Healthy and delicious, bananas are packed with vitamins and are an easy snack when you're on the go. They ripen after they're picked, turning from green to yellow and eventually developing spots as they brown. These marks are caused by ethylene, a hormone that turns complex sugars into simple ones, while also breaking down pectin, which gives fruit a firm texture. Other hormones diminish color pigments as well, according to the University of California at Santa Barbara, which causes more browning.
Bananas are native to hot, tropical climates, so there's no need to store them in the refrigerator except when you want to delay ripening. Instead, keep them uncovered on your kitchen counter. Take them out of plastic bags so that they ripen evenly. If your bananas turn too brown for your taste, put them in the freezer until you're ready to use them in a smoothie or banana bread.