The fatty acid composition of cottonseed oil at various stages of solvent extraction

The variation in the fatty acid composition of the glyceride portion of cottonseed oil at various stages of solvent extraction has been investigated. Prime cottonseed meats were flaked and extracted in glassware rate extraction apparatus, using commercial hexane up to different degrees of extractions. The fatty acid composition of cottonseed oil obtained after extracting the flakes to different residual oil contents was determined by gas-liquid partition chromatography. No difference was found.     

Present status of the filtration-extraction process for cottonseed

Summary Improvements and refinements in the process for filtration-extraction of cottonseed resulting from further pilot-plant development studies are described as well as their adaptation to the first commercial plant. These improvements which depict the present status of the process for cottonseed include principally certain modifications in the method of conditioning of the meats or flakes prior to cooking and in the procedure for crisping; selection of best conveyor type for conveying cooked material over relatively long distances without objectionable comminution; selection of filter medium combining the desired properties of durability, non-fouling, and low fines retention; determination of optimum filter-cake thickness; and development of a method for clarification of the product miscella by continuous recycling through the formed cake on the filter. Also discussed is the quality and color stability of the oil produced from comparable lots of cottonseed by the filtration-extraction process, as compared with that by hydraulic pressing, and by solvent extraction of uncooked flakes. Presented at the 45th annual meeting of the American Oil Chemists' Society, San Antonio, Tex., April 11–14, 1954. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Experiments with solvent extraction of glandless cottonseed and glanded cottonseed

Preliminary bench scale tests indicated that the rate of extraction of oil from glandless cottonseed flakes is about the same as for glanded flakes. Pilot plant experiments, using 20 lb. batches of flakes in baskets 8×8 in. in cross section, showed that the usual percolation rates can be used and will produce the same results with glandless flakes as with glanded. Solvents used were commercial hexane, nearly pure normal hexane, and a mixed solvent of acetone, hexane and water. In some runs raw flakes were extracted; in others, the meats were tempered by heating to various temperatures. Refine and bleach tests were run on the resulting oil. Colors were much lower than generally obtained with oil from glanded seed, most samples testing below one red Lovibond on a spectrophotometer. The meals from the extractions were used in rat feeding tests. The mixed solvent meal seemed to be a cut above the hexane-extracted meals in protein quality, showing up equivalent to a casein based diet. The meal from meats which had been heated to 230 F seemed very slightly inferior to those which had undergone less drastic heating. All glandless meals were much superior to a commercial prepress solvent meal which was run for the purpose of making comparisons. Deceased. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Solvent extraction of cottonseed meats

In the experimental countercurrent extraction of flaked cottonseed meats by trichloroethylene the residual oil content of the extracted flakes decreased with: first, a decrease in the final oil content of the final miscella; second, decrease in the flake moisture down to 8.64%; third, decrease in flake thickness; fourth, increase in temperature; and fifth, increase in extraction time. For the batch of cottonseed meats used the following equation was developed: whereR is percent residual extractables,b is flake thickness in feet,D is meat diameter in feet,ϑ is extraction time in hours,μ in viscosity, lb. per ft. hr.,ρ is density, lb. per cu. ft., andt is extraction temperature in degrees F. Not enough data were secured by extraction with hexane to check the equation developed for trichloroethylene extraction. Hexane is a poorer solvent for cottonseed oil than trichloroethylene. The amount of oil remaining in the meal is affected to a greater extent by the miscella concentration in hexane extraction than in trichloroethylene extraction.     

