The GM tomato, which gains its unusual colour from a natural pigment known as anthocyanin, could be picked and shipped later due to its longer shelf life, allowing more time for flavour to develop on the vine.
Tests showed the shelf life of the tomatoes more than doubled from an average of 21 to 48 days after genetic modification, and they were less likely to go mouldy after harvest.
The strain has also been found in earlier studies to fight cancer in mice due to its high levels of antioxidants, and scientists say its qualities could be replicated in other soft fruits like strawberries and raspberries.
The tomatoes were modified by scientists at the John Innes Centre in Norfolk to contain two genes from the snapdragon which “switch on” a set of dormant genes in the tomato, causing them to produce more anthocyanin.
The pigment occurs naturally in various plants and flowers, and is responsible for many of the blues, reds and purples seen in nature, but also ramps up levels of antioxidants.
The goal of the project was to produce fruit with higher antioxidant levels which could benefit health, and earlier studies have shown that they helped extend the lives of cancer-prone mice by 30 per cent.
But researchers reported in a new paper in the Current Biology journal that the genetic modified fruit also took longer to go soft and was more resistant to Botrytis cinerea, a fungus which rots tomatoes in storage.
Prof Jonathan Jones, one of the researchers, explained: “Tomatoes are often harvested green so that they are allowed to ripen closer to the consumer, and the cost of that is you have less time for aroma and flavour to develop.
“We might be able to harvest [the purple tomatoes] later so that the aroma and flavour can fully develop on the vine and they will still be hard enough to ship.”
The researchers have recruited a Canadian firm to produce a crop this summer, and hope to test its health benefits in a clinical trial within the next 12 months.
Patients at Norfolk and Norwich University Hospital will be offered purple tomato juice to help doctors determine whether it can lower the risk of coronary heart disease.
Prof Cathie Martin of the John Innes Centre, who led the project, said: “We hope to be able to see whether intervention with the purple juice can have any impact as a complementary therapy.
“When people see the tomatoes they think they are really great … I think we have got something that could really benefit people.”
The team, who have formed a spin-out company, hope to make purple tomato juice commercially available in the US within three years, and in the UK at a later stage due to this country's tougher regulatory process.