When we talk about apple-like flavors in coffee, they're usually the result of presence of malic acid. Malic acid is one of the organic acids that our found in coffee that lends certain flavors and characteristics. Sometimes when we talk about apple like flavors, we name specific apples. The apple can a a broad range of characteristics depending on the variety.
I imagine that you already realized this, but I wanted to look at a couple different varieties of apples to try to draw out how those particular flavors or characteristics show up in a coffee. Sometimes it's more of the sweetness, or tartness, or even the mouthfeel which leads us to the apple descriptor.
The 4 apples that I looked at were: Gala, Rome, Honeycrisp, and Fuji.
Gala: This is one of the softer type of apples with the meat of the fruit being more mealy than crisp. There is stil a good deal of sweetness, but very little tartness. This apple has some similar qualities to a pear, but without being as syrupy sweet. It has just the slightest bit of tartness, but is much more sweetness. In a coffee review there's a good chance you'd see them together, such as this one in the archives or the Ethiopia Wet Processed Kebado: www.sweetmarias.com/coffee.archive.new.php
Rome: THis was the dries of all 4 apples, almost astringent with very little sweetness. This apple was both mealy and a little waxy, there was a really slight cider-like apple flavor just in the middle of the palate, but the finish almost had a vegital bitterness. This was one of the deepest red apples I've ever seen. I found Rome Apple used as a descriptor for the 2005 Cup of Excellence in Bolivia where there's also some citrus rind and other sharp flavor descriptors used: www.sweetmarias.com/boliviaCoEresults2005.htm
Honeycrisp: The honeycrisp is a modern apple variety developed by the Univ. of Minnesota to be an apple that could be grown in cooler climates. The honeycrisp I had in this tasting was one of the smaller ones, where as the bigger ones tend to exceptionally crisp, as per the name, and incredibly sweet, the smaller one on the table today had a texture that was just a little more crisp than the gala, but not quite as the Fuji. It was indeed super sweet, syrupy and juicy, with a long lasting sweet finish. The Costa Rica Finca Salaca Las Brisas is described as having crisp apple and white grape nots...