Physico‐chemical properties of palm olein fractions as a function of diglyceride content in the starting material

Crude olein preparations with different amounts of diacylglycerols (DAG) were refined, bleached and deodorized (RBD) prior to the dry fractionation process. The RBD olein samples with different amounts of DAG were then individually fractionated into low‐melting (super olein) and high‐melting fractions (soft stearin). Physical and chemical characteristics, i.e. iodine value, cloud point, slip melting point, triacylglycerol (TAG) and DAG profile, fatty acid composition, thermal profile and solid fat content, of the super olein and soft stearin fractions were analyzed. The TAG profile obtained from the RBD olein having a low DAG content (0.89%) showed a higher amount of the diunsaturated TAG, i.e. dioleyl pamitoyl glycerol, in the olein fraction (57.3%). This, consequently, led to super olein fractions with a better iodine value (IV 65) and the cloud point at 1.3 °C, compared to non‐treated super olein (DAG 5%) with an IV of 60.5 and the cloud point at 4.1 °C.     

Composition and thermal profile of crude palm oil and its products

Gas-liquid chromatography and high-performance liquid chromatography (HPLC) were used to determine fatty acids and triglyceride (TG) compositions of crude palm oil (CPO), refined, bleached, and deodorized (RBD) palm oil, RBD palm olein, and RBD palm stearin, while their thermal profiles were analyzed by differential scanning calorimeter (DSC). The HPLC chromatograms showed that the TG composition of CPO and RBD palm oil were quite similar. The results showed that CPO, RBD palm oil, RBD olein, and superolein consist mainly of monosaturated and disaturated TG while RBD palm stearin consists mainly of disaturated and trisaturated TG. In DSC cooling thermograms the peaks of triunsaturated, monosaturated and disaturated TG were found at the range of −48.62 to −60.36, −25.89 to −29.19, and −11.22 to −1.69°C, respectively, while trisaturated TG were found between 13.72 and 27.64°C. The heating thermograms of CPO indicated the presence of polymorphs β₂′, α, β₂′, and β₁. The peak of CPO was found at 4.78°C. However, after refining, the peak shifted to 6.25°C and became smaller but more apparent as indicated by RBD palm oil thermograms. The heating and cooling thermograms of the RBD palm stearin were characterized by a sharp, high-melting point (high-T) peak temperature and a short and wide low-melting point (low-T) peak temperature, indicating the presence of occluded olein. However, for RBD palm olein, there was only an exothermic low-T peak temperature. The DSC thermograms expressed the thermal behavior of various palm oil and its products quite well, and the profiles can be used as guidelines for fractionation of CPO or RBD palm oil.     

Isolation and Evaluation of Stearin and Olein Fractions from Rice Bran Oil Fatty Acid Distillate by Detergent Fractionation and Conversion into Neutral Glycerides by Autocatalytic Esterification Reaction

Detergent fractionation (Lanza process) offers a valuable separation process for edible oils that contain varying amounts of saturated and unsaturated fatty acids. The rice bran oil fatty acid distillate (RBOFAD), obtained as a major byproduct of rice bran oil deacidification refining process, was fractionated by detergent solution into a fatty acid mixture as follows: low-melting (19.00 °C) fraction of fatty acids as olein fraction (44.50 g/100 g) and high-melting (49.00 °C) fatty acids as stearin fraction (37.15 g/100 g). A high amount of palmitic acid (42.75 wt%) is present in stearin fraction, while oleic acid is higher (48.21 wt%) in the olein fraction. The stearin and olein fractions of RBOFAD with very high content of free fatty acids are converted into neutral glycerides by autocatalytic esterification reaction with a theoretical amount of glycerol at high temperatures (130–230 °C) and at a reduced pressure (30 mmHg). Acid value, peroxide value, saponification value, and unsaponifiable matters are important analytical parameters to identity for quality assurance. These neutral glyceride-rich stearin and olein fractions, along with unsaponifiable matters, can be used as nutritionally and functionally superior quality food ingredients in margarine and in baked goods as shortenings.     

