Drying Fruit Fruits are generally grouped according to the climate in which they grow. Tropical fruits, such as bananas and pineapples, must have warm humid climates to flourish. Subtropical fruits need a warm constant climate with moderate moisture. These include citrus fruits. figs, dates and olives. Temperature-zone fruits include apples. apricots, berries, cherries, peaches, pears and plums. With a few exceptions, fruits from all three groups may be dried. Because of availability. most fruits used in home drying in the United States are from the temperate-zone group. Fruits contain B complex vitamins, vitamin C, carbohydrates and mineral salts such as iron, phosphorus and calcium. Some vitamin C may be lost through the drying process, but other nutrients are relatively unaffected. The amount of vitamins retained by dried fruits depends largely on how they are processed, dried and stored. In particular, the longer the drying time and the higher the temperatures, the more nutrient loss in the food. With a fast, low temperature dehydrator. there is little nutrient loss during the drying process itself. Also, all vitamins, minerals and fiber in fruits are concentrated by drying, leaving a higher density of nutrients by weight. Thus dried fruits are a good source of nutrition for snacking and as an outdoor food, and of roughage, which helps our digestion. YOU NEED TO KNOW Most truits are covered with a skin which keeps the fruit fresh and holds in the seed, juicy flesh and, incidentally, the flavor. For fruits to dry quickly enough to prevent spoilage or fermentation, that skin has to be perforated in some way to allow moisture to escape. There are various ways to do this, depending on the type of fruit and the drying method being used. HALVING - Fruits such as apricots and small peaches or pears may be cut in half. When the pits are removed, the fruit halves are dried skin-side down and the moisture gradually evaporates. The bottom portion of the skin prevents the juices from dripping out and helps keep in the flavor during drying. SLICING - To speed the drying process in larger fruits, they should be peeled and cut into slices 1/4 to 1/2-inch thick. The entire surface area of the fruit will dry in less time than in fruits left whole or halved. Also, uniform slices will dry in the same amount of time. With some fruits, such as pears or peaches, slicing lengthwise will give you fewer, larger pieces than slicing crosswise. A very sharp, high quality stainless steel knife should be used to minimize browning on the cut surface. CHECKING - Small fruits such as prunes, cherries or grapes, have a uaxy bloom or thin natural waxlike coating which keeps moisture in. This waxlike coating may be cracked or checked before drying so the moisture can escape. This will decrease the drying time. Checking is perforating the waxy bloon by chemical, heat or mechanical means. Commercially, fruits such as prunes are checked by dipping the whole fruit in a Iye solution. This is not recommended for home drying because of the danger of handling lye and the possible retention of lye in the fruit. You can speed the drying process in whole small fruits by dipping them in boiling water just long enough to crack the skins. This will hasten evaporation and shorten drying time. Fruits which have been dipped in boiling water are less flavorful than those that have not. PITTING - Fruits with a pit or stone, such as cherries, should be pitted before drying. This will shorten drying time and produce a better tasting dried fruit. Larger fruits, such as prunes, can be halved to remove the pits. You can shorten the drying time of prunes or apricots by flattening them. Use your thumbs to press the rounded side in. This process, called poppint the backs, exposes more drying surface to the air. MOISTNESS The moisture content of home dried fruits should be about 15 to 20 per cent. Because dried fruits are usually eaten without rehydration, some moisture is necessary for a chewy texture. Fruits that are over dried to a moisture level of 5 to 10 per cent lose color, flavor and nutrients and have a less palatable texture. The dryness test for home drying fruits is simply touching and tasting. The fruit should be chewy and leather-like with no moisture pockets. Home-dried fruits are considerably drier than commercially dried fruits. The dehydration industry uses chemical agents that inhibit the growth of mold and other microorganisms and slow browning during storage. With these additives, commercially dried fruits may contain as much as 30 to 35 per cent moisture without spoiling, although they will still brown somewhat during storage. DRYING FRUITS -- HOW TO BEGIN Sort and