Triacylglycerols responsible for the onset of nucleation during clouding of palm olein

This paper discusses the results of an investigation to identify triacylglycerols that induce clouding of refined bleached deodorized (RBD) palm olein, which occurred within 24 h after fractionation. The experiments were conducted in a jacketed glass vessel in which the liquid sample was cooled from 70 to 23°C at a predetermined rate. Clouding began at around 28.5°C. The presence of three different types of saturated triglycerides, namely tripalmitin, dipalmitoyl-myristoylglycerol and dipalmitoyl-stearoyl-rac-glycerol, is critical in the formation of nuclei and thus clouding of the RBD palm olein. This conclusion is based on the significant increase in the relative concentration of these components in the nuclei as compared to the mother oil.     

Trans-free vanaspati containing ternary blends of palm oil-palm stearin-palm olein and palm oil-palm stearin-palm kernel olein

Four samples of trans-free vanaspati were made using palm oil-palm stearin-palm olein (PO-POs-POo) blends (set A) and another four samples (set B) using palm oil-palm stearin-palm kernel olein (PO-POs-PKOo). Palm stearin iodine value [iodine value (IV), 30] and soft palm stearin (IV, 44) were used in this study. The products were evaluated for their physical and chemical properties. It was observed that most of the vanaspati were granular (grainy) and had a shiny appearance. Chemical analyses indicated that vanaspati consisting of PO-POs-POo had higher IV (47.7–52.4) than the PO-POs-PKOo vanaspati (37.5–47.3). The higher IV demonstrated by set A samples was due to their higher content of unsaturated fatty acids, 46.0–50.0% compared to 36.6–45.0% in set B. Decreasing the amount of palm oil while increasing palm stearin in the formulations resulted in higher slip melting points and higher yield values. Eutectic interaction was observed in PO-POs-PKOo blends. The β′ crystalline form was predominent in PO-POs-POo samples (set A). One formulation in set B exhibited β crystallinity. From the differential scanning calorimetry thermograms, samples in set B showed a high peak at the low-melting region as well as a high peak at the high-melting region. In set A, the peak at the low-melting region was relatively lower.     

A fourier transform infrared spectroscopic method for determining butylated hydroxytoluene in palm olein and palm oil

A simple, rapid, and direct FTIR spectroscopic method was developed for the determination of BHT content in refined, bleached, and deodorized (RBD) palm olein and RBD palm oil. The method used sodium chloride windows with a 50-mm transmission path. Fifty stripped oil samples of both RBD palm olein and RBD palm oil were spiked with known amounts of BHT concentrations up to 300 mg/kg (ppm). The data were separated into two sets for calibration and validation using partial least squares models. FTIR results for both oils correlated well with results obtained by the IUPAC HPLC-based method. For RBD palm olein, the coefficient of determination (R ²) was 0.9907 and the SE of calibration (SEC) was 8.47 ppm. For RBD palm oil, an R ² of 0.9848 and an SEC of 10.73 ppm were achieved. Because of the significant decrease in analysis time and reduction in solvent usage, this FTIR method for BHT is especially well suited for routine quality control applications in the palm oil industry.     

Hydrolysis of palm olein catalyzed by solid heteropolyacids

The hydrolysis activity of superacids on palm olein, including tungstophosphoric acid and molybdophosphoric acid and their partially ion-exchanged cesium (Cs) salt, were investigated and compared with macroporous cation-exchanged resin and aluminum-incorporated mesoporous molecular sieve. The activities of the superacids supported on the resin and silica were also determined. The reactions were carried out in a stirred batch reactor with continuous steam injection at temperatures from 140 to 180°C. The reaction kinetics, obtained by regression, are first order with respect to TG of the superacids and Cs salts. Of the catalysts studied, the superacids loaded onto cation-exchanged resins were the most active on a weight basis. However, in terms of the turnover number per acid site, the Cs salt of tungstophosphoric acid had 13 times the activity of the cation-exchanged resin. The original superacids had lower activities than the Cs salts in terms of their turnover number. The observations are qualitatively in line with the higher acid strengths of the catalysts, as confirmed by the low activity of the aluminum silicate mesoporous molecular sieve, which is known to have a high concentration of low-to moderate-strength acid sites. The activation energy of the reaction with the Cs salts was ∼49 kJ mol⁻¹. This is rather low as compared to that catalyzed by the cation-exchanged resin.     

