Phase relations pertaining to the solvent winterization of cottonseed and peanut oils in acetone

Summary and Conclusions Systematic physical chemical data on the solventwinterization behavior of cottonseed and peanut oils with acetone have been obtained which should serve as a basis for selecting the conditions necessary for the effective solvent winterization of these oils in acetone. Cottonseed and peanut oils are only partially miscible with acetone below certain temperatures which have been determined. In peanut oil this phenomenon may interfere with the winterization process within a certain range of concentrations. For cottonseed oil however the separation into two liquid phases does not occur until some 5°C. below the temperature required for adequate winterization. Complete data for a 3-hour holding-time have been obtained for three cottonseed oils ranging in iodine value from 106.1 to 116.4. Tables and graphs have been constructed to show the effect of oil-solvent ratio, chilling temperature, holding-time, agitation, and iodine value of the original oil on the percentage of solid removed and on the degree of winterization and iodine value of the winterized oil. Similar data have been obtained for a refined peanut oil insofar as possible without interference from separation into two liquid phases. It seems probable that if acetone were used as the winterization solvent for peanut oil, the separation into two liquid layers and the sensitivity of this phenomenon to moisture might be a source of processing difficulties especially if filtration instead of centrifugation were used to separate the solid from the supernatant. Resigned: September 2, 1949. Resigned: August 13, 1948. Resigned: January 28, 1949. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

The Viscosity of cottonseed oil,fractionation solvents and their solutions

Cold fractionation of cottonseed oil is made difficult by the high viscosity of the oil. This study was aimed at demonstrating the effect of solvents on the viscosity of mixtures between 0°C and 25°C with a view to facilitating the fractionation of refined cottonseed oil. The solvents used were acetone, methylethylketone, methylisobutylketone, hexane and heptane. Measurements of viscosity were carried out by means of a capillary viscometer. The ratio of the viscosity of cottonseed oil to that of pure solvents is of the order of 300. The viscosities of solutions of various ratios of solvent to oil (1/3, 1/1, 3/1) are between those of cottonseed oil and the pure solvents. The effect of the solvent/oil ratio overrides that of solvent nature. The effect of solvent in reducing the viscosity of cottonseed oil is by descending order: acetone, hexane, methylethylketone, heptane, methylisobutylketone.     

Phase behavior in the solvent winterization of crude cottonseed oil in 85–15 acetone-hexane mixture as related to reduction in refining loss and color

Summary Fundamental physical chemical data have been obtained which indicate on a laboratory scale the feasibility and advantages of solvent winterization of crude cottonseed oil in 85–15 acetone-hexane mixture. The results show the effect of oil-solvent ratio, chilling temperature, duration of chilling, and the addition of adsorbents on the degree of winterization, the refining loss, and the color of the winterized oil. Crystallization is markedly inhibited by the presence of a phosphatide-rich material in the crude oil, but this can be overcome by the proper control of the oil-solvent ratio and temperature and by the addition of adsorbents. Winterization in this solvent with or without adsorbents results in the separation of a large proportion of the phosphatides, and a marked reduction in refining loss and color. The advantages of winterizing hexane-extracted cottonseed oils before refining are discussed. Resigned: July 9, 1954. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

The production of salad oil by fractional crystallization with solvents

A fractional crystallization method for the winterization of cottonseed oil with solvents was developed in our laboratories and pilot plant. Small amounts of solvent (e.g., 10% by weight of acetone) were mixed with the oil. This mixture was rapidly chilled to 0°C. and kept at this temperature for 3–4 hrs.; the liquid portion was separated from the solids. After solvent evaporation a salad oil of good quality was obtained. The yield is equal to or better than that obtained with conventional methods. The method is suitable for a continuous operation since rapid chilling can be used, and only a short over-all time is necessary. Great advantages of the process are the use of low amounts of solvent and of a refrigeration system not requiring temperatures below 0°C.     

Phase relations pertaining to the solvent winterization of crude peanut oil in 85-15 Acetone-hexane mixture

Fundamental phase relation data have been obtained on a laboratory scale which show that solvent winterization of crude peanut oil is feasible in a solvent consisting of 85 parts by weight of acetone and 15 parts of commercial hexane. The results show the effect of oil-solvent ratio, chilling temperature, and holding-time upon the percentage of solid removed. The behavior of crude peanut oil is very similar to that of the refined oil in the same solvent except that a slightly lower chilling temperature is required and that the crystals tend to form a little more slowly and do not settle out as readily. The advantage of winterizing hexane-extracted peanut oils before refining is discussed.     

