Silica refining of palm oil

The amount of bleaching earth required in the physical refining process of palm oil depends on the activity of the earth, quality of the oil and final color specification of the refined products. The use of silica (Trisyl) in combination with bleaching clay in palm oil refining has been investigated. The optimum conditions required for Trisyl and bleaching clay are 95–105°C for a period of 30–40 min. Improvements in color performance for palm oil products are noted with the addition of small quantities of Trisyl (0.06–0.24%) to the bleaching clay. Addition of 0.12% Trisyl to 0.4% bleaching clay improved the color of the refined oil by as much as 1.7 Red Lovibond units. Lower phosphorus levels (18.4 and 16.9 ppm) were obtained in the refined oils with an addition of 0.12 and 0.24% Trisyl, respectively, as compared to a level of 36.2 ppm of phosphorus when no silica was added to the earth. Better color stability was also obtained with oils treated with Trisyl. An additional advantage was the reduction in filtration time, leading to possible higher throughput in refining.     

Sepiolite: An effective bleaching adsorbent for the physical refining of degummed rapeseed oil

The efficiency of Turkish sepiolite in bleaching degummed rapeseed oil has been investigated. Experimental results indicate that the bleaching efficiency is more dependent on the ratio of sepiolite to oil than on operating parameters such as contact time and temperature. An increase in the sepiolite dosage reduces the color bodies of the rapeseed oil. Its effect on oxidation state, however, is complex and related to both primary and secondary oxidation products. The removal of impurities such as chlorophyll a, β-carotene, and phosphorus increases with increasing sepiolite dosage and reaches a maxumum at 1.5% sepiolite addition and 100°C bleaching temperature. Chlorophyll a, β-carotene, and phosphorus adsorptions can be described by a mechanism involving surface are and porosity of acid-activated sepiolite as key variables. The sorption is also independent of the polarity of the adsorbate molecules. Direct comparison of activated sepiolite with the commercial bleaching earth Tonsil 210 FF shows that in some respects sepiolite offers significant advantages.     

Pretreatment of corn oil for physical refining

Crude corn oil that contained 380 ppm of phosphorus and 5% of free fatty acids was degummed, bleached, and winterized for physical refining. The pretreatment and the steam-refining conditions were studied in pilot plant scale (2 kg/batch). The efficiency of wet degumming and of the total degumming processes, at different temperatures, was evaluated. TriSyl silica was tested as an auxiliary agent in the reduction of the phosphorus content before bleaching. The experimental conditions of the physical refining were: temperature at 240 or 250°C; 8 to 18 mbar vacuum, and distillation time varying from 1 to 3 h. Degumming at 10 or 30°C resulted in the removal of more phosphorus than at 70°C. Water degumming was more efficient than the processes of total degumming or acid degumming. Corn oil, degummed at 10 or 30°C, after bleaching passed the cold test, irrespective of the degumming agent used. Degumming and winterization took place simultaneously at these temperatures. The pretreatment was able to reduce the phosphorus content to less than 5 ppm. The amount of bleaching earth was reduced by carrying out dry degumming or by using silica before bleaching. Corn oil acidity, after physical refining, varied from 0.49 to 1.87%, depending on the residence time. Contrary to alkali refining, physical refining did not promote color removal due to the fixation of pigments present in the crude corn oil.     

The effect of the refining process on the interfacial properties of palm oil

The interfacial tension of palm oil against water at 60°C was determined in the presence of monoglycerides with (i) different acyl chain lengths, (ii) the same acyl chain length but with different unsaturation, and (iii) different phospholipids. The interfacial tensions of the oil/water interface were depressed, albeit to different extents, by the presence of these substances, depending on the acyl chain length, unsaturation, and the chemical structure of the species adsorbed. The adsorption of the saturated monoglycerides C12∶0, C14∶0, C16∶0, C18∶0 and the unsaturated monoglycerides of C18∶1 and C18∶3 is consistent with a Langmuir isotherm at the palm oil/water interface. However, fitting of the data for C18∶2, l-α-phosphatidylcholine, and lysophosphatidylcholine to the Langmuir isotherm is less satisfactory. The surface areas of the materials adsorbed at the palm oil/water interface are much larger than those of liquid condensed films and closer to those for liquid expanded films. The influence of the nature of the oil (triglycerides), the minor components in the oil, and thier interactions with the added lipids at the oil/water interface are briefly discussed. The effect of the refining process on the interfacial properties of palm oil against water was also studied. The efficiency of the refining process in minor oil contaminants’ removal and the quality of the oil obtained as reflected by the interfacial properties of the oil is discussed.     

