as the reaction proceeds. Chemical interesterification is relatively inexpensive and is in industrial practice, particularly in Europe, to produce plastic saturated fats with zero or low trans fat levels (Marangoni and Rousseau, 1999) Preparation of shortenings, margarines fat bases, cocoa butter substitutes and vanaspati substitutes from tallow. After fractionation of tallow from acetone the stearines and oleins obtained, were blended and interesterified with various liquid oils in the presence of sodium methoxide. As revealed from their melting and solid fat indices, the products thus prepared were found to be suitable for shortenings, margarines fat bases and vanaspati substitute (Bhattacharyya et al. 2000) Manufacture a shortening using chemical interesterification (IT) of tallow-sunflower oil blends. The significant variables of the IT process were obtained by 24−1 fractional factorial design. The proportion of tallow (T) in the blend, catalyst concentration, and reaction temperature had a significant effect on the melting point (mp) (P≤0.05). IT of tallow and sunflower oil blends (90:10 and 70:30) diminished the melting point, dropping point, and refractive index compared to tallow. However, a non-interesterified 90:10 blend melting point was not significantly different from tallow. IT produced a solid fat content (SFC) profile of IT 90:10 blends that were appropriate for use in shortenings for the baking industry. Blending and IT of the 90:10 blends increased the melting profile of the tallow and the melting range from −40 to 60°C while the endotherms of the middle-melting triacylglycerols (TAG) decreased. The IT 90:10 blend hardness was 70% lower than tallow hardness, and the crystal network was composed of large spherulites in a network. IT resulted in an appropriate

method to improve physical properties of tallow, whereas blending did not significantly modify it. The interesterification changed the SFC profile of IT 90:10, giving a more appropriate shortening for use in the baking industry (Alicia et al. 2000) Palm oil (PO) and palm kernel oil (PKO) compositions (100/0, 80/20, 60/40, 50/50, 40/60, 20/80 and 0/100) were interesterified in laboratory scale under predetermined conditions (0.4% sodium metoxide, 20 minutes, 100°C). The fourteen samples, before and after interesterification, were characterized by solid fat content (SFC) and consistency. Results showed a presence of eutectic system at PO and PKO compositions, mainly at 80/20, 60/40 and 50/50 fractions, proved through isosolids and isoconsistency diagrams. The incompatibility among the oils was decreased after reaction and improved the composition plasticity, demonstrated by the increment of solids value and yield value at room temperature (Grimaldi et al., 2001). Interesterification of tallow and sunflower oils mixtures. They have found that interesterification resulted in an appropriate method to improve physical properties of tallow, whereas blending did not significantly modify it (Rodriguez and co-workers, 2001) Modification of the characteristics of palm oil (PO), sunflower oil, and palm kernel olein (PKO) according to conventional three-component mixture undertaken by a combination of blending and chemical interesterification (CIE) techniques. TAG composition and solid fat content (SFC) profile of the starting blends were analyzed and compared with those of the interesterified blends. Upon CIE, extensive rearrangement of FA among TAG was evident. Concentrations of several TAG were increased, some were decreased, and several new TAG was formed. The resulting changes in TAG profile were reflected in the SFC of the blends. The SFC values of the chemically interesterified blends, except binary blends of PO/PKO, revealed that they were softer than their respective starting blends. SFC data also indicated that eutectic interaction occurred between PO and PKO in the starting blends and that this interaction was diminished after CIE (Noor et al. 2002) Soybean oil interesterification at different temperatures, ranging from 10 to 80 C, 600 rpm stirring rate and 0.2–0.5% catalyst (NaOCH3) concentration. The content of palmitic acid in the 2-position of triacylglycerols was monitored during the reaction by an enzymatic method. The conversion of triacylglycerols to random distribution appeared to be a first order and reaction rate constants (k) were determined between 0.015 and 1.498. It was also observed that reaction rate increased about 8 times when catalyst ratio was increased from 0.2 to 0.5% and about 10 times when temperature was raised from 40 to 80°C (Anar et al. 2003) Blending and chemical interesterification of fats have been used to modify physical and chemical

