Researchers race to perfect first totally purple tomato

By Stephen Daniells

- Last updated on GMT

Related tags Tomato Fruit

Research groups around the world are working on breeding truly
purple tomatoes, packed full of anthocyanins, and reports suggest
that such a finished fruit may only be a few years away.

Currently leading the way are Professor Jim Myers and graduate student Peter Boches from Oregon State University and Oregon State alum Dr. Peter Mes, now working as a tomato breeder for Sakata Seed America in Florida.

Dr. Mes told that while others are working along similar lines, he and Prof. Myers are working on a different subset of genetics compared to others.

"This makes our material, for the moment, unique, though that won't last. At least two other private companies here in the USA are working on this idea, and are not far behind in terms of genetics,"​ he said.

Tomatoes are already known to contain lycopene, a carotenoid thought to reduce risk of prostate cancer and fight heart disease. Anthocyanins are the source of the blue, purple and red colour of berries, grapes and some other fruits and vegetables. These pigments also function as antioxidants, believed to protect the human body from oxidative damage that may lead to heart disease, cancer and ageing.

While these natural ingredients have been used as colouring agents in foods for some time, Frost & Sullivan estimates that there is significant potential for growth in polyphenol use as health ingredients. Revenues for the overall European polyphenols market in 2003 were thought to be worth $99 million (€77.88m), with red fruit anthocyanins, leading market expansion alongside green tea flavonoids, and grape and olive polyphenols.

Recent reports have suggested that Oregon State and Sakata Seed are in competition to put the finishing touches to the eggplant coloured tomato, but Dr. Mes told "While it is true we are both working on the idea, I wouldn't say we are in competition: the market for this tomato has not yet been established; it is at present a novelty."

Tomatoes with increased anthocyanin levels are already available, but these tend to be blotchy and not totally purple. The routes to producing nutritionally-enhanced fruit have been both the traditional crossbreeding methods and also genetic modification.

Professor Myers and Dr. Mes are following the traditional crossbreeding approach, taking advantage of genes from wild-type purple tomatoes, which are actually poisonous. During the 1960s and 70s the wild purple tomatoes were crossbred with modern edible tomatoes, producing hybrids with increased anthocyanin content that are safe for consumption.

The main challenges related to the anthocyanin-rich tomato are said to be shape, yield, and flavour.

"Flavour is a tough one,"​ said Dr. Mes. "Everyone likes a different tasting tomato. That work is ongoing, and is part of the intended first release from the breeding program."

Dr. Mes told this website that he has measured anthocyanin content of up to 300 micrograms per gram fresh weight in the skin of these tomatoes.

"That is not necessarily the highest it can go,"​ he said.

However, compared to blueberries, the anthocyanin content, gram for gram, is said to still be higher in the berries than the purple tomatoes.

"That said, the anthocyanins and other flavonoids found in these tomatoes are unique and may have health benefits not found in blueberries,"​ said Mes.

While it is well known that lycopene is more bioavailable when the tomatoes are processed and/or cooked, questions about bioavailability of the anthocyanins still remain, said the researchers, and the effects of processing are not known.

"Anthocyanin bioavailability is limited, period,"​ said Dr. Mes. "There is a lot of recent research into this; suffice it to say, it varies by individual anthocyanin.

"The anthocyanins in tomatoes do appear to be heat-stable,"​ he added. "However I do not know if processing improves the bioavailability or not."

In Europe, 8.5 million tons of tomatoes are cultivated annually with 1.5 million tons sold directly to the consumer and 7 million processed for products such as ketchup and sauces. But the global tomato processing industry has seen prices tumble in recent years, and although this situation is starting to improve, growing competition from China - now the third largest producer - means many players will be looking for ways to add value to the fruit.

And how much value would the increased anthocyanin add? "I would anticipate this sort of tomato, being a specialty item, to sell in a similar fashion to clam-shell tomatoes currently on the market,"​ said Dr. Mes. "But you are asking me to speculate, and this is outside my realm of influence and control."

A study by BASF recently reported that consumption of GMO tomatoes with high flavonoid contents could reduce the levels of a protein in a mouse that is associated with inflammation, diabetes and heart disease in humans (Journal of Nutrition​, Vol. 136, pp. 2331-2337), and Dr. Mes confirmed that a British research group is working along the same lines.

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