Solvent winterization of sunflower seed oil

Samples of oil from whole and dehulled sunflower seed were solvent winterized. The solvent mixture, 85% acetone, 15% hexane (^v/v), was used at solvent-in-oil concentrations of 20, 40, and 70% by wt and the samples winterized at 0, −5, −10, and −15 ± .01 C for 4 hr. Generally, sunflower oils from whole seed remained free from cloud formation longer on refrigeration when the oils were winterized at lower temperatures and at lower solvent-in-oil concentrations. With oil from the dehulled samples, no winterization condition produced an oil with a predictable clouding time. However, correlations were significant between residual wax content after winterization and clouding time of the oils from whole seed. Oils from dehulled seed were not as highly correlated with wax content as oils from whole seed. This study indicates that crude sunflower seed oil might be winterized with the aid of solvents and that decortication prior to extraction might not be necessary for effective winterization.     

Cottonseed extraction with mixtures of acetone and hexane

Cottonseed flakes were extracted with mixtures of n-hexane and acetone, with the concentration of acetone varying between 10 and 75%. Adding small amounts of acetone (≤25%) to n-hexane significantly increased the extraction of free and total gossypol from cottonseed flakes. Sensory testing detected no difference in the odor of cottonseed meals produced either by extraction with 100% n-hexane or by extraction with a 10∶90 (vol/vol) mixture of acetone/hexane. More than 80% of the free gossypol was removed by the 10∶90 mixture of acetone/hexane, whereas pure n-hexane extracted about 47% of the free gossypol from cottonseed flakes. A solvent mixture containing 25% acetone removed nearly 90% of the free gossypol that was removable by extraction with pure acetone; the residual meal had only a minimal increase in odor. In contrast, cottonseed meals produced by extraction with pure acetone had a much higher odor intensity. The composition of the cottonseed crude oil was insignificantly affected by the acetone concentration of the extraction solvent. The results indicate that mixtures of acetone and n-hexane can be used as extraction solvents to produce cottonseed crude oil without the concomitant development of odorous meals.     

Alternative hydrocarbon solvents for cottonseed extraction: Plant trials

Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry. Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural gas consumption decreased more than 40% as compared to hexane.     

Alternative hydrocarbon solvents for cottonseed extraction

Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane. Presented in part at the AOCS Annual Meeting & Expo, Atlanta, Georgia, May 1994.     

Modification of vegetable oils

Summary 1. An investigation has been made of low-temperature crystallization from organic solvents as a means of effecting practical separations of the solid and liquid acids of unhydrogenated and hydrogenated cottonseed oils. 2. At any fixed temperature the most efficient separations were obtained in the highly polar solvents, acetone and methyl acetate. However, it was possible in any case to make nonpolar petroleum naphtha (Skellysolve B) fully equivalent to the polar solvents simply by conducting the crystallization at a temperature approximately 10° F. lower than that employed with the polar solvents. Ethyl acetate and methyl ethyl ketone were intermediate between petroleum naphtha and acetone or methyl acetate in their effectiveness. 3. By employing a solvent-fatty acid ratio of 4 to 1 by weight and conducting crystallizations at 5° F. or lower from acetone and −5° F. or lower from petroleum naphtha, the liquid fatty acids from unhydrogenated cottonseed oil could be reduced to below −2° C. in titer and to below about 3 per cent in saturated acid content. Under these conditions there was no appreciable crystallization of oleic acid. 4. At a solvent-fatty acid ratio of 6 to 1 and the same temperatures (5° F. for acetone and − 5° F. for petroleum naphtha) equally good separations could be made of the saturated fatty acids present in the mixed acids from hydrogenated cottonseed oil (I.V.=70). Separation of “iso-oleic” acids from the fatty acids of the hydrogenated oil took place over a wide range of temperatures, beginning at 35° F. in acetone and at 25° F. in petroleum naptha, and being incomplete (according to Twitchell analyses of the liquid acids) in either solvent at −15° F. However, the bulk of the higher melting iso-oleic acids was precipitated as the temperature approached −5° F. in acetone and −15° F. in petroleum naphtha. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Extraction of lipids from cotronseed tissue: I. Comparison of hexane-acetone-water,its nonqueous components and chloroform-methanol

Flaked cottonseed was extracted with chloroform-methanol-water, chloroform-methanol, hexane-acetone-water, hexane-acetone, hexane and acetone. Amounts of total material in the miscellae were greatest with chloroform-methanol-water and decreased to acetone in the order given above. The first three solvents extracted 6% more neutral oil and over 100% more lipophilic phosphorus than the latter three solvents. All solvents showed similar rates of extraction, each removed over 70% of extractables with the first of four passes.     