Dry Fractionation Approach in Concentrating Tocopherols and Tocotrienols from Palm Fatty Acid Distillate: A Green Pretreatment Process for Vitamin E Extraction

Palm fatty acid distillate (PFAD) is a rich source of vitamin E. As compared to other vegetable oil, PFAD has higher tocotrienol (70–80%) over tocopherol content, which makes it a valuable source for vitamin E extraction. Current vitamin E extraction methods are not sustainable due to the intensive usage of chemical and high operational cost. Hence, the present study investigated for the first time using dry fractionation process as a green and economical pretreatment method for separating solid fraction (stearin) and liquid fraction (olein) in order to concentrate vitamin E from PFAD in olein fraction. We examined the dry fractionation conditions: crystallization ending temperature (36–44 °C), cooling rate (0.3 and 1.5°C min⁻¹), stirring speed (20–125 rpm), and holding time (0–60 min) on the composition of unsaturated and saturated fatty acids as well as vitamin E content in liquid fraction (olein) and solid fraction (stearin) using gas chromatography and high performance liquid chromatography, respectively. In most of these conditions, vitamin E was ultimately higher in olein fraction as compared to stearin fraction, which is correlated with the high degree of unsaturation. Under a cooling rate of 0.3°C min⁻¹, 90 rpm stirring speed, and ending crystallization of 38 °C, the highest vitamin E rich olein fraction was attained with 1479 ± 10.51 ppm in 50 g olein fraction as compared to 1366 ± 7.94 ppm in 500 g of unfractionated PFAD.     

Modifications of butter stearin by blending and interesterification for better utilization in edible fat products

This work primarily aims to further modify the stearin fractions, obtained from anhydrous milk fat, after fractionation by dry process and by solvent process using isopropanol, for extending their scope of utilization in edible fat products. Butter stearin fractions, on blending with liquid oils like sunflower oil and soybean oil in different proportions, offer nutritionally important fat products with enriched content of essential fatty acids like C_18∶2 and C_18∶3. The butter stearin fraction from isopropanol fractionation, when interesterified with individual liquid oils by Mucor miehei lipase as a catalyst, yields fat products having desirable properties in making melange spread fat products with reasonable content of polyunsaturated fatty acids and almost zero trans fatty acid content.     

Determination of mono- and diglycerides in palm oil,olein and stearin

Partial glycerides are important constituents of palm oil and can have significant effects on the physical properties of products containing palm oil or on the fractionation of palm oil. A method is described for their routine determination in palm oil. By analysis of 28 weekly composite samples of crude palm oil the following results were obtained: free fatty acids, mean=3.76%, range 2.4 to 4.5%; monoglycerides, mean=0.28%, range 0.21 to 0.34%; diglycerides, mean=6.30%, range 5.3 to 7.7%. During detergent fractionation of palm oil, diglycerides concentrate in the palm olein, but monoglycerides concentrate in the palm stearin. Palm fatty acid distillate was found to contain approximately 3% each of mono- and diglycerides. Because the refining and fractionation processes are continuous in the refinery, it is not possible to follow a single identifiable batch of crude palm oil through the refinery. To circumvent this problem, crude palm oil, stearin and olein from the refinery were bleached and steam refined in the laboratory and the partial glyceride contents determined at each stage of processing. Except for fractionation, the content of glycerides did not change during processing. For oil, olein and stearin, monoglycerides were reduced significantly both after bleaching and after steam refining.     

Monitoring milk fat fractionation: Filtration properties and crystallization kinetics

The effect of fractionation temperature, residence time, and agitation rate on the chemical composition of the stearin and olein milk fat fractions was studied. During fractionation, filtration properties of the crystal suspension were monitored; crystallization kinetics was determined by ¹H NMR. Higher fractionation temperatures result in a lower stearin yield, more oil entrapment, and a lower final solid fat content of the crystal suspension. On the other hand, the chemical composition of the resulting fractions is not influenced. Longer residence times lead to longer filtration times and lower oil entrapment, whereas the yield is not affected. Longer residence times induced lower growth rates, but chemical composition is not influenced. Agitation rates varying from 10 to 15 rpm have no influence on the chemical composition of stearin and olein milk fat fractions. Higher agitation rates decrease the filtration quality and increase stearin yield, causing a softer stearin. In designing and monitoring milk fat fractionation, filtration experiments and the assessment of crystallization kinetics are valuable techniques, but compositional chemical analysis is not favorable.     