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properties of natural fats. The objective of the study was to produce binary mixtures of butterfat and corn oil that serve as a base for a table spread, keeping the desirable organoleptic qualities of butter, yet with higher contents of omega-6 fatty acids. Chemical interesterification was performed to improve butter's physical properties, such as better spread ability. Liquefied butterfat and corn oil were mixed in different proportions and then chemically interesterified. Butterfat consisted of 66.5% saturated fatty acids, with palmitic acid being predominant. Corn oil had more than 50% of linoleic acid in its composition. Interesterification significantly reduced trisaturated and triunsaturated triacylglycerol contents and increased softening points in all blends. The negative coefficients of the blends from multiple regression of the solid fat content revealed a monotectic interaction between butterfat and corn oil in temperatures ranging from 10 to 35°C, before and after interesterification (Rodrigues and Gioielli, 2003). Fat/oil blends, by mixing fully hydrogenated palm oil stearin with vegetable oils (canola oil and cottonseed oil) in different ratios from 30:70 to 70:30 (w/w %), were subjected to chemical interesterification reactions on a laboratory scale. Fatty acid (FA) composition, iodine value, slip melting point (SMP) and solid fat content (SFC) of the starting blends were analysed and compared with those of the interesterified blends. SMPs of interesterified blends were decreased compared to starting blends because of extensive rearrangement of FAs among triacylglycerols. These changes in SMP were reflected in the SFCs of the blends after the interesterification. SFCs of the interesterified blends also decreased with respect to the starting blends, and the interesterified products were softer than starting blends. These interesterified blends can be used as an alternative to partial hydrogenation to produce a plastic fat phase that is suitable for the manufacture of margarines, shortenings and confectionary fats (Ihsan et al. 2003) The mixture of beef tallow and rapeseed oil (1:1, wt/wt). It was interesterified using sodium methoxide as catalyst. Chemical interesterifications were carried out at 60 and 90 °C for 0.5 and 1.5 h using 0.4, 0.6 and 1.0 wt-% CH3ONa. The starting mixture and the products of interesterifications were quantitatively separated into pure triacylglycerols and nontriacylglycerols fraction containing free fatty acids and mono- and diacylglycerols. It was found that the concentration of free fatty acids and partial acylglycerols increased after interesterification. The slip melting points and solid fat contents of the triacylglycerol fractions isolated from interesterified fats were lower compared with the non-esterified blends. The sn-2 and sn-1,3 distributions of fatty acids in the TAG fractions before and after interesterification were determined. These distributions were random after chemical interesterification. Addition of 0.02% BHA and BHT to

the interesterified fats improved their stabilities (Boleslaw et al. 2004) performed studies on the chemical interesterification of rapeseed oil and tallow blends with and without hydrocarbon solvent. It has appeared that the presence of solvent influenced on melting properties, solid fat contents and fatty acids distributions in triacylglycerols separated from the mixture after interesterification (Kowalski et al. 2004) Fat/oil blends, formulated by mixing fully hydrogenated palm oil stearin or palm oil stearin with vegetable oils (canola oil and cottonseed oil) in different ratios from 30:70 to 70:30 (w/w %), were subjected to chemical interesterification reactions on a laboratory scale. Fatty acid (FA) composition, iodine value, slip melting point (SMP) and solid fat content (SFC) of the starting blends were analysed and compared with those of the interesterified blends. SMPs of interesterified blends were decreased compared to starting blends because of extensive rearrangement of FAs among triacylglycerols. These changes in SMP were reflected in the SFCs of the blends after the interesterification. SFCs of the interesterified blends also decreased with respect to the starting blends, and the interesterified products were softer than starting blends. These interesterified blends can be used as an alternative to partial hydrogenation to produce a plastic fat phase that is suitable