select the highest quality ripe ready-to-eat fresh fruit. Fully ripe fruit should be firm and heavy for its size. If it's perfect for eating, it's perfect for drying! Handle fruits gently and process them quickly because when they are at the right stage for drying, they are also the most fragile. WASHING -- Gently wash all fruits to remove dirt, bacteria and insect larvae. Cold water will preserve freshness. Wash just before processing. Don't let fruit remain in water for long periods, becausc some of the nutrients will be dissolved and lost. Fruits with skins such as cherries or prunes must be washed particularly well. Insect larvae cannot be seen on fresh fruit, but may hatch after the fruit has been dried and stored unless they are washed off before drying or killed during pasteurizing. PREPARATION -- To prepare fruit for pretreatment and drying, remove stems and peels. Core or pit fruit and cut it into halves, quarters or slices. Peels may be left on sorme fruit, but they tend to be tough and occasionally bitter. Trim away any bruised or soft spots. One soft spot can spoil an entire batch! Prepare only as much fruit as you can pretreat and dry at one time. BROWNING -- oxidation and the continuous reaction of enzymes cause some fruits, such as apples, pears, peaches and apricots, to turn brown when cut and exposed to air. Unless fruits are treated to slow oxidation and enzyme reaction, browning wil] continue during processing and storage. Much f]avor and vitamins A and C will then be lost. HOLDING SOLUTIONS -- Place cut fruits that tend to brown in an ascorbic acid or sodium bisulfite holding solution as soon as you cut them. This will reduce browning during preparation. Do not keep cut fruit in a holding solution for more than 1 hour. Longer holding increases moisture content and extends drying time. See caution regarding use of sodium bisulfite. Ascorbic acid is an effective anti-oxidant used in canning and freezing to prevent discoloration. Small quantities of ascorbic acid or lemon juice, which is high in ascorbic acid, may be added to fruit-leather puree to maintain color and increase the vitamin C content. Sodium bisulfite mixed with water, slows oxidation and browning. Use 1/4 teaspoon sodium bisulfite for each quart of water. Sodium bisulfite can also be used as a pretreatment method called sulfiting or sulfite soaking when drying fruits. PRETREATMENT -- NOTE: No pretreatment is NECESSARY with any fruit. Pretreating some fruits before drying will reduce vitamin loss, flavor loss, hrowning and deterioration during storage. When not pretreating, storage in the refrigerator or the freezer will also dramatically reduce deterioration. Sulfuring, sulfiting, syrup blanching and steaming are all methods of pretreatment to keep fruits in prime condition for drying or storage. Do not hold cut fresh fruit in salted water. This gives an undesirable flavor and a gray color to the fruit. Ascorbic acid or lemon juice (used very successfully in canning and freezing to retard oxidation) may be used as an anti-oxidant pretreatment for drying fruits although the dehydration process tends to reduce its effectiveness. Sulfur-dioxide treatments are the most effective for retarding oxidation and spoilage. Fruit flavor and storage life are also improved. Sulfur dioxide is a combination of sulfur and oxygen. Sulfur is a solid nonmetallic element found in eggs and many strong smelling vegetables, such as cabbage, horseradish and onions. The small quantity of sulfur dioxide remaining in dried fruits is not harmful when consumed. Treating fruit with sulfur dioxide may be accomplished in two ways. SULFURING exposes the fruit to sulfur dioxide fumes by burning flowers of sulfur in a closed container with fruit. The fumes penetrate the surface area of the fruit about 1 to 2 millimeters deep. SULFURING MUST BE DONE IN THE OPEN BECAUSE THE FUMES ARE HARMFUL TO PEOPLE AND ANIMALS. BECAUSE OF THESE MANY CAUTIONS, I WILL NOT INCLUDE THE SULFURING INFORMATION. SULFITING -- is soaking fruit for a specified time in a solution of water and sodium bisulfite. This releases sulfur dioxide and has the same general effect as sulfuring but it is not as effective. Sulfiting may be done in your kitchen. Drying time is longer than with sulfuring because of the water absorbed during soaking. SYRUP BLANCHING You Will Need: Large saucepan, sugar, corn syrup and water. Syrup-blanched fruits have good color. However, they are sweeter and have a softer texture than sulfured and sulfited fruits. They also contain less vitamins A and C. HOW TO SYRUP BLANCH Prepare the fruit as you would for sulfuring. Prepare a sugar syrup by mixing 1 cup sugar, 1 cup white corn syrup and 2 