Monitoring milk fat fractionation: Effect of agitation, temperature, and residence time on physical properties

With the use of two central composite designs, the effects of agitation rate, fractionation temperature, and residence time on the thermal properties of the stearin and olein milk fat fractions were investigated. The main function of agitation during fat fractionation was suspending the crystal aggregates and enhancing the heat transfer. For the experimental conditions described here, crystal aggregation did not seem to be affected by agitation. The effect of fractionation temperature on the physical properties of the olein fraction was very significant. Triangle diagrams were shown to be a useful tool for monitoring and designing fractionation processes. They illustrate that oleins with similar melting properties can be produced over a range of yields of stearin, which is important from an industrial point of view. Crystallizer residence time, which influences production costs, clearly affects both stearin yield and olein melting properties. For any fractionation temperature, stearin fractions with virtually identical melting properties and yields can be obtained over a range of olein melting properties. Manipulation of both the fractionation temperature and residence time allows the fractionation process to be adapted to meet changing market demands for fractions with different melting properties.     

Sequential-refining of crude glycerol derived from waste used-oil methyl ester plant via a combined process of chemical and adsorption

A sequential stage physico-chemical refining of crude glycerol, derived from a waste used-oil utilizing biodiesel (methyl ester) production plant, was performed by acidification, polar solvent extraction and activated carbon adsorption at a laboratory scale and ambient temperature. The effect of varying the acid type (H₃PO₄, H₂SO₄ and CH₃COOH) and pH (1-6), the type of polar solvent (CH₃OH, C₂H₅OH and C₃H₇OH) and their ratio to glycerol (3:1-1:3 v/v), and adsorption with activated carbon at different ratios of activated carbon to glycerol (40-200 g/l) on the purity of crude glycerol was explored. The highest glycerol purity (95.74 wt.%) was obtained with the sequential acidification to pH 2.5 with H₃PO₄ and phase separation, followed by extraction with C₃H₇OH at a solvent:crude glycerol ratio of 2:1 (v/v). Finally, adsorption with commercial activated carbon at 200 g/l also achieved a 99.7% color reduction.     

Separation of saturated/unsaturated fatty acids

Fatty acid mixtures can be separated into one fraction rich in saturated fatty acids and the other rich in unsaturated acids. Since saturated fatty acids have a higher melting point than unsaturated, liquid mixture to be fractionated is cooled to a temperature at which the larger part of the saturated acids crystallize, while the greater part of unsaturated acids remain in liquid form. Different industrial methods to separate the two phases are described. The oldest and simplest method is slowly to cool and crystallize the mixture in shallow pans to form cakes which then are pressed in presses of different design. By applying high pressure, the liquid olein is thus squeezed out from the cake, leaving the stearin fraction behind. A new process to separate the phases is to mix an aqueous solution, containing a wetting agent, with the crystallized fatty acid mixture. The stearin crystals are thus wetted and transferred into the aqueous phase, which then can be separated from the olein phase in a centrifuge. The stearin/aqueous suspension is heated to melt the stearin, which can then be separated in a second centrifuge. Other methods to improve phase separation use organic solvents, among which are methanol, acetone, methyl formate and propane. In the solvent fraction process, the miscella has to be cooled to a lower temperature than in the aforementioned methods, due to the solubility effect of the solvents. The solvents are removed by distillation from the fraction. Typical operation results with different types of raw materials are given. The advantages and disadvantages of the different methods are discussed.     

Chicken fat dry fractionation: Effects of temperature and time on crystallization,filtration and fraction properties

A surface response experimental design was used to quantify the effects of the final cooling temperature and the residence time at this temperature on the filtration characteristics of the crystal suspension and the quality of the fractions during chicken fat dry fractionation. The crystal morphology was monitored to gain insight into the observed effects. Temperature affected crystallization and the characteristics of the olein and stearin fractions. The crystals became fragmented as the residence time increased, thus leading to a decrease in the filterability of the crystal suspension and an increase in the proportion of the entrained liquid phase. The residence time only affected the quality of the stearin fraction. This time effect was noted at high cooling temperatures in the investigated experimental domain. At low temperatures, increasing the residence time enhanced crystal growth and increased the extent of unsaturation of both fractions without modifying the filtration features.     

