Scientists bred purple tomatoes containing anthocyanin, an antioxidant said to help fight several diseases, with normal red varieties.
‘There are some dark coloured tomatoes but Indigo Rose is the only real black tomato and is the darkest that has ever been bred. "It's not genetically modified or GMO-based as many assume," said Botanist Marjorie Varga. "People often get confused between GMO and hybridization which farmers have been using to cultivate new plant varieties for thousands of years."
The new breed was the brainchild of Professor Jim Myers at the University of Oregon in the US and came about after a graduate student was interested in looking at health benefits in tomatoes.
The new variety is a novelty type intended for home gardens and the fresh market, and it is now available in seed catalogs, said Myers.
"It is the first improved tomato variety in the world that has anthocyanins in its fruit," he said.
The tomato itself is actually a botanical berry.
Myers' team found some tomatoes with purple pigmentation and tests revealed that anthocyanins were providing the colour, the same as blueberries. They crossed the purple tomatoes with some wild tomatoes and eventually came up with a black strain.
Breeding for the antioxidant potential of the purple anthocyanins in the fruit was the most important goal for OSU breeders. "It will lead to a better understanding on how the antioxidants express in tomatoes and may contribute to human health," Myers said.
During the growth process it starts out green like all tomatoes and when the sun hits the fruit it turns black rather than red.
"If you want a really, really purple tomato that can be as black as an eggplant, give Indigo Rose a try," Myers said. "Other so-called purple and black tomatoes have the green flesh gene, which prevents normal chlorophyll breakdown. A brown pigment called pheophytin accumulates and has a brownish color that makes a muddy purple when combined with carotenoids."
Anthocyanins are in the class of flavonoids -- compounds found in fruits, vegetables and beverages -- that have aroused interest because of their potential health benefits.
According to the American Cancer Society, researchers are investigating the positive effects phytochemicals such as anthocyanin may have in the human diet.
According to a 2009 study: "A growing body of evidence suggests anthocyanins and anthocyanidins may possess analgesic properties in addition to neuroprotective and anti-inď¬‚ammatory activities".
Their anti-inflammatory activity and function is connected to preventing neurodegenerative diseases, diabetes, depression, and anxiety.
"People are passionate about their tomatoes," Myers said. "The purple color draws their interest and because it's extraordinary, people tend to expect impressive flavor as well. It does have a good balance of sugars and acids and tastes just like a tomato. Anthocyanins are essentially tasteless."
Many gardeners are opting in increasing numbers for rare crops such as okra, purple carrots and specialist vegetables used in stir fries such as Pak Choi, oriental mustard and red hot chillies, which fetch high prices in the supermarkets.
The tomatoes will be purple where exposed to light, Myers said, and they tend to have a purple crown. They are ripe when their color changes from a shiny blue-purple to a dull purple-brown. The fruit also softens similarly to regular tomatoes, and the bottom of the tomatoes will turn from green to red when ripe.
Anthocyanin produces in the fruit only where exposed to sunlight. If shaded by a leaf or on the base, the purple pigment does not develop. "However, if you pick an Indigo Rose and expose the non-purple area to sunlight, it will turn purple in about a week," Myers said.
An entire generation is rediscovering the delicate flavours of vegetables cooked straight from the garden. Increasing food prices are driving households to become more self-sufficient.
"While other fruits, such as blueberries, have higher concentrations of anthocyanin, tomatoes are consumed practically daily in the United States," he said. The tomato is the nation's fourth most popular fresh-market vegetable behind potatoes, lettuce and onions, according to the USDA.
Cherry tomatoes likely will be the next of several new versions in the Indigo anthocyanin series to be bred within the next three years and are expected to have a good flavor.
John Summerly is nutritionist, herbologist, and homeopathic practitioner. He is a leader in the natural health community and consults athletes, executives and most of all parents of children on the benefits of complementary therapies for health and prevention.