Purple vegetables have been cropping up everywhere in increasingly vibrant, aisle-stopping hues.
Purple cauliflower, carrots and broccoli have seeded from farmers’ markets and now join eggplant, beetroot and cabbage on Australia’s supermarket shelves. But how do they get to be that colour, and are they any better for us?
“We dabbled in purple and orange cauliflower back in 2011 and 2012 but our customers weren’t quite ready for it back then,” says Tim Nitschke, who manages Coles’ vegetables category.
“We started selling them again in 2019 and in the last 12 months they have really taken off.’’
The supermarket chain has introduced a number of purple vegetable varieties over the past year, including purple asparagus, purple basil microherbs, kalettes (a curly cross between brussels sprouts and kale) and red darling brussels sprouts. “We recently started selling purple broccolini in some stores,” Nitschke adds.
These rich hues are totally natural. The purple colour is a flavonoid called anthocyanin, which also contributes to deciduous trees’ leaves turning red in the autumn. Depending on their pH, anthocyanin pigments can appear as red, purple, blue and black in fruits and vegetables – a reaction that comes to life in the kitchen when you squeeze lemon over a head of purple cauliflower, which promptly blushes pink.
“The plants develop this colour to defend against the heat and sometimes the cold and sunlight. Particularly sunlight, if it is intense sunlight,’’ says professor Kadambot Siddique, agriculture chair at the University of Western Australia.
The challenge in cultivating plants to express these characteristics is getting them perfectly purple. “Purple cauliflowers are now what we refer to as ‘stable genetics’,” says John Said, CEO of lettuce and brassica farm Fresh Select. “They are very stable being purple. And some of the major seed companies in the world are breeding purple, as well as orange and green very soon.”
The connection between good health and eating a wide variety of fruit and vegetables is well known, and “eating the rainbow” definitely applies to violet shades, Siddique says. “Modern research really identifies that anthocyanins are so good for you. The antioxidants are anti-inflammatory, protecting against cardiovascular diseases, noncommunicable diseases like diabetes, and there is even evidence that it is good for your brain, protecting against diseases like Alzheimer’s and motor neurone disease.
“In the supermarket there are more purple vegetables because the consumers are aware of the health benefits.”
Purple’s reign is only just beginning, says plant physiologist and associate professor Tim O’Hare, with sweetcorn potentially next in line. O’Hare is currently working on a project in conjunction with one of Australia’s major sweetcorn companies, developing purple sweetcorn as a product for commercialisation. “We are at the prototype stage; we want to get rid of the problem of potential purple spotting. We also need to decide whether we want a purple cob or a white cob,’’ he says.
“When we put it past the consumers, it has a slight raspberry undertone. Not too different to frighten people away, and a positive flavour that came with the anthocyanins.’’
O’Hare previously assessed purple strawberries for the Queensland Department of Agriculture and Fisheries’ Australian strawberry breeding program, looking at their anthocyanin profiles and consumer acceptability.
He says the technical feasibility of developing a number of pigmented products is there, but consumer acceptance is vital. “It’s the consumer that guarantees the success or failure of the product. The genetic diversity is out there for a lot of fruit and vegetables. It is just so broad and some of it is so underutilised.”