Interesterification of fats

Interesterification changes the distribution of the fatty acids among the glycerides of fats or mixtures of fats from what was present originally. This affects the physical nature and behavior of fats. A discussion of this process from the standpoints of mechanism, catalysts, methods of monitoring the reaction and applications will be presented.     

Interesterification of edible fats

Journal of the American Oil Chemists' Society -     

Some observations on the microscopy of lard and rearranged lard

Summary Phase contrast and polarized light microscopy were employed to observe the crystalline nature of lard and rearranged lard. Special attention was given to the technique of specimen preparation, controlled conditions of tempering the sample, and photographic reproduction of crystal appearance. Photomicrographs are reproduced to show the difference in appearance of the crystals from lard and rearranged lard when both polarized light and phase contrast are employed. The peculiar long, thread-like crystals characteristic of lard are more clearly shown with phase contrast. Presented at the meeting of the American Oil Chemists’ Society, Philadelphia Pa., Oct. 10–12, 1955. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Interesterification products and processes

Interesterification as applied to fats and oils is a process whereby the fatty, acid moieties of glyceride molecules are rearranged in a random or directed manner. Either type of rearrangement may involve production of new triglyceride compositions in a predictable manner. A number of patented processes for accomplishing interesterification are discussed. Effective rearrangement catalysts are listed. Typical applications to commercial products are reviewed. Presented at the AOCS Short Course, East Lansing, Aug. 29–Sept. 1, 1966.     

Interesterification of edible oils

Types of interesterification discussed are (a) interchange between a fat and free fatty acids, in which the most important reaction is the introduction of acids of low mol wt into a fat with higher fatty acids; (b) interchange between a fat and an alcohol, e.g., with glycerol, in order to produce emulsifiers like monoglycerides; (c) rearrangement of fatty acid radicals in triglycerides, the so-called transesterification which in recent years has taken on the same importance as hydrogenation or fractionation. In natural fats, the fatty acid radicals are not usually randomly distributed but become so by rearrangement; the distinctive physical properties of natural fats and oils can be changed within limits by this transesterification. Well-known examples are cocoa butter, palm oil, and lard. More important is the transesterification of a mixture of different fats and oils; e.g., the combination of hydrogenation and interesterification allows the production of a solid fat with high linoleic acid content. The composition of glycerides after random interesterification can be calculated by formulas. Distinct from random is such directed interesterification. This is done by working at low temperatures that glycerides with higher melting point crystallize from the reaction mixture. Directed interesterification can be combined with fractionation, for instance, to get a higher yield of liquid fraction from palm oil than is obtained by fractionation alone. The transesterification process can be performed in a batch or continuously. A small amount of metallic sodium or sodium ethylate is used as catalyst, which is destroyed by water or acid and removed after the reaction.     

Interesterification reactions of triglycerides

Summary A study of the interesterification reaction has been undertaken using synthetic triglyceride systems (triolein in varying proportions with tripalmitin) and also combinations of lard and hydrogenated lard. An empirical crystallization method has been used in determining the amount of trisaturated glycerides present in a mixed fat. The results indicate that the end-products of interesterification approach the composition expected from the principle of random distribution. Presented before the fall meeting of the American Oil Chemists’ Society, Nov. 7–9, 1945, in Chicago.     

Composition and thermal analysis of lard stearin and lard olein

Lard being an edible fat could be used in different forms in food systems. In this study, composition and thermal analysis of lard stearin (LS) and lard olein (LO) were undertaken to determine some common parameters which would enable their detection in food. A sample of native lard was partitioned into LS and LO using acetone as solvent and the fractions were compared to the original sample with respect to basic physico-chemical parameters, fatty acid and triacylglycerol (TAG) composition, and thermal characteristics. Although LS and LO displayed wider variations in basic physico-chemical parameters, thermal properties and solidification behavior, they do possess some common characteristic features with regard to composition. In spite of the proportional differences in the major fatty acids, both LS and LO are found to possess extremely high amount of palmitic (C16:0) acid at the sn-2 positions of their TAG molecules. Similar to native lard, both LS and LO contained approximately equal proportions of TAG molecules namely, linoleoyl-palmitoyl-oleoyl glycerol (LPO) and dioleoyl-palmitoyl glycerol (OPO). Hence, the calculated LPO/OPO ratio for LS and LO are comparably similar to that of native lard.     

