Cottonseed oil

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Cottonseed oil is cooking oil from the seeds of cotton plants of various species, mainly Gossypium hirsutum and Gossypium herbaceum, that are grown for cotton fiber, animal feed, and oil.[1]

Cottonseed oil
Cotton seeds

Cotton seed has a similar structure to other oilseeds, such as sunflower seed, having an oil-bearing kernel surrounded by a hard outer hull; in processing, the oil is extracted from the kernel. Cottonseed oil is used for salad oil, mayonnaise, salad dressing, and similar products because of its flavor stability.[2]

Composition

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Mississippi Cottonseed Oil Co. seed house, Jackson, Mississippi

Its fatty acid profile generally consists of 70% unsaturated fatty acids (18% monounsaturated, and 52% polyunsaturated), 26% saturated fatty acids.[3] When it is fully hydrogenated, its profile is 94% saturated fat and 2% unsaturated fatty acids (1.5% monounsaturated, and 0.5% polyunsaturated).[4] According to the National Cottonseed Products Association, cottonseed oil does not need to be hydrogenated as much as other polyunsaturated oils to achieve similar results.[2]

Undesireable components in raw extract

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Gossypol is a toxic, yellow, polyphenolic compound produced by cotton and other members of the order Malvaceae, such as okra.[5] This naturally occurring colored compound is found in tiny glands in the seed, leaf, stem, tap root bark, and root of the cotton plant. The adaptive function of the compound facilitates natural insect resistance. Raw extracts that have not undergone post processing, such as hydrogenation, will also contain the undesirable component cyclopropene fatty acid, but purportedly are mostly removed during refining, particularly deodorization and also hydrogenation. As such, processed/food-grade cottonseed oils are not considered to present a health hazard from cyclopropene fatty acids.[citation needed] The three key steps of refining, bleaching, and deodorization in producing finished oil act to eliminate the gossypol level. Ferric chloride is often used to decolorize cotton seed oil.[6]

Comparison to other vegetable oils

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Properties of vegetable oils[7][8]
The nutritional values are expressed as percent (%) by mass of total fat.
Type Processing
treatment[9]
Saturated
fatty acids
Monounsaturated
fatty acids
Polyunsaturated
fatty acids
Smoke point
Total[7] Oleic
acid
(ω−9)
Total[7] α-Linolenic
acid
(ω−3)
Linoleic
acid
(ω−6)
ω−6:3
ratio
Avocado[10] 11.6 70.6 52–66
[11]
13.5 1 12.5 12.5:1 250 °C (482 °F)[12]
Brazil nut[13] 24.8 32.7 31.3 42.0 0.1 41.9 419:1 208 °C (406 °F)[14]
Canola[15] 7.4 63.3 61.8 28.1 9.1 18.6 2:1 204 °C (400 °F)[16]
Coconut[17] 82.5 6.3 6 1.7 0.019 1.68 88:1 175 °C (347 °F)[14]
Corn[18] 12.9 27.6 27.3 54.7 1 58 58:1 232 °C (450 °F)[16]
Cottonseed[19] 25.9 17.8 19 51.9 1 54 54:1 216 °C (420 °F)[16]
Cottonseed[20] hydrogenated 93.6 1.5 0.6 0.2 0.3 1.5:1
Flaxseed/linseed[21] 9.0 18.4 18 67.8 53 13 0.2:1 107 °C (225 °F)
Grape seed   10.4 14.8 14.3   74.9 0.15 74.7 very high 216 °C (421 °F)[22]
Hemp seed[23] 7.0 9.0 9.0 82.0 22.0 54.0 2.5:1 166 °C (330 °F)[24]
High-oleic safflower oil[25] 7.5 75.2 75.2 12.8 0 12.8 very high 212 °C (414 °F)[14]
Olive (extra virgin)[26] 13.8 73.0 71.3 10.5 0.7 9.8 14:1 193 °C (380 °F)[14]
Palm[27] 49.3 37.0 40 9.3 0.2 9.1 45.5:1 235 °C (455 °F)
Palm[28] hydrogenated 88.2 5.7 0
Peanut[29] 16.2 57.1 55.4 19.9 0.318 19.6 61.6:1 232 °C (450 °F)[16]
Rice bran oil 25 38.4 38.4 36.6 2.2 34.4[30] 15.6:1 232 °C (450 °F)[31]
Sesame[32] 14.2 39.7 39.3 41.7 0.3 41.3 138:1
Soybean[33] 15.6 22.8 22.6 57.7 7 51 7.3:1 238 °C (460 °F)[16]
Soybean[34] partially hydrogenated 14.9 43.0 42.5 37.6 2.6 34.9 13.4:1
Sunflower[35] 8.99 63.4 62.9 20.7 0.16 20.5 128:1 227 °C (440 °F)[16]
Walnut oil[36] unrefined 9.1 22.8 22.2 63.3 10.4 52.9 5:1 160 °C (320 °F)[37]

