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.     

Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil

The effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while for alkali-refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount (0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9, 3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%), physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95% of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high-performance liquid chromatography indicated 24-methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars.     

A rapid alkali-wash method of refining cottonseed oil for refined color determination

Summary A very simple, rapid, reproducible method of refining crude cottonseed oils, for refined color measurement, has been developed. The results can be used to predict the colors of these oils when refined by the American Oil Chemists' Society Cup Method. The method has the advantages of rapidity and use of simple equipment and techniques and requires only small quantities of oil. Furthermore variations in results because of the amount and strength of lye and of “break” are not encountered since uniform conditions are employed. Because the method is used when it is desired to measure refined color without determining refining loss, it is not a substitute for the official cup refining method. The oil color research described in this paper was conducted as a cooperative project of the Texas Engineering Experiment Station and the Cotton Research Committee of Texas.     

Effect of refining on the phenolic composition of crude olive oils

By definition, virgin olive oil is consumed unrefined, although a great proportion of the olive oil produced has to be refined to render it edible. Phenolic compounds are among the substances eliminated during the refining process; in the present work these were characterized by HPLC, and their evolution during the different refining steps was studied. The complete refining process removed most polyphenols from oils, but the behavior of individual compounds at each step also was observed. o-Diphenols (hydroxytyrosol, catechol, and hydroxytyrosol acetate) and flavonoids (luteolin and apigenin) were eliminated first during the alkaline treatment. Tyrosol and 4-ethylphenol remained in the oil until the deodorization step. A large amount of phenolic compounds was discovered in the refining by-products such as soapstocks and deodorization distillates. In the latter streams, the concentrations of tyrosol and 4-ethylphenol reached up to 149 and 3720 mg/kg by-product, respectively. This high level of 4-ethylphenol and its well-known strong off-odor can interfere during further processing of the deodorization distillates, and this must be taken into account when deciding what is to become of them. Similarly, the results of this work open the possibility of recovering phenolic compounds from the “second centrifugation olive oils” by adding a new washing step prior to the refining process. By including this new step, the most polar polyphenols, hydroxytyrosol and tyrosol, will diffuse from oil to water and a concentration of up to 1400 mg/L of hydroxytyrosol may be achieved.     

Quantitation of steryl ferulate andp-coumarate esters from corn and rice

The principal steryl ferulate andp-coumarate esters of different fractions from processed corn brans and corn oils, unrefined and refined, and from rice bran and rice bran oil were quantified by high-performance liquid chromatography. The results show that hexane-extracted corn oils yield more than five times the amount of esters compared to expeller processed oils. The yields of esters from bran and related products ranged from 0.07 to 0.54 mg/g of bran. Unrefined corn oils had levels from 0.18 to 8.6 mg/g for oil from hexane-extracted bran. By comparison, rice bran had ester levels of 3.4 mg/g of bran, and rice bran oil had levels of 15.7 mg/g of oil. The predominant esters from corn were sitostanyl and campestanyl ferulate, and sitostanyl and campestanylp-coumarate. The principal esters from rice bran were cycloartenyl, 24-methylenecy-cloartanyl, and campesteryl ferulate. Rice bran oils had low levels of 24-methylenecycloartanyl but high levels of cyclobranol esters. The data presented provide a direct comparison of steryl ferulate andp-coumarate levels in the two cereals, and will aid in selecting the most suitable sources for the isolation of these compounds from corn products. Based on a paper presented at the Symposium on the “Regulation of Biosynthesis and Function of Isopentenoids,” Atlanta, Georgia, May 1994.     

Rice brain oil. I. Oil obtained by solvent extraction

1. Freshly milled rice bran has been extracted with commercial hexane and the recovered oil and extracted meal examined for their respective content of wax. The oils were refined and bleached by standards as well as several special methods. The crude, caustic soda refined, and several refined and bleached oils were examined spectrophotometrically.
2. When freshly milled rice bran of good quality is extracted with commercial hexane, an oil of relatively low free fatty acid content is obtained. This oil possesses good color and is as stable as other similar types of crude oils.
3. If the oils is extracted from the brain at a temperature below about 10°C. and the extraction is discontinued at the right time, the extracted oil represents 90–95% of the total lipids in the brain and contains very little wax. This wax, which is readily extracted with hot commercial hexane as well as other types of solvents, amounts to about 3–9% of the total extractable lipids.
4. When subjected to ordinary caustic soda refining methods, good rice brain oils behave much like cottonseed oils of comparable free fatty acid content. Both caustic soda refining in a hydrocarbon solvent and refining with sodium carbonate result in refining losses approximating the absolute or Wesson loss.
5. Some of the refined oils when bleached according to usual practice produce products acceptable for use in the edible trade. However, refined rice bran oil has a definitely greenish cast resulting from the presence of chlorophyll, but this color can be removed by bleaching with a small amount of activated acidic clay.

