The effect of processing conditions on the properties of screw-press cottonseed meal and oil

Summary Processing conditions, particularly cooking procedures, have a marked influence on the chemical properties of screw-pressed meal and oil. Cooking prepared meats at 240–250°F., as in normal mill practice, produced meals with low free gossypol content but at the expense of considerable protein damage. The resultant crude oils showed some color reversion upon storage at 95°F. Dry cooking (7% moisture) at temperatures not exceeding 200°F. gave meals of improved chemical properties, but the crude oils exhibited considerable color reversion on storage. Wet low-temperature cooking (200–210°F.), followed by evaporative cooling, yielded a meal intermediate in quality between that for normal mill practice and dry low-temperature cooking. The crude oils, which corresponded to hydraulic-pressed oil, did not exhibit any appreciable color reversion upon storage at elevated temperatures. The selection of processing conditions, notably cooking, enables wide variations in the distribution of gossypol between meal and oil. The increase in the bleach color of crude oils stored at 95–100°F. was found to be directly related to the initial gossypol content of the crude oils. Presented at 44th Annual Meeting of the American Oil Chemists’ Society, New Orleans, La., May 4–6, 1953. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Service, U. S. Department of Agriculture.     

Note on gossypol and its relation to color fixation in cottonseed oil

1. The crude oils studied contained from 0.00 to 0.04% gossypol.
2. Much of the gossypol added to crude cottonseed oils disappeared in one hour.
3. The disappearance of gossypol from refined, bleached, and deodorized cottonseed oil, from highly purified tripelargonin, and from ethyl acetate is demonstrable after the lapse of one hour.
4. It is suggested that the initial reaction of gossypol in the oils is an ester exchange reaction.
5. It is further suggested that secondary reactions result in the production of a red coloration product that is not removable from the oil by the standard refining and bleaching methods.

     

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.     

Studies on the pigments of some citrus,prune and cucurbit seed oils when processed with or without cottonseed oil

Pigments of citrus, prune and cucurbit fruit seed oils were studied spectrophotometrically. The citrus fruits used were: orange (O), mandarin (M), bitter orange (BO) and lemon (L). The prunes used were apricot (A), peach (P) and plum (PL); while melon (M), watermelon (WM) and Winter squash (S) were the cucurbits. Absorption spectra and Lovibond color were studied for crude, refined and bleached oils. Cottonseed oil (CSO) was mixed with some of the previous oils in the crude state, then refined and bleached. Absorption spectra of the crude fruit seed oils revealed carotenoid pigments at 400, 425, 455 and 480 nm, chlorophyll at 610 and 670 nm and unknown pigments at 525, 570 and 595 nm. Refining did not remove these pigments, whereas bleaching eliminated them completely. In oil mixtures of CSO+A, CSO+M and CSO+S, interference occurred between gossypol ‘360 nm’ from CSO and the pigments of A, M and S seed oils. Refining the oil mixtures removed gossypol, but its effect on carotenoids, chlorophyll and unknown pigments was limited. Bleaching completely removed all these residual pigments. Lovibond color for all bleached oils was very low (0.2–2 yellow). The refined oils, except those containing Winter squash seed oil, were found to have an acceptable color (0.8–15 yellow). Results of the proposed process reveals the possibility of mixing crude edible oil with crude fruit seed oils, then processing the oil mixture by the conventional methods of refining and bleaching.     

Rice brain oil. I. Oil obtained by solvent extraction

1. Freshly milled rice bran has been extracted with commercial hexane and the recovered oil and extracted meal examined for their respective content of wax. The oils were refined and bleached by standards as well as several special methods. The crude, caustic soda refined, and several refined and bleached oils were examined spectrophotometrically.
2. When freshly milled rice bran of good quality is extracted with commercial hexane, an oil of relatively low free fatty acid content is obtained. This oil possesses good color and is as stable as other similar types of crude oils.
3. If the oils is extracted from the brain at a temperature below about 10°C. and the extraction is discontinued at the right time, the extracted oil represents 90–95% of the total lipids in the brain and contains very little wax. This wax, which is readily extracted with hot commercial hexane as well as other types of solvents, amounts to about 3–9% of the total extractable lipids.
4. When subjected to ordinary caustic soda refining methods, good rice brain oils behave much like cottonseed oils of comparable free fatty acid content. Both caustic soda refining in a hydrocarbon solvent and refining with sodium carbonate result in refining losses approximating the absolute or Wesson loss.
5. Some of the refined oils when bleached according to usual practice produce products acceptable for use in the edible trade. However, refined rice bran oil has a definitely greenish cast resulting from the presence of chlorophyll, but this color can be removed by bleaching with a small amount of activated acidic clay.

