The “Arctic” is a Canadian-designed apple that will not brown if bruised or cut open. Already approved by the U.S. Department of Agriculture, it has now been given the thumbs-up by Health Canada. In 2012, in a survey in British Columbia, where the apple was developed, 69 per cent of respondents were not comfortable with the non-browning phenomenon. I don’t necessarily fear the new apple, but I find applying this relatively new genetic technique to a fruit and commercializing it to be frivolous use of science. When cells of a regular ripe apple are ruptured through a bruise, slice, or bite, polyphenoloxidases (PPOs) (enzymes, found near the cell wall ) mix with polyphenolics found elsewhere in the cell. PPO catalyzes the oxidation of polyphenolics, eventually creating melanins, which cause the apple to turn brown.
Genetically modified Arctic apples produce practically no PPOs so that the enzymatic browning reaction is muted. When the apple’s genome was mapped, scientists learned that only four genes control PPO-production. To create a non-browning Arctic version of an existing apple variety, gene-silencing was used. This is not the same GM gene-splicing technique of the past. Silencing involves turning off the expression of PPOs with the use of double-stranded RNA(dsRNA). This is what eliminates most PPO production and prevents browning of the injured apple.
It’s believed that the browning plays no important role in the ecology of apples. But it does play an important role to the human consumer. With browning intact, bruises become more obvious.(Maybe sellers of apples don’t want bruises to be obvious?) Moreover, if an apple has been cut and has been lying around, it gives one an idea of how long ago it was sliced. The browning is proportional to the time that the apple has been exposed to oxygen.* With regard to GMOs in general, scaring the daylights out of people is not the right approach. But demonstrating unabashed enthusiasm for GMOs is also unscientific.
“The joint statement developed and signed by over 300 independent researchers, and reproduced and published below, does not assert that GMOs are unsafe or safe. Rather, the statement concludes that the scarcity and contradictory nature of the scientific evidence published to date prevents conclusive claims of safety, or of lack of safety, of GMOs. Claims of consensus on the safety of GMOs are not supported by an objective analysis of the refereed literature.” http://www.enveurope.com/content/27/1/4
*On a lighter note, how will I do in-class demonstrations of acid’s inhibitive effect on PPOs if apples don’t turn brown, even in the absence of lemon juice?