cups water. Bring to a boil; add 1-1/2 pounds prepared fruit. Simmer 5 minutes. Drain and rinse lightly with cold water. Dry on drying trays. STEAMING You will need: a steamer, an ascorbic-acid solution Steaming destroys the natural flavor and texture of fruit and much of the vitamins A and C. Steamed fruit doesn't have the full flavor of sulfured fruit nor the sweetness of syrup-blanched fruit. It is the least-effective way to pretreat fruits for drying, but is used by people who prefer not to use sulfur dioxide or a sweetened syrup. HOW TO STEAM As you prepare the fruit, place it in an ascorbic-acid or a weak sodium-bisulfite solution. Drain and place the fruit in the perforated section of a steamer without letting the fruit touch the water. Cover tightly and steam until heated through. To test for heat penetration, bite into a piece or break it and touch the center. Place the fruit on drying trays. HOW DO YOU KNOW THEY'RE DRY?? Most people will rely on the taste and touch test; see the Dryness Test for each fruit in the following "Fruits A - Z" charts. If you taste and touch and are still not sure, comparing the weight of the fruit before and after drying will help you. After peeling the fruit and removing the pits, seeds or cores, weight it. Write down the weight and begin the drying process. To calculate the desired weight after drying, first look up the water content of the fruit you are drying. This figure is given for each fruit in the following "Fruits A - Z" charts. For example: if you are drying apricots, weigh them after removing the pits. Suppose you have 25 pounds. In chart 1 of "Fruits A - Z", the water content of apricots is given at 85% or 0.85. The percent of water most fruits must lose in the drying process is 80% to 85%. We can use 0.80, the decimal equivalent of 80%. 1. Find the total weight of water in the fruit: Weight of edible fresh fruit times the percent of water content equals the total weight of water. For your apricots: 25 x 0.85 = 21.25 pounds of water. 2. To find the weight of water which must be removed, multiply the total weight of water by the percent of water to be removed: Total weight of water times the percent of water to be removed equals the weight to be removed. For your apricots: 21.25 x 0.80 = 17 pounds to be removed. 3. To find out how much the apricots should weigh after they are dried, subtract the weight of water to be removed from the weight of the fresh apricots: Weight of fresh fruit minus the weight of water to be removed equals the weight of dried fruit. For your apricots: 25 - 17 = 8 pounds of dried fruit. When you think the apricots are sufficiently dried, weigh them. They should weigh about 8 pounds. If they weigh 9 pounds or more, they need to be dried longer. HOW TO DRY FRUITS Preheat the dryer to get the drying process under way immediately. Arrange prepared and pretreated fruit on drying trays, leaving small spaces between slices or pieces for air circulation. Different fruits may be dried together because they do not have the strong flavor or odor of some vegetables. Dry fruit halves or slices of similar size on the same tray to save sorting near the end of the drying process. Smaller fruits, such as cherries, should be stirred occasionally to promote even drying. Try to interrupt the drying process as little as possible. Sun drying is slowed at night because the temperature drops or the fruit is brought inside. Prolonging drying at low temperatures or interrupting the drying of fruits may result in fermentation or spoilage. Do not add fresh moist pieces to a dryer filled with partially dried fruit. The increased humidity will greatly increase the drying time of the partly dried fruit. Check the suggested drying temperatures for each fruit, please see the charts "Fruits A - Z." Some fruits contain considerably more water than others and the initial drying temperature can be as high as 160øF (70øC) to remove surface moisture quickly. Other fruits should not exceed 140 or 150øF (60 to 65øC) in the initial stages because higher temperatures will destroy heat-sensitive nutrients. If you dry two fruits which have different suggested drying temperatures at the same time, make a compromise between the two. If it is impossible to vary the temperatures, the fruit will still dry, but the quality will suffer. Sun dried fruit should be placed in direct sunlight for the first 2 or 3 days of drying. After that, the fruit can be placed in the shade for the remainder of drying time. This will give you fruit with better flavor and less loss of color and nutrients. This is sometimes called "sun-shade drying." TESTING FOR DRYNESS Watch fruits carefully near the end of the drying process. Test