     

Effect of temperature on the content of pigments of stored cottonseed

Summary Three pure-bred varieties of cottonseed,G. hirsutum, which were planted and grown under similar environmental conditions were stored at 38°, 77°, and 85°F. After determining the initial contents of lipids, nitrogen, moisture, gossypol, and gossypurpurin each lot of seed was stored at the different temperatures and analyzed periodically with respect to changes in pigmentation. The content of gossypurpurin was found to increase during storage in all of the samples. Its increase was proportional to the temperature and length of storage. On the other hand, gossypol decreased during storage of all samples. The antimony trichloride test for gossypol was found to be applicable only to extracts prepared from fresh cottonseed. During storage of the seed another yellow-colored pigment(s) developed which could be separated from gossypol by alkaline extraction of the original chloroform extract of the stored seed. The alkali extractable portion of the chloroform extract gave a red-colored antimony trichloride reaction product characteristic of gossypol. It is postulated that at least a fraction of the non-acidic pigment(s) in the crude chloroform extracts obtained from stored cottonseed is diaminogossypol. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Report of the Du Bosq colorimeter committee

1. The DuBosq Colorimeter is a beautiful instrument for measuring the relative amounts of the same coloring matter in two different liquids, providing the liquids are optically the same, and the coloring matter the same in both liquids.
2. Cotton Seed Oils contain several different coloring matters.
3. The effects of decomposition of the seed and the various conditions used in refining processes affect the light absorption of the oils, and the characteristics of the color.
4. These differences are made painfully apparent by the DuBosq instrument.
5. It seems quite apparent, considering the limitations of the human eye and the great differences of hue and brilliancy of different oils, that any system of numerically recording color differences must allow reasonable tolerances.
6. Although results to date appear discouraging, it is believed that by the aid of a modified Du-Bosq instrument a satisfactory practical method of oil colorimetry may yet be developed if carefully worked out.

     

Processing of cottonseed

Summary Processing of cottonseed by the hydraulic press method has been carried out at two mills, one located about 100 miles farther south than the other. The varieties of seed processed and conditions during processing, which included cooking of moistened seed, were essentially the same at both mills. Seed was also processed at the more southerly mill by the screw press method for which seed was cooked without added moisture. The crude hydraulic- and screw-pressed oils produced at the two mills were stored at different temperatures for a total of ten months, and samples of the oils were periodically refined and bleached. Seed was also stored at the two mills, and was periodically processed for comparison of the oils produced from stored seed with the stored oils. The absorption spectra of the crude, refined, and bleached oils were determined. The rate of increase of bleach color in the oils during storage of the seed and crude oils has been correlated with temperature of storage and changes in the absorption spectra of the oils. Presented before the 38th Annual Meeting of the American Oil Chemists' Society, New Orleans, Louisiana, May 20–22, 1947. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Oxidative stability of high-fatty acid rice bran oil at different stages of refining

The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude ≥ degummed > bleached = deodorized > alkali-refined oil.     

Gossypol content and refining losses on crude cottonseed oil

Summary 1. Gossypol has been found to be almost universally present in hot pressed crude cottonseed oils from all of the important cotton growing sections in the United States. 2. The average amount found in crude oils from 62 scattered mills was 0.05 per cent. The highest percentage found in a hot pressed oil was 0.210. Only 7 out of 124 oils failed to show the presence of gossypol. 3. Since gossypol content was not found to be proportional to deviation from average refining loss, it was concluded that at least a portion of the gossypol occurs in the oil in the bound state, associated with protein fragments.     

