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.     

A new method of detoxification of cottonseed by means of mixed solvent extraction

For several decades, scientists in the field of vegetable oils tried unsuccessfully to detoxify cottonseed by a practical method. By using 20-30% (by wt) of ethyl alcohol (90% in vol) with commercial hexane as a mixed solvent, we were able to extract effectively both gossypol and oil from cottonseed prepressed cake or flakes. Free gossypol in meal was reduced to ca. 0.013-0.04%; total gossypol was reduced to 0.32-0.55%; residual oil was reduced to ca. 0.5% or less. Any aflatoxin present also can be eliminated by this process. The detoxified cottonseed meal can be used as animal feed. Cottonseed protein can be used to substitute for soy protein. The extracted oil is of better quality than that obtained by the usual hexane extraction method, and gossypol is a valuable byproduct.     

Note on acetone-soluble material in cottonseed meals

Summary In connection with a study of methods of eliminating traces of “free” gossypol from cottonseed meals a procedure for isolation of gossypol from the 70% acetone extracts of the meals by transfer to benzene solution has ben developed. A procedure is also given for quantitative determination of the isolated gossypol. Analysis of four samples of cooked cottonseed meats and meal by the method showed that in each instance substances other than gossypol are measured by the A.O.C.S. method for “free” gossypol in meals containing low concentrations of residual “free” gossypol. This procedure promises to provide another analytical tool for the study of residual material in processed cottonseed meal that causes egg discoloration when fed to laying hens. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

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.     

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.     

Practical significance of gossypol in feed formulation

It has been recognized that gossypol has a limiting effect on the usage of cottonseed meal in nonruminant rations. Extensive research supported by practical experience has shown that cottonseed meal may be a major oilseed supplemental protein source in nonruminant rations when care is taken to accept and adjust for gossypol limitations. Scientifically derived gossypol limitations will not significantly restrict cottonseed meal usage in practical nonruminant rations. Presented at the Carl M. Lyman Memorial Symposium on Gossypol, AOCS Meeting, New Orleans, April 1970.     

Preparation of gossypol from cottonseed pigment glands

Summary Cottonseed pigment glands, produced from whole cottonseed meal and defatted cottonseed meal by the gland flotation process, have been investigated as a raw material for the production of gossypol. Methods based on the previously reported properties of gossypol and cottonseed pigment glands have been developed for the relatively rapid isolation of gossypol from pigment glands. Extraction of gossypol from pigment glands with acetone followed by precipitation of gossypol acetic acid from the extract was found to be the preferable method for obtaining pure gossypol in good yields. The precautions which must be applied in order to produce gossypol on a large scale by the acetone-acetic acid method are discussed together with methods for the purification and preservation of gossypol. Presented at the Fall Meeting of the American Oil Chemsits' Society, October 20–22, 1947. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Acidic ethanol extraction of cottonseed

Ethanol (EtOH) is being evaluated as an alternate solvent to hexane for the extraction of glanded cottonseed. Hot EtOH, needed for efficient oil and aflatoxin extraction, binds gossypol to protein. However, this binding can be minimized by acidifying aqueous EtOH with a tribasic acid, such as phosphoric or citric. While this solvent extracts oil and gossypol, it does not affect EtOH’s ability to extract aflatoxin. The defatted cottonseed meals produced from this process contained 0.03% total gossypol (which is lower than meal prepared by most other processes) and the aflatoxin content was reduced from 69 to 2.9 ppb. These are preliminary results and additional research is needed to determine commercial feasibility. The removal of essentially all gossypol from an extracted meal has the potential to expand the use of cottonseed meal as a feed, increasing its value to both the cotton farmer and the seed processor. Presented in part at the 40th Oilseed Processing Clinic, March 4, 1991, New Orleans, LA.     