Comparative absolute yields of crude and neutral oils from variously prepared cottonseed meats

Summary Experiments utilizing cottonseed meats of diverse origin and composition were conducted for the purpose of determining the effect of the method of meats preparation on the yields of crude and neutral oil obtainable from differently prepared, comparable meats by solvent extraction. Three methods of meats preparation were employed,i. e., simple flaking of raw meats “as is”, tempering of cracked meats prior to flaking, and cooking by the modified hydraulic method developed for use with the filtration-extraction process. Commercial hexane was used as the extraction solvent. The experiments were carried out by procedures which eliminated the effects of any variables other than the method of preparing the meats for extraction The results of the studies showed that the method used in preparing cottonseed meats for extraction had a significant effect on the yields of crude oil obtained but that the yields of neutral oil, the valuable constituent of crude oils, were virtually unaffected. Analyses of the crude oils showed that the differences in crude oil yields were caused by the relative amounts of non-neutral oil materials in the crudes from the differently prepared meats. The greatest yields of crude oil were obtained from raw flakes, intermediate yields from tempered flakes, and the smallest yields from cooked flakes. The impurities content in the respective crude oils followed the same order,i. e., crudes from raw flakes were highest in impurities and lowest in neutral oil, crudes from tempered flakes were lower in impurities and higher in neutral oil, and the crudes from the cooked meats were outstandingly low in impurities and high in neutral oil. Virtually equal amounts of neutral oil were obtained from equivalent quantities of comparable meats regardless of the method used in preparing the meats for extraction. Presented at the meeting of the American Oil Chemists’ Society, Chicago, Ill., September 24–26, 1956. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U.S. Department of Agriculture.     

Pilot-plant fractionation of cottonseed. I. Disintegration of cottonseed meats

Disintegration of cottonseed meats is an important unit operation in the cottonseed fractionation process. The results of tests utilizing a high-speed, “dissolver-type” impeller for disintegration by liquid shear are presented including curves to show the effect of moisture, hulls, solvents, peripheral speed, etc. Over 90% of through-80-mesh material can be obtained. Moisture content over 5% appreciably reduced the efficiency and increased power consumption and the viscosity of the slurry. Whole flakes resulted in a finer end product than flakes pre-pulverized in the dry state. It was found that the presence of hulls slightly increased disintegration, power consumption, and viscosity; that higher speeds (up to 6,000 FPM peripheral speed) were more efficient; and that the effect of solvents was small. Presented at 39th annual meeting of the American Oil Chemists' Society, New Orleans, La., May 4–6, 1948. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

The effects of alkali cooking on the yields of crude and neutral oil from cottonseed meats

Summary Equal quantities of flaked cottonseed meats of identical composition were similarly cooked at high moisture conditions with and without alkali present. The cooked flakes were exhaustively extracted with commercial hexane, and the yields of crude oil, neutral oil, and meal were determined. The yields from an equal quantity of uncooked flakes were similarly determined, chiefly to serve as a neutral oil control. Analyses of the crude oils and meals were compared to determine the effects of the presence of alkali while cooking on the composition of the products. These experiments show that there was a reduction in the yields of both crude and neutral oil resulting from the admixture of alkali with cottonseed flakes while cooking. Assuming yields from flakes cooked with water as 100%, and average of 0.6% less crude oil was obtained from alkali-cooked than from watercooked flakes. A similar comparison of the yields of neutral oil shows that those from the alkali-cooked flakes averaged about 0.75% less than from the flakes cooked with water. The crude oils from alkali-cooked flakes contained only about one-fifth as much gossypol as those from the water-cooked flakes and were appreciably lower in free fatty acids. The crude oils from alkali-cooked flakes were significantly higher in phosphorus. The sodium content of the oils from alkali-cooked flakes indicated that their content of soaps ranged from 0.07% to 0.19%. Presented at the spring meeting, American Oil Chemists’ Society, New Orleans, La., April 28–May 1, 1957. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Hygroscopic equilibrium of cottonseed

Summary and Conclusion An investigation has been made of the hygroscopic equilibrium of cottonseed over a range of 31% to 93% relative humidity. From 31% to 71% relative humidity the moisture content of cottonseed increased linearly from 6.03% to 10.27%. From 71% to 93% relative humidity the moisture content increased rapidly from 10.27% to 22.19%. When cottonseed was separated into meats and hulls, including linters, it was found that the hulls contained more moisture than the meats. On the basis of these results it is apparent that, when stored cottonseed is aerated, consideration should be given to the effect of local atmospheric conditions. The relative humidity of the air used for aeration can affect the moisture content of the stored seed either favorably or adversely. Although it may temporarily reduce heating by conduction of the heat of respiration, it may increase the moisture content and thus stimulate further respiration and heating. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Pilot plant studies on extracting cottonseed with methylene chloride