Cocoa butter extender from Simarouba glauca fat

Simarouba glauca is a rich source of fat, having a melting point of about 29°C and consisting of palmitic (12.5%), stearic (27%) and oleic (56%) as major fatty acids. It consists of about 30% of symmetrical monounsaturated-type triacylglycerols and appears to be a good source of fat for preparation of cocoa butter (CB) extender. The stearin fraction (35% yield) obtained by solvent fractionation showed an increased supercooling property and a sudden rise in temperature during solidification compared to native fat as shown by cooling curves. The fraction had a narrow melting range and consisted of a high content (66%) of symmetrical monounsaturated-type triacylglycerols like CB. The fraction was compatible with CB even at 50% substitution. In addition, the fraction did not affect the formation of stable or other polymorphic forms of CB at different tempering conditions. The fraction obtained by dry fractionation also had properties similar to that obtained by solvent fractionation. The conditions of the fractionation determine the yield of stearin, which in turn alters the melting characteristics of the fractions. The stearin obtained after removal of about 60–65% olein was found to be suitable as a CB extender to replace up to 25% of CB in chocolate products.     

Isopropanol fractionation of butter oil and characteristics of fractions

Fractionation of butter oil from isopropanol and characterization of the chemical composition and the melting properties of the fractions obtained have been investigated. Butter oil was fractionated from isopropanol (1∶4 wt/vol) at 15 to 30°C. The yields of stearins and oleins were dependent on the temperature employed during fractionation. Thus, 24.8 to 48.9% of stearins and 51.5 to 75.2% of oleins could be obtained as the crystallization temperature varied from 15 to 30°C. The stearin fractions displayed a distinct variation in the fatty acid compositions. The palmitic acid content of the stearin fractions varied from 39.1 to 44.0%, and that of stearic from 15.1 to 16.8%, respectively. The olein fractions contained 43.2% stearic acid, and 2.4 to 2.8% palmitoleic acid (C16∶1). The solid fat content values of the stearin fractions obtained were 62–67, 39–50, and 21–25 at 10, 20, and 30°C, respectively. From the results, it is evident that anhydrous milk fat can be fractionated at relatively high temperatures from isopropanol to produce stearin and olein fractions of specific composition and properties.     

Effect of triglycerides containing 9,10-dihydroxystearic acid on the solidification properties of sal (Shorea robusta) fat

Components affecting solidification properties of sal (Shorea robusta) fat have been studied. Triglycerides containing 9,10-dihydroxystearic acid (DHS-TGs) present to about 3% have been found to affect the supercooling property of sal fat at as low a level as 2%. The DHS-TGs were composed of 57.5% stearic, 5.8% arachidic, 6% palmitic and 30.5% 9,10-dihydroxystearic acids. As DHS-TGs are soluble in acetone, solvent fractionation using acetone improved the supercooling capacity of stearin while that of the olein fraction was not affected. When the fat was subjected to dry fractionation at 35 C, DHS-TGs, due to their high melting nature, were removed to a greater extent in the form of stearin, thereby improving the supercooling capacity of the olein.     

Production of cocoa butter substitutes <Emphasis Type="Italic">via</Emphasis> two-stage static fractionation of palm kernel oil

As are traditional fractionation technologies, static dry fractionation is a highly reliable technology for the consistent production of good-quality palm kernel stearin (PKS) for use as cocoa butter substitute (CBS) after total hydrogenation. A new process route now permits the production of unhardened yet high-quality CBS. Also an increase in total stearin yield can be achieved, via a successful refractionation of palm kernel olein. DSC analysis together with pilot static fractionation trials on the palm kernel olein indicates that a cooling water temperature that is too low (e.g., 17°C) may result in the quick formation of unstable crystals that are possibly later converted to a more stable form. The resulting mixture of crystals with a possibly different polymorphic structure is easily squeezed through the filter cloth during filtration, whereas a slower, but more homogeneous co-crystallization occurs at higher temperature (18°C or higher) and results in a much more stress-resistant slurry. Polarized light microscopy analysis confirmed that crystal size is not the only determining factor for a successful filtration. The total two-stage static fractionation of palm kernel oil (PKO) [iodine value (IV) 18] on a pilot scale results in the following three end products: PKS IV 5 (yield: 29%, for direct use as CBS), PK olein IV 27 (yield: 58%), and PKS IV 7 (yield: 13% for use as CBS after full hydrogenation). The unhardened PKS IV 5 has outstanding melting and crystallization properties, comparable to traditional hydrogenated stearin fractions. Therefore, rather than the higher stearin yield, the reduced hydrogenation capacity is most probably the most important benefit of the two-stage static fractionation process.     

