Vegetables You Can Chop in Advance (and the Ones You Shouldn’t)

It’s almost impossible to over-prep Thanksgiving. I say “almost” because my mum once cooked an entire Thanksgiving meal in advance, then reheated it on the big day. It was very much like we had all been in The Blip, and came back on the day after Thanksgiving. Some things just don’t age well, especially once they’ve been cooked, but even the act of cutting a vegetable can kick off a process that affects the flavour and texture of the final dish. Some vegetables do fine when prepped a few days in advance, but some are best when chopped, sliced, and diced just before using. Here’s how to tell the difference.

Non-starchy root vegetables

Let’s start with the good news: There are a fair number of vegetables that you can peel and slice two or three days beforehand without any terrible side effects, like oxidization, significant loss of moisture, and decomposition. Non-starchy root vegetables, like sweet potatoes, beets, carrots, radishes, and onions all have a two- or three-day window for peeling and cutting. For onions, wrap the cut ones in aluminium foil before packing it in a closed container to keep your fridge from becoming an oniony Pandora’s box.

Some cruciferous veggies and fruits

Cruciferous veggies happen to be some of the hardiest edible plants around. These are vegetables that have tough stalks and leathery leaves. You’re more likely to see them packaged in various stages of chopping at your grocery store. You can cut broccoli, cauliflower, Brussels sprouts, cabbage, and kale three or four days ahead of time; celery and mushrooms can be cut two or three days ahead of time. Fruits that we commonly consider vegetables, like peppers, cucumbers, and squash, can be cut about two days beforehand.

Better to wait on delicate leaves

Think twice before cutting anything with a tender or delicate leaf. For some plants, cutting can severely damage the plant cells which will quickly manifest in bruising, and dark, mushy edges within hours (and sometimes minutes). Baby spinach, lettuces, herbs, and, surprisingly, fresh green beans, are all best left to chop on game day. Particularly with herbs, you’ll get the most aromatic impact for finishing dishes if you mince them just before serving.

If you absolutely must chop any of these in advance, make sure you use a sharp knife. This goes for cutting in general, but a sharp knife with a fine cutting edge is going to cause less damage, slicing cleanly through plant cells, rather than crushing them like a dull knife will.

Starchy root vegetables oxidize quickly

Although non-starchy root vegetables will hold up days in advance, the starchy ones are more susceptible to oxidation and enzymic browning. You’ve probably seen this happen after slicing or biting into an apple, after five or ten minutes, the apple’s flesh begins to turn brown. This is a reaction the enzymes of the fruit or vegetable have once they’ve been exposed to oxygen from slicing. Starchy root vegetables like potatoes, parsnips, and turnips oxidize more readily than the vegetables mentioned above.

If you hate the idea of waiting until Thursday to peel five pounds of parsnips, you have a couple choices. The night before, peel or cut them and submerge them in water. The water will keep oxygen from interacting with the exposed vegetable flesh. The downside to this is that a vegetable like potatoes will lose starch to the soaking water, and if you leave them in the bowl for too long, they can become waterlogged and break apart. Another option is to toss any cut starchy vegetables in an acid like lemon juice. The acid contained in lemon juice will stop the enzymes from doing their browning business. Either way, chopping and treating starchy vegetables is best done the night before.