9.6: Selecting, Purchasing and Storing Fruits

Nutrition

Most fruits are quite nutritious. They have a high water content (usually 75 to 95 percent), low protein, and fat contents, all of which makes them low in calories. They are also an excellent source of fiber, and the sugar content of ripe fruits is a good source of energy. Some fruits, such as citrus, melons and strawberries, contain large amounts of vitamin C (which may be destroyed, however, by cooking or processing). Deep yellow and green fruits, such as apricots, mangoes and kiwis are high in vitamin A; bananas, raisins and figs are a good source of potassium.

Selecting Fresh Fruits

Fresh fruits have not been subjected to any processing (such as canning, freezing or drying). Fresh fruits may be ripe or unripe, depending on their condition when harvested or the conditions under which they have been stored. In order to use fresh fruits to their best advantage, it is important to make careful purchasing decisions. It is important to pay attention to the size of e ach piece of fruit, its grade or quality, its ripe ness on delivery and its nutritional content in order to serve fruit in an appropriate and cost-effective manner.

Grading

Fresh fruits traded on the wholes ale market may be graded under the USDA's voluntary program. The grades, based on size and uniformity of shape, color and texture as well as the absence of defects, are U.S. Fancy, U.S. No. 1, U.S. No. 2 and U.S. No. 3. Most fruits purchase d for food service operations are U.S. Fancy. Fruits with lower grades are suitable for processing into sauces, jams, jellies or preserves.

Ripening

Several import ant changes take place in a fruit as it ripens. The fruit reaches its full size; its pulp or flesh becomes soft and tender; its color changes. In addition, the fruit's acid content declines, making it less tart, and its starch content converts into the sugars fructose and glucose, which provide the fruit's sweetness, flavor and aroma.

Unfortunately, these changes do not stop when the fruit reaches its peak of ripeness. Rather, they continue, deteriorating the fruit's texture and flavor and eventually causing spoilage. Depending on the species, fresh fruits can be purchased either fully ripened or unripened. Figs and pineapples, for example, ripen only on the plant and are harvested at or just before their peak of ripeness, then rushed to market. They should not be purchased un-ripened, as they will never attain full flavor or texture after harvesting. On the other hand, some fruits, including bananas and pears, continue to ripen after harvesting and can be purchased unripened.

With most harvested fruits, the ripening time as well as the time during which the fruits remain at their peak of ripeness can be manipulated. For instance, ripening can be delayed by chilling. Chilling slows the fruit's respiration rate (fruits, like animals, consume oxygen and expel carbon dioxide). The slower the respiration rate, the slower the conversion of starch to sugar. For quicker ripening, fruit can be stored at room temperature.

Ripening is also affected by ethylene gas, a colorless, odorless hydrocarbon gas. Ethylene gas is naturally emitted by ripening fruits and can be used to encourage further ripening in most fruits. Apples, tomatoes, melons, and bananas give off the most ethylene and should be stored away from delicate fruits and vegetables, especially greens. Fruits that are picked and shipped unripened can be exposed to ethylene gas to induce ripening just before sale. Conversely, to extend the life of ripe fruits a day or two, isolate them from other fruits and keep them well chilled.

Fresh fruits will not ripen further once they are cooked or processed. The cooking or processing method applied, however, may soften the fruits or add flavor.

Purchasing Specifications

Fresh fruits are sold by weight or by count. They are packed in containers referred to as crates, bushels, cartons, cases, lugs or flats. The weight or count packed in each of these containers varies depending on the type of fruit, the purveyor and the state in which the fruits were packed. For example, Texas citrus is packed in cartons equal to 7/10 of a bushel; Florida citrus is packed in cartons equal to 1/s of a bushel. Sometimes fruit size must be specified when ordering. A 30-pound case of lemons, for example, may contain 96, 112, or 144 individual lemons, depending on their size.

Some fresh fruits, especially melons, pineapples, peaches and berries are available trimmed, cleaned, peeled or cut. Sugar and preservatives are sometimes added. They are sold in bulk containers, sometimes packed in water. These items offer a consistent product with a significant reduction in labor costs. The purchase price may be greater than that for fresh fruits, and flavor, freshness and nutritional qualities may suffer somewhat from the processing.

Purchasing and Storing Preserved Fruits

Preservation techniques are designed to extend the shelf life of fruits in essentially fresh form. These methods include irradiation, acidulation, canning, freezing and drying. Except for drying, these techniques do not substantially change the fruits ' texture or flavor. Canning and freezing can also be used to preserve cooked fruits.

Irradiated Fruits

Some fruits can be subjected to ionizing radiation to destroy parasites, insects and bacteria. The treatment also slows ripening without a noticeable effect on the fruits ' flavor and texture. Irradiated fruits must be labeled "treated with radiation," "treated by irradiation" or with the appropriate symbol.

Acidulation

Apples, pears, bananas, peaches and other fruits turn brown when cut. Although this browning is commonly attributed to exposure to oxygen, it is actually caused by the reaction of enzymes. Enzymatic browning can be retarded by immersing cut fruits in an acidic solution such as lemon or orange juice. This simple technique is sometimes referred to as acidulation. Soaking fruits in water or lemon juice and water (called acidulated water) is not recommended. Unless a sufficient amount of salt or sugar is added to the water, the fruits will just become mushy. However, if enough salt or sugar is added to retain texture, the flavor will be affected.

