Sweet corn grown by colours tests if purple is best

2 October 2020

There is always a chance for a grower to move into something entirely unexpected, and that’s what coming out of a five-year cross-industry project providing research into more appealing varieties of sweet corn, strawberries and macadamias.

Some of the offshoots on offer from traditional produce are in fact more nutritious, stand-out in the marketplace and are visually attractive with more flavour according to researchers from the University of Queensland who are collaborating with the Department Agriculture and Fisheries (DAF) Queensland.

The Naturally Nutritious project is researching the development of more innovative food products and varieties and one of the products being developed is purple sweet corn, with high levels of specific phytonutrients for human health.

Fruit, vegetables and nuts play an important role in human health reminds Dr Tim O’Hare, Senior Research Fellow at the Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation (QAAFI).

Dr Tim O’Hare (back) in a vegetable patch.

And he said while most Australians are aware of the ‘Go For 2 & 5’ program of how many fruits and vegetables they should eat, most are not actually doing it.

“A major thrust of the Naturally Nutritious project was to investigate if we could increase the nutrient content of a range of products, so that you could get more nutrition per serve,” Dr O’Hare said.

One of the considerations was the ‘look’ of the product that was being developed. As Dr O’Hare explained, humans are visual beings, so it is important for the product to look attractive and visually differentiated from a ‘standard’ product of the same type.

“For example, purple sweet corn, developed from Peruvian purple maize, clearly looks different to yellow sweet corn.

“Of course, the product has to taste as good – if not better – that the standard product, because after all, this is food and it should taste great. If it doesn’t taste great, then the likelihood of you buying it a second time drops dramatically,” he said.

In some products, the pigment is actually the active nutrient, in which case Dr O’Hare said that can make it easy to look attractive to consumers.

“For example, the orange colour in orange capsicum is zeaxanthin, which is important for slowing the progress of age-related macular degeneration.

“Purple and red anthocyanin pigments have been linked to improving cardio-vascular health. So, increasing purple colour also increases the health value of vegetables.”

Dr O’Hare began creating purple sweet corn a couple of years before Naturally Nutritious was established, however he believes the project can make the development of a supermarket product move forward faster. Though, as he explained, it is not that simple.

“The difficulty is that the natural mutation that makes sweet corn ‘supersweet’ is positioned extremely close to the mutation that ‘blocks’ purple pigment production.

“The challenge was to break this tight genetic linkage, so that the supersweet mutation is now alongside a ‘working’ part of the anthocyanin purple pigment pathway,” he said.

“The good news is that we have done this for two different ‘supersweet’ mutations now, including ‘shrunken-2’, which the Australian sweet corn industry and much of the world is based upon.”

Dr O’Hare and his team are currently developing molecular markers, or fragments of DNA, to help accelerate their future research.

“This is important if we want to introduce other commercial aspects in the future, such as disease resistance, from yellow sweet corn into the purple sweet corn,” he said.

Dr O’Hare said the products may not necessarily replace artificial nutritional supplements; however, the research team’s investigation into nutrient biofortification – or increasing nutrient content in produce – has produced promising results, including in purple sweet corn.

It has also identified highfolate strawberries, where a single punnet of strawberries will supply the recommended daily folate intake (four times higher than average).

“We have also identified orange capsicums that have the equivalent zeaxanthin content to 30 macular degeneration supplement tablets.

Orange capsicums and chillies

We are exploring the potential to make macadamia nuts even better for you than they are already. We are looking at purple strawberries, which may have different health benefits to regular strawberries.

Plus we’re planning to extend the narrow season of the high-anthocyanin Queen Garnet plum, by bringing it forward into the Christmas festive season (it currently produces in February),” Dr O’Hare said.

“On top of that, we are undertaking consumer evaluation of the product concepts, as well as two clinical studies about to go underway to back up the science (one on Queen Garnet plum, and one on the high-folate strawberries).

“We also have a study on the comparative benefit of different fruit and vegetables, specifically which ones make you feel full faster and which make you last longer before wanting to eat again. This is all good for the waistline.”

Purple sweet corn will become available to Australia’s vegetables growers following the issue of a public tender once the product is closer to a commercial hybrid.

“Through issuing a public tender, we can get the best people out there to carry it forward into the commercial world,” Dr O’Hare said.

He added that with two years remaining, the project is progressing as planned.

“Not everything happens at once, but we are getting to the stage where different industries can decide if they want to take things further in separate focused projects; that is, beyond the proof of concept stage.

“We know that not everything will be a winner – some things would obviously suit ‘niche markets’ better, while others have wider market appeal.

“We’d definitely like to see a Naturally Nutritious 2 in the future. Horticulture includes so many crops that a single project simply cannot cover everything. We know there is so much more out there to achieve.”

More about the Naturally nutritious project here. 

The Queensland Alliance for Agriculture and Food Innovation is a research institute at The University of Queensland supported by the Queensland Government via the Queensland Department of Agriculture and Fisheries.

Media: Dr Tim O’Hare, t.ohare@uq.edu.au, +61 7 3708 8718; Margaret Puls, QAAFI Communications, m.puls@uq.edu.au, +61 7 3346 0553, +61 (0) 409 578 356.