     

Refining cottonseed oil at high rates of shear

Summary Ten crude cottonseed oils obtained from different areas in the South and Southwest were refined with and without the use of high-shear agitation in the step involving the initial mixing of the crude oil and caustic soda solution. In each instance the use of high shear produced a lower color in the refined oil. The improvement with some oils was not marked because they either refined very well by the ordinary method or failed for some unexplained reason to respond readily to high-shear mixing. However a good proportion of the oils which were quite dark after refining by the ordinary method refined to a much lighter oil when high shear was used. It was established that in high shear refining the color of the refined oil decreased as the temperature at which high shear was used decreased, the time at high shear increased, and the rate at which shear was applied increased. However an increase in the latter above a certain value had no effect. Also it was found that the color of the refined oil decreased as the amount and strength of the caustic soda solution increased. Absorption spectra of some of the processed oils indicated that high shear was more effective than ordinary mixing in removing from an oil the gossypol-like and carotenoid color bodies. Presented at the 28th fall meeting of The American Oil Chemists’ Society, Minneapolis, Minn., Oct. 11–13, 1954. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Frying Quality Characteristics of French Fries Prepared in Refined Olive Oil and Palm Olein

The objective of this study was to compare two oils with different polyunsaturated/saturated (P/S) fatty acid ratios, refined olive oil (P/S 0.75) and palm olein (P/S 0.25), in frying French fries. The chemical qualities of the oil residues extracted from the French fries were assayed for five consecutive batches fried at 1-h intervals. The levels of total polar compounds, free fatty acids, p-anisidine value and phytosterol oxidation products (POPs) were elevated in French fries fried in both oils. The level of total polar compounds increased from 4.6 in fresh refined olive oil to 7.3% in final batches of French fries. The corresponding figures for palm olein were 9.8–13.8%. The level of free fatty acid in fresh refined olive oil increased from 0.06 to 0.11% in final products. These figures for palm olein were 0.04–0.13%. The p-anisidine value increased from 3.7 to 32.8 and 2.5 to 53.4 in fresh oils and in final batches of French fries in refined olive oil and palm olein, respectively. The total amount of POPs in fresh refined olive oil increased from 5.1 to 9.6 μg/g oil in final products. These figures were 1.9 to 5.3 μg/g oil for palm olein.     

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.     

The hydrocarbon fraction of virgin olive oil and changes resulting from refining

In numerous Spanish virgin olive oils, 6,10-dimethyl-1-undecene, various sesquiterpenes, the series ofn-alkanes from C14 to C35, n-8-heptadecene and squalene are the only less volatile components detected by gas chromatography in the hydrocarbon fraction. In oils from olives of the Arbequine variety, a series ofn-9-alkenes has also been found. In refined oils, notable features are the absence of the most volatile compounds and the appearance of other hydrocarbons produced during the refining process. Among these,n-alkanes, alkadienes (mainlyn-hexacosadiene), stigmasta-3,5-diene, isomerization products of squalene, isoprenoidal polyolefins coming from hydroxy derivatives of squalene and steroidal hydrocarbons derived from 24-methylene cycloartanol were identified. Physical refining produces larger amounts of degradation products and greater losses ofn-alkanes than chemical processing. Squalene is the major hydrocarbon component in all oils, both virgin and refined. The ranges of concentration for the different hydrocarbons found in Spanish virgin olive oils are presented.     

Refining,bleaching and hydrogenating meat fats

Meat fats are most often steam refined. This has been the accepted practice for at least 35 years. Meat fats are caustic refined for a few specialized products. The caustic refining conditions differ from those used for vegetable oils primarily in the amount of mixing used after the addition of caustic. Bleaching of meat fats is accomplished easily. Most meat fats are light in color and require clarification more than bleaching. The green color of tallows containing large amounts of chlorophyll is easily removed with activated earth. Meat fats are hydrogenated to develop the SFI curves needed for various products and also are hydrogenated to saturation for use as plasticizing agents. The hydrogenation of lard and tallow is not as complicated as that of most vegetable oils, because the original fat is more saturated and the reaction has fewer possible routes to follow.     