Enzymatic interesterification of palm stearin and palm kernel olein

Palm stearin (POs) and palm kernel olein (PKOo) blends were modified by enzymatic interesterification (IE) to achieve the physical properties of margarine fats. POs and PKOo are both products of the palm oil industry that presently have limited use. Rhizomucor miehei lipase (Lipozyme IM 60) was used to catalyze the interesterification of oil blends at 60°C. The progress of interesterification was monitored by following changes in triacylglyceride composition. At 60°C interesterification can be completed in 5 h. Degrees of hydrolysis obtained through IE for all blends were decreased from 2.9 to 2.0 by use of dry molecular sieves. The solid fat contents of POs/PKOo 30:70 and 70:30 interesterified blends were 9.6 and 18.1 at 20°C, and 0 and 4.1 at 35°C, respectively. The slip melting point (SMP) of POs/PKOo 30:70 was 40.0°C before interesterification and 29.9°C after IE. For POs/PKOs 70:30, SMP was 47.7 before and 37.5°C after IE. These thermal characteristics of interesterified POs/PKOo blend ratios from 30:70 to 70:30 were comparable to those of commercial margarines. Results showed that IE was effective in producing solid fats with less than 0.5% trans.     

Effect of enzymatic transesterification with flaxseed oil on the high-melting glycerides of palm stearin and palm olein

The effects of enzymatic transesterification on the melting behavior of palm stearin and palm olein, each blended separately with flaxseed oil in the ratio of 90∶10 and catalyzed by various types of lipases, were studied. The commercial lipases used were Lipozyme IM, Novozyme 435, and myceliumbound lipases of Aspergillus flavus and A. oryzae. The slip melting point (SMP) of the palm stearin/flaxseed oil (PS/FS) mixture transesterified with lipases decreased, with the highest drop noted for the mixture transesterified with Lipozyme IM. However, when palm stearin was replaced with palm olein, the SMP of the palm olein/flaxseed oil (PO/FS) mixture increased, with the commercial lipases causing an increase of 41 to 48% compared to the nontransesterified material. As expected, the solid fat content (SFC) of the transesterified PS/FS was lower at all temperatures than that of the nontransesterified PS/FS sample. In contrast, all transesterified PO/FS increased in SFC, particularly at 10°C. Results from DSc and HPLC analyses showed that the high-melting glycerides, especially the tripalmitin of palm stearin, were hydrolyzed. Consequently, 1,3-dipalmitoylglycerol was found to accumulate in the mixture. There was no difference in the FA compositions between the transesterified and nontransesterified mixtures.     

Application of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification

The utilization of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification was studied. Vanaspati fat was made from ternary blends of palm olein (POL), low‐erucic acid rapeseed oil (RSO) and sunflower oil (SFO) through direct interesterification of the blends or by blending interesterified POL with RSO and SFO. The slip melting point (SMP), the solid fat content (SFC) at 10–40 °C, the carbon number (CN) triacylglycerol (TAG) composition, the induction period (IP) of oxidation at 120 °C (IP₁₂₀) and the IP of crystallization at 20 °C of the final products and non‐interesterified blends were evaluated. Results indicated that all the final products had higher SMP, SFC, IP of crystallization and CN 48 TAG (trisaturated TAG), and lower IP₁₂₀, than their non‐interesterified blends. However, SMP, SFC, IP₁₂₀, IP of crystallization and CN 48 TAG were higher for fats prepared by blending interesterified POL with RSO and SFO. A comparison between the SFC at 20–30 °C of the final products and those of a commercial low‐trans Iranian vanaspati showed that the least saturated fatty acid content necessary to achieve a zero‐trans fat suitable for use as Iranian vanaspati was 37.2% for directly interesterified blends and 28.8% for fats prepared by blending interesterified POL with liquid oils.     

Kinetic studies of epoxidation and oxirane cleavage of palm olein methyl esters

The kinetics for the epoxidation of methyl esters of palm olein (MEPOL) by peroxyformic acid and peroxyacetic acid generatedin situ were studied. The rate-determining step was found to be the formation of peroxy acid. Epoxidized MEPOL (EpMEPOL), with almost complete conversion of the unsaturated carbon and negligible ring-opening, can be synthesized by thein situ technique described. The kinetics of the oxirane cleavage of EpMEPOL by acetic acid were studied at various temperatures. The reaction was found to be first-order with respect to the epoxy concentration and second-order to the acetic acid concentration. The activation energy and the entropy of activation for the epoxidation of MEPOL were comparable to those for the oxirane cleavage of EpMEPOL by acetic acid, suggesting that the two reactions are competitive. The success of the epoxidation of MEPOL with only negligible oxirane cleavage is attributed to the heterogeneous nature of the system employed in thein situ technique.     