Comparison of alternative solvents for oils extraction

A comprehensive review of the literature about use of solvents for extraction of oilseeds is presented. Mention has been found of over 70 solvents. Currently, hexane is the major solvent in use, but recent price increases and safety, environmental and health concerns, have generated interest in alternatives. Solvents vary considerably in chemical and physical properties which affect their performance in oil extraction. The choice of solvent depends upon the primary end product desired (oil or meal). Recent research on alternative solvents has focused on ethanol, isopropanol, methylene chloride, aqueous acetone, and hexane/acetone/water mixtures.     

Phase equilibrium data pertaining to the extraction of cottonseed oil with ethanol and 2-propanol

Summary Basic phase relation data have been obtained relative to the extraction of cottonseed oil with ethanol and 2-propanol, especially as affected by water in the solvent. Mutual solubility diagrams have been constructed for cottonseed oil with ethanol and 2-propanol of various aqueous concentrations. Tie-line data at 30° C. have been obtained for the ternary ethanol-cotton-seed oil-water and 2-propanol-cottonseed oil-water systems. These combined data will be of assistance in the selection of the most desirable temperatures and moisture concentrations in the solvent extraction of cottonseed with these alcohols. Comparison with results previously published for soybean oil suggests that the mutual solubility data for cottonseed oil and aqueous ethanols are applicable to other vegetable oils over a wide range of iodine values. In general, the results indicate that 2-propanol is the more desirable solvent since complete miscibility with the oil can be attained at temperatures below its normal boiling point even at moisture contents as high as 10% by weight whereas ethanol can tolerate only about 1.5% of water. High moisture contents result in more effective separation of the oil from the solvent when the miscella is cooled after extraction. Constant boiling aqueous ethanol and 2-propanol present the disadvantage of requiring greater than atmospheric pressure during extraction in order to attain complete miscibility with the oil. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Hexane and heptane as extraction solvents for cottonseed: A laboratory-scale study

For many years, commercial-grade hexane has been the preferred solvent for extracting oil from cottonseed. Recent environmental and health concerns about hexane may limit the use of this solvent; therefore, the need for a replacement solvent has become an important issue. Heptane is similar to hexane, but does not have the environmental and health concerns associated with the latter. On a laboratory scale, delinted, dehulled, ground cottonseed was extracted with hexane and heptane. The solvent-to-meal ratio was 10:1 (vol/wt). The yield and quality of the oil and meal extracted by heptane were similar to that extracted by hexane. Extraction temperature was higher for heptane than for hexane. A higher temperature and a longer time were required to desolventize miscella from the heptane extraction than from the hexane extraction. Based on these studies, heptane offers a potential alternative to hexane for extracting oil from cottonseed.     

Characterization of the high-melting glyceride fraction isolated from cottonseed oil stearin by fractional crystallization in isopropanol

Cottonseed oil stearin is generally produced commercially from cottonseed oil by winterization. In Egypt, the byproduct stearin is often used for lower-priced industrial applications. It can be turned into a high-value, cost-effective edible product by further fractionation to produce low-melting cottonseed oil stearin (LMCS) and a higher melting cottonseed oil stearin (HMCS). In the present investigation, isopropyl alcohol (IPA) helps to obtain good fractionation of HMCS having useful solidification and melting properties. The advantage of using IPA is that fractionation can be carried out at higher temperatures than hexane with better separation efficiency. A direct relationship between yield, quality of HMCS, and crystallization temperature during fractionation with IPA was achieved. HMCS could be fractionated from IPA at 4°C in a much higher yield but the melting point and the solid fat contents were much lower than that fractionated at 18°C. The thermal profile of the HMCS fractionated with hexane lies between those fractionated at 4 and 18°C with IPA. On the other hand, all the LMCS fractions could be considered as good quality salad oils.     

Thermal properties of fats and oils

Summary 1. The heat content of a quickly chilled sample, and that of a slowly chilled and tempered sample, of almost completely hydrogenated cottonseed oil, has been measured over a temperature range within which there is in each case complete transformation of the oil from a solid to a liquid form. 2. Heat capacity data have been calculated for the liquid oil and for the quickly chilled and the tempered solid oil. Equations expressing the changes in heat capacity with temperature have been derived. A correlation of the heat capacity data on highly hydrogenated cottonseed oil and similar data previously obtained on unhydrogenated cottonseed oil, and on partially hydrogenated oil, in both liquid and solid states, is presented. 3. The heat of fusion calculated for the quickly chilled and for the tempered solid oil is given. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Optimization of Solvent Extraction of Moringa (Moringa Oleifera) Seed Kernel Oil Using Response Surface Methodology