Physical properties

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Once processed, cottonseed oil has a mild taste and appears generally clear with a light golden color, the amount of color depending on the amount of refining.[38] It has a relatively high smoke point as a frying medium. Density ranges from 0.917 to 0.933 g/cm3 (7.65 to 7.79 lb/US gal).[39] Like other long-chain fatty acid oils, cottonseed oil has a smoke point of about 450 °F (232 °C),[5] and is high in tocopherols, which also contribute its stability, giving products that contain it a long shelf life, hence manufacturers' proclivity to use it in packaged goods.

Production of cottonseed oil
2019[40]
Country Millions of tonnes
  China 1.28
  India 1.20
  Pakistan 0.32
  Brazil 0.28
  United States 0.22
  Turkey 0.21
World 4.45

Production

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A cotton oil mill in Shreveport, Louisiana, 1941

In 2019, world production of cottonseed oil was 4.45 million tonnes, led by China and India with 56% combined of the total.[40]

Economic history

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Marketed under a variety of brand names, cottonseed oil shortening emerged as the leading substitute for lard late in the 19th century. (1912 ad)

The by-product of cotton processing, cottonseed was considered virtually worthless before the late 19th century.[41] While cotton production expanded throughout the 17th, 18th, and mid-19th centuries, a largely worthless stock of cottonseed grew. Although some of the seed was used for planting, fertilizer, and animal feed, the majority was left to rot or was illegally dumped into rivers.[42]

In the 1820s and 1830s Europe experienced fats and oils shortages due to rapid population expansion during the Industrial Revolution and the after-effects of the British blockade during the Napoleonic Wars.[42] The increased demand for fats and oils, coupled with a decreasing supply caused prices to rise sharply. Consequently, many Europeans could not afford to buy the fats and oils they had used for cooking and for lighting.[41] Many American entrepreneurs tried to take advantage of the increasing European demand for oils and America's increasingly large supply of cottonseed by crushing the seed for oil. But separating the seed hull from the seed meat proved difficult and most of these ventures failed within a few years.[42] This problem was resolved in 1857, when William Fee patented a huller, which effectively separated the tough hulls from the meats of cottonseed.[43] With this new invention, cottonseed oil began to be used for illumination purposes in lamps to supplement increasingly expensive whale oil and lard.[41] But by 1859, this use came to end as the petroleum industry emerged and the American Civil War (and the resulting end of slavery in the United States) disrupted the cotton industry.[41]

Cottonseed oil then began to be used illegally to fortify animal fats and lards.[41] Initially, meat packers secretly added cottonseed oil to the pure fats, but this practice was uncovered in 1884. Armour and Company, an American meatpacking and food processing company, sought to corner the lard market and realized that it had purchased more lard than the existing hog population could have produced.[41] A congressional investigation followed, and legislation was passed that required products fortified with cottonseed oil to be labeled as lard compound."[42] Similarly, cottonseed oil was often blended with olive oil. Once the practice was exposed, many countries put import tariffs on American olive oil and Italy banned the product completely in 1883.[42] Both of these regulatory schemes depressed cottonseed oil sales and exports, once again creating an oversupply of cottonseed oil, which decreased its value.[42]

