http://www.wicca-spirituality.com/goddess-symbols.html
The apple has long been associated with the worship of the Goddess.
Note the story of Eve and the Serpent (one of the eternal Goddess symbols). When Eve ate the apple, she was taking in Divine wisdom - the knowledge that she is Divine. Thus she would become immortal.
The apple seems to have always been associated with death and eternal life.
Walker writes,
"Graves [in Greek Myths, vol. 2] points out that the whole story of Eve, Adam, and the serpent in the tree was deliberately misinterpreted from icons showing the Great Goddess offering life to her worshipper, in the form of an apple, with the tree and its serpent [the sacred guardian] in the background." (Barbara Walker, The Woman's Encyclopedia of Myths and Secrets, p 49.)
Naturally a jealous God - who wants to be the only god - would outlaw such knowledge of one's divinity! But since it is Truth, He couldn't keep it hidden forever. So when it came out, He decided to keep us so busy with survival and pain that we wouldn't have time to notice our divinity.
It worked pretty well!
Luckily the Goddess is more compassionate, and not threatened by others being empowered. She gave us plenty of hints along the way, to remember.
One of these is the apple. Cut in half, its seed bed - the most potent part of the fruit - reveals the sacred 5-pointed star within the circle of apple skin.
This is the pentacle - the expression of One Divinity as all facets of the world.