Peeling and preparing vegetables ahead can save time the next day, but many vegetables begin to brown as soon as you slice into them. This oxidation occurs when enzymes beneath the peel react to oxygen exposure. An acid dip slows the enzyme actions so the vegetables brown more slowly, which allows you to store them for a short period. Treat peeled vegetables immediately to stop browning, but still use them within one day for the best flavor and texture.
Fill a bowl with cold water. Dissolve 1/2 tablespoon of citric acid powder or 3 vitamin C tablets in two quarts of water. These acids delay browning without compromising flavor.
Submerge the cut vegetables in the solution. Herbs and leafy greens only require a quick dip to prevent browning. Starchy vegetables, including potatoes or jicama, can soak in the solution overnight. Lettuce and other salad greens turn slimy after soaking and brown more slowly, so they do not require an acid treatment before wrapping and storing.
Shake off the excess moisture and pat the vegetables dry, unless you are leaving them in the water to soak overnight.
Wrap whole peeled vegetables tightly in plastic wrap. Press the wrap down so it's in full contact with the peeled vegetable surface, which keeps out air and further slows oxidation. Place sliced vegetables in a zip-top bag and press out the excess air before sealing. Store the vegetables overnight in a 33- to 40-degree-Fahrenheit refrigerator.