The processing and storage characteristics of glandless cottonseed

Two consecutive storage tests of seven and six-months' duration were conducted to determine the relative effects of adverse storage conditions on glandless and glanded cottonseed and the products derived from each. The moisture conditions during storage resulted in extreme quality deterioration in both glandless and glanded seed. The damage sustained by glandless seed was not substantially different from damage occurring to glanded seed. Neither did glandless seed appear to deteriorate at a faster rate. Normal direct solvent extraction processing methods were followed to process seed for products quality evaluations as measured by nitrogen solubility, epsilon amino free lysine, and gossypol content for meals and FFA, cup refining loss, refined color, bleach color and gossypol content for oils. Oil from glandless seed refined and bleached to lower AOCS colors than corresponding glanded seed oils. Refining losses for oils from damaged seed were slightly higher for glandless seed oils. The meal quality from glandless seed was superior in all categories measured. A laboratory of the Cotton Research Committee of Texas operated by the Texas Engineering Experiment Station.     

Improved method for determining gossypol in crude cottonseed oils

Summary The p-anisidine method for the determination of gossypol in crude cottonseed oils has been reinvestigated and modified to make it applicable to all crude oils obtained by the newer methods of processing cottonseed. The modifications included a change in the composition of the solvent, a higher reaction temperature, and the use of a more concentrated panisidine reagent. The modified method was found satisfactory where different colorimeters and spectrophotometers were used for measuring the color developed. Comparison of aniline and p-anisidine as reagents for the analysis of gossypol pigments showed that the presence of modified gossypol in some crude oils resulted in an over-correction for background absorption and led to significant errors when aniline was used as the color development agent. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Characterization of oils from low-gland and glandless cottonseed

New varieties of cotton which contain few or no gossypol pigment glands are being developed. Commercial production of such varieties should contribute to improving meal quality and reducing the color problems encountered with cottonseed oil. Samples of gland-containing, low-gland, and glandless seed grown in California were obtained, and the oils were extracted and characterized. With regard to the over-all characteristics the oils from the low-gland and glandless seed were indistinguishable from regular cottonseed oil. Iodine values, contents of unsaponifiables, cloud- and pour-points, response to the Halphen test, and similar characteristics resembled those of commercial cottonseed oil. No differences were found in behavior during winterization. Determination of the component fatty acids by gas chromatography showed the fatty acid composition of the oils to be typical. Determination of the positions of the double bonds in the unsaturated acyl groups showed no differences between the oils from gland-containing, low-gland, and glandless seed. Ultraviolet, visible, and infrared spectra of the oils revealed no differences other than the presence of gossypol in the crude oil from the gland-containing seed. The infrared spectra of the unsaponifiable fractions obtained from the oils showed some differences, which were not believed to be important. Presented at the fall meeting, American Oil Chemists’ Society, New York, N.Y., October 17–19, 1960. Trainee, Institute of International Education, UNESCO (present address: Union of Burma Applied Research Institute, Rangoon, Burma). One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Rice bran oil. V. The stability and processing characteristics of some rice bran oils

1. The extraction, processing, characteristics, and stability properties of nine batches of hexane-extracted rice bran oil were investigated. The oils were refined, bleached, and deodorized and their color and stability determined. Samples of the bleached oils were hydrogenated to approximately shortening consistency, deodorized, and the stability of the hydrogenated products determined.
2. Pilot plant extractions of five batches of rice bran yielded crude oils equivalent to 91% of the hexane-soluble portions of the bran.
3. The nine crude oils whose content of free fatty acids ranged from 2.0 to 6.3% were refined by the cup method with losses ranging from 12.0 to 23.5% although the neutral oil content of six crude rice bran oils ranged from 89.9 to 92.6%.
4. The Lovibond color of the nine refined oils ranged from 35 yellow and 4.5 red to 70 yellow and 9.5 red, and the color of the bleached oils ranged from 15 yellow and 1.5 red to 35 yellow and 3.2 red.
5. Steam-refining, employed in conjunction with alkali-refining, proved effective as a means of reducing the losses in refining rice bran oil.
6. The nine batches of refined, bleached, and deodorized rice bran oils had iodine values ranging from 101.3 to 105.7 and stabilities averaging 24 hours.
7. Nine bleached oils hydrogenated to approximate shortening consistency had iodine values averaging approximately 66 and stabilities averaging 370 hours.
8. Refined, bleached, and deodorized rice bran oil is bland but has some tendency toward flavor reversion.
9. The most outstanding characteristics of rice bran oil is its exceptional stability after hydrogenation.

