The prospect of genetically modified purple tomatoes reaching the shelves has come a step closer.
Their dark pigment is intended to give tomatoes the same potential health benefits as fruit such as blueberries.
Developed in Britain, large-scale production is now under way in Canada with the first 1,200 litres of purple tomato juice ready for shipping.
The pigment, known as anthocyanin, is an antioxidant which studies on animals show could help fight cancer.
Scientists say the new tomatoes could improve the nutritional value of everything from ketchup to pizza topping.
The tomatoes were developed at the John Innes Centre in Norwich where Prof Cathie Martin hopes the first delivery of large quantities of juice will allow researchers to investigate its potential.
"With these purple tomatoes you can get the same compounds that are present in blueberries and cranberries that give them their health benefits - but you can apply them to foods that people actually eat in significant amounts and are reasonably affordable," she said.