Determination of iodine value of palm olein mixtures using differential scanning calorimetry

Differential scanning calorimetry (DSC) was used to determine the iodine value (IV) of various palm olein (PoO) mixtures. Eight different PoO mixtures, namely, PoO:PKO, PoO:CoO, PoO:PS, PoO:PO, PoO:CaO, PoO:OeO, PoO:CnO and PoO:SFO were prepared at different ratios (w/w) to give various IV (PKO represents palm kernel olein; CoO, coconut oil; PS, palm stearin; PO, palm oil; CaO, canola oil; OeO, olive oil; CnO, corn oil; and SFO, sunflower oil). Each sample was then scanned from 80 to ‐ 100 �C at ‐5 �C/min using a DSC. All the mixtures showed two exothermic peaks in their cooling thermograms, except PoO:SFO mixtures which showed three peaks. Results of stepwise multiple linear regression (SMLR) analysis showed that five independent variables extracted from each of these peaks, namely, on‐set temperature, off‐set temperature, peak temperature, peak height and peak enthalpy could predict well the IV of each mixture. The calibration models developed showed appreciable effectiveness, re‐producibility and accuracy, and specificity towards the calibration data set. A shared calibration model for each group of PoO mixtures i.e. high‐lauric (PoO:PKO and PoO:CoO), high‐palmitic (PoO:PS and PoO:PO) and high‐oleic (PoO:CaO and PoO:OeO) mixtures was also developed. SMLR analysis showed that the shared models were also capable in predicting IV of the PoO mixtures, even though the coefficient of determination, R² , was slightly lower than that of their individual models. The shared calibration models also had good reproducibility and accuracy when compared with the standard chemical method. In conclusion, DSC provides an effective method in determining IV for routine analysis in the industries, whereby one single model could be calibrated for the use of all oil and fat products that have similar chemical compositions such as high‐lauric, high‐palmitic or high‐oleic mixtures in the industry.     

Effect of chemical interesterification on triacylglycerol and solid fat contents of palm stearin,sunflower oil and palm kernel olein blends

Palm stearin (POs) with an iodine value of 41.4, sunflower oil (SFO) and palm kernel olein (PKOo) were blended in various ratios according to a three‐component mixture design and subjected to chemical interesterification (CIE). Triacylglycerol (TAG) and solid fat content (SFC) profiles of the chemically interesterified (CIEed) blends were analyzed and compared with those of the corresponding non‐CIEed blends. Upon CIE, extensive rearrangement of fatty acids (FA) among TAG was evident. The concentrations of several TAG were increased, some decreased and several new TAG might also have been formed. The changes in the TAG profiles were reflected in the SFC profiles of the blends. The SFC of the CIEed blends, except the binary blends of POs/PKOo which experienced an increase in SFC following CIE, revealed that they were softer than their respective starting blends. Randomization of FA distribution within and among TAG molecules of POs and PKOo led to a modification in TAG composition of the POs/PKOo blends and improved miscibility between the two fats, and consequently diminished the eutectic interaction that occurred between POs and PKOo.     

Determination of free fatty acids in crude palm oil and refined-bleached-deodorized palm olein using fourier transform infrared spectroscopy

A rapid direct Fourier transform infrared (FTIR) spectroscopic method using a 100 μ BaF₂ transmission cell was developed for the determination of free fatty acid (FFA) in crude palm oil (CPO) and refined-bleached-deodorized (RBD) palm olein, covering an analytical range of 3.0–6.5% and 0.07–0.6% FFA, respectively. The samples were prepared by hydrolyzing oil with enzyme in an incubator. The optimal calibration models were constructed based on partial least squares (PLS) analysis using the FTIR carboxyl region (C=O) from 1722 to 1690 cm⁻¹. The resulting PLS calibrations were linear over the range tested. The standard errors of calibration (SEC) obtained were 0.08% FFA for CPO with correlation coefficient (R ²) of 0.992 and 0.01% FFA for RBD palm olein with R ² of 0.994. The standard errors of performance (SEP) were 0.04% FFA for CPO with R ² of 0.998 and 0.006% FFA for RBD palm olein with R ² of 0.998, respectively. In terms of reproducibility (r) and accuracy (a), both FTIR and chemical methods showed comparable results. Because of its simpler and more rapid analysis, which is less than 2 min per sample, as well as the minimum use of solvents and labor, FTIR has an advantage over the wet chemical method.     

