Developing ‘superyellow’ enhanced pigment sweetcorn for eye-health (VG07081)
This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.
What was it all about?
When you think of sweet‐corn, you don't necessarily think of macular degeneration. Macular degeneration was the leading cause of blindness in Australia, and the rest of the developed world. The total cost of vision loss associated with macular degeneration in Australia was estimated at $5 billion dollars in 2010. The science was increasingly stacking up that the yellow pigments, zeaxanthin and lutein, in the macula protected the eye against the progress of macular degeneration, and that people with low levels of these pigments were more likely to suffer. As the human body cannot synthesize these pigments, they have to be obtained through our diet or supplements. While lutein can be sourced readily from green leafy vegetables, zeaxanthin was much rarer in the diet. Sweet‐corn was one of the best sources of zeaxanthin, but the levels present in a normal cob of corn would require you to consume somewhere between 4‐11 cobs per day to achieve a zeaxanthin‐intake equivalent to that used in clinical studies with supplements. Consequently, the aim of this project was to develop a sweet‐corn which could supply a supplemental dose of zeaxanthin (2 mg/person) as part of a normal meal (100 g kernels, or a small cob of corn), potentially minimising the need for an artificial supplement.
Inspiration for this research originally came from the knowledge that zeaxanthin had been linked to a lower incidence of macular degeneration, and that zeaxanthin was one of the main pigments in sweet‐corn. We also had access to the DAF sweet‐corn breeding program, and a wide range of sub‐tropical germplasm to work with. As Australian consumers wanted a natural (non‐GMO) product, we used a combination of selection, colour and carotenoid analysis, and cross‐breeding to develop a range of high‐zeaxanthin sweet‐corns. This process was gradual, and required us to select for lines producing a lot of carotenoids (zeaxanthin is a carotenoid) and lines that favoured the synthesis of zeaxanthin over lutein, which competed with the building blocks for zeaxanthin. We then combined these attributes together, to give us sweet‐corn lines with a zeaxanthin‐concentration approximately 10 times higher (1000%) than standard sweet‐corn. To complicate matters further, we then had to develop hybrids (matching 2 parents together) that produced commercially‐sized cobs from vigorous, healthy plants. We now had the first cobettes of sweet‐corn in the world that supplied as much zeaxanthin as a supplement, with our hybrids producing 7‐10 times the concentration of zeaxanthin concentration of a regular yellow sweet‐corn.
An additional benefit of increasing the zeaxanthin concentration was that it gave the sweet‐corn a deeper golden colour, so it can be easily differentiated in the marketplace from regular sweet‐corn. This was seen as a major advantage, as the compound that changed the colour of the corn was also the active compound for ameliorating the effects of macular degeneration (what you see is what you get). Consumer assessment was carried out to determine how orange was too orange, and a working colour‐range for hybrids was established, to which we fitted our hybrids. Equally important, flavour and texture was found to be as good as, if not better than, regular yellow sweet‐corn. Other factors were also investigated, including the effect of seasonality on zeaxanthin concentration, refrigerated storage on zeaxanthin stability, cooking on changing colour intensity, the transient effect of freezing on kernel colour (if you were to freeze your corn), as well as whether an increase in zeaxanthin caused a change in flavour, through carotenoid‐derived volatile compounds.
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This project was funded by Hort Innovation (then Horticulture Australia Limited) with co-investment from The Department of Agriculture and Fisheries (DAF).
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