Why Fruits and Vegetables Turn Brown when it is cut ?

Why Fruits and Vegetables Turn Brown | Prevent Fruits from Turning Brown | Prevent Vegetables from Turning Brown | Tips Why Fruits and Vegetables Turn Brown When fresh fruits and vegetables are peeled or cut open, the enzyme called polyphenol oxidase (also called tyrosinase) contained in the cells is exposed to and reacts with the oxygen in the air. The reaction that occurs, which is called oxidation, is what turns the fruits and vegetables brown. The bruising seen on some fruit, such as apples and pears, is caused by the same type of reaction. If an apple is damaged by being hit or dropped, the apple's cells in that area are damaged and the enzymes are exposed to the air inside the apple, causing them to turn brown. When preparing fruits and vegetables for use, an anti-browning solution should be used to prevent them from turning brown. Prevent Fruits from Turning Brown Some of the fruits that turn brown are apples, pears, peaches, and bananas. There are several techniques that can be used to prevent fruit from browning. Some of these anti-browning techniques are shown below. Fruit Citrus Juices Prevent browning by brushing the surface of the fruit with juice from citrus fruits, such as lemons, limes, oranges, and grapefruits. Lemon juice is often used for this purpose. Soak in Acidulated Water Another method is to place the fruit in water that has had lemon juice or cider vinegar added to make it acidulated. The squeezed lemon can also be cut into slices and added to help acidulate the water. Juice from other citrus fruit can also be used, such as limes, oranges and grapefruit. Use approximately 1/4 cup lemon juice to 1 quart of cold water. The lemon juice in the water with help reduce the pH on the surface of the fruit and the water will reduce the amount of oxygen the fruit is exposed to. Do not over soak fruit. Do not allow fruit such as apples to soak for more than 15 minutes and bananas should soak for no more than 3 to 5 minutes. Drain and pat dry before using. Other Options: Ascorbic acid, a commercial product, can also be added to water to create an anti-browning solution. Ascorbic acid is actually Vitamin C. Dip the slices in lemon-lime soda. Soak apples slices in apple juice until ready to use. The acidity in the apple juice prevents the apple slices from browning and doesn't change the flavor of the apple. Prevent Fruits and Vegetables from Turning Brown Some of the vegetables that turn brown are potatoes, sweet potatoes, parsnips, and artichokes. There are several techniques that can be used to prevent vegetables from browning. Some of these anti-browning techniques are shown below. Vegetables Cold Water When the potato is completely peeled, place it in cold water immediately until ready to cook or ready to cut to desired size. The cold water will prevent the outer surface of the potato from discoloring. Acidulated Water Create the acidulated water by adding lemon juice to cold water. Juice from other citrus fruits, such as limes, oranges, and grapefruit can also be used. Use approximately 1/4 cup lemon juice to 1 quart of cold water. Place the vegetables in the water and allow them to soak until ready to use. Vinegar can also be used in place of the lemon juice. Other Options: Ascorbic acid, a commercial product, can also be added to water to create an anti-browning solution. Ascorbic acid is actually Vitamin C. Cook the vegetables immediately to deactivate the enzyme. This will stop the reaction from happening and turning the vegetable brown. Rub the cut surface of the vegetable with the cut edge of a lemon. Tips Instead of using a commercial product containing ascorbic acid, use Vitamin C in the water for soaking fruits and vegetables. Break up and crush a 500-milligram Vitamin C tablet and dissolve in a gallon of water. Be sure the knife you are using to cut up fruits and vegetables does not contain any corrosion. The corrosion will cause fruits and vegetables to brown faster and will increase the amount. ----------------   ANTI-BROWNING SOLUTIONS PRESERVE NATURAL COLOR OF FRUITS AUBURN, JULY 2---Anti-browning solutions are used to preserve the natural color of dried, cored or cut fruits. If untreated, fruits oxidize and turn brown vegetables Ascorbic acid is vitamin C, and volume for volume, it's the most effective anti-browning solution. Most drugstores and natural-food stores carry pure crystalline ascorbic acid, says Dr. Evelyn Crayton, an Extension foods and nutrition specialist with the Alabama Cooperative Extension System. About 3,000 milligrams of ascorbic acid are in a teaspoon of the fine pure crystals. Ascorbic acid tablets also are available at most drugstores. To use tablets as an anti-browning agent, crush 400-500 milligram tablets. Ascorbic acid dissolves easily in water or juice, both of which should be boiled and cooled before the solution is made. Ascorbic acid is used most often with apples, apricots, nectarines, peaches and pears. The strength of the solution depends on the food being preserved. . For apples, dissolve 3 teaspoons of pure crystalline ascorbic acid in a cup of cold water. Dissolve 1 1/2 teaspoons of pure crystalline ascorbic acid in a cup of cold water for peaches, apricots, pears and nectarines Citric acid also preserves fruit color. However, It takes three times more citric acid than ascorbic acid to help prevent browning. Citric acid crystals (almost powder) can be purchased at most drugstores. It also comes in large crystals bottled as "sour salt" from a Kosher food store or the special-foods section of large supermarkets. These crystals are easily pulverized. Dissolve the required amount in 2 or 3 tablespoons of cold water then follow directions for the individual fruit using measures for ascorbic acid as your guide. Delicate flavors of some fruits may be masked when using citric acid. Lemon juice contains both ascorbic and citric acid. However, it's about only one-sixth as effective as pure ascorbic acid. Lemon juice also can alter taste of foods. Several commercial color-preservers also are available in supermarkets. They are located near the parrafin wax and commercial pectins, mostly in 5-ounce tins. The best known brand has a sugar base, with ascorbic acid and an anti-caking agent. It's expensive to use because of the small proportion of ascorbic acid in the mixture. The label tells how much to use for canning or freezing. Another brand contains sugar and citric acid, plus several other ingredients, but no ascorbic acid. Read labels to learn what each product contains. Crayton says any of these solutions will help prevent browning if used in the right proportions. SOURCE: DR. EVELYN CRAYTON, Extension foods and nutrition specialist, Alabama Cooperative Extension System. Thanks to : http://www.recipetips.com/kitchen-tips/t--945/why-fruits-and-vegetables-turn-brown.asp http://www.aces.edu/dept/extcomm/newspaper/antibrowning.html