Will it affect the quality of the filling if you cut the apples the day before assembling apple desserts?
Cutting damages the cells of apples, allowing enzymes and compounds stored separately within each cell to mix with one another and with the oxygen in the air, creating brown-colored pigments. To see if this brown color does anything more than mar the fresh look of the fruit, we compared an apple crumble made with just-cut fruit with crumbles made with apples that we had cut and peeled (and refrigerated in zipper-lock bags) one and two days earlier. The brown apples and the fresh apples baked up equally tender and juicy and were similar in flavor, and—surprisingly—all had pretty much the same light golden color. It turns out that as the apples’ cell walls rupture during baking, acids are released that partially break down the brown pigments, resulting in a lighter color.
THE BOTTOM LINE: If you’re going to cook apples, it’s fine to prep them a day or two in advance.