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Cottonseed is abundant and rich in protein, but a compound within the plant means it's toxic to humans unless refined into cooking oil. Will biotech research solve the conundrum? Roger East investigates.
Cotton growing isn’t all about textiles. Could it become a major world food source too? Researchers have their eye on a prize well worth aiming for.
Cottonseed is protein rich. It’s abundant; along with an annual global total of around 25 million tonnes of cotton, you get over 40 million tonnes of cottonseed. Which could, in theory, meet the needs of 500 million people.
There’s a hitch. It’s called gossypol. A naturally occurring compound found in little glands throughout the cotton plant and within each seed, gossypol is toxic to humans. It is also toxic to pigs and poultry, although cows can deal with it in moderation thanks to the digestive power of the microflora in their multi-stomach systems. (Gossypol also has contraceptive properties, but interest in exploiting this attribute, notably in China, has waned in view of its other negative effects.)
The gossypol problem has meant that, up to now, cottonseed has been at best a by-product of fibre production, and at worst a waste stream. After cottonseed has been separated out from the fibre in the ginning process, the main current ways of extracting value from it are crushing out the oil, and turning the hulls and meal into cow-cake.
It could represent a significant opportunity. The oil can be classed as edible because its gossypol content is reduced right down by the refining process, to well within food safety standards. But edible cottonseed, with its protein content at an impressive 20% or more, could conceivably transform cotton from a source of secondary oil to a crucial part of the staple diet of millions.
Generations of Americans learned to cook with cottonseed oil
Generations of Americans learned to cook with cottonseed oil, first marketed over a century ago as Wesson oil, and then popularised in the form of Crisco (Proctor and Gamble found a way of emulsifying it). It was largely displaced in US homes when soya became cheaper, but its absence of trans-fats has helped it make a bit of a comeback. It’s now more widely used in cereals, breads and snack foods, although it remains a popular source of domestic edible oil in India.
Now, biotech research is encouraging new hopes on that score. “The big picture is to be able to help solve the food problem, to be able to feed hungry people”, says Professor Keerti Rathore, at Texas A&M University’s Institute of Plant Genomics and Biotechnology.
We have known, since the late 1950s, that it’s possible to breed a ‘glandless’ strain of cotton. But that’s not necessarily all to the good. Without gossypol, at least in the leaves and roots, the plants lose their own front-line defences against insect predators. Growers would face an unacceptably high risk of seeing their crop simply devoured in the fields.
In New Mexico, however, where pest eradication efforts (including the release of sterile pink bollworm moths) have reduced this threat, there is now something of a revival of interest in growing glandless cotton. Farmers who agree to try planting it are supported by the US industry association Cotton Incorporated, with a tie-in to a New Mexico State University programme that is demonstrating a whole cycle of use for the gossypol-free seeds. The oil, extracted by cold pressing and used to cook food on campus, has a second life as biodiesel on the university farm, powering the irrigation pumps, the tractors and the delivery trucks. Shrimp are being raised on the leftover cottonseed meal mixed with algae, potentially a more sustainable resource than the usual fishmeal shrimp-food. Meanwhile, university food technologist Nancy Flores is enthusiastic about a healthy cottonseed-based snack food mixed with corn flour and green chilli. Her colleague Lisa McKee is working on baked goods from cottonseed flour, a gluten-free wheat substitute for which she envisages a potential market in dry mixes for making cookies.
To build more revenue prospects for New Mexico’s glandless cotton growers, Cotton Incorporated’s Tom Wedegaertner took some of its cottonseed to a food innovation centre in Portland, Oregon, to develop a wider range of food products. The menu could include a replacement for peanut butter, a milk replacement product, and even a vegetarian jerky stick.
As imaginative as these experiments are, the attractions of glandless cotton remain limited to areas of low insect threat. And that leaves out most of the world. Rathore’s research team in Texas, however, has pioneered a genetic intervention that can cut gossypol production by 95% or more in the seeds alone, leaving the rest of the plant with its natural defences intact. What Rathore does, in simple terms, is to deactivate an existing process within the seed, rather than adding extraneous genes to its make-up. So he believes that his plants, though they’re genetically modified, may meet less public resistance than other GM organisms. As he says, “this is a very big deal, because it clearly opens up this huge resource, either directly as food, in the form of cottonseed for human nutrition, or as feed for chickens and pigs”.
What works in the laboratory is now being tested, through experimental growing of the new GM strains. Even with a series of successful field trials, it will still be several years before anything is ready for approval and commercial release. But to say that cotton growers are watching with interest would be an understatement, to judge by the enthusiastic comments of Kater Hake, Vice-President for Agricultural Research at Cotton Incorporated. “We’re going through an opportunity of expanding the utility of cotton”, says Hake, “not just to clothe people and feed livestock and produce cooking oil, but also to be a major supplier of protein to feed people on a global basis.”
How appetising does that sound? In Rathore’s lab, he says, “people actually like the taste. I’d much rather eat cottonseed than soya beans.”
Good enough to eat?
In the US, cotton is regulated as a food crop by the Food and Drug Administration (FDA), and regulations restrict the amount of pesticide residue allowed in cottonseed. Since most US cotton is now GM (see ‘What does the future hold for GM cotton?’), it’s no surprise that cotton also features frequently on the list of voluntary FDA consultations with producers before they bring to market a food product made from GM plants. As of April 2013, there had been 30 such consultations involving cotton. – Roger East
Roger East is a freelance writer and editor, and a regular contributor to Green Futures.
Photo credit: Willard Culver/National Geographic Society/Corbis; Louella 938/shutterstock