Last weekend I picked up a fairly new variety of apple, SnowSweet. The fruit is very very white when you cut it open, and it doesn’t really brown. 24 hrs ago, I cut one up into slices. 5 hrs later, after sitting on the counter top, uncovered, there was almost no browning. Having spent the last 18 hrs in a plastic container in the fridge, there is a small amount of browning, but much less than I would expect from an apple.
There is nothing involved here but an apple and a knife. So what is different about this apple that delays/reduces browning?
According to this Scientific American article, apple browning is caused by polyphenol oxidase enzymes oxidizing phenolic compounds in the apple to o-quinones which then react with amino acids to produce brown colored compounds. (I would think that much would be obvious. It goes on to say that different varieties may brown differently because they contain different amounts of either polyphenol oxidase or the phenolic compounds that they react with.
It may be genetically engineered to silence the gene for poly phenyl oxidase (the enzyme mentioned above by markn+). I’ve eaten the non-browning Arctic apples and they tasted great. These GMOs use exactly that gene silencing approach, as described in the link.
I just cut them in half and place the uneaten half face down on a plastic lid in the fridge, and don’t worry a bout them. They keep at least 48 hours without browning, if the cut surface is unexposed to air. Same for onions, most other firm fruits and veggies.
It goes on to say that different varieties may brown differently because they contain different amounts of either polyphenol oxidase or the phenolic compounds that they react with.