Alcoholic extraction of vegetable oils. Part IV. Solubilities of vegetable oils in aqueous 2-propanol

Summary Solubilities of 14 vegetable oils in four different concentrations of aqueous 2-propanol at various temperatures were determined by a direct and simple method. Comprehensive solubility data of these oils and the critical solution temperatureversus 2-propanol composition data are presented in tabular form. Solubility of each oil in aqueous 2-propanol increases with temperature until the critical solution temperature is reached, at and above which oil and the solvent are miscible in all proportions. Further the critical solution temperatures of all the oils with aqueous 2-propanol solutions increased with the increase in water content of 2-propanol solutions. There appears to be a general relation between fatty acid contents of the oils and critical solution temperatures which needs further study. Presented at the 30th fall meeting, American Oil Chemists' Society, September 24–26, 1956, Chicago, Ill.     

Solubilities of vegetable oils in aqueous ethanol and ethanol-hexane mixtures

Summary The solubility of vegetable oils in aqueous ethanol depends on the concentration of alcohol and temperature of the system. At ordinary temperatures even absolute alcohol is not a good solvent for vegetable oils since the solubility is even less than 10 g. of oil per 100 g. of alcohol. Mowrah, safflower, peanut, and cottonseed oils are soluble in absolute alcohol at 70°C. All the oils investigated are found to be miscible above the boiling point of alcohol even if the concentration is 98%. In 95% ethanol they are miscible between 90° and 100°C. Addition of a good solvent, like n-hexane, increases the solubility of oils, and the solubility temperatures are lowered. From the results obtained by various methods of solubility determination it is found that the apparatus employed in the present work yields more reliable results by eliminating the visual observation of turbidity temperatures, ensuring vigorous stirring and allowing sufficient amount of time to attain equilibrium conditions in determining the solubilities of vegetable oils. Presented at fall meeting, American Oil Chemists' Society, Cincinnati, O., September, 30–October 2, 1957.     

An aqueous ethanol extraction process for cottonseed oil

A bench-top process for the extraction of cottonseed flakes with aqueous ethanol has been developed. The process consists of cottonseed meat flaking, drying and extraction with boiling, aqueous ethanol (95% by volume) at atmospheric pressure. The resulting miscella is chilled, producing free oil, emulsified oil and mucilaginous gum. The heterogeneous solution is processed through a phase separator where free and emulsified oil and gum are separated from oil-lean miscella. The oil and gum phases are treated with caustic soda and centrifuged to produce semirefined oil containing about 4% volatiles. The miscella phase, containing about 3.3% lipid-like material and 1% petroleum ether insolubles, is reheated and recycled to the extractor. After the marc is pressed foots are added, and it is desolventized to produce a meal having a residual oil content less than 1%. Although not yet otpimized, the process shows potential for scaleup to pilot plant processing and adaptability to current oil mill solvent operations. Presented at the AOCS annual meeting, Chicago, May 1983.     

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.     

Modeling the solvent extraction of oilseeds

A computer model and an experimental procedure for generating data needed in the model have been developed for the oilseed extraction process. The experiments are relatively simple and are performed with a bench-top extractor. Experimental results and modeling calculations are presented for the extraction of cottonseed using hexane, isopropanol and ethanol. The calculations show that in an alcohol extraction using a chill separation, isopropanol’s greater oil miscibility allows for a lower solvent-to-feed ratio than does ethanol. Using the latter solvent, however, achieves lower residual lipids in the extracted meal because recycled ethanol contains less oil than recycled isopropanol. Presented in part at the AOCS meeting in Honolulu, HI, in 1986.     

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.

     

Solvent extraction of cottonseed and peanut oils. VIII. Effects of moisture on the preparation and flaking of cottonseed

Conclusions The results indicate that 9 to 10% moisture in the meats is the best level for the preparation of cottonseed into flakes for solvent extraction. At lower moisture the flakes contain more fines before and after agitation in solvent, and the percolation rate of solvent through a flake bed is lower because of reduced particle size. At higher moisture the amount of oil in the hulls from the beater is greater. Also the flakes produce more fines, and the percolation rate becomes slower because of the softness and pliability of the flaked meat. It is likely that in commercial continuous operations this packing or balling up tendency of the flaked meats may lead to periodic channeling or plugging in the extractor, dryer, conveyors, and filters. These conclusions have been applied in the continuous pilot plant solvent extraction of three lots of prime cottonseed. The results substantiate the findings herein and will be reported in a separate publication. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Prepress-solvent extraction of cottonseed,processing conditions and characteristics of products

