Apple Peel

[bluemoon]

Does anyone know why some varieties of apple, especially Bramleys, seem to have a greasy feel to their skin? It doesn't bother me, and I don't find it off-putting, but I was preparing the last of ours for the freezer today (it's our first real crop from this tree) and I thought, well even if I didn't know the variety, I'd have been able to guess with my eyes closed.

[FB.]

I'm not sure why (or maybe I've forgotten) but, as you say, some varieties have a skin that develops a greasy coating after picking. It's just a feature of the variety.
Annie Elizabeth is another large cooker (I am of the belief that Annie is a sister of Bramley) and it also has greasy skin develop after picking.
The "in-laws" Lord Lambourne tree also has fruit that turns greasy.

[bluemoon]

Thanks FB, if you don't know then no-one does! I'll just have to put it down to one of life's great mysteries.

[Tam]

"Granny Smith and Royal Gala are two cultivars which can become greasy in storage. Greasy fruit is very unappealing to the end consumer as shown by a HortResearch consumer panel which perceived fruit with a high level of surface grease to be over-ripe. For a very greasy apple, it was the greasiness more than any other attributes (softness and size of fruit) which made the consumers consider the fruit to be over-mature. The consumer panel considered the "ideal" level of greasiness on the fruit to be no grease at all or else a very low level of greasiness.

Skin greasiness can develop on the tree, particularly in the upper and outer zones of the tree, or during storage in fruit of late maturities. Greasiness develops due to changes in the waxes on the surface layers of the fruit. In particular, farnesyl ester has been determined as a major component in the surface wax of ‘Granny Smith’, ‘Fiesta’, ‘Royal Gala’ and ‘Braeburn’ apples.

It would be a huge advantage if we could predict whether lines of fruit were going to become greasy before they were put in storage. One way of predicting potential greasiness is to determine the levels of farnesyl ester on the fruit. Farnesyl esters are easily detectable as they turn a yellow/brown colour when exposed to iodine vapour. In an experiment where the surface waxes of the fruit were extracted and place in a chamber with iodine vapour for 5 minutes, the iodine staining was greatest on the wax from the greasy fruit. There was only a slight iodine staining on the wax from non-greasy fruit.

The iodine will stain the wax before the fruit even feels greasy. This means that the iodine test can be used to predict greasiness and could be useful for segregating apples for short, long-term and CA/MA storage on the basis of their potential to develop skin greasiness. Further work needs to be done to refine the test using a range of cultivars and locations."

I forget where this came from, but it has some relevance to your question.