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.     

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.     

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.     

A new method for determining gossypol in cottonseed oil by FTIR spectroscopy

A new method was developed to determine the gossypol content in cottonseed oil using FTIR spectroscopy with a NaCl transmission cell. The wavelengths used were selected by spiking clean cottonseed oil to gossypol concentrations of 0–5% and noting the regions of maximal absorbance. Transmittance values from the wavelength regions 3600–2520 and 1900–800 cm⁻¹ and a partial least squares (PLS) method were used to derive FTIR spectroscopic calibration models for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils. The coefficients of determination (R ²) for the models were computed by comparing the results from the FTIR spectroscopy against those obtained by AOCS method Ba 8-78. The R ² were 0.9511, 0.9116, and 0.9363 for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils, respectively. The SE of calibration were 0.042, 0.009, and 0.060, respectively. The calibration models were cross-validated within the same set of oil samples. The SD of the difference for repeatability and accuracy of the FTIR method were better than those for the chemical method. With its speed (ca. 2 min) and ease of data manipulation, FTIR spectroscopy is a useful alternative to standard wet chemical methods for rapid and routine determination of gossypol in process and/or quality control for cottonseed 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.     

Isopropanol as a solvent for extraction of cottonseed oil

Phase equilibrium data for the system; cottonseed oil-isopropanol-water were determined at 30°C. and compared with data for the system; cottonseed oilethanol-water. The relative phase distribution of fatty acids and cottonseed oil in mixtures with isopropanol and water was studied under varying conditions of water and fatty acid concentrations. These tests showed the fatty acids to be highly concentrated in the alcohol-water phase. Flaked cottonseed meats were extracted in continuous extraction apparatus with 91% isopropanol, 99% isopropanol, and mixtures of commercial hexane and isopropanol. Analytical data on the extractions show that 91% isopropanol is an efficient solvent for extracting active gossypol along with the oil. Rat and swine feeding tests of the isopropanol extracted meal showed it to be highly superior to hydraulic meal as a source of protein. A method was developed for treatment of the cottonseed-isopropanol miscella by liquid-liquid extraction to separate purified oil and fatty acid fractions from other materials in the extract.     

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.     

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.     

Adsorptive gossypol removal

Gossypol is extractable from cottonseed by using aqueous ethanol. The equilibrium between undissolved gossypol in cottonseed and that dissolved in the solvent determines the residual gossypol. To move the equilibrium toward extraction from the seeds, the dissolved gossypol needs to be removed from the gossypol-solvent-oil mixture. Gossypol removal from the mixture by adsorption on alumina, silica and molecular sieve 5Å was tested. Experimental results indicated that gossypol was more selectively adsorbed than triglycerides by these adsorbents. Alumina and silica had higher gossypol adsorption capacities than molecular sieve 5Å.     

An improved ultrasound‐assisted extraction process of gossypol acetic acid from cottonseed soapstock

To investigate the extracted process of gossypol acetic acid (G‐AA) from cottonseed soapstock and explore the improvement of its yield and purity, a novel ultrasound‐assisted extraction and crystallization method was introduced to this process. Under the optimized conditions, preliminary G‐AA with the yield of 1300 mg and the purity of 95.9% could be obtained from 100 g of fresh soapstock by ultrasound‐assisted extraction. In addition, UV, IR, and NMR spectrum further confirmed the detailed chemical structure of G‐AA. Assay of inhibiting human prostate tumor cell line PC‐3 and human breast cancer cell line MDA‐MB‐231 revealed its biological activity, the values of IC₅₀ are 9.096 μmol/L and 14.37 μmol/L respectively. In comparison with the conventional solvent extraction, this novel process increases the content of G‐AA over 90%, reduces the time of crystallization by 75%, and retains the anticancer activity of gossypol. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Ethanol vapor deactivation of gossypol in cottonseed meal