for the manufacture of margarines, shortenings and confectionary fats (Karabulut et al., 2004). Esters of carboxylic acids including 2methylhexanoic, 2-methylbutyric, 2; 2-dimethyl-4pentenoic, palmitic, and oleic acids were tested as substrates in methoxide-catalyzed interesterification and transesterification. The aliphatic acid esters participated in the ester-ester interchange upon addition of catalytic sodium methoxide. Their isopropyl esters also produced methyl esters on heating with sodium methoxide. The esters of α-methyl-substituted acids did not participate in the ester-ester interchange. Their isopropyl esters did not react with methoxide to produce methyl esters. However, upon addition of methanol with sodium methoxide, their methyl esters were produced. These results indicate that the first step in interesterification is possibly that methoxide abstracts the α-hydrogen of an ester to form a carbanion. Interesterification is then likely completed via a Claisen condensation mechanism involving the β-keto ester anion as the active intermediate. The β-keto ester anion contains positively charged ketone and acyl carbons that are active sites for nucleophilic attack by anions such as methoxide and glycerinate, which would produce a methyl ester or rearrange acyls randomly. On the other hand, transesterification is a nucleophilic substitution by methoxide at the acyl carbon in the presence of methanol (Linsen, 2004) Speciality plastic fats with no trans fatty acids suitable for use in bakery and as vanaspati are prepared by interesterification of blends of palm hard fraction

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(PSt) with mahua and mango fats at various proportions. It was found that the interesterified samples did not show significant differences in solid fat content (SFC) after 0.5 or 1 h reaction time. The blends containing PSt/mahua (1:1) showed three distinct endotherms, indicating heterogeneity of triacylglycerols (TG), the proportions of which altered after interesterification. The SFC also showed improved plasticity after interesterification. Similar results were observed with other blends of PSt/mahua (1:2). These changes in melting behavior are due to alterations in TG composition, as the trisaturatedtype TG was reduced and the low-melting TG increased after interesterification. The blends containing PSt/mango (1:1) showed improvement in plasticity after interesterification, whereas those containing PSt/mango (2:1) were hard and showed high solid contents at higher temperature and hence may not be suitable for bakery or as vanaspati. The blends with palm and mahua oils were softer and may be suitable for margarine-type products. The results showed that the blends of PSt/mahua (1:1, 1:2) and PSt/mango (1:1) after interesterification for 1 h at 80degreesC showed an SFC similar to those of commercial hydrogenated bakery shortenings and vanaspati. Hence, they could be used in these applications in place of hydrogenated fats as they are free from trans acids, which are reported to be risk factors involved in coronary heart disease. For softer consistency like margarine applications, the blends containing palm oil and mahua oil are suitable (Khatoon and Reddy, 2005). Changes in physico-chemical characteristics of fat blends containing hydrogenated palm kernel oil (HPKO) and goat milk fat (GMF), before and after chemical interesterification using sodium methoxide as catalyst. HPKO : GMF blends were prepared in six ratios: 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 (w/w). Melting characteristics were studied by differential scanning calorimetry. Peak melting temperatures (Tp) of non-interesterified blends decreased as the percentage of GMF increased. Generally, the interesterified blends showed lower Tpvalues compared to the noninteresterified blends at their respective blending ratios. Decrease in melting enthalpy (Ep) occurred with the increase in percentage GMF in the blends for both the non-interesterified and interesterified blends. Interesterified blends had greater Epvalues than those of the non-interesterified blends at respective ratios. Results from X-ray diffraction analysis showed that all blends possessed a β' polymorph. HPKO : GMF (0:100) was the only blend in which the presence of both β' and β polymorphs was detected. Chemical interesterification had no effect on polymorphic crystal behavior. Based on solid fat content (SFC) results, eutectic effect did not occur in all HPKO : GMF blends studied. It was shown that the percentage of SFC decreased as percentage of GMF increased. Decrease in percentage SFC of blends was brought about by interesterification. The HPKO : GMF (100:0) blend had the highest percentage