Antioxidant Activity of Sesame (Sesamum indicum L.) Cake Extract for the Stabilization of Olein Based Butter

This study investigated the effect of ethanolic sesame cake extract on oxidative stabilization of olein based butter. Fractionation of cream was performed by the dry fractionation technique at 10 °C, ethanolic sesame cake extract (SCE) was incorporated into olein butter at three different concentrations; 50, 100, 150 ppm (T₁, T₂, T₃) and compared with a control. The total phenolic content of SCE was 1.72 (mg gallic acid equivalent g^?1 dry weight). The HPLC characterization of ethanolic sesame cake revealed the presence of antioxidant substances viz. sesamol, sesamin and sesamolin in higher extents. The DPPH free radical scavenging activity of SCE was 83 % as compared to 64 and 75 % in BHA and BHT. Fractionation of milk fat at 10 °C significantly (p < 0.05) influenced the fatty acid profile of olein and stearin fractions from the parent milk fat. Concentration of oleic acid and linoleic acid in olein fraction was 29.62 and 33.46 % greater than the parent milk fat. The loss of C18:1 in 90 days stored control and T₃ was 24.37 and 3.58 %, respectively, 58 % C18:2 was broken down into oxidation products over 8.55 % loss in T₃. The peroxide value of control, T₁, T₂, BHT and T₃ in the Schaal oven test was 8.59, 8.12, 5.34, 4.52 and 2.49 (mequiv O₂/kg). The peroxide value and anisidine value of 3 months stored control and T₃ were 1.21, 0.42 (mequiv O₂/kg) and 27.25, 13.25, respectively. The concentration of conjugated dienes in T₃ was substantially less than the control. The induction period of T₃ was considerably higher than BHT with no difference in sensory characteristics (p > 0.05). Ethanolic SCE can be used for the long‐term preservation of olein butter, with acceptable sensory characteristics.     

D. K. Bhattacharyya,Modification of tallow fractions in the preparation of edible fat products

Investigation has been carried out with an intention to prepare shortening, margarine fat bases, and value-added edible fat products like cocobutter substitute from tallow. For this, tallow was fractionated at low (12 and 15 °C) and intermediate (25 °C) temperatures by solvent (acetone) fractionation process. The stearin fractions (yield: 23—40% (w/w) and slip melting point: 45—50.5 °C) thus obtained were blended and interesterified with liquid oils, such as sunflower, soybean, rice bran etc. by microbial lipase catalyzed route. The olein fractions (yield: 60—77% (w/w) and slip melting point: 21—32.5 °C) were also chemically interesterified (using NaOMe) and biochemically (using Rhizomucor miehei lipase, Lipozyme IM 20). The olein fractions were also blended with sal (Shorea robusta) fat, sal olein, and acidolysed karanja (Pongamia glabra) stearin. As revealed from their slip melting point and solid fat index, the products thus prepared were found to be suitable for shortening, margarine fat bases, and vanaspati substitute.     

