What happens inside food when heat, water, mixing, fermentation and other cooking processes change its structure.
There is no universal winner. Cooking can reduce heat- and water-sensitive nutrients such as vitamin C and folate, while also breaking cell walls and increasing the availability of carotenoids such as lycopene in tomatoes and beta-carotene in carrots and spinach.
Climacteric fruits can continue ripening after harvest: bananas, avocados, pears, apples, mangoes, kiwifruit, peaches, and plums are common examples. Pineapple, citrus, grapes, strawberries, cherries, and watermelon are non-climacteric and do not develop much additional sweetness once picked.
Bananas respond strongly to ethylene, a gaseous plant hormone that triggers ripening. Apples, pears, avocados, and other climacteric fruits also release ethylene, so grouping ripe fruit together can increase local exposure and speed softening, yellowing, aroma development, and starch-to-sugar conversion.
Bananas darken as they ripen because tissues change and phenolic compounds oxidize. Bruising and cold exposure can accelerate the browning. A nearly black peel can still hide usable flesh; mold, leaking liquid, a rotten odor, or badly decayed flesh are different warning signs.
Cut avocado browns when enzymes in the flesh react with oxygen. Refrigerate it, minimize air contact with wrap pressed directly onto the surface or a small airtight container, and add a little lemon or lime juice if you do not mind the flavor.
Most U.S. extension guidance still recommends a cool, dark, ventilated place rather than a standard refrigerator because cold storage can convert starch to sugars and make potatoes taste sweeter and brown faster. A recent UK review, however, found that home refrigeration did not materially increase acrylamide-forming potential compared with a cool dark place.
Internal black spots have several possible causes. A dry localized patch may be a bruise caused by impact or pressure; corky areas can come from growth disorders. Wet, soft, slimy, moldy, or bad-smelling tissue points toward spoilage and is a reason to discard the potato.
Black or brown strings in avocado flesh are usually vascular bundles—the fruit’s natural transport tissues—that have darkened. A few strings in otherwise normal flesh are usually a quality issue; widespread blackening, slime, mold, or a rancid smell points toward spoilage.
Put a firm avocado in a paper bag at room temperature with an apple, banana, or tomato. Those fruits release ethylene, which speeds natural ripening. Heating an avocado may soften it, but it does not create the same flavor and texture as true ripening.
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.