Summary A study has been made of the relation between processing conditions and the chemical characteristics of cottonseed meals and oils produced by prepressing-solvent extraction. Twenty-six complete sets of mill samples of known processing history and representative of the production at 11 mills were used in the investigation. Cooking conditions were the major factor influencing the distribution of the gossypol between the meal and oil. Reduction in free gossypol during cooking was due to binding with meal components while that occurring during prepressing and solvent extraction resulted mainly from removal of gossypol in the prepressed and solvent-extracted oils. Nitrogen solubility data, which have been suggested as a measure of protein damage, indicated that the major change or reduction in nitrogen solubility occurred during cooking. Very little reduction was noted for prepressing or solvent extraction. The reduction in nitrogen solubility during prepressing is much smaller than that previously reported for normal screw-pressing operations. Prepressed oils gave lower refining losses and lower refined and bleached color than did the solvent-extracted oils. Bleach color reversion, after storage of crude oils for 30 days at 100°F., was greater for solvent-extracted than for prepressed oils. A number of meals exhibited the desirable characteristics of low free gossypol content and high nitrogen solubility. Values calculated for chemical indexes of protein quality, as suggested by Lyman and associates (11), indicate that many of the meals should have good protein quality. Presented at the 45th Annual Meeting of the American Oil Chemists' Society, April 11–14, 1954, San Antonio, Tex. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

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.     

Supercritical carbon dioxide extraction of cottonseed with co-solvents

Extraction of cottonseed lipids with supercritical carbon dioxide (SC-CO₂) was conducted with and without a cosolvent, ethanol or 2-propanol (IPA). At 7000 psi and 80°C, the reduced pressure, temperature and density of SC-CO₂ was at 6.5, 1.17 and 1.85, respectively; the specific gravity was 0.87. Under these conditions, CO₂ is denser than most liquid extraction agents such as hexane, ethanol and IPA. The extraction of cottonseed with SC-CO₂ gave a yield of more than 30% (moisture-free basis). This is comparable to yields obtained by the more commonly used solvent, hexane. The crude cottonseed oil extracted by SC-CO₂ was visually lighter than refined cottonseed oil. This was substantiated by colorimetric measurements. No gossypol was detected in the crude oil. However, crude oil extracted by SC-CO₂, to which less than 5% of ethanol or IPA as co-solvent was added, containedca. 200 ppm of gossypol, resulting in the typical dark color of cottonseed crude oil with gossypol. CO₂ extracted a small amount of cottonseed phosphatides, about one-third of that extracted by pure ethanol, IPA or hexane. A second extraction with 100% ethanol or IPA after the initial SC-CO₂ extraction produced a water-soluble lipid fraction that contained a significant amount of gossypol, ranging between 1500 and 5000 ppm. Because pure gossypol is practically insoluble in water, this fraction is believed to be made up of gossypol complexed with polysaccharides and phosphatides. Partially presented at the AOCS 1993 Annual Meeting & Expo in Anaheim, California.     

Alcoholic extraction of vegetable oils. V. Pilot plant extraction of cottonseed by aqueous ethanol

Summary Cottonseed flakes were extracted by aqueous ethanol in a countercurrent pilot plant unit to determine the effect of operating variables and the optimum operating conditions. This investigation has shown that direct extraction of cottonseed, using aqueous ethanol as a solvent, is a feasible process in the type of equipment developed previously in this laboratory. The optimum operating conditions for the ethanol extraction of cottonseed have been established. The pilot plant extractions have shown that in this process a prime quality of crude oil and lightcolored meal of good quality, with negligible free gossypol content, are obtained. Presented at the spring meeting, American Oil Chemists' Society, April 29-May 1, 1957, New Orleans, La.     

Determination of free gossypol in cottonseed materials

Summary A method for the determination of free gossypol in cottonseed materials is described. The method consists of extraction of gossypol with a measured volume of 70% aqueous acetone on a shaker for one hour, filtration, and colorimetric analysis for gossypol in an aliquot of the filtrate by means of the reaction between gossypol andp-anisidine. The conditions for complete extraction of gossypol from various types of cottonseed materials have been investigated, the stability of gossypol in aqueous acetone has been demonstrated, and data are presented on recovery of gossypol added to cottonseed materials. The method has been compared with the method of Smith (2). One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

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.     