Effects of epoxidation on the thermal oxidative stabilities of fatty acid esters derived from palm olein

A variety of esters from the reactions of monoalcohols with palm olein were prepared, epoxidized byin situ peroxyacid techniques, and some of their physical properties were compared. The thermal oxidative stabilities of these esters andbis(2-ethylhexyl) phthalate were studied. The esters were placed in an oven maintained at 120°C, and the loss of mass and acid, iodine, percent oxirane, hydroxyl, and peroxide values were monitored periodically. The epoxidized esters had higher densities and lower volatilities, and were more resistant toward oxidation than their unepoxidized counterparts. The stability of the oxirane was related to the initial acid value of the sample. Higher initial acid value resulted in a greater decrease in the oxirane content, indicating acid-catalyzed cleavage of the oxirane ring.     

Resistance to crystallization of blends of palm olein with soybean oil stored at various temperatures

The aim of the study was to determine the resistance to crystallization of palm olein (POo) with soybean oil (SBO) at different temperatures. POo of iodine value (IV) 65 gave better resistance to crystallization than POo of IV 60 or IV 63. For applications such as salad oil, the use of POo of IV 65 is limited to 30% when blended with SBO. If POo of either IV 60 or IV 63 is chosen, its use in salad oil is limited to 10% only. However, for applications other than salad oil, such as for cooking or frying, 100% POo of any IV could be used. For cold climates, the amount of POo (IV 60 or 63) recommended to get a clear oil is 10–30%. Alternatively, up to 40% POo of IV 65 can be blended with SBO. For temperate climates, the amount of POo (IV 60 or 63) recommended can be up to 60%. With POo of IV 65, the amount recommended is as high as 80–90% for application as a cooking or frying oil.     

Determination of anisidine value in thermally oxidized palm olein by fourier transform infrared spectroscopy

Fourier transform infrared (FTIR) spectroscopy with transmission cell is described to predict anisidine value of palm olein. The calibration set was prepared by mixing the thermally oxidized palm olein and the unoxidized palm olein with certain ratios (w/w) covering a wide range of anisidine values. A partial least square (PLS) regression technique was employed to construct a calibration model. This model was further accomplished by a validation step. The standard error of prediction found was 0.51. The precision of this method was shown to be comparable to the accuracy of the American Oil Chemists’ Society method used for measurement of anisidine value, with coefficient of determination (R ²) of 0.99. The study showed that mid-band FTIR spectroscopy combined with a PLS calibration technique is a versatile, efficient, and accurate technique for the estimation of anisidine value of palm olein within about 2 min with less than 2 mL of sample.     

Oxidative stability of blends and interesterified blends of soybean oil and palm olein

Improvement of oxidative stability of soybean oil by blending with a more stable oil was investigated. Autoxidation of blends and interesterified blends (9∶1, 8∶2, 7∶3 and 1∶1, w/w) of soybean oil and palm olein was studied with respect to fatty acid composition, fatty acid location and triacylglycerol composition. Rates of formation of triacylglycerol hydroproxides, peroxide value and volatiles were evaluated. The fatty acid composition of soybean oil was changed by blending. Linolenic and linoleic acids decreased and oleic acid increased. The triacylglycerol composition of blends and interesterified blends was different from that of soybean oil. Relative to soybean oil, LnLL, LLL, LLO, LLP, LOO and LLS triacylglycerols were lowered and POO, POP and PLP were higher in blends and interesterified blends (where Ln, L, O, P and S represent linolenic, linoleic, oleic, palmitic and stearic acids, respectively). Interesterification of the blends leads to a decrease in POO and POP and an increase in LOP. Linoleic acid concentration at triacylglycerol carbon-2 was decreased by blending and interesterification. Rates of change for peroxide value and oxidation product formation confirmed the improvement of soybean oil stability by blending and interesterification. But, blends were more stable than interesterified blends. Also, the formation of hexanal, the major volatile of linoleate hydroperoxides of soybean oil, was decreased by blending and interesterification.     

