Concerns for the determination of free fatty acid in cottonseed

The official AOCS method for the determination of free fatty acid (FFA) in cottonseed requires dehulling the seed, grinding the meats with a 12-blade food processor, and extracting the ground meats in a butt tube with three portions of room-temperature petroleum ether. The extracted oil, after desolventization, is then titrated with NaOH to the end point of phenolphthalein in a mixed solvent of isopropanol and hexane. Our study showed that this procedure tends to underestimate the amount of FFA present in the oil of cottonseed by as much as 11.5%. It was also found that to obtain consistent and accurate FFA content, a desirable particle size is smaller than 10 mesh (preferably <14 mesh), minimum extraction temperature should be no less than 40°C (preferably greater than 50°C), and the extraction time should be longer than 2 h in a Soxhlet extractor.     

Extraction of lipids from cottonseed tissue: IV. Use of hexane-acetic acid

Hexane and mixtures of hexane and 2–25% acetic acid (v/v) were used to prepare oil and protein from glanded cottonseed by solvent extraction. As the amount of acetic acid in the solvent increased, the amounts of total lipid, phospholipid, neutral oil, and gossypol in each miscella increased, but the amount of free fatty acids did not change significantly. However, the solubility of protein in 0.02N NaOH decreased as the amount of acetic acid in the solvent used to prepare each meal increased. Other aspects of using acidified hexane are described. A preliminary report was presented at the AOCS Meeting in New Orleans, April 1973. ARS, USDA.     

Extraction of lipids from cottonseed tissue: III. Cyclopropenoid fatty acids from glanded and glandless seed

Principal storage sites of cyclopropenoid fatty acids in glanded and glandless cottonseed tissues were investigated by measuring the content of cyclopropenoid fatty acids in lipids obtained by a cytoplasmic disruptive solvent (hexane-acetone-water) and a non-disruptive solvent (hexane-acetone). The content of cyclopropenoid fatty acids in lipid obtained by either solvent did not differ quantitatively, indicating that cyclopropenoid fatty acids are not stored preferentially in extraspherosomal cytoplasm. Since this observation was also made with glanded tissue, whose glands are thoroughly disrupted by hexane-acetone-water but not by hexane-acetone, the lipoidal material of glands are also not rich in cyclopropenoid fatty acids. These observations indicate that oil-rich spherosomes are the principal sites of cyclopropenoid fatty acids, as well as the reserve oil of cottonseed, and suggest that the greater content of cyclopropenoid fatty acids in lipid prepared by increased periods of solvent-extraction is from release of binding to tissue components, rather than a thorough extraction of somewhat inaccessible (extraspherosomal) areas of tissue. Previous paper in this series is given in Reference 2. ARS, USDA.     

Extraction of lipids from cottonseed tissue: V. Ultrastructural effects of extraction with hexane-acetic acid

Cottonseed tissue was extracted with acidified hexane (hexane containing 2–25% acetic acid, v/v) and then examined with an electron microscope. In all cases, the contents of the oil-rich spherosomes were emptied and cytoplasm remained intact after lipid extraction. However, membranous elements of the cytoplasm appeared diffuse and disorganized. The possible effect of this disorganization of membranes in accounting for the greater amount of lipid extracted by acidified hexane than by hexane is discussed. Presented in part at the AOCS Meeting in New Orleans, April 1973. ARS, USDA.     

Determination of phosphorus in oils using oxygen bomb ashing

A fast method for phosphorus determination in an oil matrix is described. The principle of the method is similar to that of the AOCS method, but the ashing of the oil is accelerated using an oxygen bomb. In addition, a rapid molybdovanadate reagent is used for colorimetry rather than the molybdenum blue reagents specified in the AOCS method. Agreement with the air ashing procedure averages less than 5% difference above 10 μg/g. The detection limit is in the order of 1~2 μg/g.     

Interference of polar lipids with the alkalimetric determination of free fatty acid in fish lipids

An examination of the suitability of an alkalimetric method for the determination of free fatty acid (FFA) contents in fats, oils, and lipid extracts was conducted by comparing AOCS method Ca 5a-40 with a method based on a Chromarod-latroscan thin-layer chromatography-flame-ionization detector (TLC-FID) system. The FFA contents determined by the alkalimetric method were consistently higher than the genuine FFA contents obtained by the latroscan TLC-FID method. Phospholipids were found to be the major components that contributed to the alkali-titratable, nongenuine FFA in the total FFA determined alkalimetrically. Contributions from other polar lipid components were smaller, but they dominated as the proportion of phospholipids fell. The other alkali-titratable polar components may include oxidized lipids and their by-products bound to protein fragments. The accurate determination of FFA contents by alkalimetric methods may only be applicable to those commercially refined fats and oils that contain negligible amounts of phospholipids. Corrections for the alkalimetrically determined FFA contents should be made for those fats and oils with relatively high phospholipid contents by correlating the nongenuine FFA contents and the phospholipid contents.     

