Apparently Snow White's wicked stepmother knew something about chemistry and toxicology. She brewed up a remarkable poison to put the anemic young lady into a state of suspended animation. But how to get her to ingest it? Who, thought the evil queen, could resist a bright, shiny apple? Certainly not Snow White. And you know the rest of the story.聽
Well, according to some current fear mongering, you don't need a depraved queen to taint apples with poison; you just need some apple processors who apply wax to the fruit. The wax may contain a compound called morpholine, which according to some presents a risk to humans. Why?聽 Because morpholine under certain conditions can be converted into nitrosomorpholine, a compound known to cause cancer in rodents. Perhaps a little reality check is in order.
Most fruits and vegetables are naturally covered by a thin layer of wax. This prevents moisture loss and makes it harder for fungi to get a foothold in the fruit. You can pick an apple straight off the tree and note the waxy coating. This is not man-made. When processors wash apples in order to remove dirt, microbes and pesticide residues, much of the protective waxy layer is lost. This means that the fruit loses moisture more readily, is more susceptible to attack by fungi and looks less appealing. To counter this problem a variety of waxes that can readily replace the natural wax have been developed. Almost all these waxes are derived from one of the following sources: beeswax, carnauba wax, candelilla wax, shellac or oxidized polyethylene. Beeswax of course is processed from honeycombs. Carnauba and candelilla wax come from plant leaves and shellac derives from the resin that Indian "lac" bugs secrete to protect their eggs. Polyethylene is a synthetic plastic that upon reaction with chemicals such as potassium permanganate is converted into a waxy substance that can adhere to fruit.
Sometimes, under conditions of high humidity, the waxy coating cracks and the fruit takes on a milky appearance. This is cosmetically unattractive but does not present any added risk. You will note that it is almost impossible to wash off the wax since it is not soluble in water. If you are afflicted with 鈥渨axaphobia,鈥� peeling the fruit is the only answer. Some people routinely peel fruit because they fear that the wax seals in pesticide and fungicide residues while others advise against peeling, fearing the loss of nutrients in the peel. Actually, peeling in order to get rid of microbes is probably more realistic than peeling for pesticide residues. As far as loss of nutrients goes, no need to worry. If you are eating the recommended 5-10 servings of fruit a day, the nutrients lost by peeling are insignificant.
The amount of wax applied to any individual piece of fruit is extremely small. Only about 0.1% of the final weight of the fruit is due to the wax. In order to affix such a thin coating, the wax is mixed with a solvent, usually a combination of water and alcohol, and is sprayed onto the fruit. A thin waxy layer is left behind as the solvent evaporates. To ensure that the wax is uniformly dispersed in the solvent, a variety of processing chemicals are used. One of these is morpholine, an emulsifier that helps distribute the wax evenly. This is the chemical that in some press reports has been targeted as a cancer risk.
So how much morpholine is there in the wax? A typical range is 3-4% by weight of the wax solution that is applied. Morpholine is volatile, meaning that some of this evaporates during application. The amount left on the fruit is in the range of millionths of a gram. How much of this is absorbed into the body? This is almost impossible to determine but given that the wax is indigestible (meaning most of it comes out the other end), and that morpholine is embedded in the wax, the amount is likely to be trivial. Furthermore, morpholine itself, (chemically an "amine,") is not the problem. It has to undergo 鈥渘itrosation鈥� to nitrosomorpholine, which indeed is a carcinogen. While in theory this can happen in the body, the amount formed would be extremely small. And why worry only about nitrosating morpholine? Our diet contains many amines that can be nitrosated. Proline occurs naturally in meat and yields nitrosoproline. Fish contain numerous amines. Vegetables are not benign in this business either. They are high in nitrates, which the body converts to nitrites, which in turn react with amines to form nitrosamines. Basically, the message is that carcinogens are everywhere! We cannot possibly avoid them. So enjoy that waxed apple. It may not keep the doctor away, but it isn鈥檛 going to call for one either.