The practical feasibility of using methylene chloride to extract oil, aflatoxin and gossypol simultaneously from cottonseed flakes was demonstrated in a 56-hr experimental run using a pilot-scale, continuous extractor. Nine different trials varying in extraction time, solvent:flake ratio, flake preparation method and blending with 5% ethanol were evaluated. Residual oil contents were lower than typically achieved in extraction with hexane. Aflatoxin contents of the meals were reduced by 73–92% of the level in cottonseed meats, making possible the upgrading of a large portion of cottonseed meal that otherwise would exceed current action levels. Because gossypol also was extracted, it was possible to produce cottonseed meal that was well suited for use in poultry feeds, especially when a blend of 5% ethanol in methylene chloride was used. Meal desolventized easily, and residual levels of methylene chloride were generally less than 12 ppm. The oil was refined and bleached to acceptable quality standards, and no residual aflatoxin was detected in alkali-refined oil.     

Water accumulation in the alcohol extraction of cottonseed

The critical moisture content of cottonseed flakes extracted with an aqueous alcohol solvent can be defined as that flake moisture level at which the flakes lose no moisture during extraction. This study shows that the critical moisture content for aqueous ethanol (92%, w/w) is 3%. For aqueous isopropanol (88%, w/w) this value is 6%. If the moisture contents of the flakes are above these levels, then the solvents pick up moisture. For moisture contents below this level, the flakes adsorb moisture and actually dry the alcohol. It is proposed that this latter capability can be used as a basis for a method to control water accumulation in aqueous alcohol solvent extractions.     

Solvent cooking of cottonseed meats for extraction

Data have been presented for a solvent-cooking method of preparing cottonseed meats for extraction. The study includes experiments in which the flake moisture contents were increased to as high as 40% during the initial solvent cooking phase and decreased to about 10% by the end of the cooking cycle, and in which hexane and heptane were used as the cooking solvent in the presence of chemicals such as NaOH, NaCl, CaCl₂, and NH₃. Results showed specific trends with varying condiditions. Examples are: increase in the initial moisture content during cooking increases granulation and consequently the mass velocity; increase to 30% moisture content is sufficient to result in mass velocities above the desirable 2,000 lbs. per square foot per hour; free gossypol content of the extracted meals is lower with the higher initial cooking moisture contents and with the addition of certain chemicals (NaOH-CaCl₂) ; and the addition of the combination of NaOH and NaCl resulted in better overall filtration-extraction characteristics than either the NaOH-CaCl₂ or the NH₃-NaCl combinations. On the basis of the above results the following general conclusions can be made:

1. Solvent cooking offers the possibility of combining cooking, crisping, and slurrying (extraction) steps into a single operation in a process, such as filtration extraction for the direct solvent extraction of cottonseed.
2. Chemicals can be introduced as needed to promote free gossypol reduction and possibly maintain a high alkali protein solubility in the solvent extracted meal.
3. Agglomeration and extractability of the solvent-cooked cottonseed meats can be controlled.

     

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.     

Application of the antimony trichloride-spectrophotometric method to the determination of gossypol in cottonseed and cottonseed products

Summary A method is described which permits application of the antimony trichloride spectrophotometric method to the determination of gossypol in a variety of cottonseed products. Gossypol is determined by means of the following series of operations: 1. extraction of gossypol from cottonseed or cottonseed products by use of chloroform or aqueous ethanol; 2. isolation of gossypol from the extracts by use of aqueous alkali; and 3. application of the antimony trichloride-spectrophotometric test. Data are presented to show the results obtained by application of this procedure to the determination of gossypol in pigment glands, raw cottonseed meats, cooked cottonseed meats, hydraulic- and screw-pressed meals, solvent-extracted meals, gland-free meals, and oils, both expressed and solvent-extracted. Presented at the 39th Annual meeting of the American Oil Chemists' Society in New Orleans, May 4–6, 1948. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Aflatoxin distribution in fines and meats from decorticated cottonseed

