Practical methods, temperatures, timings and techniques for more reliable cooking results.
To speed up a firm banana, place it in a paper bag with a ripe apple, pear, avocado, or mango. Those fruits release ethylene, which accumulates and stimulates ripening. To slow bananas down, separate them from ripe ethylene producers and refrigerate once yellow; the peel may darken while the flesh changes more slowly.
For most intact fruit, washing shortly before you eat or cut it is the simplest approach. Rinse under running water, do not use soap, and dry if needed. If you wash before storage, dry the fruit thoroughly because lingering moisture can encourage faster deterioration.
Cut potatoes can be held under cold water in the refrigerator to prevent browning. For home cooking, using them within about 24 hours is a good quality target. Longer soaking removes more starch and soluble material and can gradually weaken texture.
You do not need oil in pasta water. Oil and water do not mix, so most of it stays at the surface instead of coating each piece while it cooks. A roomy pot and frequent stirring during the first minutes are much more effective against sticking.
To prepare potatoes a day ahead, cover peeled potatoes completely with cold water and refrigerate them in a covered container. Water limits oxygen exposure and slows browning. Drain them the next day, and dry thoroughly if they are going into hot oil or a dry oven.
For Italian-style pasta going straight into sauce, do not rinse it. Water washes away the surface starch that helps sauce bind to the noodles. Rinsing can make sense for some cold dishes or certain Asian noodles, but it is not a universal step.
Pasta water is useful because it is hot, seasoned, and contains starch released by the noodles. Added gradually to a sauce, it replaces moisture lost during finishing and helps stabilize mixtures of water and fat so they coat the pasta more evenly. Reserve about a cup before draining, then use it a splash at a time rather than pouring it all in.
Pasta sticks because cooking leaves its surface wet and rich in gelatinized starch. Once drained, noodles rest against one another and that starch can behave like adhesive as the pasta cools. Stirring during the first minutes of cooking and moving the pasta directly into its sauce work better than adding oil to the boiling water.
Salt is added to pasta water mainly to season the pasta while it hydrates. The boiling-point effect is far too small to be the practical reason: about 10 g of salt in 1 liter of water raises the boiling temperature by only roughly 0.2°C, or about 0.3°F—not enough to make pasta cook noticeably faster.
Mashed potatoes turn gluey when too many cooked potato cells are ruptured and release gelatinized starch. A blender or food processor can take a fluffy mash to stretchy paste in seconds. Starchy potatoes, a ricer or hand masher, and minimal mixing after adding butter and warm liquid greatly reduce the risk.
Fries turn soggy when their surface retains too much moisture or the oil temperature drops so far that the crust cannot dry and set efficiently. Even cuts, optional soaking, thorough drying, smaller batches, and a two-stage fry make it much easier to build a crisp shell around a fluffy interior.
A cold-water soak washes away some of the loose starch released when potatoes are cut and also keeps the cut surfaces from browning while they wait. That can reduce sticking and help create a cleaner crust. The safety-critical step comes afterward: drain and dry the potatoes thoroughly before they go near hot oil.