Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.     

Lipid composition of selected vegetable oils

This paper gives analytical data on the composition of 14 selected consumer-available liquid vegetable oils, including soybean, soybean-cottonseed blends, corn, safflower, peanut, olive and apricot kernel oils. Label information identified six samples as specially processed or refined and three samples as cold pressed with no preservative added; the labels of the remaining five samples did not mention processing. Data are given for fatty acid composition,trans content, location of the double bonds in the unsaturated fatty acids, percent conjugation, tocopherol content, fatty acid composition of the 2-poisition of the triglycerides, polyunsaturated to saturated fatty acid (P/S) ratio, and the ratio of α-tocopherol to polyunsaturated fatty acids (α-T/P). The ranges of values found were: conjugated unsaturation, 0.18–1.09%; α-tocopherol, 0.01–0.60 mg/gm; total tocopherol 0.14–1.52 mg/gm; P/S, 0.5–8.7; and α-TP, 0.03–2.26. The compositions of the fatty acids on the 2-position and on the 1,3-position of the triglycerides were compared with those calculated by the Evans’ hypothesis and found to agree well for all but olive and apricot kernel oils. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable. Deceased     

The effect of bleaching and physical refining on color and minor components of palm oil

An industrially degummed Indonesian palm oil was bleached and steam refined in a pilot plant to study the effect of processing on oil color and on the levels of carotenoids and tocopherols. Five concentrations of one natural and two activated clays mixed with a fixed amount of synthetic silica were used for bleaching. For color measurement, the Lovibond method was compared to the CIE (Commission Internationale de l’Eclairage) L^*,a^*,b^* method. The results showed that the L^*,a^*,b^* method is repeatable and that the values found are highly correlated with the carotenoid content of bleached oil samples. The various clays and synthetic silica mixes removed 20–50% of the carotenoids in the degummed oil, depending on clay concentration and activity. For the two activated clays, pigment adsorption increased with clay amount. Steam refining totally destroyed carotenoids in the claytreated oils by heat bleaching. Total tocopherols in the crude oil amounted to 1000 mg/kg, with γ-tocotrienol as the main tocopherolic component followed by α-tocopherol, α-tocotrienol, and δ-tocotrienol. Tocopherol concentrations increased after the bleaching treatment with the most acid clay, and the increase was proportional to the amount of clay used. Both bleaching and steam refining changed the ratios between the various to copherolic components, especially increasing the relative concentration of α-tocotrienol in the refined oil. An average 80% tocopherol retention was obtained after the treatment with acid clay + synthetic silica and steam refining of palm oil.     

A study of the caustic refining of vegetable oils

Summary In the caustic refining of vegetable oils using liquid-mixing the concentration of caustic solution required, the amount of excess caustic used, the length of time of mixing the oil-soapstock mixture in the cold, and the oil content of the soapstock are governed by the amount and kinds of phosphatides present in the oil. In the mist-mixing process of refining vegetable oils using caustic, the mixing time is kept constant, the concentration of the caustic is kept constant for a particular kind or type of oil, the excess caustic is kept constant for a particular kind or type of oil, and the oil content of the soapstock is governed by the amount and kinds of phosphatides present in the oil, and by the use of sodium silicate.     

Pretreatment of edible oils for physical refining

Physical refining of edible oils is briefly reviewed. Recent developments regarding the pretreatment of oils and fats are described in detail and methods are critically evaluated with special emphasis on their effectiveness in removing undesired minor components, their cost of operation and their effect on the environment.     

Tocol-derived minor constituents in selected plant seed oils

Various crude and processed seed oils were analyzed for tocopherols (T) and tocotrienols (T₃) by reversed-phase HPLC with fluorescence detection (FL). The oils included processed canola oil, crude corn oil, crude milkweed oil, crude palm oil, crude/processed rice bran oils, crude/processed soybean oil, crude/processed sunflower oil, and related modified oil, crude/processed sunflower oil, and related modified oil varieties. The HPLC system consisted of a pentafluorophenylsilica (PFPS) column and a mobile phase of methanol and water. The results of comparative methodological studies with rice bran oils and milkweed oils indicated that the reversed-phase PEPS-HPLC method in conjunction with the use of less hazardous solvents proved to be superior and a viable alternative to the conventional normal-phase HPLC method. Unlike the traditional nonpolar octadecylsilica phase, which fails to resolve β-γ pairs of T and T₃, HPLC with the unique polar PFPS column enables separations of all compounds of interest. Except for palm oil, βT and γT were detected in all other crude oils. Although most milkweed oils contained moderale levels of βT and γT, the βT species was present in relatively low abundance in edible oils despite the observation of fairly high concentrations of γT in the latter oils. βT₃ and γT₃ were detected along with αT₃ and σT₃ only in palm and rice bran oils. Tocolderived antioxidant distribution data for zero-time processed oils provided potential utility in correlation studies of frying quality and stability. The variable distribution data for crude oils shed some light on market profitability of oilseeds with rich sources of vitamin E-related minor constituents.     