frequently to avoid overdrying. Let a piece of fruit cool to rooin tenlperature. Touch and taste it. It should feel pliable and leather-like, and have no pockets of moisture. Most fruits should contain between 15 and 20 percent moisture when properly dried. CONDITIONING When drying is completed, some pieces will be more moist than others because of the size of the pieces or their location in the dryer. "Conditioning" is a process used to distribute the residual moisture evenly in the fruit. It reduces the chance of spoilage, particularly from mold. After the dried fruit has cooled, loosely pack it in plastic or glass containers to about 2/3 full. Metal containers may give an unpleasant flavor to the fruit. Cover the containers tightly and let them stand for 2 to 4 days. The excess moisture in some pieces will be absorbed by the drier pieces. Shake the containers daily to separate the pieces and check for signs of condensation on the lids. If condensation occurs, the fruit should be returned to the drying trays for more drying. PASTEURIZING Washing fruit does not always remove insect larvae, so fruits which have been exposed to insects before or during the drying process must be pasteurized to prevent spoilage during storage. Two methods of pasteurizing may be used. FREEZER METHOD - After the fruit has heen dried and conditioned, seal it in heavy plastic bags. Place them in a freezer set below 0øF (-20øC) for at least 48 hours or up to 2 weeks before storing. OVEN METHOD - A second method of pasteurizing fruit is done after conditioning but before the fruit is packaged. Vitamin loss is high with this method. Layer the fruit loosely. not more than 2 inches deep, in a roasting pan. Place the pan in an oven preheated to 175øF (80øC) for 15 minutes or 160øF (70"C) for 30 minutes. Remove and cool the fruit and package it for storage. PACKAGING Dried fruit should be cooled and conditioned before packaging, then vacuum packaged in bags or jars (if possible) or packed in plastic freezer bags with excess air removed. See Vacuum Packaging of Dried Foods. Package fruit in amounts that can be used within several days after opening. Every time dried fruit is exposed to air, there will be a slight deterioration in the quality. Seal freezer bags with a heat sealer or heavy rubber band and store smaller bags inside large plastic or metal containers. STORAGE Storage life of dried fruits is dependent upon the moisture in the fruits and their storage conditions (light and temperature). MOISTURE CONTENT - The desired moisture content in most dried fruits is 15 to 20%. Store fruits with 20 to 30% moisture in the freezer to prevent mold. LIGHT - Dried fruit colors tend to fade when exposed to light. Light also destroys Vitamins A and C. TEMPERATURE - Dried foods take from 1/10th to 1/20th of the stored volume of frozen or canned. Dried fruit should be stored in the very coolest place available, preferably below 60øF (15øC) or frozen to keep the highest quality and nutritional value. For every 18øF (10øC) drop in temperature, the shelf life of dried fruits increases 3 to 4 times. For example: if a fruit will remain in good condition for 4 months at 70øF (20øC), storing it at 0øF (-20øC) will keep it in prime condition for 5 to 8 years! HOW TO USE DRIED FRUIT REHYDRATION Most dried fruit is eaten or used in recipes as it is. However, you may wish to plump or soften the fruit slightly to make it more chewable. You can use one of three methods. 1. Cover the dried fruit with boiling water or fruit juice. Let it stand 5 to 10 minutes, then drain. 2. Place the dried fruit in the top of a steamer over boiling water and steam 3 to 5 minutes until the fruit is plump. 3. Sprinkle the dried fruit with fruit juice or water and let it stand several minutes. Once moisture has been returned to dried fruits, they are quite perishable and should be used soon or refrigerated. COOKING Dried fruit may be cooked in hot water or juice until it is tender. Soaking first, then simmering, gives a more tender fruit. Sugar and spices should be added near the end of the cooking time. HOW TO CHOP DRIED FRUIT With kitchen scissors or a knife: * Run the scissors or knife through hot water occasionally to prevent stickiness, or * Coat the scissors or knife with vegetable oil, or * Toss the fruit lightly with vegetable oil, or * Toss the fruit lightly with flour from the recipe you are using. In a blender or food processor: * Freeze the dried fruit first. Then chop with the appropriate blade and speed. In a food grinder: * Freeze the fruit first. * If the grinder gets gummy or sticky, put a few small pieces of dry bread through the grinder. "How To Dry Foods" by Deanna DeLong (1992)