It makes perfect sense to stock up on fresh produce while it's in season. That's when it's at its best and cheapest, whether you get it at the farm stand or from a supermarket. Of course, once you do that, you've still got to preserve it one way or another. Freezing is the simplest and most versatile option for most produce, and you'll often be advised to blanch your vegetables before you freeze them. That doesn't really apply to fresh fruits, like apples, though you might have another reason to blanch them.
Blanching is a pretty simple process. Basically it just means plunging your fruit or vegetable into boiling water or steam for a brief time: Not long enough to cook it, but just long enough to thoroughly heat its skin or – in the case of greens – to make it wilt. Ideally you'll do this in small batches in a large quantity of water, so the water stays at or very close to a full rolling boil. After just a few seconds for delicate vegetables or up to a few minutes for sturdier ones, you'll lift them from the water with a slotted spoon and transfer them to a bowl of ice water. That second step is called "shocking" the produce, which keeps it from cooking any further.
Zap Those Enzymes
The reason you blanch and shock your fresh produce is rooted in nature. Every food contains enzymes that exist for the sole purpose of breaking it down once it's dead. That's how they turn back into compost to nourish future plants, which in turn nourish herbivores and so on. It's also why meats become tender when they're aged, because those enzymes start breaking down the muscle tissues. Unfortunately, while this is all very natural and necessary, you don't want it to happen to your own food. Blanching your vegetables before you freeze them puts a stop to the enzymes and their work, which means your veggies will last longer in the freezer. With green vegetables, it has the added advantage of enhancing their color.
Don't Do It With Fruit
With apples and other fruits, the situation is a bit different. For one thing, a lot of fruits and berries are delicate, and blanching would take away from their flavor and texture. More important, it's unnecessary. You bring the enzymes in fruit to a relative standstill by tossing them with an acid, like lemon juice or ascorbic acid, or by packing the fruit in a light sugar syrup. Both of these techniques protect a fruit's fresh flavor and keep more of its original texture, even after it's frozen. It's the same technique you use when you're treating sliced apples for a packed lunch or a fruit salad, and it works just as well in the freezer. The only reason you'd occasionally want to blanch apples is to remove their skins.
Peel Those Skins
It's not difficult to peel an apple, but if you have 10 or 20 pounds to peel, it definitely becomes a chore. Besides, even the best handheld or rotary peeler takes away a layer of apple with it. That's fruit you've paid good money for and won't get to use. For large quantities of apples, it makes sense to blanch them instead. Just plunge the apples a few at a time into boiling water for 30 to 60 seconds, then transfer them to a sink or large bowl filled with ice water. The skins should just slip off when you rub them, though a bit might remain around the stem and blossom ends. Then you can cut up the apples any way you want and use them immediately or pack them for the freezer.