Conductivity analysis for free fatty acids in oil from glandless cottonseed

Attempts to determine free fatty acids in petroleum ether extracts of cottonseed and crude cottonseed oil by conductivity measurements were unsuccessful due to interference of gossypol. With new strains of glandless cottonseed, which do not contain gossypol, analysis of free fatty acids by conductivity was successful on both the petroleum ether extracts and on the crude oil. An important advantage of conductivity over titration is that sample preparation is eliminated, since conductivity measurements are made on the oil extracts from the total oil determination.     

Comparative study of the extraction and measurement of cottonseed free fatty acids

Crude oil was extracted from cottonseed by three different methods to study the influence of extraction technique on the free fatty acid (FFA) concentration. Extraction procedures that recovered more oil had higher levels of FFA. In addition, the highest concentration of FFA was found in oil recovered by Soxhlet reextraction of a meal initially defatted by a room-temperature extraction process. The FFA concentrations of oils recovered by Soxhlet extraction were highly correlated with the FFA concentration of oils recovered by the other extraction methods studied (R ²>0.96). Titration of oil and gas chromatography of silylated oil were compared as methods to determine FFA concentration. The methods compared well (R ²=0.998) with the titration method, giving ∼5% higher values for FFA than the chromatography method. Half of this difference appeared to be due to the oleic acid approximation used in the titration approach. The other half of the difference is likely due to the detection of other acidic components in crude oil.     

Mycoflora,aflatoxins and free fatty acids in California cottonseed during 1967–1968

In central California, neither fungal infections nor aflatoxins are significant problems in cottonseed during the receiving and storage seasons. However, in southern California, the 1967 harvest contained a relatively high percentage of seed which were invaded before harvest by fungi, includingAspergillus flavus. Seed infection and concentrations of aflatoxins in seed increased significantly during the time between harvest and storage in southern California. For a short time during storage, seed infection byA. flavus increased because of the moisture the seed received late in the season; however, aflatoxin concentrations in seed did not increase in storage. The aflatoxin content of the seed removed from storage was a reflection of the relative amount of aflatoxins the seed contained when they were received for storage. In 1967, the conditions that existed in the large, densely packed seed pile did not favor accummulation of aflatoxins in seed, even thoughA. flavus was active.     

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.     

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.     

Hydrogenation of cyclopropenoid fatty acids occurring in cottonseed oil

The hydrogenation of cyclopropenoid acids and their relative reactivities during hydrogenation as compared to linoleic and oleic acids were examined. Pure methyl sterculate and purifiedSterculia foetida oil and its methyl esters, which have a cyclopropene content more than 60 times that of cottonseed oil, were used for the hydrogenation experiments. Nickel, palladium and platinum catalysts were used. The effect of temperature and type of catalyst were demonstrated in a series of hydrogenation experiments of safflower andS. foetida oil mixtures, and methyl oleate and methyl dihydrosterculate mixtures. Partial hydrogenation of methyl sterculate formed as many as twenty compounds in addition to the cyclopropenoid derivatives. Most of these compounds were monounsaturated. The cyclopropene group hydrogenated very readily compared to the 9,12-diene system in linoleate. The cyclopropane group obtained by hydrogenating the cyclopropenoid acids group was quite resistant to further attack by hydrogen and nickel catalyst had little effect. With palladium catalyst, a temperature of 180 C was necessary for the reaction to go to completion. Platinum in acetic acid was a good system for hydrogenolysis of the cyclopropane group at 80 C. Retired.     

Quantitative determination of cyclopropenoid fatty acids in cottonseed meal

A rapid analytical procedure for determining the residual cyclopropenoid fatty acids (CPA) in cottonseed meal has been developed. The procedure involves room-temperature extraction of crude CPA-containing lipids with a hexane-water-acetone azeotrope solvent, followed by a benzenemethanol wash. The crude lipids are then converted to methyl esters by methanolysis with sodium methoxide. Extraction with petroleum ether, followed by washing with aqueous acetone, results in a substance which is free from interfering materials. The purified methyl esters are then analyzed for CPA by a spectrophotometric modification of the Halphen reaction.     

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.     

Some observations on the increase of free fatty acid in cottonseed

The foregoing tests were conducted in the laboratory to observe the tendencies of seed to form free fatty acid when subjected to certain atmospheric and temperature conditions. The results of individual tests are given in all cases to elicit a discussion from others who may have conducted similar tests in hopes of arriving at more definite conclusions or to arrive at properties which may be attributed as common to all cotton seed. The following statements are to be taken merely as tendencies and by no means as conclusive. Cottonseed having less than 10 per cent moisture will remain stable under ordinary storage conditions. Seed of 10 to 14 per cent moisture may or may not remain stable while seed having 14 per cent or more moisture will deteriorate in storage with a rapid increase of free fatty acid. Deterioration of high moisture seed is inhibited either by cold storage or by heating seed to reduce moisture content. Seed pre-heated to 175° F. to kill the germ is more sensitive than live seed to the formation of free fatty acid in moist atmosphere. More experimental work is necessary to prove whether or not all cotton seed will increase appreciably in free fatty acid when subjected to the pre-drying treatment as prescribed by the official method of the National Cottonseed Products Association for determining this constituent.     

