An Apple a Day May Kill You? You can imagine that is the sort of headline that grabs my attention. This one was on a website that goes by the name organic authority. I have absolutely no qualms about the promotion of organic agriculture, which ideally would be the way to feed the world. But I do object to unnecessary fear-mongering. In this case the article that portrays conventionally grown apples as villains focuses of diphenylamine, a chemical that is used to prevent “storage scald” in apples. It is actually regulated as a pesticide although apple scald is not actually caused by a pest unless one considers oxygen in the air to be a pest. Scald shows up as irregular patches of dead skin that appear when the fruit warms up after cold storage. Most apples do go into cold storage so that they can be consumed year round.
The chemistry of scald revolves around alpha-farnesene, a naturally occurring compound in apples. Under storage conditions it is oxidized to compounds such as farnesyl hydroperoxide that cause tissue injury. Storage under low oxygen conditions can control scald but the texture and taste of the fruit can be adversely affected. The preferred method is to apply the antioxidant diphenylamine with a week of harvest. Antioxidants prevent reaction with oxygen and therefore reduce the risk of scald formation. Different varieties of apples have different susceptibilities to scald likely due to differences in their content of natural antioxidants. As with any pesticide, stringent regulations about application and residues apply. In the case of diphenylamine, the maximum residue allowed is 4.3 mg per kg of apples. The actual amount detected on apples is 0.35 mgs, which is less than one tenth the limit. And it should also be pointed out that the maximum residue allowed already has a large safety factor built into it as determine from animal feeding studies. If numbers are ignored, one can paint a dire picture of diphenylamine. The compound can react with naturally occurring nitrates to form nitrosamines which are known carcinogens. But this is exactly the sort of information that is taken into account by regulatory agencies and the conclusion has been that the levels are way too low to be of any significance. So that apple a day is not killing us.
Dipheylamine, however, is not the only pesticide found on apples. Thiabendazole, an anti-fungal agent, is also commonly found on apples which can be attacked by as many as fifty eight different varieties of fungi. Again, the question is not whether thiabendazole is detected or not, the question is how much. The legal limit in this case is 7.4 mg per kg of apples and the amount detected is 0.26 mg, or one thirtieth the limit. Again, this is a negligible amount.. Another point to remember is that pesticides are also used on organic produce, with the only stipulation being that they cannot be synthetic. The pyrethrins, a class of pesticides derived from chrysanthemums that are approved for use in organic farming, are more toxic by weight than Roundup, Captan, and Pyrimethanil. Basically, pesticide residues are not much of an issue. So let’s not worry about that apple a day. Or two. Or three. And if you want more reason to stock up on apples, a recent study has shown that eating an apple after a garlicky meal will make your breath acceptable. Forget the chlorophyll, amuch touted remedy for garlic breath. The same study showed it doesn’t work.