Fractionation studies of palm oil by density gradient

The paper describes a method of fractionating vegetable, animal and fish oils, and in particular palm oil. The method involves addition of a medium comprising two common solvents to the semisolid oils. On centrifugation, the olein and stearin are separated by the medium in the middle. Thirteen media made up from binary combinations of nine solvents, viz. water, propylene glycol, glycerine, methanol, ethanol,n-propanol, isopropanol (IPA), acetone and butanone, are found to be effective in olein-stearin separation. However, only the water/IPA and water/methanol systems have been studied in detail. The aqueous IPA provides a higher yield of olein than water/ methanol but intersolubility between oil and medium is also greater. The fractionation process can be carried out at any suitable temperature. Fractionation of the special prime bleached (SPB) palm oil at 16 C yields an olein with a cloud point of 4.8 C. Some hybrid palm oils produce a large quantity of low cloud point olein which can be bleached readily. The process can be extended to include degumming and neutralization by using an alkaline medium for centrifugation. The olein fractions obtained have been found to be free of phosphatides and the free fatty acids reduced to as low as 0.02%. Metal-scavenging agents have also been added to the medium in an attempt to remove copper and iron. The development of this process into a continuous one has been demonstrated on the AlfaLaval LAPX 202 Separator. Fractionation of crude palm oil using a density gradient provides seven fractions of different characteristics. The iodine values vary from 37.5 to 57.4 and the unsaturated fatty acids range from 32.7% to 51.2%. Triglyceride analysis by carbon numbers shows great differences in the C₄₈ and C₅₂ constituents of the fractions. aThe volume ratio of oil to medium in each case was 1:1. The separation involved the oil and wax.     

Cyclic alkanes as geochemical markers in coal liquefaction products

Branched-chain/cyclic alkanes have been obtained, by solvent extraction and molecular-sieve adsorption, from a UK low-temperature (Rexco) coal tar, a USA fluidized-bed pyrolysis (FMC COED) coal tar, and a novel supercritical-gas-extract of a Turkish (Elbistan) lignite. Mass spectrometry (with gas chromatography and field-desorption) established the presence of mono-, di (including sesquiterpanes), tri-, tetra- (steranes only), and pentacyclic (triterpanes only) alkanes, including several steranes and triterpanes not previously reported as coal-tar constituents. The potential of cyclic alkanes as geochemical markers, even for commercial coal products subjected to appreciable heat treatment, is demonstrated by the identification of C₁₂, C₁₃, C₁₅ and C₁₆ dicyclics (including isoprenoid alkanes), C₁₇-C₂₆ tricyclics, and C₂₇ and C₂₉ hopane-type pentacyclics (triterpanes) in FMC, and of C₁₆-C₃₈ monocyclics, C₃₄-C₃₆ dicyclics, C₂₂-C₃₆ tricyclics, C₂₇-C₃₀ tetracyclics (steranes), and C₂₇, C₂₉, C₃₀, C₃₁, C₃₂, and C₃₃ hopane-type pentacyclics (triterpanes) in Rexco tar. Tetra- and pentacyclic alkanes were also preserved in the lignite extract.     

A Review on the Fundamentals of Palm Oil Fractionation: Processing Conditions and Seeding Agents

Fractionation is a well-established process adopted in the fats and oils industries. It involves the separation of low and high melting triacylglycerol under controlled cooling conditions into olein and stearin fractions with distinct chemical and physical properties. Amongst the other vegetable oils, palm oil is one of the most fractionated oils in the past few decades mainly attributed to its semisolid properties. The various fraction of palm oil allows it to be used in different types of food products such as margarine, frying oil, and cocoa butter substitute. In fractionation, proper control of the fractionation conditions is important to produce the fractions with desirable stearin and olein quality. The purpose of this paper is to critically review the fractionation conditions (crystallization temperature, agitation, cooling rate and crystallization time) that affect the yield and quality of the oil produced. Additionally, it also provides the latest updates on the influence of seeding agents (diacylglycerol, monoacylglycerol, hard fat, phytosterol, phospholipid, lecithin, essential oil, sugar, polyglycerol ester, and talc) used in fractionation. This article is useful to provide a fundamental understanding of fractionation to scientists from the industries or academia working in the fats and oils industries. Practical Applications: This paper provides an in-depth understanding of fractionation particularly on the parameters of fractionation in influencing the quality and yield of the stearin and olein produced. It also for the first time presents the effect of addition of various seeding agents on palm oil fractionation which can help the industry to select the appropriate seeding agents to improve the currently employed fractionation process. Thus, it can act as a guideline for the industry to understand and select the appropriate fractionation conditions when developing a new product using this approach. The fractionation conditions discussed here can also be used as a reference when fractionating other types of fats and oils as most of them share a common background.