Evaluation of cottonseed meals prepared by extraction with acetone-hexane-water mixtures

Eleven cottonseed meals have been prepared by batch extractions of a given lot of cottonseed with various acetone-hexane-water mixtures using several different extraction schedules. These meals, together with eight meals of commercial origin and a commercial soybean meal, have been subjected to chemical evaluation and assayed for protein quality using the growing chick as a test animal. In general the acetone-hexane-water meals were superior to the commercial cottonseed meals for promoting the growth of the chicks and, considering all the meals, a linear correlation was obtained between the logarithm of the weight gains and the available lysine contents of the meals. The free and total gossypol contents of the cottonseed meals appeared to have little or no influence on the growth rates. Presented at the 52nd Annual Meeting of the American Oil Chemists' Society, St. Louis, Missouri, May 1–3, 1961. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Combined Production of Biodiesel and Nontoxic Cottonseed Meal Using Two‐Step Two‐Phase Solvent Extraction

The preparation of biodiesel and nontoxic cottonseed meal from cottonseed by two‐step two‐phase solvent extraction (TS‐TSE) combined with the transesterification reaction was investigated. The TS‐TSE process could significantly reduce the biodiesel production costs when compared with the two‐phase solvent extraction (TSE) process due to the reduction in methanol. A series of experiments was conducted to evaluate the effects of some factors on the fatty acid methyl ester (FAME) yield and free gossypol (FG) content. These conditions resulted in a maximum FAME yield and reduced the FG content in the cottonseed meal far below the Food and Drug Administration standard. The nontoxic cottonseed meal could be used as animal feed protein source.     

Biological vs. Chemical evaluation of toxicity and protein quality of cottonseed meals

Summary 1. Toxicological evaluation of 68 cottonseed meals in rats failed to show a direct correlation between their toxicity and their free, total or combined gossypol content. The common practice of considering the free gossypol content of cottonseed meal as a yardstick for its toxicity is questioned. 2. There was poor correlation between biologically evaluated protein quality of cottonseed meals and their nitrogen solubility in 0.02N sodium hydroxide. Application of this chemical test for indicating the protein quality of cottonseed meals is likewise questioned on the basis of existing evidence. Presented at the Conference on Cottonseed Meal Quality as Related to Processing, Southern Regional Research Laboratory, New Orleans, La., January 24–25, 1955.     

A modification of the p-anisidine method for the determination of free and total gossypol

Summary A modification of the Pons and Guthrie method for determining free gossypol in cottonseed materials is presented. The use of aniline, rather than p-anisidine, as the color-producing reagent is necessary if meals containing dianilinogossypol are to be analyzed correctly. Increasing the reaction temperature eliminates a serious weakness in the method and results in greater accuracy. The proposed method is applicable to all types of cottonseed meal now marketed. A slight modification of the Pons method for total gossypol is also presented. By doubling the strength of the oxalic acid used to hydrolyze bound gossypol and by using aniline to develop the color, the method is made applicable to chemically treated meals containing dianilinogossypol. Presented at 45th annual meeting, American Oil Chemists' Society, San Antonio, Tex., Apr. 12–14, 1954.     

Continuous extrusion cooking of cottonseed kernels and of partially defatted meal

Continuous extrusion cooking produces a short time pressure cooking of the material in process. The Wenger extruder-cooker has been successfully applied by others to soybeans for manufacture of full fat flour. This is a report of an investigation of the extruder-cooker applied to glanded cottonseed kernels and to partially defatted cottonseed meal. The purpose was production of cottonseed flour for human food. The principal objective in extruder processing was lowering of free gossypol to 0.12% of protein. On full fat kernels the extruder system was effective in lowering free gossypol. Most of the binding occurred in the preconditioner, and the extruder itself was relatively ineffective in binding gossypol. However the contribution of the extruder was necessary to allow free gossypol levels of 0.12% of protein to be reached. Flaked kernels cooked in this manner and then dried were successfully screwpressed. The extruder system was effective also in binding gossypol in ground, screened (through 30 mesh) meal but not in ground, unscreened meal. Presented at the AOCS Meeting, San Francisco, April 1969.     

Feed value and protein-quality determinations on cottonseed meals

Summary Twenty-four cottonseed meals fed to chicks in practical feeding rations for eight weeks led to good growth performance and favorable feed efficiency in many cases, despite the unusually high free gossypol content of the rations. The results from replicated, protein-quality evaluations in chicks fed for eight weeks at the 15% protein level were closely parallel to those from similar experiments in rats fed at the 9% protein level and showed that the percent nitrogen solubility in 0.02N sodium hydroxide of cottonseed meals is a poor indicator of protein quality. Constant gossypol levels of 0.1%, supplied by additions of different amounts of cottonseed pigment glands, caused greater body-weight depressions than did the same gossypol level supplied by pure gossypol. The toxicity of cottonseed pigment glands and of cottonseed meals cannot be accounted for solely on the basis of analyzed gossypol content.     