It was cottonseed's depressed value that led a newly formed Procter & Gamble to utilize its oil.[42] The Panic of 1837 caused the two brothers-in-law to merge their candlestick and soap manufacturing businesses in an effort to minimize costs and weather the bear market.[41] Looking for a replacement for expensive animal fats in production, the brothers finally settled on cottonseed oil. Procter & Gamble cornered the cottonseed oil market to circumvent the meat packer's monopoly on the price. But as electricity emerged, the demand for candles decreased.[42] Procter and Gamble then found an edible use for cottonseed oil. Through patented technology, the brothers were able to hydrogenate cottonseed oil and develop a substance that closely resembled lard.[41] In 1911, Procter & Gamble launched an aggressive marketing campaign to publicize its new product, Crisco, a vegetable shortening that could be used in place of lard.[44] Crisco placed ads in major newspapers advertising that the product was "easier on digestion ... a healthier alternative to cooking with animal fats ... and more economical than butter."[45] The company also gave away free cookbooks, with every recipe calling for Crisco. By the 1920s the company developed cookbooks for specific ethnicities in their native tongues.[45] Additionally, Crisco started airing radio cooking programs. Similarly, in 1899 David Wesson, a food chemist, developed deodorized cottonseed oil, Wesson cooking oil.[42] Wesson Oil also was marketed heavily and became quite popular too.

Over the next 30 years cottonseed oil became the predominant cooking oil in the United States.[41] Crisco and Wesson oil became direct substitutes for lard and other more expensive oils in baking, frying, sautéing, and salad dressings. By World War Two, cottonseed oil shortages forced the utilization of another direct substitute, soybean oil.[41] By 1944, soybean oil production exceeded cottonseed oil production due to cottonseed shortages and soybean oil costs falling below that of cottonseed oil.[41] By 1950, soybean oil replaced cottonseed oil in the use of shortenings like Crisco due to soybeans' comparatively low price. Prices for cottonseed were also increased by the replacement of cotton acreage by corn and soybeans, a trend fueled in large part by the boom in demand for corn syrup and ethanol.[41] Cottonseed oil and production continued to decline throughout the mid- and late 20th century.

In the mid- to late 2000s, the consumer trend of avoiding trans fats, and mandatory labeling of trans fats in some jurisdictions, sparked an increase in the consumption of cottonseed oil,[46] with some health experts[47]: 220  and public health agencies[48] recommending it as a healthy oil. Crisco and other producers have been able to reformulate cottonseed oil so it contains little to no trans fats.[49] Still, some health experts claim that cottonseed oil's high ratio of polyunsaturated fats to monounsaturated fats and processed nature make it unhealthy.[50]

Regulation

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Cottonseed oil in Canada must be pressed from the seed of the Gossypium plant. As a single-source vegetable oil, 100% cottonseed oil must appear as "cottonseed oil" on the labels of any products sold.[51]

Cottonseed oil sold as an edible product must be processed and refined to eliminate specific components that could present as a food safety hazard, in particular gossypol, which can act as a toxin to humans, and can lead to infertility in men.[52]

Extraction

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Cottonseed oil processing steps

Cottonseed oil, like other vegetable oils, is extracted from the seed of the plant, through either mechanical processes such as crushing or pressing,[53] or by chemical processes such as solvent extraction.[54] Cottonseed oil is most commonly extracted commercially via solvent extraction.[55]

Use in food

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Cottonseed oil has traditionally been used in foods such as potato chips and was for many years a primary ingredient in Crisco, the shortening product. The current formulation of Crisco is primarily made from soybean oil and palm oil.[56] Significantly less expensive than olive oil or canola oil, cottonseed oil was a popular frying oil for the restaurant and snack-food manufacturing industries.[57]

