The bright yellow hue of a banana may seem ruined when it develops brown spots. Your first instinct may be to throw away any discolored bananas. However, the appearance of brown spots does not destroy this highly nutritious and portable fruit, that is readily available year round.
Unlike fruits that need to ripen on the tree or plant, growers pick bananas that are firm, green and fleshy. Once the fruit leaves the tree, amino acids inside began to change to ethylene gas. This gas eventually ripens the banana. The enzymes soften the banana, sweeten the fruit and change the color from green to yellow. Growers often ship bananas long distances, and thicker, tougher peel of green, unripened bananas often makes the journey with less damage. Some growers add ethylene gas to ripen bananas more quickly if they are close to the marketplace.
Brown Spots from Ripening
As the banana ripens, brown spots generally develop as it moves through the ripening stage. The sugar content in the banana increases from almost zero to about 80 percent as the banana ripens, according to Kathy Wollard, author of Newsday's “How Come?” The more brown spots the banana has, the more sugar the banana contains, and the sweeter it becomes. Brown spots on a banana generally do not indicate disease. Bananas with spots should be safe to eat.
Although brown spots on bananas are often a result of the ripening process, you may encounter a banana that has long brown streaks and appears split. This condition, caused by too much humidity during the ripening process, may make the banana inedible. Plant pathologist Scot Nelson at the University of Hawaii says that small brown flecks on the banana’s peel may be an indication of senescent spots. These spots develop from already mature fruit spending time in a specialized ripening facility. Bananas with senescent spots are safe to eat. If you put your bananas in the refrigerator for longer than one day, Nelson says you may injure the bananas skin and cause dark areas to form. Of course, sometimes brown spots occur from bruising from rough handling. These bruises are harmless and don't make the banana inedible.
The high sugar content of bananas with brown spots makes them good for use in baking. Using very ripe bananas often means you can reduce the amount of sugar in recipes for banana bread, muffins and cakes. Other options for very ripe bananas include mashing the fruit and freezing them in quart-sized bags. You can use the puree in smoothies or baked goods. If you are trying to eat a nutritionally balanced diet, one banana counts as a serving of fruit. A 7-inch 118-gram banana has about 105 calories, making it a good choice if you try to limit your snacks to the 100-calorie range.
Before you throw out a banana because it has turned brown and seems past its eating prime, consider the potential nutritional benefits it provides. A brown banana has a higher level of antioxidants than yellow or green, unripe bananas. It's also easier to digest for people with digestive ailments, including irritable bowel and functional abdominal bloating.
A brown, yellow or green banana are all a good source of potassium, vitamin B-6 and fiber. As a banana reaches the brown stage, its concentration of antioxidants increases. Antioxidants are important in helping protect your body against disease-causing inflammation. As bananas turn brown, some of the micronutrients present do diminish. Store ripe bananas in the refrigerator to reduce this loss.
In brown bananas, the resistant starch has almost completely transformed into simple sugars. When you eat a brown banana, you're blood sugar spikes more quickly than it would when you eat a green one. Type-2 diabetics are thus recommended to avoid brown-spotted or fully brown bananas, which are mostly sugar. Less ripe bananas are healthier for people who are trying to cut back on sugar.
Because a brown banana is mostly simple sugar, it's easy to digest. People with irritable bowel and other digestive ailments may find brown bananas are more agreeable to their systems. Watch for brown bananas that are too far past their prime. If it smells, is squishy or shows signs of leaking or mold, it's not fit to eat.
A Japanese study published in a 2009 issue of "Food Science and Technology Research" determined that the brown spots on bananas produce a substance called Tumor Necrosis Factor, which breaks down abnormal cells -- including those that cause cancer. Brown bananas can't cure cancer, but consuming them might boost your immune function.