Natural refining of extruded-expelled soybean oils having various fatty acid compositions

Simple, low-capital-investment oil refining techniques, which may also meet the needs of natural or organic food industries, were explored to process extruded-expelled (E-E) soybean oils with various fatty acid compositions. Most settled E-E oils are naturally low in phosphatides (<100 ppm phosphorus) and were easily water degummed to low phosphorus levels (<55 ppm). Free fatty acids were reduced to 0.04% by adsorption with 3% Magnesol^®. Magnesol reduced residual phosphorus contents to negligible levels. This material also adsorbed primary and secondary oil oxidation products. Our adsorption refining procedure was much milder than conventional refining, as indicated by little formation of primary and secondary lipid oxidation products and less loss of tocopherol. The remaining challenge to effective natural refining is the removal of off-flavor components. Our adsorption treatment reduced the natural flavor of soybean oil but flavor was still present, probably too strong for many consumers. Polyunsaturated oils oxidized more easily than did the other types of oils; therefore, precautions should be taken when refining such oils. High-oleic soybean oil, on the other hand, had excellent oxidative stability and better flavor characteristics after degumming and adsorption with Magnesol compared with other oils.     

<Emphasis Type="Italic">Trans</Emphasis> FA in sunflower oil at different steps of refining

The contents of total trans FA of sunflower oils at different stages of refining processes were determined by capillary GLC. The contents of 18∶1, 18∶2, and 18∶3 trans acids were 0.22±0.03, 2.31±0.23, and 0.03±0.01%, respectively, in physically refined sunflower oils, and 0.05±0.01, 0.69±0.26, and 0.02±0.01%, respectively, in chemically refined sunflower oils. The total trans FA contents drastically increased at the end of the physical refining process. The total trans FA contents of chemically refined sunflower oils were <1%. Because of the high temperature applied in the last stage of physical refining, the content of total trans FA was higher than in chemically refined sunflower oils. The last-stage conditions should be carefully evaluated to reduce the formation of trans FA during physical refining.     

The effect of heat on pure triglycerides

A knowledge of the mechanism of the degradation of triglycerides at temperatures from 190°C. is important in predicting the type of breakdown products likely to be formed in processing oils at elevated temperatures, or in the usage of oils and fats in frying or baking. The effect of heat on tricaprin and 2-oleo-dipalmitin has been studied both in the absence and in the presence of oxygen. The results show that even a pure fully saturated triglyceride is rendered organoleptically unacceptable, due to breakdown in the temperature range studied, although the mechanism differs according to whether oxygen is present or not. Unsaturated glycerides are more readily degraded, fission at or near the double bonds being superimposed on the processes previously established for saturated triglycerides. Many of the degradation products have been identified. Degraded triglycerides can be refined to an acceptable standard by conventional means but their keeping times, in the refined state, are considerably less than those of the original pure materials. Hence, it is inferred that precursors of off-flavors persist in the products and survive the refining operations.     

Quality of fried foods with palm oil

The amount of imported palm oil in Japan during the past few years has been 140,000–150,000 tons per year, or about 9% of the total consumption of vegetable oils in Japan. In 1975, part of the palm oil was imported as refined type from Malaysia. At the present time, almost all of the palm oil from Malaysia is refined. At the starting point quality of the refined palm oil was not so good, but today it is fairly improved by efforts of Malaysian processers. Palm oil has excellent properties against oxidation, and it has been generally accepted by consumers as a vegetable oil for health foods. There also is a big potential for increasing consumption of palm oil in fried foods. Severe regulation of food additives restricts the use of artificial antioxidants and therefore strict quality control is required to get stable frying oils. Consumer knowledge of foods is increasing, and our responsibility for making good quality frying fats is very important.     

Thermooxidative stability of vegetable oils refined by steam vacuum distillation and by molecular distillation

Semi‐refined rapeseed and sunflower oils after degumming and bleaching were refined by deodorization and deacidification in two ways, i.e., by steam vacuum distillation in the deodorization column Lurgi and by molecular distillation in the wiped‐film evaporator. The oxidative stability of the oils before and after the physical refining has been evaluated using non‐isothermal differential scanning calorimetry. Treatment of the experimental data was carried out by applying a new method based on a non‐Arrhenian temperature function. The results reveal that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. Practical applications : (i) A method for the refining of edible oils by the molecular distillation in the wiped film of a short‐path evaporator is presented and applied. (ii) Oxidative stability of the oils refined by molecular distillation and steam vacuum distillation is compared. It has been found that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. (iii) Experimental data were treated by applying a new method based on a non‐Arrhenian temperature function. The method enables trustworthy predictions of oil stabilities for the application temperatures.     