Use of the multistage countercurrent contactor for degumming and refining of vegetable oils

Conclusions Duozon centrifugal contactors seem to have the following advantages in the refining of glyceride oils: decreased losses and increased yields of products; large capacity in a single machine resulting in low first cost, reduced requirement for floor space, and simple flow and installation; because of comparatively low speed, low maintenance cost and low power requirement; practically automatic operation; continuous operation unhampered by particles of meal in the charge; and an entirely enclosed system, allowing no oxidation of hot oil. Presented before the American Oil Chemists’ Society, Houston, Tex., April 23, 1956.     

Biodiesel from minor vegetable oils like karanja oil and nahor oil

The present study investigated the scope of two minor vegetable oils, i.e. karanja (Pongamia glabra) oil and nahor (Mesua ferrea L., Guttiferae) oil, as raw material for biodiesel fuel. The distilled fatty acid methyl esters obtained from karanja oil and nahor oil have the following characteristics: cetane indices 56.2, 54.6; heat of combustion (kcal/mol) 8.26, 8.39; flash points (°C) 134, 142; cloud points (°C) 8.3, 6.1, respectively. All these properties of the distilled methyl esters reveal that karanja oil and nahor oil can be suitably used as cheap raw material for the synthesis of biodiesel.     

Deacidification and recovery of distillates in the physical refining of edible oils

A pilot plant‐scale continuous deodorization installation was developed to simultaneously test several technological changes in the classical deodorization process: use of nitrogen as stripping gas, heating of the gas above the liquid oil, and use of shell‐and‐tube condensers for the recovery of distillates. Deacidification trials were first carried out on mixtures of commercial refined sunflower oil and high‐oleic distillates, and subsequently on bleached olive and sunflower oils. The performance of usual working conditions was analyzed: nitrogen mass flow rate, oil temperature and oil mass flow rate. Marked differences were not observed in the results of the final acidity, compositions of free fatty acids and sterols in the deacidified oil. However, the use of shell‐and‐tube condensers makes it possible to recover liquid distillates in better conditions than in the classical process for their further concentration, while at the same time reducing process pollution.     

Studies on the properties of polyesters and polyester blends of selected vegetable oils

Melon‐seed and rubber‐seed oils have been used in the synthesis of polyester resins. Results reveal that rubber‐seed oil can completely be substituted for linseed and soyabean oils in the synthesis of both long and medium‐oil–length polyester resins. Melon‐seed oil was found to be a substitute for 50% of linseed oil and 50% of soyabean oil in the synthesis of long‐oil–length polyester resins. It also substituted for 15% of linseed oil and 50% of soyabean oil in the synthesis of medium‐oil–length polyester resins. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1441–1446, 2000     

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%.     

Effect of brominated vegetable oils on heart lipid metabolism

Normal rats fed for 105 days on an experimental diet made up of standard laboratory chow supplemented with 0.5% of a mixture of brominated sunflower-olive oil (BVO) developed a significant increase in the triacylglycerol content of the heart, liver and soleus muscle compared to controls. In addition, BVO-treated rats had a decrease in plasma levels of triacylglycerol and total and HDL cholesterol. Plasma fatty acid levels and plasma post-heparin lipolytic activities, such as H-TGL, LPL, T-TGL and MGH were similar to those of control animals fed the standard chow alone. Heart PDH_a (active portion of pyruvate dehydrogenase) was dramatically decreased in the BVO-fed rats. A faster rate of spontaneous lipolysis was recorded in the isolated perfused preparation of hearts from the experimental animals. The addition of 10⁻⁷ M of glucagon to the perfusate, however, revealed a lipolytic effect comparable to the one observed in the control rats. In summary, our findings of normal fatty acids and low triacylglycerol plasma levels associated with normal activities of the various PHLA (post-heparin lipolytic activity) enzymes suggest that accumulation of triacylglycerol in heart muscle may not be explained essentially in terms of an elevated uptake and/or increased delivery of plasma fatty acids or plasma triacylglycerol. A decreased in situ catabolism of tissue triacylglycerol also appears unlikely because the spontaneous as well as the glucagon induced lipolysis in the heart both were found to be unimpaired. Our results suggest that the mechanisms involved in the toxicologic effects of a BVO diet on heart lipid metabolism could be exerted mainly at the level of triacylglycerol biosynthesis rather than a derangement in some known step of their catabolic pathway. Additional studies are necessary to clarify this matter. An abstract pertaining to this work was presented in November 1984 at the IV Congress of the Pan American Association of Biochemical Societies (PAABS), Buenos Aires, Argentina.     