Cottonseed oil was used in the production of edible food products, such as cooking oils, salad oils, margarines and shortenings. In the United States, cottonseed oil was used in Procter & Gamble's Olestra and Olein products as a type of non-digestible fat substitutes used to create creamy textures and rich flavors in fried foods.[58]

The FDA released its final determination that Partially Hydrogenated Oils (PHOs), which include partially hydrogenated cottonseed oil, are not Generally Recognized as Safe (GRAS) in 2015. However, to allow for time for reformulation, the agency extended the compliance date to stop manufacturing foods with these specific, limited petitioned uses of PHOs until June 18, 2019. The final compliance date to allow manufacturers time to reformulate foods and ensure an orderly transition in the marketplace was established as January 1, 2021. Then, on December 22, 2023, the FDA completed final administrative actions on the revocation of uses of PHOs in food. So, it can be said that the GRAS status of cottonseed oil, specifically in its partially hydrogenated form, was effectively lost by January 1, 2021.[59][60][61][62]

Nonfood uses

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For agricultural applications, cottonseed oil generally has the greatest insecticide power among all the vegetable oils. It is traditionally used because of its effectiveness in hard to treat pest problems in fruit trees. Cottonseed oil can also be mixed with other insecticides to provide a broader spectrum and increased control on pests. Spider mites, whiteflies and young stages of scales are common pests that can be controlled using cottonseed oil.[63]

In an agricultural context, the toxicity of untreated cottonseed oil may be considered beneficial: Oils, including vegetable oils, have been used for centuries to control insect and mite pests.[64] More recently, cottonseed oil has been used to protect the trunks of apple trees from the apple clearwing moth, which burrows into the trees' bark, potentially killing them.[65] This oil has been generally considered the most insecticidal of vegetable oils.[64]