Comparative evaluation of palm oil color measurement using a prototype palm oil colorimeter

The color of refined palm oil and palm oil products is conventionally measured using the manually operated Lovibond^® Tintometer. In the present study, one manual/visual and three automatic colorimeters for the measurement of vegetable oil color were used for color measurements of refined palm oil. All colorimeters used were commercially available instruments except for an automatic palm oil colorimeter developed specifically for the measurement of palm oil color. The color values obtained from all four instruments were compared using the visually obtained readings as reference values. Results showed that all three automatic instruments gave correlation coefficients of greater than 0.9300 for red color measurements. In addition, the Student t-test showed no difference between the analysis of red color using the visual method and the palm oil colorimeter. This investigation concludes that, although it is extremely difficult to reduce the lack of precision in color measurement of palm oil, a properly designed and calibrated automatic instrument may still be the better choice because reproducibility and repeatability are required in all standard test methods. The palm oil colorimeter offers a ready and relatively inexpensive solution to the problem of color matches based on visual observations.     

Pretreatment efficiency for physical refining of sunflowerseed oil

The appropriate pretreatment of crude oil is of crucial significance for the application of physical refining. This paper presents a simplified process for the preparation of sunflowerseed oil by applying multistep acid degumming as the only pretreatment step. Amorphous silica hydrogel was used instead of treatment with bleaching earth. The results obtained showed that samples of crude-pressed and extracted sunflowerseed oil differ significantly with respect to the content and composition of phosphatides, which is important for the pretreatment. The proper choice of oil and the application of multistep acid degumming results in an effective pretreatment of sunflowerseed oil for physical refining.     

The effect of carotene extraction system on crude palm oil quality, carotene composition, and carotene stability during storage

Palm carotene was successfully concentrated from crude palm oil (CPO) by an adsorption process using a synthetic adsorbent followed by solvent extraction. Evaluation of feed CPO and CPO which underwent the carotene extraction process was conducted. The quality of CPO after the extraction process was slightly deteriorated in terms of free fatty acid, moisture content, impurities, peroxide value, anisidine value, discriminant function, and deterioration of bleachability index. However, the CPO still can be refined to produce refined, bleached, deodorized palm oil that meets the Palm Oil Refiners Association of Malaysia specifications. No extra cost was incurred by refining this CPO as the dosage of bleaching earth used was very similar to the refining of standard CPO. The triglyceride carbon number and fatty acid composition of CPO after going through the carotene extraction process were almost the same as CPO data. The major components of the carotene fraction were similar to CPO, which contains mainly α- and β-carotene. The carotene could be stored for at least 3 mon.     

Degumming and bleaching ofLesquerella fendleri seed oil

A lesquerella species (Lesquerella fendleri) being investigated as a domestic source of seed oil containing hydroxy fatty acids shows good agronomic properties and is being tested in semi-commercial production.Lesquerella fendleri seeds contain 25% oil, of which 55% is lesquerolic acid (14-hydroxy-cis-11-eicosenoic). Oils produced in pilot-plant quantities by screw press, prepress-solvent extraction and extrusion-solvent extraction processes have been refined in the laboratory by filtering, degumming and bleaching. Two American Oil Chemists’ Society (AOCS) standard bleaching earths and two commercial earths were compared for effectiveness in bleaching these dark, yellow-red, crude lesquerella oils. Free fatty acids (1.3%), iodine value (111), peroxide value (<4 meq/kg), unsaponifiables (1.7%) and hydroxyl value (100) were not significantly affected by degumming and bleaching, but phosphorus levels of 8–85 ppm in the crude oils were reduced to 0.5–1.1 ppm in the degummed and bleached oils. Crude oils had Gardner colors of 14, which were reduced to Gardner 9–11 in the degummed and bleached oil, depending on bleach type and quantity used. AOCS colors in the range of 21–25R 68–71Y were obtained. By including charcoal in the bleaching step, a considerably lighter oil could be obtained (Gardner 7).     

Influence of chemical refining on the major and minor components of rice brain oil

The effects of each individual step of the chemical refining process on major and minor components of rice bran oil were examined. In comparison with common vegetable oils, rice brain oil contains a significantly higher level of several bioactive minor components such as γ-oryzanol, tocotrienols, and phytosterols. Alkali treatment or neutralization results in a significant loss of oryzanol. In addition, it gives rise to a change in the individual phytosterol composition. After bleaching, some isomers of 24-methylenecycloartanol were detected. Because of their relatively high volatility, phytosterols and tocotrienols are stripped from the rice brain oil during deodorization and concentrated in the deodorizer distillate. At the same time, oryzanol is not volatile enough to be stripped during deodorization; hence, the oryzanol concentration does not change after deodorization. Complete refining removed 99.5% of the FFA content. Depending on the applied deodorization conditions, trans FA can be formed, but the total trans content generally remains below 1%.     