Chemical inactivation of cyclopropenoid fatty acids in cottonseed meals and their physiological evaluation

Chemical inactivation of cyclopropenoid fatty acids in commercial cottonseed meals was explored with three classes of compounds: anhydrous gases, organic acids and sulfhydryl compounds. Of the reagents screened, sulfur dioxide reduced the cyclopropenoid content by over 90% while free cottonseed fatty acids and thioglycollic acid reduced the cyclopropenoid fatty acid content by over 30%. Large batches of the above three selected meals, as well as a control commercial screw-pressed meal, were then incorporated at 20 wt % levels in the rations of laying hens. A negative control containing 25% soybean meal and a positive control containing a 2% refined cottonseed oil of known CPA content were also employed. During a four-week feeding period, eggs were collected during the third and fourth week and stored at 35 F for periods of 3 and 6 months. Overall egg quality and the fatty acid distribution of the yolk lipids were determined after the 3 and 6 months’ storage periods.     

Removal of cyclopropenoid fatty acids from cottonseed meals by solvent extraction

Direct solvent-extraction procedures were explored for their effectiveness in removing the residual levels of cyclopropenoid fatty acids from commercial cottonseed meals. Of the seven solvent systems screened, a simple stepwise extraction with an acetone/hexane/water azeotrope was found suitable for the removal of up to 88% of the original CPA content of the meal.     

Cyclopropenoid fatty acids in abutilon ramosum seed oil

Seed oil of Abutilon ramosum was found to contain the following fatty acids (wt.%): malvalic (2.48%), sterculic (1.29%), myristic (1.0%), C₁₅:0 (1.78%), palmitic (19.1%), palmitoleic (0.51%), stearic (6.53%), oleic (23.72%), linoleic (42.55%) and linolenic (0.91%). The qualitative and quantitative analysis of the fatty acids were carried out by HBr-titration and the gas-liquid chromatography of the silver nitrate-methanol-treated esters using the fatty acid esters of the oil of sterculia foetida as reference standard.     

Novel fatty acids in azima tetracantha seed oil

Azima tetracantha Lam, belonging to the Salvadoraceae plant family, was found to contain ricinoleic acid (9.8%) and cyclopropenoid fatty acids (9.6%) along with normal fatty acids.     

Dihydroxy fatty acids inCardamine impatiens seed oil

The oil ofCardamine impatiens L. (Cruciferae) seed includes glycerides of a series of saturated long-chain vicinal dihydroxy fatty acids, which make up 25% by weight of the mixed fatty acids. The mixture of diols, after transesterification of the oil with methanol, can be crystallized from an ether solution of the mixed methyl esters and has the following composition: methyl 13,14-dihydroxydocosanoate, 66%; methyl 15,16-dihy-droxytetracosanoate, 24%; methyl 9,10-dihydroxyoctadecanoate and methyl 11,12-dihydroxyeicosanoate, about 5% each. Chemical proof is presented showing that essentially all the diols have thecrythro configuration. Presented at AOCS meeting, Chicago, Ill., October 1964. A laboratory of the No. Utiliz. Res. and Dev. Div., ARS, USDA.     

Keto fatty acids formCuspidaria pterocarpa seed oil

The seed oil ofCuspidaria pterocarpa contains three keto fatty acids with unusually long carbon chains: 15-oxo-cis-18-tetracosenoic (5.4%), 17-oxo-cis-20-hexacosenoic (13.4%), and 19-oxo-cis-22-octacosenoic (3.3%) acids. These acids were isolated by countercurrent distribution of the corresponding methyl esters. Their structures were established by oxidative degradation, by reduction to known compounds, and by nuclear magnetic resonance and infrared spectra. Presented at the AOCS Meeting, Los Angeles, April 1966. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Rapid colorimetric determination of free fatty acids

In 1964, a method was described for the determination of free fatty acids (FFAs) in vegetable oil. This paper describes an expansion of that work, improving the sensitivity and reproducibility of the method, as well as examination of solubilities of the copper soaps as a function of chain length and unsaturation. Involvement of the micellar structure was reviewed. Finally, a procedure is described that permits very rapid determination of FFA at the 2.0–14.0 μmol (0.5–4.0 mg oleic acid) level, and the results with several oils are given. Particular attention was given to evaluation of solvent systems which would extract the copper complexes. Presented in part at the AOCS Meeting in San Francisco, April 1969. Technical Paper No. 4036, Oregon Agricultural Experiment Station.     

Urea-based fractionation of seed oil samples containing fatty acids and acylglycerols of polyunsaturated and hydroxy fatty acids

The selectivity and efficiency of urea complex (UC) formation-based fractionation of free fatty acids (FFA) were examined. A rapid, simple, and inexpensive procedure recently developed for urea fractionation was applied to lipid mixtures containing various polyunsaturated and hydroxy FFA species. Urea treatment proved useful for isolating polyunsaturated FFA (PUFA) from FFA derived from fish, borage, and linseed oils by removal of saturated and monounsaturated FFA, but was not effective for isolating hydroxy FFA from the FFA derived from castor, Lesquerella, and Dimorphotheca oils. In situations where FFA within the crystalline or UC phase were rich in PUFA, the urea/FFA mole ratio of the UC was relatively higher, with lower recovery of FFA in this phase. The distribution of urea between the crystalline phase and the solvent was not significantly affected by the FFA composition of feed nor the overall ratio of FFA to urea. It was strongly dependent on the overall mass fraction of solvent. Phospholipids and mono-, di-, and triacylglycerols were poor templates for UC formation relative to FFA. Their inclusion in acylglycerol mixtures containing FFA reduced UC formation.