of free fatty acid followed by HPKO : GMF (0:100). Interesterification caused a 2- to 3-fold increase in the percentage of free fatty acids compared to noninteresterified blends. Iodine values of the blends increased with an increase in GMF proportion. A rapid increase in iodine was observed in blends containing 0– 20% GMF. Interesterification did not have any effect on the iodine value of fat blends (Nazaruddin et al. 2005) Blends of hydrogenated and non-hydrogenated tea seed oil (30:70, w/w) by chemically interesterification at 60, 90, and 120°C for 30, 60, and 90 min in the presence of 1% (w/w) NaOH. Physico-chemical properties of the products were compared with those of the non-interesterified mixture. Statistical comparison of melting point, iodine values (IV), and solid fat contents (SFC) showed that the sample having the highest ranking was interesterified at 120°C for 30 min. The sample was used as a hard stock (40%), with liquid tea seed oil and sunflower oil (ratios of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100) as, a soft stock (60%) for production of table margarine, and the properties of these margarines were compared with those of commercial ones. Samples E and D (ratio of 80:20 and 60:40 liquid tea seed oil/sunflower oil, respectively) had the lowest significant differences with commercial table margarine for physicochemical (M.P., IV, and SFC) and organoleptic characteristics, respectively. Generally, based on M.P. and SFC, margarines E and D were classified as soft margarine. The trans FA content of E, D, and commercial margarines were 1.8, 1.8, and 2.2%, respectively (Elham et al. 2006) The effect of interesterification on oxidative stability of cottonseed, palm and soybean oils stored under oven conditions at 45, 60 and 75°C was evaluated by measuring the peroxide values (PV), anisidine values (AV) and Totox values at different time intervals. Fatty acid composition and tocopherol contents of oil samples were determined before and after interesterification. Interesterification reduced the tocopherol content of oils. The interesterified oils showed lower PV and AV than their non-interesterified counterparts in all temperatures and time intervals. The primary and secondary oxidation reaction constants and reaction orders were investigated as a function of the reaction temperature. The interesterified oils showed lower reaction rate constants than the non-interesterified samples. Based on PV, AV and reaction rate constants, the oxidative stability of interesterified oils were higher than their noninteresterified counterparts (Basturk et al., 2007). The process of interesterification results in changes in triacylglycerol (TAG) structure and is used to increase the melting point of dietary fats. The acute health effects of this process on palmitic acid-rich fats are uncertain with regard to postprandial lipemia, insulin and factor VII activated (FVIIa) concentrations. Two randomized crossover trials in healthy male subjects compared the effects of meals containing 50 g fat [interesterified palm oil (IPO) versus native palm oil

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(NPO); n = 20, and IPO versus high-oleic sunflower oil (HOS); n = 18], on postprandial changes in lipids, glucose, insulin, chylomicron composition and FVIIa. Compared with NPO, IPO decreased postprandial TAG and insulin concentrations. Both NPO and IPO increased FVIIa concentrations postprandial; mean increases at 6 h were 21 and 19%, respectively. Compared with HOS, IPO decreased postprandial TAG (47% lower incremental area under the curve) and reduced the postprandial increase in FVIIa concentration by 64% at 6 h; no significant differences in hepatic and total lipase activities or insulin concentrations were noted. All three test meals increased postprandial leukocyte counts (average 26% at 6 h). The fatty acid composition of the chylomicron TAG was similar to the test fats following all test meals. It is concluded that interesterification of palm oil does not result in adverse changes in postprandial lipids, insulin or FVIIa compared to high oleate and native palm oils (Berry et al., 2007). Beef tallow stearin was blended at various proportions with rapeseed oil and the blends were interesterified using sodium methoxide as the catalyst. The starting blends and the products of interesterification were quantitatively separated into the triacylglycerols and non-triacylglycerol