Steam stripping of lard

Conclusion The rate of steam stripping of free fatty acids from lard can be evaluated in terms of a rate·constant K defined by Equations 5 and 6. Reproducible results were realized for many different batches of leaf and prime steam lards. The effects of temperature, total pressure, and steam rate were evaluated, thus making possible the calculation of stripping rate constants on a comparable basis. Comparable values of the rate constant K have been compared for conditions with and without the use of mechanical agitation with a flat-blade mixing impeller. Use of the rotating mixing impeller showed substantial increases (30 to 50%) in the reaction rate constant, over those obtained with steam sparging without the mixer. Accordingly the use of this type mixer should result, in large savings of steam for stripping and for maintaining the necessary vacuum by the steam jet condenser. Presented at the 1952 Spring Meeting, American Oil Chemists' Society, Houston, Tex., Apr. 28–30.     

Determination of tri-saturated glycerides in lard,hydrogenated lard,and tallow

Summary Crystallization conditions are described which are suitable for obtaining almost quantitative precipitation of tri-saturated glycerides from lard, hydrogenated lard, and tallow. Based on the weight and analysis of the precipitate obtained, a practical method for calculating the amount of tri-saturated glycerides in lard and tallow is proposed. When applied to several hydrogenated lards the method gave constant and reproducible fractions, which contained, in addition to tri-saturated glycerides, considerable amount of “isooleins.” Some uncertainty is attached to the direct application of the method of calculation to these materials because of possible presence of mono-saturated-di-“isooleins.” Several samples of commercial lard examined contained about 2.5% of tri-saturated glycerides whereas a sample of edible tallow contained about 14.0%. The proposed method, when applied to lard, gives results in good agreement with those obtained by the acetone-permanganate oxidation method of Hilditch and Lea. The chief advantage of the crystallization method is that much less time is required for the analysis. Presented at 37th annual spring meeting, American Oil Chemists’ Society, New Orleans, La., May 15–17, 1946. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.     

Solvent Interesterification of Vegetable Oils III

Directed interesterification reaction in solvents of cottonseed, peanut and cottonseed containing peanut, sesame and safflower oils was investigated with special reference to the influence of amount of sodium methoxide catalyst, oil content in solvent, temperature during the reaction and the nature of solvent on the characteristics of the reaction. The parameters were first studied with cottonseed oil and the conditions that favoured the reaction were adopted for peanut oil and cottonseed oil mixtures.     

Interesterification of tallow and sunflower oil

The objective of this study was to manufacture a shortening using chemical interesterification (IT) of tallow-sunflower oil blends to replace fish oil in the present formulation, which is now in short supply in Chile. 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 mp, dropping point, and refractive index compared to tallow. However, a noninteresterified 90∶10 blend mp was not significantly different from tallow. IT produced a solid fat content (SFC) profile of IT90∶10 blend that was appropriate for use in shortenings for the baking industry. Blending and IT of the 90∶10 blend 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 IT90∶10 blend hardnesswas 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 IT90∶10, giving a more appropriate shortening for use in the baking industry.     

Enzymatic Interesterification of Palm Oil and Fractions: Monitoring the Degree of Interesterification using Different Methods

Interesterification is an important modification technique for fats and oils resulting in the redistribution of the fatty acids among the glycerol backbone and thus changing the physico-chemical properties of the modified fat. In this study palm oil, palm olein and soft palm mid fraction (PMF) were subjected to both enzymatic (batchwise) and chemical interesterification. The reaction products were characterized before, during and after interesterification by HPLC, pulsed NMR (p-NMR) and differential scanning calorimetry (DSC). Interesterification led to more uniform triacylglycerol (TAG) compositions with smaller differences in final physico-chemical properties between the studied substrates. The degree of interesterification was evaluated on the basis of TAG composition and solid fat content (SFC). Significant differences between both methods were observed. The degree of interesterification based on SFC is therefore a better tool to evaluate the rate constant of the reaction as the TAG composition method does not take into consideration the formation of positional isomers at the end of the enzymatic process.     

Interesterification of starch with methyl palmitate

Thermoplastic polymers derived from natural products have been prepared by interesterifying starch with methyl palmitate. The degree of substitution (DS) of the esters has been found to be strongly dependent upon catalyst concentration and the ratio of methyl palmitate to starch, but is largely independent of temperature and starch concentration over the range studied. Replacement of methyl palmitate with methyl esters of shorter chain acids does not appear to affect the DS. These observations are interpreted from the results of studies on the effect of DS on the solubility parameter, the nature of the interchain bonding and the specific gravity of the polymers.     