Canned Fruit

Almost any type of fruit can be canned successfully; pineapple and peaches are the largest sellers. In commercial canning, raw fruits are cleaned and placed in a sealed container, then subjected to high temperatures for a specific amount of time. Heating destroys the microorganisms that cause spoilage, and the sealed environment created by the can eliminates oxidation and retard s decomposition. However, the heat required by the canning process also softens the texture of most fruits. Canning has little or no effect on vitamins A, B, C and D because oxygen is not present during the heating process. Canning also has no practical effect on proteins, fats or carbohydrates.

In solid-pack cans, little or no water is added to the product. The only liquid is from the fruits ' natural moisture. Water-pack cans have water or fruit juice added, which must be taken into account when determining costs. Syrup-pack cans have a sugar syrup added: light, medium, or heavy. The syrup should also be taken into account when determining food costs, and the additional sweetness should be considered when using syrup-packed fruits. Cooked fruit products such as pie fillings are also available canned.

Canned fruits are purchased in cases of standard -sized cans (see Appendix II). Once a can is opened, any unused contents should be transferred to an appropriate storage container and refrigerated. Cans with bulges should be opened and discarded immediately.

Frozen Fruits

Freezing is a highly effective method for preserving fruits. It severely inhibits the growth of microorganisms that cause fruits to spoil. Freezing does not destroy nutrients, although the appearance or texture of most fruits can be affected because of their high water content. This occurs when ice crystals formed from the water in the cells burst the cells' walls.

Many fruits, especially berries and apple and pear slices, are now individually quick-frozen (IQF). This method employs blast s of cold air, refrigerated plates, liquid nitrogen, liquid air or other technique s to chill the produce quickly. Speeding the free zing process can greatly reduce the formation of ice crystals.

Fruits can be trimmed and sliced before freezing and are also available frozen in sugar syrup, which acids flavor and prevents browning. Berries are frozen whole, while stone fruits are usually peeled, pitted, and sliced. Fruit purees are also available frozen.

Frozen fruits are graded as U.S. Grade A (Fancy), U.S. Grade B (Choice or Extra Standard), or U.S. Grade C (Standard). The ''U.S." indicates that a government inspector has graded the product, but packers may use grade names without an actual inspection if the contents meet the standards of the grade indicated.

IQF fruits can be purchased in bulk by the case. All frozen fruits should be sealed in moisture-proof wrapping and kept at a constant temperature of 0°F (- 18°C) or below. Temperature fluctuations can cause freezer burn. Frozen berries such as blueberries and blackberries should not be thawed before adding to batters because their juice can easily discolor the batter.

Dried Fruits

Drying is the oldest known technique for preserving fruits, having been used for more than 5000 years. When ripe fruits are dried, they lose most of their moisture. This concentrates their flavors and sugars and dramatically extends shelf life. Although most fruits can be dried, plums (prunes), grapes (raisins, sultanas and currants), apricots and figs are the fruits most commonly dried. The drying method can be as simple as leaving ripe fruits in the sun to city naturally or the more cost-efficient technique of passing fruits through a compartment of hot, dry air to quickly extract moisture. Dried fruits actually retain from 16 to 26 percent residual moisture, which leaves them moist and soft. They are often treated with sulfur dioxide to prevent browning (oxidation) and to extend shelf life.

Dried fruits may be eaten out of hand; added to cereals or salads; baked in muffins, breads, pies or tarts; stewed for chutneys or compotes; or used as a stuffing for roasted meats or poultry. Before use, dried fruits may be softened by steeping them for a short time in a hot liquid such as water, wine, rum, brandy or other liquor. Some dried fruits should be simmered in a small amount of water before use.

Store dried fruits in airtight containers to prevent further moisture loss; keep in a dry, cool area away from sun light. Dried fruits may mold if exposed to both air and high humidity.

Juicing

Fruit juice is used as a beverage, alone, mixed with other ingredients, and as the liquid ingredient in other preparations. Juice can be extracted from fruits (and some vegetables) in two ways: pressure and blending.

Pressure is used to extract juice from fruits such as citrus that have a high water content. Pressure is applied by hand squeezing or with a manual or electric reamer. All reamers work on the same principle: A ribbed cone is pressed against the fruit to break do w n its flesh and release the juice. Always strain juices to remove seeds, pulp or fibrous pieces.

A blender or an electric juice extractor can be used to liquefy less- juicy fruits and vegetables such as apples, carrots, tomatoes, beets and cabbage. The extractor pulverizes the fruit or vegetable, then separates and strains the liquid from the pulp with centrifugal force.

Interesting and delicious beverages can be made by combining the juice of one or more fruits or vegetables: pineapple with orange, apple with cranberry, strawberry with tangerine and papaya with orange. Color should be considered when creating mixed-juice beverages, however. Some combinations can cause rather odd color changes. Although yellow and orange juices are not a problem, those containing red and blue flavonoid pigments (such as Concord grapes, cherries, strawberries, raspberries and blueberries) can create some unappetizing colors. Adding an acid such as lemon juice helps retain the correct red and blue hues.