Symbolism, Imagery, Allegory
Far from the Tree
While in the time loop, Emma picks an apple and gives it to Jacob shortly before they share their first kiss. The next morning, in the present, Jacob holds it as it "crumbled […] like a clump of soil" (8.1). Yikes. That's what happens when you don't buy organic, we guess.
Jacob shakes it off, as if apples disintegrate over night all the time, but he later learns that this is what happens when things leave the time loop. And the same would happen to Emma if she left.
Apples are generally considered forbidden fruit, and that comparison could be applied (appled?) to this apple in a couple of different ways. If Emma = the apple, then she is forbidden fruit, as an eighty-year-old woman who's dated your grandfather probably should be. Or maybe it isn't the apple itself that's forbidden, but leaving the time loop which is super verboten. Whichever it is, as is oh so very often the case in art and literature, the apple is a warning sign.