     

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.     

A quantitative evaluation of a color problem in safflower oils

The dark color occasionally found in crude solvent-extracted oils from a new high-yield brown striped safflower variety originates from colorless precursors in the kernel and precursors in the hull. The precursors from the hull and the pigments formed upon heating from hull and kernel precursors are only partially removed by refining and bleaching if they are present in substantial amounts. The pigment precursors extracted from the kernels are completely removed by precipitation with water or refining. Although substantially more hull and kernel precursors are found in oil from the brown striped safflower variety, the oil can be produced in a spectrographic quality comparable to that of commercial oil if the crude extracted oil is not heated above 100 C, and if extracted and press oils are jointly refined.     

Storage of cottonseed and peanuts under conditions which minimize spectrophotometric changes in the extracted oil

1. Cottonseed was stored for over a year without appreciable change in red gossypol content by adjusting the moisture content to 8% or less and placing in closed containers at 1° or at −18°C. Cottonseed stored at room temperature, 27°C., showed a large increase in red gossypol content.
2. Cottonseed stored in the above manner at 1° or at −18°C. showed little or no increase in the non-gossypol absorption of the extracted oil at 236 mμ, the region of diene conjugation. This property of the extracted oil showed a large increase when cottonseed was stored at room temperature, 27°C.
3. Gossypol dissolved in cyclohexane has spectrophotometric extinction coefficients (concentration in g. per liter, solution depth 1 cm.) of 207, 70, and 40 at the maxima at 236 mμ, 286 mμ, and 358 mμ, respectively.
4. The extracted oil from peanuts stored for over four years at room temperature, 27°C., showed a much greater absorption in the region of 227 mμ to 234 mμ than did peanuts stored for the same time at 1° or at −18°C.

     

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 pigments of crude cottonseed oils. I. The inhibition of color reversion in crude cottonseed oils

Summary Treatment of freshly prepared crude cottonseed oils withp-aminobenzoic acid and subsequent removal of the di-p-carboxyanilinogossypol formed makes it possible to store the oils at a relatively high temperature (37–38°C.) and for an extended period of time (30 days) without incurring any adverse changes in the refining and bleaching properties of the oils. In addition, a considerable decrease in the refining loss of the crude oil is obtained, and the stability of the bleached oil is not affected by the treatment. Spectrophotometric studies made during all phases of the chemical treatment and during the refining and bleaching procedures show that thep-aminobenzoic acid removes almost completely the gossypol-like pigments which are present in the crude oils and yields oils having the characteristic carotenoid spectrum. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Pilot plant development of the alkali cooking process for cottonseed meats. I. Effect of flake,thickness and of time,temperature, and moisture content during cooking

Summary and Conclusions Results obtained from alkaline cooking experiments show that all of the four variables studied—cooking mousture content, temperature, time and flake thickness—influenced the properties of the resultant meals in varying degrees. Under the experimental conditions used a high initial moisture content, above 18%, is necessary to lower the free gossypol content in the finished meal to less than 0.04%. When this amount of moisture is used, a plastic mass results at the beginning of the process which requires special equipment to supply the mechanical action necessary to break the pigment glands at a low temperature. In the presence of high moisture content and alkali the gossypol, which is released when the glands are ruptured, is bound to the meal. When sufficient initial moisture is present (24–31%), only traces of gossypol (0.010% or less) are found in the extracted crude oil. High temperatures in the presence of high moisture content reduce the solubility of the meal protein (in 0.02N NaOH). Under the conditions of moisture, temperature, and time of cooking used in the experiments the maximum nitrogen solubility obtained under conditions necessary to produce low free gossypol content was 64%. This differs from results obtained in previous work performed under different conditions. A probable reason for the difference is given based on the interrelationship of the three variables. The results demonstrated further that finer comminution of the raw meats by rolling to 0.005-in. thick flakes results in lower free gossypol content in the finished meal and lower gossypol content of the oils as well as more complete removal of the oil by the filtration-extraction procedure used. One of the laboratories of the Southern Utilization Research Branch. Agricultural Research Service, U. S. Department of Agriculture.