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.     

The plant geneticist’s contribution toward changing the lipid and amino acid composition of cottonseed

Gossypol is well known to be responsible for the troublesome dark color of cottonseed oil. It may depress growth, cause discoloration of eggs, and create metabolic disturbances when fed to nonruminant animals in excessive amounts. All but a trace of seed gossypol is contained in pigment glands present in the cottonseed kernel. Genetical research conducted by USDA scientist, S.C. McMichael, led to his discovery of a glandless seeded cotton in 1953. Glandless cottonseed are essentially free of gossypol. Using McMichael’s genetic lines as gene sources, cotton breeders have developed breeding programs in the last 10 years from which three commercial glandless cotton varieties have so far been released. More glandless cotton varieties are on the way. Due to the elimination of gossypol, the color of the oil and utility of the meal from glandless cottonseed is distinctly superior to that from glanded cottonseed. The advent of glandless cottonseed, its potential value in the field of human protein nutrition, and the success in breeding improved oil and protein quality in other oilseeds, have recently caused cotton geneticists to become interested in the possibility of genetically manipulating lipid and amino acid composition in cottonseed. However specialized genetic techniques involving interspecific gene transfer or use of wild photoperiodic uplands may be required in making such improvements. One of seven papers presented at the Symposium, “The Plant Geneticist’s Contribution Toward Changing the Lipid and Amino Acid Composition of Oilseeds,” AOCS Meeting, Houston, May 1971.     

Gossypol material balance,denaturation of protein,and loss of thiamine in commercial processing of cottonseed

Summary The processing of cottonseed by five commercial mills has been systematically examined with reference to free gossypol reduction, nitrogen solubility, thiamine reduction, material balances of total gossypol, and the distribution of gossypol in processing. One hydraulic mill reduced the free gossypol in the meal to a low level, approximating the level obtained in screw pressing. For a given mill the free gossypol contents of the meals were found to be fairly uniform. Low free gossypol content of hydraulic-pressed meals depends on the thoroughness with which the gossypol is bound in the cooking. Gossypol is bound in both the cooking and pressing in the production of screw-pressed meals. A relatively small amount of total gossypol is lost or destroyed in processing cottonseed by either hydraulic- or screw-pressing methods. This small loss occurs while the meats are being prepared for pressing. No significant loss was found which could be attributed to the pressing operations. Serew-pressed oils appear to contain several times as much gossypol as hydraulic-pressed oils, with the amount dependent on the extent of the binding of gossypol in the cooking and mechanical preparation of the meats for pressing. The high temperatures developed in screw pressing contributed to a higher reduction in thiamine and nitrogen solubility than was observed for hydraulic pressing. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Determination of free and total gossypol by high performance liquid chromatography

Existing HPLC methods determine only pure gossypol whereas the official AOCS method determines both gossypol and other physiologically active gossypol-like compounds that react with 3-amino-1-propanol and aniline. The feed industry uses the official AOCS method, which is complex and produces results that do not correlate well among laboratories. HPLC methods were developed, using 3-amino-1-propanol as a complexing agent, for the quantitative determination of free and total gossypol in cottonseed meal, oil, and ethanolic miscella. These methods are simple, sensitive, and provide reproducible results. In addition the use of toxic aniline is eliminated.     

The pigments of cottonseed

Summary A method for the purification of gossypol has been developed which yields material differing in optical properties from those previously reported for gossypol preparations. A colorimetric test for extractable gossypol has been described. It has been shown that cottonseed contains at least three pigments in addition to gossypol. Some of the properties of the three pigments have been reported. One of these newly detected pigments, gossypurpurin, has been shown to be the substance which, mixed with gossypol, constitutes the so-called “red gossypol” of Podol’skaja. The frequently reported water-dispersable blue pigment of cottonseed has been shown to be either a complex of gossypol, gossypurpurin and protein or a mixture of two protein-pigment complexes. Its dissociation into the two pigments and protein has been accomplished. Presented before the 34th Annual Meeting of the American Oil Chemists’ Society, New Orleans, Louisiana, May 12–14, 1943.     

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.