Extraction of seed kernel oil from moringa (Moringa oleifera) was investigated with hexane, petroleum ether and acetone as the first extraction medium at various kernel particle size, extraction temperature and residence time, which were called as independent variables. Central composite rotatable design (CCRD) of experiments was used to study the effect of solvent type, particle size, extraction temperature and residence time of solvent on the oil yield, which was called as dependent variable. The maximum oil yield of 33.1% for hexane, 31.8% for petroleum ether and 31.1% for acetone was obtained. Among the three solvents, hexane yielded the maximum oil from moringa seed kernels. Among three process parameters studied, particle size had the most significant effect on the oil yield followed by extraction temperature and time for all the solvents. Response surface methodology technique was used to optimize the independent variables for maximum oil extraction. From the optimized values of particle size (0.62 mm), extraction temperature (56.5°C) and residence time (7 h), maximum oil yield obtained was 33.5%, using hexane. Optimized values of independent variables for maximum yield were varied for other two solvents. This protocol provides improved opportunities for the medicinal use of moringa oil in addition to its popularity as a vegetable in south Asia.     

Solubility of 1-monostearin in various solvents

Summary The practical limits of the solubility of pure monostearin in various solvents at different temperatures has been determined for isopropyl alcohol, ethanol, acetone, methanol, and commercial hexane. The synthetic method was employed, in which the temperature of known quantities of solvent and solute was decreased until crystallization of the solute began. This temperature, corrected for supercooling and heat loss to the surrounding bath, was taken as the equilibrium temperature between the known weight of solute and the known weight of solvent. The solubility-temperature data of monostearin in each of the various solvents are presented both graphically and in tabular form. A comparison of the solubility of monostearin in the various solvents at comparative temperatures indicates that its solubility is greatest in isopropyl alcohol and decreases in the order ethanol, acetone, methanol, and hexane. Presented at the 45th annual meeting of the American Oil Chemists' Society, San Antonio, Tex., April 12–14, 1954. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Concentration of Stearidonic Acid in Free Fatty Acid and Fatty Acid Ethyl Ester Forms from Modified Soybean Oil by Winterization

The concentration of stearidonic acid (SDA, 18:4 ω-3) in free fatty acid (FFA) and fatty acid ethyl ester (FAEE) forms by low temperature crystallization (winterization) was studied. For this purpose, modified soybean oil (initial SDA content, ~23%) was transformed into its corresponding FFA and FAEE by chemical hydrolysis and ethanolysis, respectively. In the first study, the FFA and FAEE were used as starting material for winterization and variables such as winterization time, type of solvent, and the oil:solvent ratio were evaluated until optimization of the process was achieved. In the second study, changes in the winterization procedure were introduced to obtain a remarkable improvement on the SDA purity of the final products. Since winterization of FAEE was not efficient due to its low melting points, the second study focused on FFA. The best relationship between SDA purity (59.8%) and SDA yield (82.3%) was attained by performing winterization of FFA with hexane at 10% oil:solvent ratio for 24 h. Scaled-up processes were also performed to obtain 59 g of FFA (purity 59.6%; yield 82.6%) enriched in SDA. The products obtained can be used as starting materials for the production of functional lipids and for clinical trials.     

Tocopherol concentrates by the fractional crystallization of cottonseed oil from solvents

Summary 1. Tocopherol concentrates equivalent in tocopherol content and antioxygenic activity to molecularly distilled concentrates, have been obtained from cottonseed oil by hydrogenating the oil and removing the bulk of the glycerides and sterols by low temperature crystallization from acetone. 2. High-tocopherol concentrates can be obtained only from hydrogenated oils. Completely hydrogenated oils are the best source of concentrates at crystallization temperatures down to −60° C.; below this temperature partially hydrogenated oils are equally as good. 3. A solvent-oil ratio of 8:1 by weight appears to be about the optimum. At this ratio, crystallization from acetone at the temperature of Dry Ice (−78° C.) yields a concentrate containing 34 percent tocopherols from an oil originally containing 0.05 percent tocopherols. 4. The direct addition of Dry Ice to the solvent and oil is to be avoided, since this lowers the recovery of tocopherols. 5. Petroleum naphtha and methyl ethyl ketone are less suitable solvents than acetone, because of their greater capacity for dissolving glycerides at low temperatures. Presented before the American Oil Chemists’ Society Meeting, New Orleans, Louisiana, May 10 to 12, 1944. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.