fractions containing free fatty acids and of mono-and diacylglycerols. It has been found that after interesterification the contents of free fatty acids and of mono-and diacylglycerols increased. On the other hand the slip melting temperatures and solid fat contents of triacylglycerols separated from interesterified samples were lower if compared with nonesterified blends. The total fatty acid composition of fats before and after interesterifications remained unchanged but their distributions were random after chemical interesterification (Kowalska et al., 2007). Minor compounds such as tocopherols and phytosterols in vegetable oils play an important role in their stability and nutritional value. This study monitored the effects of chemical interesterification on the levels of tocopherols, tocotrienols, phytosterols and phytosterol oxidation products (POPs) in an olive oil and palm stearin blend (50/50 w/w). Tocopherols and tocotrienols were dominated by a-tocopherol (192 ppm) and gammatocotrienol (70 ppm) and decreased during interesterification. Among the tocopherols, deltatocotrienol had the highest decrease (35%) at 120°C. During interesterification at 90 and 120°C, total sterol content in the oil blend (509 ppm) declined slightly, by 3 and 5%, respectively. Phytosterols were esterified at a higher level at 120°C (7%) than at 90°C (4%) during this process. Distribution of fatty acids in the esterified sterols followed the fatty acid composition of the oil blend. Total POP content was 4.3 ppm, and remained generally unchanged during interesterification. Among the nine POPs tentatively identified by their mass spectra, 6hydroxysitostanol and 6-hydroxycampestanol dominated in the oil blend and in the interesterified product. The

formation pathways of these saturated dihydroxyphytosterols have yet to be identified. Although the interesterification process comprised several treatments, there were only minor losses of tocopherols and phytosterols and virtually no increases in the POPs (Azard and Dutta, 2008). The effects of chemical interesterification on the levels of tocopherols, tocotrienols, phytosterols and phytosterol oxidation products (POPs) in an olive oil and palm stearin blend (50/50 w/w). Tocopherols and tocotrienols were dominated by α-tocopherol (192 ppm) and γ-tocotrienol (70 ppm) and decreased during interesterification. Among the tocopherols, d-tocotrienol had the highest decrease (35%) at 120°C. During interesterification at 90 and 120°C, total sterol content in the oil blend (509 ppm) declined slightly, by 3 and 5%, respectively. Phytosterols were esterified at a higher level at 120°C (7%) than at 90°C (4%) during this process. Distribution of fatty acids in the esterified sterols followed the fatty acid composition of the oil blend. Total POP content was 4.3 ppm, and remained generally unchanged during interesterification. Although the interesterification process comprised several treatments, there were only minor losses of tocopherols and phytosterols and virtually no increases in the POPs (Sodeif and Paresh, 2008) The physical and chemical characteristics of the fruit of the oily palm coming from the river basin of the Maniti (Region Loreto - Peru). Also, the fractionation of the palm oil and the interesterification of mixtures of palm oil/estearin was carried out. Physico- chemical properties of the crude oil and of the products obtained and fatty acids were analysed by gas chromatography. The level of saturated fatty acids increased from 51, 17% in the palm oil to 54, 31% in the stearin.The best products for the food industry were the interesterified samples as they had melting points close to 37°C (De-Sotero et al. 2008) Fat blends formulated by blending palm oil (PO) with sunflower oil (SFO) and soybean oil (SBO) in different ratios were subjected to chemical interesterification (CIE) reactions at bench scale using sodium methoxide (NaOMe) as catalyst. The blends before and after interesterification (IE) were investigated for slip melting point (SMP), solid fat content (SFC), melting characteristics, fatty acid composition (FAC), triacylglyceride (TAG) composition, polymorphic forms and bioactive components. Interesterified blends of 8090% PO and 10 to 20% SFO: SBO had higher SMP and SFC than their respective non-interesterified blends. Upon CIE, extensive rearrangement of fatty acids (FA) among TAG was evident. The interesterified blends with 80-90% PO and 10-20% SFO: SBO had SFC in the range of all purpose type shortenings. CIE facilitated the formation of beta polymorphic form (Mayamol et al., 2008).