See also

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References

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  1. ^ "Texas is Cotton Country". Archived from the original on 2013-10-21. Retrieved 2013-10-23.
  2. ^ a b "Twenty Facts About Cottonseed Oil from cotton plant". National Cottonseed Products Association. Archived from the original on 2015-10-17.
  3. ^ "Basic Report: 04502, Oil, cottonseed, salad or cooking". United States Department of Agriculture. Archived from the original on August 24, 2012.
  4. ^ "Nutrient data for 04702, Oil, industrial, cottonseed, fully hydrogenated". United States Department of Agriculture. Archived from the original on 2013-09-05. Retrieved 2012-02-13.
  5. ^ a b Jones, Lynn A.; King, C. Clay (1996). "Cottonseed oil". In Y. H. Hui (ed.). Bailey's Industrial Oil and Fat Products, Edible Oil and Fat Products: Oils and Oilseeds. New York: Wiley. ISBN 978-0-471-59426-0.
  6. ^ Yatsu, L. Y.; Jacks, T. J.; Hensarling, T. (1970). "Research abstract: Southern Regional Research Laboratory". Journal of the American Oil Chemists' Society. 47 (2): 73–74. doi:10.1007/BF02541462. S2CID 84360576.
  7. ^ a b c "US National Nutrient Database, Release 28". United States Department of Agriculture. May 2016. All values in this table are from this database unless otherwise cited or when italicized as the simple arithmetic sum of other component columns.
  8. ^ "Fats and fatty acids contents per 100 g (click for "more details"). Example: Avocado oil (user can search for other oils)". Nutritiondata.com, Conde Nast for the USDA National Nutrient Database, Standard Release 21. 2014. Retrieved 7 September 2017. Values from Nutritiondata.com (SR 21) may need to be reconciled with most recent release from the USDA SR 28 as of Sept 2017.
  9. ^ "USDA Specifications for Vegetable Oil Margarine Effective August 28, 1996" (PDF).
  10. ^ "Avocado oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  11. ^ Ozdemir, Feramuz; Topuz, Ayhan (June 2004). "Changes in dry matter, oil content and fatty acids composition of avocado during harvesting time and post-harvesting ripening period". Food Chemistry. 86 (1): 79–83. doi:10.1016/j.foodchem.2003.08.012.
  12. ^ Wong M, Requejo-Jackman C, Woolf A (April 2010). "What is unrefined, extra virgin cold-pressed avocado oil?". Aocs.org. The American Oil Chemists' Society. Retrieved 26 December 2019.
  13. ^ "Brazil nut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  14. ^ a b c d Katragadda, Harinageswara Rao; Fullana, Andrés; Sidhu, Sukh; Carbonell-Barrachina, Ángel A. (May 2010). "Emissions of volatile aldehydes from heated cooking oils". Food Chemistry. 120 (1): 59–65. doi:10.1016/j.foodchem.2009.09.070.
  15. ^ "Canola oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  16. ^ a b c d e f Wolke RL (May 16, 2007). "Where There's Smoke, There's a Fryer". The Washington Post. Retrieved March 5, 2011.
  17. ^ "Coconut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  18. ^ "Corn oil, industrial and retail, all purpose salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  19. ^ "Cottonseed oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  20. ^ "Cottonseed oil, industrial, fully hydrogenated, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  21. ^ "Linseed/Flaxseed oil, cold pressed, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  22. ^ Garavaglia J, Markoski MM, Oliveira A, Marcadenti A (2016). "Grape Seed Oil Compounds: Biological and Chemical Actions for Health". Nutrition and Metabolic Insights. 9: 59–64. doi:10.4137/NMI.S32910. PMC 4988453. PMID 27559299.
  23. ^ Callaway, James; Schwab, Ursula; Harvima, Ilkka; Halonen, Pirjo; Mykkänen, Otto; Hyvönen, Pekka; Järvinen, Tomi (April 2005). "Efficacy of dietary hempseed oil in patients with atopic dermatitis". Journal of Dermatological Treatment. 16 (2): 87–94. doi:10.1080/09546630510035832. PMID 16019622.
  24. ^ Melina V. "Smoke points of oils" (PDF). veghealth.com. The Vegetarian Health Institute.
  25. ^ "Safflower oil, salad or cooking, high oleic, primary commerce, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  26. ^ "Olive oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  27. ^ "Palm oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  28. ^ "Palm oil, industrial, fully hydrogenated, filling fat, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  29. ^ "Oil, peanut". FoodData Central. usda.gov.