Changes of the tocopherol and fatty acid contents in rapeseed oil during refining

Among the most important metabolic compounds there are some which are not synthesized by human and animal organisms and have to be supplied in appropriate quantities in due time. Vitamin E and the essential unsaturated fatty acids have crucial physiological significance, and their greatest quantities occur in plant oils. During refining, apart from unnecessary substances, nutritionally advantageous compounds are also being eliminated. In the present paper changes of tocochromanols taking place during refining of rapeseed oil obtained from seeds of two subsequent crops were investigated. It was observed that losses of tocopherols exceeded 30%, two thirds of which resulted from distilling off during deodorization. The ratio of vitamin E to essential unsaturated fatty acids expressed as the Harris coefficient decreased in the refined oil obtained from seeds of two subsequent crops by about 28%.     

Effects of physical refining on contents of waxes and fatty alcohols of refined olive oil

Changes in the contents of waxes and fatty alcohols during deodorization/physical refining of bleached olive oil were studied. Experiments were carried out with 1.85% acidity oil, which was physically refined in a discontinuous deodorizer of 250-kg maximum capacity using nitrogen as stripping gas instead of steam. The variables studied were load and temperature of oil in the deodorizer as well as N₂ flow. Analyses of waxes and alcohols were carried out at different operation times. The maximum content of wax was always observed when the oil reached the deodorization temperature. The variation in the wax content depended on temperature and N₂ flow. Wax decomposition started and continued during the operating time, and a progressive decrease, which was pronounced between 3 and 4 h, was observed. Small changes in waxes were observed between 4 and 5 h. Total content of fatty alcohols diminished throughout the operating time, and changes did not depend on the variables studied.     

Miscella refining test method for the determination of cottonseed oil color

Most of the cottonseed oil mills in the United States have already converted to expander solvent extraction and miscella refining. This practice permits mills to produce and market a consistently light-colored, prime bleachable summer yellow cottonseed oil at reduced cost and refining loss. A laboratory-scale miscella refining test was developed to asses the oil quality in terms of its color. The test involves the addition of 3 parts oleic acid per 100 parts of crude oil in the miscella followed by refining with 2.5 parts NaOH when crude oil contains less than 4.5% free fatty acid (FFA). When crude oil contains FFA between 4.5 and 7.5%, no oleic acid is added prior to refining with 2.5 parts NaOH. When crude oil contains FFA higher than 7.5%, no oleic acid is added and the caustic addition table in American Oil Chemists' Society Method Ca 9a-52 is followed. The test was conducted at room temperature and gave reproducible colors comparable to commercially refined oils.     

Temperature effect on the viscosities of palm oil and coconut oil blended with diesel oil

One of the major difficulties in using crude vegetable oils as substitute fuels in diesel engines is their relatively high viscosities. Increasing the temperature of the crude vegetable oil, blending it with diesel oil, or the combination of both offers a simple and effective means of controlling and lowering the viscosities of vegetable oils. This work reports viscosity data, determined with a rotational bob-and-cup viscometer, for crude palm oil and cononut oil blended with diesel oil over the temperature range of 20–80°C and for different mixture compositions. All the test oil samples showed a time-independent newtonian type of flow behavior. The reduction of viscosity with increasing liquid temperature followed an exponential relationship, with the two constants of the equation being a function of the volume percentage of the vegetable oil in the mixture. A single empirical equation was developed for predicting the viscosity of these fuel mixtures under varying temperatures and blend compositions.     

The effect of fruit storage on palm oil bleachability

Storage of oil palm fruits resulted in crude oil that was difficult to bleach, especially from bruised fruits. Fruits stored in the shade were less affected than those exposed to sun and rain. Surprisingly, oil from fruits stored at 5°C was highly hydrolyzed and difficult to bleach.     

Decolorisation of crude palm oil by acid-activated spent bleaching earth

Regeneration of spent bleaching earth by acid activation and heat treatment has been investigated. Spent bleaching earth was activated by H₂SO₄ of various concentrations (1–40%) and heat treated at 120°C–350°C. The experimental results indicate that treatment of spent bleaching earth with 10% H₂SO₄ at 350°C produced a material which was most effective in removing coloured pigments from crude palm oil. Subsequent experiments were conducted using this particular acid-treated spent bleaching earth. Various parameters which affect the sorption process were studied. They include initial crude palm oil concentration, sorbent dosage and temperature. Applicability of both the Freundlich and Langmuir isotherms to the acid-treated spent bleaching earth–palm oil hexane miscella system indicates that both physiosorption and chemisorption were involved in the sorption process. Measurements of various quality parameters of bleached and crude palm oils were carried out. They include Lovibond Colour index, carotene content, peroxide value, free fatty acid, fatty acid composition and iodine value. The results show that the bleached palm oil retained good oil quality after the decolorisation process using 10% acid-treated spent bleaching earth with a Lovibond Colour of 6·4. © 1998 SCI     

Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils

Due to the global drive towards biodegradable products, trimethylolpropane [2‐ethyl‐2‐(hydroxymethyl)‐1, 3‐propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters were considered: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Lubrication properties such as viscosity, viscosity index (VI) and pour point (PP) were determined according to methods of the American Society for Testing and Materials. Wear and friction properties were evaluated using a four‐ball test machine, while oxidative stability was studied with the Penn State Micro‐oxidation thin‐film test. High VI ranges between 170 to 200 were recorded for these base stocks. PP were relatively high, between 4 to —1 °C, but were improved to at least —33 °C in high oleic palm oil TMP esters. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono‐ and diesters had negative effects at high concentrations. Differences in chemical structures of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids.     

Physical refining of edible oils

Crude oils obtained by oilseed processing have to be refined before the consumption in order to remove undesirable accompanying substances. The traditional alkali refining is often replaced by physical refining in which the use of chemicals is reduced. The most widely used method is steam refining. The crude oil quality is very important in order to obtain high quality refined oil. Furthermore, the oil should be efficiently degummed to remove phospholipids as well as heavy metals and bleached to remove pigments. The most important step consists of the application of superheated steam under low pressure and at temperatures higher than 220 °C. Both free fatty acids and objectionable volatiles, formed by cleavage of lipid oxidation products, are removed. A disadvantage is the partial loss of tocopherols. Side reactions, particularly isomerization of polyunsaturated fatty acids, should be minimized. The quality of physically refined oil is close to that of alkali refined oils, but losses of neutral oil are lower and the environment is less polluted. Among other methods of physical refining the application of selective membranes is promising.     

Chemical and physical characteristics of soap made from distilled fatty acids of palm oil and palm kernel oil

Manufacture of soaps from distilled fatty acids of palm oil (PO) and palm kernel oil (PK) is a well-established technology in Malaysia. Data on quality and characteristics of various blends of PO/PK fatty acid-based (palm-based) soaps made in Malaysia are not available, however. In view of this, the study described in this paper was undertaken. Eleven blends of palm-based bar soaps were made, and their properties were evaluated. There was an increase in the acid value of blended raw materials with increasing amounts of PK fatty acids. The iodine value and titer (°C) of blended raw materials, however, bear an inverse relationship with the amount of PK fatty acids. As expected, the hardness of the soap bars from the various blends increased with increasing PK fatty acid. Total fatty matter ranged from 76–85%, free caustic content was 0.1%, and sodium chloride content was 0.3–0.4%. Characteristics of soap blends made for this study were comparable with those from other countries. Quality of the soap obtained was comparable to those produced commercially.     

Refining high-free fatty acid wheat germ oil

Wheat germ oil was refined using conventional degumming, neutralization, bleaching, and continuous tray deodorization, and the effects of processing conditions on oil quality were determined. The crude wheat germ oil contained 1,428 ppm phosphorus, 15.7% free fatty acid (FFA), and 2,682 ppm total tocopherol, and had a peroxide value (PV) of 20 meq/kg. Degumming did not appreciably reduce the phosphorus content, whereas neutralization was effective in removing phospholipid. Total tocopherol content did not significantly change during degumming, neutralization, and bleaching. A factorial experimental design of three deodorization tempeatures and three residence times (oil flow rates) was used to determine quality changes during deodorization. High temperatures and long residence times in deodorization produced oils with less FFA, PV, and red color. Deodorization at temperatures up to 250°C for up to 9 min did not significantly reduce tocopherol content, but, at 290°C for 30-min residence time, the tocopherol content was significantly reduced. Good-quality wheat germ oil was produced after modifying standard oil refining procedures.     

Effects of minor components on the crystallization of coconut oil

Variations in the crystallization behavior of fats have important consequences for the processing of fatty foods. This paper is concerned with the changes in the crystallization of coconut oil due to refining, and the effects of diacylglycerols, free fatty acids and phospholipids on oil crystallization. The changes in coconut oil crystallization due to changes in oil composition have been studied by pulsed nuclear magnetic resonance spectroscopy. Bleaching or neutralization of crude coconut oil caused a dramatic reduction in the induction time before the onset of detectable crystallization at 15°C. The addition of oleic and lauric acid caused a large increase in the induction time of refined coconut oil whereas palmitic acid had a smaller effect. However, the changes in coconut oil crystallization during refining are not completely explained by the removal of free fatty acids. Dilaurin retarded the nucleation of coconut oil whereas diolein did not have any significant effect. Phosphatidylcholine also retarded the nucleation of coconut oil at 15°C, but this effect is not significant in practice for coconut oil because of the low levels of phospholipids present in the crude oil.