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.     

Application of two heating methods in physical refining of high-FA olive and sunflower oils

Two classes of vegetable oils, olive and sunflower, were processed by physical refining in a pilot plant with a capacity of up to 30 L by means of discontinuous deodorization, and distillates were recovered by condensing and freezing using steam and nitrogen as stripping gases. Two heating systems were evaluated in the deodorizer. In the first, the deodorizer oil and the distilled gases were heated so as to maintain the same temperature in both. In the second, only the oil was heated, resulting in a difference in temperature between the oil and the distilled gases. In addition, two different oil temperatures were evaluated for each stripping gas. By means of the first heating system, the deacidification time for both oils was reduced and the efficiency of the process was notably improved. On the other hand, the higher temperature had a negative influence over both parameters. For both heating systems the sterol contents did not suffer significant variations. Substantial variations in trans FA were not observed, and the composition of FA remained stable except for linoleic acid, which decreased, although more slowly than when the temperature was not maintained, as a result of the rapid formation of its trans FA.     

A comparative study of two heating procedures in the physical refining of edible oils

Two mixtures of refined sunflower seed oil, one with oleic acid and the other with olive oil distillates from a laboratory plant, were physically refined using nitrogen as stripping gas in a discontinuous deodorization pilot-plant scale installation (30-L capacity). Two heating procedures were tested: one using independent electrical heating for the oil and the gas distillates so as to maintain the same temperature in both, and another in which only the oil was heated and controlled, resulting in a difference in temperatures in the oil and the gas distillates. Two different oil temperature values and three nitrogen flow rates were also assayed. The statistical technique of blocking with paired comparisons was used to analyze the results. These results showed that maintaining the same temperature in the oil and gas distillates had a positive effect on free fatty acid distillation rate and vaporization efficiency. Oil temperature and nitrogen flow rate also influenced some of the aforementioned responses.     

Impurities in vegetable oil refining soapstock

Summary The nature of the impurities in vegetable oil foots renders them resistant to treatment by acids as in normal acidulation. Strong caustic was found to attack the gums and make them at least partially soluble in a 5 to 10% aqueous caustic solution. At this concentration a soap phase of 45–60% TFA could be centrifugally separated, and the majority of the impurities or their degraded products were discharged in the lye. The ratio of Oxidized Acids and Insoluble Impurities to the TFA was much lower in the soap than in the raw soapstock; the Oxidized Acids/Black Acids ratio could generally be reduced to 5% or less. This reduction in impurities was found to improve laboratory still yields markedly without the necessity of Twitchell- or pressure- splitting the black acids from treated stocks. Distillate yields of 86–89% were obtained from treated stocks, compared to 69–70% from untreated stocks.     

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.     

Comparative performance of steam and nitrogen as stripping gas in physical refining of edible oils

Olive, sunflower, and soybean oils were physically refined in a discontinuous laboratory system with either nitrogen or steam as stripping gas during the deodorization step. Comparative assays were also carried out on olive oil in a 10-MT discontinuous industrial plant. Vaporization efficiency of free fatty acids was calculated, and quality of refined oils and composition of deodorizer distillates were analyzed. Results indicated that, in all assays, the efficiency of free fatty acid distillation was higher when nitrogen was used. The amount of nitrogen needed was much lower than that of steam for refined oils of similar high quality. The results also suggested that the amount of stripping gas had a clear influence on the composition of deodorizer distillates because lower quantities of triglycerides and unsaponifiable matter were found when nitrogen was employed.