Keeping properties of edible oils—Part I. The use of accelerated tests for assessment of the keeping properties of oils and the value of antioxidants

Assessment of oil quality by two accelerated oxidation tests gave little or no correlation with organoleptic asessment during storage. Improvements in quality of oils refined in the factory, to which antioxidants had been added, are indicated by the accelerated tests but are not reproduced in normal storage. Howver a treatment of the oils with alumina, as a part of the refining process replacing earth bleaching, appears to remove antagonistic factors, and under these circumstances the addition of antioxidant has a pronounced effect.     

The difficultly extractable lipides of cottonseed meats,their composition and effect on the refining characteristics of the crude oils

Summary and Conclusions Crude lipides fractions were produced from raw, tempered, and cooked meats from two lots of cottonseed by a series of successive stepwise extractions, designed to obtain fractional portions of the total lipides in the order of the difficulty of their extraction. The proximate composition of the crude lipides fractions was determined. It was found that the composition of successive lipides fractions varied with the degree of exhaustiveness of extraction. The fractions obtained by more exhaustive extraction contained greater amounts of undesirable non-neutral oil material and lesser amounts of desirable neutral oil. It was also established that the method used in preparing meats for extraction was of paramount importance in its effect on the composition of the crude lipides obtained. The crude lipides fractions from raw and tempered meats contained large amounts of impurities while the crude lipides fractions similarly obtained from cooked meats were relatively low in impurities. Crude oils equivalent to varying degrees of total lipides extraction were reconstituted from the crude lipides fractions and evaluated for refining characteristics. The impurities content of the reconstituted oils varied as the degree of total lipides extraction and increases in the impurities content of the oils were generally reflected in disproportionate increases in refining losses and/or refined oil color. The oils obtained from the cooked meats at all degrees of extraction were outstandingly low in refining losses as compared to the oils from the raw and the tempered meats. Presented in two parts at the spring meeting, American Oil Chemists’ Society, New Orleans. La., Apr. 18–20, 1955, and at the fall meeting, Philadelphia, Pa., Oct. 10–12, 1995. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Sterols and Oxidized Sterols in Feed Ingredients Obtained from Chemical and Physical Refining Processes of Fats and Oils

The by-products obtained from conventional chemical and physical refining processes for edible fats and oils are important sources of valuable fatty components such as sterols, tocopherols, fatty acids, etc., and are also used as ingredients in animal feed formulations. Reports on sterol composition and content are limited, and the levels of oxidized sterols in these valuable by-products are unknown. This study analyzed by-product fractions from European refineries intended for use as ingredients in animal feeds for their content and composition of sterols and sterol oxidation products. The complex mixtures of sterol oxidation products were separated and quantified by multidimensional capillary columns, a medium polar DB-17MS and an apolar DB-5MS, in GC and GC–MS. Sterol content ranged from 0.l to 3.4 and 0.03 to 5.0 g/100 g in the by-product fractions collected from chemical and physical refining processes, respectively, while the corresponding ranges for sterol oxidation products were 0.02–17 and 0.02–1.5 mg/100 g.     

Effects of plant‐scale alkali refining and physical refining on the quality of rapeseed oil

The physical refining of soybean oil was introduced as an energy saving and environmentally friendly procedure alternative to the traditional alkali refining, and the process was successfully applied to other vegetable oils. We had compared the two procedures in industrial refining under conditions, which enable a clear comparison. In nine plant‐scale experiments, crude rapeseed oil, taken from the same tank of crude oil, was processed on the same day both by alkali refining and by physical refining. Quality changes (free fatty acids, peroxide value, conjugated fatty acids, polar lipids, minor constituents) were determined, and also their stability against oxidation (Rancimat and Schaal Oven Test), and the fatty acid composition. In refined oils, the sensory acceptabilities and the sensory profiles were assayed. Finally deodorized oils, produced by the two methods, did not appreciably differ in their sensory characteristics and chemical composition, excepting slightly higher concentration of isomeric polyunsaturated fatty acids in physically refined oils. During storage for one year in commercial packagings at 15 °C, oxidative and sensory changes were negligible.