Most cottonseed cultivars contain gossypol, a polyphenolic antinutritional compound. “Free” gossypol is a physiologically active form of gossypol, which is toxic to young- and nonruminant animals. To utilize solvent-extracted cottonseed meal as a general feed, gossypol must be either removed or deactivated to a minimum level specified for each class of animal. Normally, deactivation is carried out prior to oil extraction; however, the desired level of deactivation is not always attained. A new supplemental method of deactivation has been found by using either ethanol or isopropanol vapors on solventextracted meal. In a bench-top set-up, ethanol vapor reduced free gossypol from 0.115 to 0.053%, and a further reduction to 0.026% has been observed with the addition of ferrous sulfate. The supplemental deactivation method can, in most cases, reduce free gossypol to significantly safer levels for feeding, thus increasing utility, and possibly demand, for cottonseed meal as a general animal feed protein source. Presented in part at the AOCS Annual Meeting, Atlanta, GA, May 8–12, 1994.     

Color stability of glandless cottonseed oil

The color stability of oil extracted from glandless cottonseed contaminated with various levels of glanded cottonseed was studied. The rate of darkening in bleached color of cottonseed oil during storage was proportional to the original glanded cottonseed or gossypol content in the oil and to time and temperature of storage. Glandless cottonseed with 0–10% glanded seed contamination, as might be expected in commercial production of glandless cotton, yielded oil with equivalent or better color when conventionally refined and bleached after 30 days storage at 25 to 40 C than miscella refined oil from glanded cottonseed. This indicates that new oil mills for extracting glandless cottonseed need not invest in miscella-refining units in order to produce high quality oil.     

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.     

An efficient method for the purification of arachidonic acid from fungal single-cell oil (ARASCO)

PUFA, such as arachidonic acid (AA), have several pharmaceutical applications. An efficient method was developed to obtain high-purity arachidonic acid (AA) from ARASCO, a single-cell oil from Martek (Columbia, MD). The method comprises three steps. In the first step, AA was enriched from saponified ARASCO oil by low-temperature solvent crystallization using a polar, aprotic solvent, which gave a FA fraction containing 75.7% AA with 97.3% yield. The second step involved enriching AA content via lipase-catalyzed selective esterification of FA with lauryl alcohol. When a mixture of 1 g FA/lauryl alcohol (2∶1 mol/mol), 50 mg Candida rugosa lipase, and 0.33 g water was incubated at 50°C for 24 h with stirring at 400 rpm, the AA content in the unesterified FA fraction was as much as 89.3%, with ca. 90% yield. Finally, a solvent extraction procedure, in which acetonitrile was the extracting solvent, was used to enrich AA from FA fraction dissolved in n-hexane. The best results were obtained when 2 g FA was dissolved in 80 mL hexane and extracted twice, each time with 20 mL acetonitrile at −20°C, by allowing 2 h storage. This step gave a FA fraction containing 95.3% AA with 81.2% yield. By using this three-step process the AA content in the saponified single-cell oil (ARASCO) was increased from 38.8 to 95.3% with a total yield of ca. 71%.     

Extraction Separation of Rhamnolipids by n-Hexane via Forming Reverse Micelles

Rhamnolipids (RL) have been regarded to be insoluble in n-hexane. Unexpectedly, we have noticed that RL could be extracted together with vegetable oil by n-hexane at analyzing oil content of fermentation broth. This paradoxic phenomenon was assumed to be due to the formation of reverse micelles. As found in this paper, the micelle size as well as conductivity increased due to water solubilization, illustrating the formation of reverse micelles of RL in n-hexane. In this reverse micellar system, the maximal water solubility was detected to be 6.26 mol H₂O/mol RL while the reverse critical micelle concentration of RL was around 3% (w/w). Hence, it seems that the presence of water could increase the dissolution of RL in n-hexane via forming the reverse micelles of RL/n-hexane/water. Lastly, the formation of reverse micelles was further applied for extraction of RL by n-hexane. Using this method, over 99.0% of RL was extracted under the appropriate pH of 4.5. This extraction separation using n-hexane instead of chloroform proposed a much cleaner and safer strategy in RL manufacture. Moreover, the capability of RL in forming reverse micelle system could benefit the future application on improving enzymatic reactions, stabilizing nanoparticles, environmental treatment, and protein folding, etc.     

