Cottonseed

Cottonseed is the seed of cotton plants, mainly Gossypium hirsutum, a shrubby plant grown for its white fibre. Each cotton boll holds several seeds, each about the size of a small bean, covered with short, fuzzy fibres called linters that remain after the long fibres are ginned. Inside is an oil-rich kernel, speckled with tiny dark glands.

These glands contain gossypol, a yellow polyphenolic pigment that is toxic to many animals and humans. Cottonseed is crushed to produce oil and a protein meal, and the oil is refined to remove gossypol. The seeds are rarely eaten whole, though breeders have developed low-gossypol glandless varieties.

Cotton was domesticated independently in several regions, including the Indus Valley, Africa and Arabia, Mesoamerica and Peru, thousands of years ago, for its fibre. Gossypium hirsutum, upland cotton, originated in Mesoamerica and now accounts for most world production. The seeds are a by-product of ginning.

The genus name Gossypium comes from a Latin term for the cotton plant, and the English cotton traces to the Arabic qutn. Gossypol is named after the genus. For much of history seeds were discarded or fed to livestock, but the nineteenth century brought their use for oil.

For most of history cotton was valued for fibre alone, and cottonseed was a nuisance to be burnt, buried or used as fertiliser. In the nineteenth century, particularly in the American South, processing techniques made it possible to produce oil from the seed, and cottonseed oil began to be used in lamps, soaps and cooking, and as a cheaper alternative to lard and olive oil.

In 1911 Procter and Gamble introduced Crisco, a vegetable shortening made from hydrogenated cottonseed oil, and cottonseed oil became a prominent American cooking fat, used in salad dressings, frying and snack foods. Later, soybean and other oils overtook it in market share.

Cotton production has grown in India, China, the United States, Brazil, Pakistan and Uzbekistan, and the oil and meal continue to be significant products. Researchers developed glandless cotton varieties with low gossypol in seeds to make a food protein, though adoption has been limited. In India, whole cottonseed and cake, known as binola, are important cattle feed.

Refined cottonseed oil is used for frying, in snack foods, baked goods, margarine, shortening and salad dressings, valued for its neutral flavour and stability. Linters are processed into cellulose for paper and film, and the hulls are used as cattle roughage. Cottonseed meal and cake are used in animal feed after treatment to reduce gossypol.

Whole cottonseed is fed to dairy cattle. Experimental food uses of glandless cottonseed flour have been explored for human nutrition. Cottonseed oil is also used in cosmetics and industrial products and as a biodiesel feedstock.

Refined cottonseed oil is high in polyunsaturated linoleic acid and also contains a substantial proportion of saturated palmitic acid, giving it a more stable profile for frying than some other vegetable oils. As with other refined oils, it supplies energy and vitamin E and no meaningful protein.

Gossypol has been studied for its effects on male fertility, and experimental trials explored it as a contraceptive, though side effects limited that use. The health impact of cottonseed oil depends on overall diet, and it is best used in moderation like other refined fats.