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Use of interesterified fats in different products The oxidative stability of partially hydrogenated menhaden fish oil (PHMO) shortening/canola oil blends with added antioxidant tertiary butylhydroquinone (TBHQ) and various blended partially hydrogenated vegetable oil (PHVO) shortenings without antioxidant in aged cookies and crackers was analyzed by anisidine value (AV), peroxide value (PV), and Totox value. The results showed no significant differences (ρ<0.05) for PV, AV, or Totox value between the PHMO shortening containing TBHQ and the PHVO shortening in cookies, crackers, and deep-fried extruded snacks, except for the AV and Totox value of crackers (Kathryn et al., 1996). Three interesterified vegetable oils prepared from palm, cottonseed and olive oils, respectively, have been studied for application to Frankfurters. Beef fat (10 %) was replaced by one of the interesterified vegetable oils at 20, 60 of 100 %. Fatty acid composition of lipid fraction in Frankfurters and saturated/unsaturated ratios were estabilished for all batches. We found that the total or partial replacement of beef fat by interesterified vegetable oils did not lead to significant changes in appearance, color, texture, flavour or sensory score. We conclude that interesterified vegetable oils may be successfully applied as beef fat substitutes in Frankfurters (Halil and Issa, 2002). Cake is one of the most loved bakery products. Formula constituents affect cake quality. Especially, fat in the formula alters internal and external attributes, shelf life and nutritional value of the cake. The type of fat is important for conscious consumers for health reason. Chemically interesterified palm (in-es PO) and cottonseed oils (in-es CO) were used instead of hydrogenated cake shortening (HS) in this study. The layer cakes were prepared according to modified American Association of Cereal Chemists Method. Physical characteristics such as batter density and consistency, cake volume, crust and crumb properties and sensory attributes such as moistness, flavour, mouth-feel of cake samples prepared with chemically interesterified (in-es) and non-interesterified palm and cottonseed oil (non-in-es) blends at 0, 25, 50 and 100 (wt%) levels were compared with that of the layer cake prepared with HS. An increase in the level of CO in the interesterified and non-interesterified blends lowered the solid fat content, thus increasing batter density and fluidity. Favourable cakes close to the standard cake have been made by using in-es (PO:CO) at the ratio of 75:25 and 50:50 (wt%) without any significantly adverse change in sensorial properties (Dogan et al., 2007). Chemical properties of the flours prepared with residues from organic king palm processing, and also to determine the cookie-making performance of residue blends from organic king palm processing and wheat flour, as well as the effect of the blends on the consumers' acceptance and purchase intent of high-fibre cookies. The king palm flours (PFs) contained high contents of total

dietary fibre and total ash. Blends containing 0%, 10%, 15%, 20% and 25% of either PF or sieved king-palm flour (SPF) replacing wheat flour were prepared. The total dietary fibre content of the cookies ranged from 4 to 7 g /100 g on a dry-matter basis. The level of these components improved with increased amounts of PF and SPF in the blends. All the cookies were acceptable and approved in relation to purchase intent (Vieira et al. 2008) Chemically interesterified blends (CIB) and noninteresterified blends (NIB) of corn and palm oils (75%w/ 25%w) were studied in the production of Turkish White cheese (TWC) to modify the fatty acid composition of traditional product. Milk fat (3%) was replaced by CIB and NIB for 25%, 50%, 75% and 100%. All cheese groups were ripened at 5°C for 90 days. Samples were taken from each group after 3, 30, 60 and 90 days and analysed for their basic composition, lipolysis and proteolysis. CIB-incorporated cheeses showed a higher degree of lipolysis than the control sample and the NIBincorporated counterparts. Fatty acid composition and sensory properties of the final product showed that the incorporation of CIB and NIB in TWC improved the nutritional content of the product because it altered the fatty acid composition without any adverse effect on sensorial quality. We concluded that in production of TWC, 50% of milk fat could be successfully replaced with CIB and NIB, preferably CIB, because of its superior sensory quality (Issa and Yusuf, 2007). CONCLUSION Trans fats are nutritionally unnecessary and important risk factor for cardiovascular disease. The presence of trans fats in dairy and meat products will make complete elimination from a balanced diet impossible. As food manufacturers and the food industry seek alternatives to trans fats, hurdles include supply of ingredients and unknown health squeal of new processes. Trans fats gained popularity as a means of replacing saturated fats in the diet. However, we now know that trans fats have greater adverse health implications than the saturated fats they sought to replace. Eliminating trans fats by returning to a high-saturated-fat diet is inappropriate. Now days there is hot issue regarding trans fatty acids, which are formed during hydrogenation, the industry needs to find alternatives to hydrogenated fats. So interesterified fats, with particular reference to interesterified palm products as alternatives to hydrogenation can be used for health conscious people. The random or chemical interesterification is the most applied interesterification modification process of oils and fats as it is simpler, cheaper and easier to carry out compared to directed or enzymatic interesterification.

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