DSC study on the melting properties of palm oil, sunflower oil, and palm kernel olein blends before and after chemical interesterification

Changes in DSC melting properties of palm oil (PO), sunflower oil (SFO), palm kernel olein (PKOo), and their belends in various ratios were studied by using a combination of blending, and chemical interesterification (CIE) techniques and determining total melting (ΔH _f ) and partial melting (ΔH _i°C ) enthalpies. Blending and CIE significantly modified the DSC melting properties of the PO/SFO/PKOo blends. PO and blends containing substantial amounts of PO and PKOo experienced an increase in their DSC ΔH _f and ΔH _i°C following CIE. The DSC ΔH _f and ΔH _i°C of PKOo, blends of PO/SFO at 1∶1 and 1∶3 ratios, and all blends of PKOo/SFO significantly decreased after CIE. The DSC ΔH _f and ΔH _i°C of SFO changed little following CIE. Randomization of FA distribution within and among TAG molecules of PO and PKOo led to modification in TAG composition of the PO/PKOo blends and improved miscibility between the two fats and consequently diminished the eutectic interaction that occurred between PO and PKOo.     

Enzymatic incorporation of stearic acid into a blend of palm olein and palm kernel oil: Optimization by response surface methodology

Response surface methodology was used to model the incorporation of stearic acid into a blend of palm olein and palm kernel oil in hexane using the sn-1,3-regiospecific lipase Lipozyme RM IM. The factors investigated were incubation time, temperature, and substrate molar ratio. A second-order model with interaction was used to fit the experimental data. The coefficients of determination, R ² and Q ², were 0.96 and 0.90, respectively. The adjusted R ² was 0.95. The regression probability was less than 0.001, and the model showed no lack of fit. Also, a linear relationship was observed between the predicted and observed values. All parameters studied had positive effects on incorporation of stearic acid, with substrate molar ratio having the greatest effect. The interaction terms of substrate molar ratio with temperature and time also had positive effects on incorporation, whereas the effect of the squared term of substrate molar ratio was negative. The quadratic terms of temperature and time, as well as their interaction term, had no significant effect on incorporation at α_0.05. Model verification was done by performing a chi-square test, which showed that there was no significant difference between predicted values and a new set of observed responses.     

Composition of crystals of palm olein formed at room temperature

The composition of purified plam olein crystals formed at room temperature (25°C) was identified in this study. Two peaks were obtained when the crystals were analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC). The retention times of these peaks suggested that they were not triglycerides. Gas-liquid chromatography of fatty acid methyl ester analysis of the crystals showed the presence of C16, C18:0, and C18:1 fatty acids. Further analysis by gas-liquid chromatography of carbon number, after collecting the fractions from RP-HPLC, concluded that the major peak A was 1,3-dipalmito-glycerol. The minor peak B was tentatively identified as 1-palmito-3-stearo-glycerol and/or 1-palmito-3-oleo-glycerol due to unavailability of respective standard glycerides. The differential scanning calorimetry thermogram of the crystals show that A and B were indeed the high melting glycerides, with melting and crystallization points of 70.4 and 53.8°C, respectively.     

Enzymatic transesterification of palm olein with nonspecific and 1,3-specific lipases

The enzymatic transesterification of palm olein was conducted in a low-moisture medium with nonspecific and 1,3-specific lipases from microbial sources. The enzymes were first immobilized on Celite, lyophilized for 4 h and then added to a reaction medium that consisted of 10% (wt/vol) palm olein in water-saturated hexane. The catalytic performance of the enzymes was evaluated by determining the changes in triglyceride (TG) composition and concentrations by reverse-phase high-performance liquid chromatography (HPLC) and the formation of free fatty acids by titration. Studies with lipase fromCandida rugosa showed that the degree of hydrolysis was reduced by drying the immobilized preparation and that the best drying time was 4 h. In all cases, the transesterification process resulted in the formation of PPP, a TG initially undetected in the oil, and increases in the concentrations of OOO (1.3–2.1-fold), OOL (1.7–4.5-fold), and OLL (1.7–4.3-fold), where P, O, and L are palmitic, oleic, and linoleic acids, respectively. SOS (where S is stearic acid), another TG not detected in the oil, was synthesized byRhizomucor miehei andPseudomonas lipases, with the latter producing more of this TG. There was a corresponding decrease in the concentrations of POP, PLP, POO, and POL. PPP concentration ranged from 1.9% (w/w) forMucor javanicus lipase to 6.2% (w/w) forPseudomonas lipase after 24 h. The greatest degree and fastest rate of change were caused byPseudomonas lipase, followed by the enzymes fromR. miehei andAspergillus niger. The effects of transesterification and hydrolysis of palm olein by the various lipases resulted in changes in the overall degree of saturation of the triglyceride components. There seems to be no clear correlation between the enzyme positional specificity and the products formed. Possible mechanisms for the formation of PPP, OOL, OLL, OOO, and SOS are discussed.