Nine samples of fuzzy cottonseed potentially high in aflatoxin were separated into hulls, fines and meats. Assays for aflatoxin on triplicate 50-g portions from fines (small, dry particles of kernels) and meats from each of the nine samples indicated a marked concentration of toxin in the fines. On average, there was a 17-fold difference between the aflatoxin content of the fines and that of the meats; the average toxin level in fines was 4024 μg/kg and that in the meat samples was 232 μg/kg. These results indicate a potential for marked reduction in aflatoxin content of processed cottonseed meal by physical removal of fines from meats after dehulling and before processing of meats into oil and meal.     

Measurement of extractability of raw and cooked cottonseed flakes

A batch co-current laboratory method for measuring comparative extraction rates and extraction efficiencies of oleaginous materials in solvent is described. The method, a modification of that by Winward and Shand, was carefully tested with raw and cooked cottonseed flakes of various thicknesses and in various hexane miscella concentrations. It enables measurement of intrinsic extraction rates and extractabilities of materials, unaffected by diffusional effects in the liquid medium, and yields accurate and concordant results even with extracting miscellas of considerably high concentration. It is equally applicable for evaluating and predicting the effect upon extractability of different material preparation operations, particle sizes, moisture contents, temperature, solvents, etc. The method was used in this investigation to compare the rate and degree of extraction under the specified testing conditions of raw and cooked cotton-seed flakes of .005-in., .015-in., and .025-in. thicknesses in miscella concentration of 0%, 25% and 50% oil. The results may be summed up as follows:

1. the extractability of both raw and cooked flakes in each of the miscella concentrations decreases as the flake thickness increases.
2. the cooked material prepared from the medium and thick flakes extracted at a more rapid rate and to a greater degree in all miscella concentrations than the raw flakes of comparative thicknesses, but the rate and degree of extraction were about equal for the very thin flakes.
3. the effect of increasing miscella concentration for both the raw and the cooked flakes of medium and thick sizes was to slow down the initial extraction rate; but for the very thin flakes the effect was negligible.
4. the effect of increasing miscella concentration in extracting the cooked material, regardless of flake thickness, was to increase the degree of extraction. For the raw flakes the effect was to increase the degree of extraction only of the very thin flakes.

     

The extraction of wheat germs,milkweed seeds,and cottonseed by trichloroethylene

Summary Specific gravity-concentration data have been determined for wheat germ oil, milkweed seed oil, and cottonseed oil miscellas where trichloroethylene is used as a solvent. Extraction rate data at two temperatures and pilot plant runs on wheat germs, cottonseed, cottonseed meats, and milkweed seeds indicate increasing extraction time in the order given.     

Analytical Control of Experimental Extraction of Oilseed

A study was made of methods for measuring relevant components at different stages of an experimental process for mixed solvent extraction of raw cottonseed flaked meats. The principles discussed should apply to other complex oilseed separation procedures.     

The reduction of free gossypol in cottonseed flakes during solvent extraction

Conclusions Extraction with trichloroethylene was found to be an effective method of reducing the free gossypol content of flaked cottonseed meats. The reduction was found to be a function of both extraction temperature and residual extractables in the extracted meal. Because of the low temperatures involved the meal produced by this method has a higher soluble protein content than a meal in which the free gossypol is reduced by heat treatment.     

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.     

Characterization and processing of cottonseed oil obtained by extraction with supercritical carbon dioxide

Extraction of flaked cottonseed with supercritical carbon dioxide at temperatures of 50–80 C and pressures of 8,000–15,000 psi yields an improved crude cottonseed oil compared to those obtained by conventional solvent or expeller processes. Improvements include lighter initial color, less refining loss and lighter refined bleached colors. Crude cottonseed oils obtained by supercritical fluid extraction require less refining lye and show less tendency to undergo color fixation while in storage. Presented at the AOCS annual meeting, Chicago, May 1983.