热碱法脱除游离棉酚的实验研究

介绍了用热碱法对棉籽粕进行脱酚的工艺原理,并对棉籽粕进行了脱酚实验研究。通过正交试验,热碱法脱酚的最适合条件为pH值8～9,温度60℃,时间3h,最终棉籽蛋白液棉酚含量为12×10-6,完全低于联合国咨询委员会规定的食用棉籽蛋白质中游离棉酚含量≤0.06%标准。     

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.     

The acute oral toxicity of cottonseed pigment glands and intraglandular pigments

Acute oral toxicity studies were carried out on cottonseed pigment glands, gossypol, diaminogossypol and gossypurpurin using rats as experimental animals. It was found that both diaminogossypol and gossypurpurin are considerably less toxic than pure gossypol. The pigment glands were more toxic than gossypol and it was concluded that the toxicity of pigments cannot be accounted for entirely on the basis of their gossypol content. Administration of gossypol with cottonseed oil orSterculia foetida oil, both of which contain cyclopropene fatty acids, increased the toxicity very slightly over that found when gossypol was administered in corn oil. In the case of corn oil andSterculia foetida oil, the difference was statistically significant. Less gossypol was also found in the feces when the test dose was given in cottonseed oil orS. foetida oil indicating a possible effect of the cyclopropene fatty acids in increasing gossypol absorption.     

Cottonseed preparation

Conventional methods of cottonseed preparation are reviewed and described, including seed cleaning, saw delinting, dehulling, conditioning, and flaking. The use of screw presses for prepress conditioning ahead of solvent extraction is discussed as compared to conditioning for direct solvent extraction. Newer methods and proposed alternate methods of cottonseed preparation are discussed including: abrasive delinting, acid delinting by gas and liquid acid, and the decorticating of undelinted seed. The effect of cracking rolls, moisture addition, moist cooking and flaking on gossypol gland rupture, the binding of gossypol to protein, and the effect of these processing or preparation variables on the residual oil in the extracted meal and on the oil quality are discussed.     

Removal of gossypol from cottonseed by solvent extraction procedures

Summary The relative efficiencies of organic, polar solvents and of solvent-water pairs for use in the extraction of gossypol and related compounds from cottonseed flakes were determined in a specially devised glass laboratory extractor. Of the solvents tested a butanone-water pair containing 10% of water by volume was the most effective, and chlorine-substituted hydrocarbons were the least effective. Under equilibrium conditions maximum extraction of gossypol was obtained with a butanone solvent containing 2.5% of water by weight. The rate of extraction of gossypol from cottonseed meal with butanone-water pairs increased with increase in the amount of water in the system and with increase in temperature of the extraction system. The greater amounts of water in the extraction system resulted in swelling and packing of the flakes and in a decrease in extraction efficiency. Flakes extracted at 26°C. contained 0.08% free gossypol and those extracted at 71°, 0.054%. This decrease may be due, in part, to the reaction of gossypol with the protein to form bound gossypol. Report of a study carried on under the Research and Marketing Act of 1946. This paper is No. 9 in the series on “Processing of Cottonseed” from the Southern Regional Research Laboratory. References to other papers in this series are: J. Am. Oil Chem. Soc.24, 97–108 (1947); J. Am. Oil Chem. Soc.24, 276–283 (1947); J. Am. Oil Chem. Soc.24. 362–369 (1947); J. Am. Oil Chem. Soc.26, 28–34 (1949); Oil Mill Gaz.54 (2), 12–15 (1949); Cotton Gin and Oil Mill Press51 (9), 18–20 (1950); Official Proc. Natl. Cottonseed Products Asso,55, 32–34, 36 (1951); and J. Am. Oil Chem. Soc. (in press), “The Effect of Screw Press and Hydraulic Press Processing Conditions on Pigment Glands of Cottonseed”, by D. M. Batson. F. H. Thurber, and A. M. Altschul. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.