Studies in Solvent Interesterification I: Interesterification of Mahua (Madhuca latifolia) Oil in Hexane

Random and directed interesterification characteristics of Mahua (Madhuca latifolia) oil in solution in n-hexane (60% w/w) were investigated. The results obtained were comparable with the corresponding conventional non-solvent reactions with respect to the physical and chemical properties induced by the interesterification reactions, although the time for reaching equilibrium was longer in the case of solvent interesterification. The results indicate the possibility of commercial utilization of the process for the production of plastic fats with greater ease and economy than the conventional non-solvent interesterification.     

A direct spectrophotometric determination of butylated hydroxyanisole in lard and in hardened lard

Summary A direct spectrophotometric method for the determination of butylated hydroxyanisole has been presented. This procedure allows good precision in the analysis of lard and hardened lard containing from 0 to 100 p.p.m. of BHA and is more reliable than existing colorimetric techniques, especially in the lower range of antioxidant concentrations.     

Metal deactivation in lard

Summary A number of compounds, including known synergists, amino acids, and amines, have been evaluated as deactivators for copper, iron, nickel, and tin in lard. Some were effective in deactivating copper but were relatively poor for iron. One compound was better for iron than for copper. Ascorbyl palmitate, potassium ascorbyl palmitate, and ascorbic, tartaric, citric, and phosphoric acids were the most effective. This deactivation may in part explain the synergistic effect of these compounds with phenolic antioxidants. The more powerful antioxidants however are generally poor metal deactivators, and in the presence of traces of metallic pro-oxidants become relatively ineffective unless metal deactivators are also added. Presented at the Fall Meeting of the American Oil Chemists' Society, October 31–November 2, 1949. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U.S. Department of Agriculture.     

Studies on Interesterification of Fungal Oil

Interesterification of fungal oil was carried out using sodium methoxide as catalyst. In this case intramolecular rearrangement of fatty acids in the triglyceride molecule gives rise to a randomized mixture leading to a new fat which is rich in saturated glycerides.     

Pseudomonas fluorescens Lipase-catalysed Interesterification of Butter Fat

Butter fat was subjected to interesterification reactions catalysed by Pseudomonas fluorescens lipase in media of variable water content. The reaction products were analysed by gas chromatography on an immobilised phenylmethylsilicone capillary column. Triacylglycerol compositions were determined by normalisation, and free fatty acid and mono-and diacylglycerol compositions and contents by internal standardisation. In general, the triacylglycerol compositions of interesterification products were similar to each other and distinctly different from those of untreated butter fat. The compositions of triacylglycerols of the reaction products were similar to the composition calculated according to random distribution, except for the higher proportions of saturated triacylglycerols with 36 and 42–50 acyl carbons and monoene triacylglycerols with 38 acyl carbons in the reaction products. Enzymatic deacylation of reaction products showed the fatty acyl groups to be nearly randomly distributed among the three positions of glycerol. The contents of the hydrolysis products (MAGs, DAGs and FFAs) depended on the water content of the reaction medium.     

Interesterification,chemical or enzymatic catalysis

The interesterification process is one of the oil modification processes the refiner can use to alter the physical properties of oils and fats, The reaction requires a catalyst to proceed. This can be a base or a lipase enzyme. In the currently accepted mechanism of the base‐catalysed interesterification reaction, two anionic intermediates are involved: the enolate anion and the glycerolate anion. The presence of the enolate anion explains why an equivalent amount of FAMEs are formed when sodium methanolate is added to oil and why FFAs are formed when the catalysts is inactivated with water. Based on this insight, process development can aim at avoiding these by‐products and thereby increase the cost advantage of the chemical process over the enzymatic process even further. The chemical process is also more flexible than the solely continuous enzymatic process, which latter requires extensive purification of the oil to be interesterified.     

A lard trade mark disputed

Summary The chemical and physical characteristics of a sample of expressed pecan oil have been determined. The composition of a pecan oil, which had an iodine number of 100 and a saponification value of 190, has been determined with the following results: Glycerides of Per cent Oleic acid 77.8 Linolic acid 15.8 Myristic acid trace Palmitic acid 3.3 Stearic acid 1.9 Archidic acid 1 Unsaponifiable matter 35