  30. ^ Orthoefer, Frank T. (2020). "Rice Bran Oil". Bailey's Industrial Oil and Fat Products. pp. 1–25. doi:10.1002/047167849X.bio015.pub2. ISBN 978-0-471-38460-1.
  31. ^ "Rice bran oil". RITO Partnership. Retrieved 22 January 2021.
  32. ^ "Oil, sesame, salad or cooking". FoodData Central. fdc.nal.usda.gov. 1 April 2019.
  33. ^ "Soybean oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  34. ^ "Soybean oil, salad or cooking, (partially hydrogenated), fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  35. ^ "FoodData Central". fdc.nal.usda.gov.
  36. ^ "Walnut oil, fat composition, 100 g". US National Nutrient Database, United States Department of Agriculture.
  37. ^ "Smoke Point of Oils". Baseline of Health. Jonbarron.org.
  38. ^ "Cottonseed oil" (PDF). National Cottonseed Products Association. Retrieved 29 November 2010.
  39. ^ "Cottonseed oil". Transport Information Service, Gesamtverband der Deutschen Versicherungswirtschaft e.V. Retrieved 6 August 2012.
  40. ^ a b "Cottonseed oil production in 2019, Crops/Regions/World list/Production Quantity (pick lists)". UN Food and Agriculture Organization, Corporate Statistical Database (FAOSTAT). 2022. Retrieved 12 July 2022.
  41. ^ a b c d e f g h i j k l O'Brien, Richard D., et al. "Cottonseed oil." Chapter 5 in Bailey's Industrial Oil and Fat Products, Volume 2: Edible Oil & Fat Products: Edible Oils. Editor, Fereidoon Shahidi. John Wiley and Sons, Inc 2005. ISBN 978-0-471-67849-6
  42. ^ a b c d e f g h i Nixon HC. (1930). "The Rise of the American Cottonseed Oil Industry". Journal of Political Economy. 38 (1): 73–85. doi:10.1086/254082. JSTOR 1823218. S2CID 153333994.
  43. ^ U.S. patent 17961A
  44. ^ Drew Ramsey and Tyler Graham for The Atlantic. April 26, 2012. How Vegetable Oils Replaced Animals Fats in the American Diet.
  45. ^ a b "Crisco Corporate Historical Timeline". J.M. Smucker Co. Archived from the original on 2013-10-26.
  46. ^ Staff, Cotton247.com. September 12, 2009 Cottonseed Oil Production, Consumption On The Rise - Crushers expect over 100 million pound increase.
  47. ^ Willett WC and Skerrett PJ. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Free Press 2005 (paperback), sold in ebook form by Simon and Schuster Digital Sales Inc.
  48. ^ New York City Department of Health and Mental Hygiene (March 2005). "Health Bulletin: Healthy Heart - Eat Less Trans Fat" (PDF). Archived from the original (PDF) on October 21, 2013.
  49. ^ Associated Press. January 25, 2007 Crisco drops trans fats from shortening formula
  50. ^ Danielle Walsh (January 27, 2012). "3 Best and Worst Oils For Your Health". Bon Appetit Magazine. Archived from the original on 2013-04-25.
  51. ^ Canadian Food Inspection Agency (2014-02-18). "Labelling Requirements for Fats and Oils". inspection.gc.ca. Retrieved 2018-08-10.
  52. ^ "Cottonseed Oil and Food Safety". www.cfs.gov.hk. Retrieved 2018-08-07.
  53. ^ "Cottonseed Oil Extraction". GOYUM GROUP - INDIA. 18 April 2019.
  54. ^ Čmolík, Jiří; Pokorný, Jan (2000-08-01). "Physical refining of edible oils". European Journal of Lipid Science and Technology. 102 (7): 472–486. doi:10.1002/1438-9312(200008)102:7<472::AID-EJLT472>3.0.CO;2-Z.
  55. ^ Saxena, Devesh K.; Sharma, Surendra Kumar; Sambi, Surinder Singh (January 2011). "Comparative Extraction of Cottonseed Oil by n-Hexane and Ethanol". ARPN Journal of Engineering and Applied Sciences. 6 (1). S2CID 44046228.
  56. ^ "All-Vegetable Shortening - Crisco - Vegetable Shortening".
  57. ^ "Cottonseed oil use on the rise". cotton 247.com. Archived from the original on July 8, 2011.
  58. ^ Gunstone, Frank D., ed. (2011-04-01). Vegetable Oils in Food Technology. Wiley. doi:10.1002/9781444339925. ISBN 978-1-4443-3992-5.
  59. ^ Final Determination Regarding Partially Hydrogenated Oils.
  60. ^ FDA Completes Final Administrative Actions on PHOs.
  61. ^ Code of Federal Regulations Title 21 - accessdata.fda.gov.
  62. ^ FINISHED PRODUCT SAFETY DATA SHEET (SDS) - Ventura Foods.
  63. ^ "Insect Control: Horticultural Oils - 5.569 - Extension". Extension. Retrieved 2018-08-07.
  64. ^ a b W.S. Cranshaw and B. Baxendale, Colorado State University Extension. Updated Friday, April 19, 2013 Insect Control: Horticultural Oils
  65. ^ Erler, Fedai (2010-01-01). "Efficacy of tree trunk coating materials in the control of the apple clearwing, Synanthedon myopaeformis". Journal of Insect Science. 10 (1): 63. doi:10.1673/031.010.6301. PMC 3014806. PMID 20672979.
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