Filtration-extraction of flaxseed as affected by preparation variables

Summary The data presented show that the filtration-extraction process can be applied to the extraction of oil from flaxseed. General conditions for preparing the material and for extraction have been established. Adequate comminution, cooking, and crisping yielded materials having necessary characteristics for the successful application of the filtration-extraction process. Mass velocities in excess of 2,000 and residual lipides contents below 1% were obtained when these materials were slurried and extracted at slightly elevated temperatures (130°F.). The conditions of rolling had an appreciable effect upon the efficiency of extraction of flaxseed. One pass through five-high rolls with clearances of 0.002 in., 0.002 in., 0.002 in., and 0.000 in. between respective rolls proved satisfactory. Apparent optimum cooking moisture levels for efficient oil extraction fall between 17 and 24% maximum initial, and 8.0 to 10.5% as discharged from the cooker. Mass velocities were significantly lowered when maximum initial cooking moisture contents were below 14% since at these moisture levels it becomes necessary to reduce the moisture content to below 8%, as discharged from the cooker, to achieve suitable cooking. At these low moisture levels crisping by evaporative cooling is not effective. The versatility of the filtration-extraction process, which had been previously adapted to the extraction of oil from cottonseed, soybeans, sesame seed, peanuts, and rice bran, has been extended, with some minor but important modifications in the preparation and extraction conditions, to the extraction of oil from flaxseed. Presented at the fall meeting of the American Oil Chemists’ Society, Philadelphia, Pa., Oct. 10–12, 1955. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, 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.     

Solvent extraction of aflatoxins from contaminated agricultural products

Solvent extraction of agricultural products has been suggested as an effective means of removing aflatoxins from mold-damaged commodities. The use of various polar solvents such as the azeotrope of acetone-hexane-water and of 2-propanol-water, aqueous acetone, and aqueous ethanol has been reported in the literature. This paper examines the overall aspects of solvent extraction, in particular the use of the azeotrope of 2-propanol-water, to remove aflatoxins from prepress solvent extracted cottonseed meal.     

Extraction of lipids from Yarrowia Lipolytica

BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high‐lipid‐content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO₂) extraction using ethanol as a co‐solvent. Also, high pressure solubility measurements in the systems ‘CO₂ + yeast oil’ and ‘CO₂ + ethanol + yeast oil’ were carried out. RESULTS: The solubility experiments determined that, at the conditions of the supercritical extractor (40 °C and 20 MPa), a maximum concentration of 10 mg of yeast oil per g of solvent can be expected in pure CO₂. 10% w/w of ethanol in the solvent mixture increased this value to almost 15 mg of yeast oil per g of solvent. Different pretreatments were necessary to obtain satisfactory yields in the extraction experiments. The Soxhlet and the ASE method were not able to complete the lipid extraction. The ‘SCCO₂ + ethanol’ extraction curves revealed the influence of the different pretreatments on the extraction mechanism. CONCLUSION: Evaluating the effectiveness of a given pretreatment, ASE reduced the amount of material and solvent used compared with Soxhlet. In all three cases, the best total extraction performance was obtained for the ethanol‐macerated yeast (EtM). Addition of ethanol to the solvent mixture enhanced the oil solubility. Oil can be extracted from Y. lipolytica in two different steps: a non‐selective ethanol extraction followed by TAG‐selective SCCO₂ purification. © 2012 Society of Chemical Industry     

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.     

Ethanol extraction of oil,gossypol and aflatoxin from cottonseed

Commercial processing of cottonseed requires hexane to extract and recover edible oil. Gossypol and aflatoxin are not removed from extracted meals. A bench-top extraction process with 95% (vol/vol) aqueous ethanol (EtOH) solvent has been developed that extracts all three of the above materials with a much less volatile solvent. In this process, cottonseed is pretreated and extracted with ambient 95% EtOH to remove gossypol and then extracted with hot 95% EtOH to extract oil and aflatoxin. Membranes and adsorption columns are used to purify the various extract streams, so that they can be recycled directly. A representative extracted meal contained a total gossypol content of 0.47% (a 70% reduction) and 3 ppb aflatoxin (a 95% reduction). Residual oil content was approximately 2%. Although the process is technically feasible, it is presently not economical unless a mill has a continual, serious aflatoxin contamination problem. However, if a plant cannot meet the hexane emission standards under the Clean Air Act of 1990, this process could provide a safer solvent that may expand the use and increase the value of cottonseed meal as a feed for nonruminants. Presented in part at the AOCS annual meeting, Toronto, Canada, May 1992.     

Cottonseed extraction with a new solvent system: Isohexane and alcohol mixtures

A solvent system, consisting of isohexane and 5 to 25% alcohol, either ethanol (EtOH) or isopropyl alcohol (IPA), was tested for extracting gossypol and oil from cottonseed. The test results indicate that this new solvent system not only is effective in removing free and total gossypol but also is as efficient as n-hexane when extracting oil. The amino acid analysis of cottonseed meal, produced by the new solvent system, is similar to that produced by commercial n-hexane. Present commercial cottonseed extraction and downstream processing of cottonseed oil refining may need little change to adopt this new solvent system. This new solvent system may lead to a solution to the gossypol problem of cottonseed extraction.