When apple (Malus domestica) fruits are cut or bitten, we all know that the cut surfaces turn brown. To stop this happening, here’s a range of genetically modified (GM, genetically engineered, GE) apples called Arctic apples.
Ordinary apples turn brown when the fruit’s ‘phenolic’ compounds react with oxygen. We don’t want to lose phenolic compounds because, if we eat them with plenty of fats and carbohydrates, they’re good for our health. It’s one of the reasons why my grandparents’ generation learned, ‘An apple a day keeps the doctor away.’
When apple surfaces turn brown, it’s because phenolics are oxidising (reacting with oxygen in the air.) This change is driven by an enzyme called polyphenol oxidase (PPO). So if you want to eat wholesome phenolics you’ll want to eat your apples before their cut surfaces turn brown. Every chef knows that you can delay the browning by sprinkling the cut apples with lemon juice, which of course is acidic (low pH). Low pH delays the action of PPO.
If you grow apples you might want them to make plenty of PPO. It’s part of the plants’ defence against insect pests. Therefore, genetic engineers have made plants with extra PPO to improve plants’ defence against insects.
On the other hand, if you grow apples you might not want them to make very much PPO. Because PPO makes fruit turn brown after harvest, if it gets cut or damaged, and then it doesn’t look so nice. It doesn’t give consumers so much health benefit from phenolics either.
Here’s how the ‘less PPO’ strategy was used to make nonbrowning apples. Then scientists at the Canadian biotech company Okanagan Specialty Fruits (OSF) developed nonbrowning apples and called them Arctic apples. (I don’t know whether they taste good or not.)
These GM apples don’t turn brown when cut because their genes for PPO have been ‘silenced’. Scientists at OSF used the bacterium Agrobacterium tumefaciens to insert ‘antisense’ DNA sequences to make this happen.
Arctic apples haven’t yet been licensed for growing in the States or Canada but perhaps they soon will be grown there. The opportunity for public comments has been extended until the end of January 2014. OSF urges us to support Artic apples although they seem to have forgotten to update their request, to remind us that it’s not too late.
What do you think? Should apple growers continue to benefit from PPO, keeping pests away? Perhaps in time, American and Canadian growers will have the choice of GM apples which make more PPO. Or should growers have the choice of GM apples with less PPO, such as the Arctic range whose fruits keep so well? Or do you want apples which are not GM at all?