Variation of cyclopropenoid fatty acids in cottonseed lipids

The proportions of the cyclopropenoid fatty acids (CPA) esters, malvalate and sterculate, varied little in lipids from individual cottonseeds. Coefficients of variation were 10% and 20% for seeds from a lock and 13 varieities, respectively. Within the seed, variations in CPA concentrations were very large. Cyclopropenoid fatty acid concentration in the lipids decreased from 28% in the root tip to 2% in the top of the axis, and to 0.02% in the portion of the cotyledons nearest to the hull. The axial portion was only ca. 5% of the kernel, yet it contained 75% of the CPA. Distribution of dihydrosterculic acid, the precursor of CPA, was similar to that of CPA. High concentrations of CPA were found in immature seeds, root tip and radicle of germinated seeds, and root tips of cotton plants. Presented at the 73rd annual AOCS meeting, Toronto, Ontario, May 1982. One of the facilities of the Southern Region, Agricultural Research Service, U.S. Department of Agriculture. Names of companies or commercial products are given solely for the purpose of providing specific information; their mention does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Determination of oil and lipids in cottonseed meal

Two simple methods for determining total oil equivalent in cottonseed meal are described. The meal is extracted with methanol, and the crude extract is either (a) saponified and subsequently acidified to find the weight of acids set free, or (b) subjected to methanolysis to determine the weight of esters formed. When applied to a meal previously extracted with petroleum ether, these methods determine lipids. Results obtained on three commercial cottonseed meals were in excellent agreement with those obtained by the more cumbersome method requiring direct saponification of the ground meal. The methods described should also be applicable to soybean and sunflower seed meals and to other systems containing lipids, such as flours, doughs, and leaf proteins. One of the methods is particularly useful as a preliminary step in the determination of cyclopropenoid acids in cottonseed meal because much larger lated as methyl esters.     

An improved ashing procedure for the determination of heavy metals in edible oils

An accurate, reliable, and simple method was described for the determination of Pb, Cu, Cd, Mn, Zn, an d Fe in edible oils by atomic absorption spectrophotometry following burning of the sample in a restricted air supply. Recoveries for the six heavy metals by the proposed methods were about 100%. The relative standard deviation of the analysis for the lead at the level of 0.074 ppm was 6%, and the copper at the levels of 0.064 ppm and 0.158 ppm were 7% and 2%, respectively. The recovery of lead was found to be suppressed by the presence of a large quantity of iron in the oil, but the suppression was alleviated by adding a Mg(NO₃)₂ solution to the charred residue before ashing.     

Pilot-plant fractionation of cottonseed. III. Process development of differential settling

Chemical engineering data are presented to show the pilotplant process development of cottonseed fractionation employing the differential settling principle. The purpose of the process is to produce a cottonseed meal fraction essentially free of pigment glands and hulls, and a second fraction in which the pigment glands are concentrated sufficiently to serve as a raw material if pharmaceutical or other industrial use is developed for the glands or the pigments. The non-lipids fraction will make available a meal of high nutritive value and a source of industrial protein. Unit operations involved, including machinery and other equipment required, and proposed flow diagrams for commercial application are discussed. In brief the unit operations are as follows: material preparation; disintegration for proper size reduction of cottonseed flakes (either defatted or undefatted) in solvent slurries; separation by tank differential settling or by centrifugal differential settling at 62 times gravity; meal recovery to recover separated fractions by either centrifuging at 1450 times gravity or by pressure filtration; desolventization of solvent-damp meal; and oil and solvent recovery. Report of a study made under the Research and Marketing Act of 1946. Presented at the apring meeting of the American Oil Chemists' Society, held in New Orleans, La., May 1949. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research administration, U. S. Department of Agriculture.     

Spectrophotometric determination of total gossypol in cottonseed meal and cottonseed meats

Summary An improved method has been developed for the determination of total gossypol in cottonseed and cottonseed meal. The sample is heated with aniline to convert the gossypol to dianilinogossypol, which is extracted with chloroform and measured spectrophotometrically. The values for total gossypol are slightly higher and more accurate and precise as determined by the proposed method because of more complete extraction than by a recent p-anisidine method or the revised A.O.C.S. Tentative Method Ba 8-55. The advantages of the proposed method are its simplicity, accuracy, reproducibility, and expeditiousness. Published with the approval of the Director of Research, N. C. Agricultural Experiment Station, as paper No. 758 of the Journal Series.     

Determination of silica in soaps and soap flakes. Perchloric acid method

Soap and soap flakes are decomposed by nitricperchloric acid, with the aid of a catalyst. Silica is then dehydrated, filtered off, and determined in the usual manner.     

Miscella refining test method for the determination of cottonseed oil color

Most of the cottonseed oil mills in the United States have already converted to expander solvent extraction and miscella refining. This practice permits mills to produce and market a consistently light-colored, prime bleachable summer yellow cottonseed oil at reduced cost and refining loss. A laboratory-scale miscella refining test was developed to asses the oil quality in terms of its color. The test involves the addition of 3 parts oleic acid per 100 parts of crude oil in the miscella followed by refining with 2.5 parts NaOH when crude oil contains less than 4.5% free fatty acid (FFA). When crude oil contains FFA between 4.5 and 7.5%, no oleic acid is added prior to refining with 2.5 parts NaOH. When crude oil contains FFA higher than 7.5%, no oleic acid is added and the caustic addition table in American Oil Chemists' Society Method Ca 9a-52 is followed. The test was conducted at room temperature and gave reproducible colors comparable to commercially refined oils.     

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.