How far in advance can I prepare vegetables without it detracting from their flavour/ texture etc?

Question

I've seen there is a related thread about restaurant practices and how long to retain food, but I don't think food safety comes into this as I'm only talking about cut vegetables kept for maybe 3 to 4 hours? It's more the issue of the effect on flavour I'm concerned with.

I'm a keen beginner, so my knife skills aren't yet good enough to prep veg quickly. As such, if I'm cooking for others, I try and prepare as much as possible in advance to serve food up in a reasonable time. I'd be very grateful if anyone can tell me:

How far in advance can I slice/ dice things like onions, celery, carrots etc without it having a detrimental effect on the flavours and textures?

Once they are sliced/ diced is it better to refrigerate them or might that make them wet/slimy?

If preparing the veg in advance does have a detrimental effect on the flavours and textures, are we talking a small difference that hardly anyone will notice or does it have a dramatic effect?

Thanks in advance.

Answer 1

The easy answer is that almost all things will start to deteriorate at soon as cut, but noticeable is the key. John points out, this will vary by item. Most fruits and softer items will be far less forgiving. Potatoes, a relatively hard item tends to oxidize badly, but water dunking tends to fix that with them as well. Items as you mention though, carrots, celery, lettuce, cabbage, any item that is pickled, these type of items tend to be more forgiving. An hour, maybe two, you likely will not notice any loss of quality. Plastic wrap to prevent drying will help and maybe extend this time. Wrapping and then ice or refrigerate, even better for dry items, but for wet items like cucumbers the weeping can be detrimental. With things like onions, garlic and herbs, well I would classify these as aromatics and part of their flavor is being lost anytime you can smell them so I would tend to save them for prep closer to use if possible. If you do need to prep them ahead, I have minced garlic a hour ahead for instance, then tossed it with olive oil that I was going to use in the dish. Please do this short term only though, as raw garlic stored is olive oil is classified by USDA as a salmonella risk. Hour should be fine, days not so much.

Answer 2

Some fruits and vegetables will oxidize and discolor when cut - potatoes and apples, most notably. If prepped in advance, these should be stored in cool water with some acid (lemon juice or vinegar) added.

Vegetables in the gourd family (cucumber, squash) will exude liquid from the cut surfaces that will bead up and eventually harden.

As for your other texture questions, I'm afraid it depends on what you're going to be doing with them - serve raw, saute, boil, roast, deep-fry?