Pick an apple off a tree, buff it a little and it will shine! That’s because the fruit is coated with a layer of natural wax that protects it from drying out and helps to prevent fungi from getting a foothold. The wax is a mixture of up to fifty different compounds, most of which fall into the chemical category known as esters. There are also alcohols like heptacosanol and malol as well as hydrocarbons such as triacontane, C30H62. This compound can also be isolated from petroleum and is sometimes applied to fruit to supplement its natural wax. In that case chemophobes kick and scream about a petroleum derivative being applied to their fruit but there is no difference between triacontane produced by an apple isolated from petroleum.
Natural wax also contains compounds in the triterpenoid family. Ursolic acid has a variety of biochemical effects that have been demonstrated in laboratory experiments. For example, it can inhibit the proliferation of various cancer cells and also has weak aromatase inhibitor activity. Aromatase is an enzyme that leads to the synthesis of estradiol, the body’s main estrogen that is implicated in some cancers. This of course does not mean that the amount of ursolic acid in the peel of an apple can have a beneficial effect on human health, but it is at least another plus for eating apples.
After apples are picked they are washed before they appear in the supermarket to remove dirt and chemical residues. This process also removes the wax. Since the waxy layer prevents moisture in the apple from escaping, its loss shortens the storage time for the fruit. Producers therefore spray the fruit with a thin layer of wax to prevent such moisture loss as well as to make the apple look more appealing. The applied layer is very thin, only about 3 mg of wax coat an apple.
Several different types of wax are used, mostly Carnauba wax that comes from the leaves of the Brazilian palm, Candelia wax from a dessert plant, as well as food grade shellac from the Indian lac bug. There are also some synthetic esters made by combining sucrose with fatty acids. Polyethylene, the same plastic used to make disposable shopping bags can also be applied in a very thin layer. Interestingly, this can be termed as being vegan because it is made from ethylene which in turn is made from ethanol that is produced by the fermentation of corn. A trace of an emulsifier morpholine oleate is added to allow the wax to be spread in a thin layer. Some concerns have been raised that the wax seals in pesticide residues that cannot be removed by washing but studies have shown that the prior washing removes most traces of pesticide residues. As far as the wax itself goes, it presents no health issue since it is not absorbed and passes right through the digestive system. Wax coatings can also be used on organic produce with the proviso that they must come from a natural source like beeswax or Carnauba wax or wood resin. While there is no worry about eating the wax on fruits, they should be well washed mostly to remove bacteria that may have stuck to the surface.
A video has been circulating in which boiling water is poured over an apple resulting in the formation of white splotches as a voice drones on warning people not to eat waxed apples because of the pesticide residues. The message is that the boiling water reveals the pesticide residues. That is not the case. The heat cracks the wax coating allowing air to enter between the wax and the skin of the apple resulting in white patches due to the way the air pockets reflect light.
It is not just apples that are waxed. Citrus fruits, rutabagas, cucumbers, many tomatoes, melons and peppers also are treated with wax. Even jellybeans are coated with beeswax to prevent them from drying out and to increase their appeal.