Dehydrating or drying fruits, vegetables, herbs and meats is one of the oldest methods of food preservation. It is simple to do, although varying factors such as the climate, outside temperature, and quality of products used can make it more of a practiced art. It takes little equipment and little time to prepare the food before drying, but depending on the type of food, the thickness of the cut, the method used, and environmental factors, it can take quite a long time to actually dry completely, anywhere from 3 hours to several days. Drying you own foods makes for quick and healthy snacks and trail foods to have on hand. It preserves precious nutrients, and it is a great method of preservation for those who do not have much pantry or freezer space.
Overview
Dry prepared fruits, vegetables, herbs, and meats by one of three methods: sun drying, oven drying, or using an electric or solar dehydrator. As a general rule, dry fruits at 125F, vegetables at 135, and meats at 145. Store properly dried foods (with 80-95% of the moisture removed) for 6 months to a year. Use dry foods in their dry state (most fruits, herbs, and meats) or a rehydrated state (most vegetables and some fruits).
How To
Choose a Method of Dehydrating
Sun Drying: is the trickiest method because weather conditions vary so dramatically, even within one region. The most ideal environment and time to successfully sun dry food is in the warmest months when temperatures are 85 degrees F or warmer and the humidity is less than 60%. Dehydrating with the sun’s energy might be the best environmentally, but it also requires more energy from you to keep away bugs and birds and bring it inside at night so food doesn’t reabsorb moisture during the cool night. Use only food safe materials for drying. (See Safety Tips.) “Breathable” (mesh, netting, or screen) materials are best for air circulation. Elevating your drying rack and placing it over concrete or a reflective surface helps speed drying. Placing cheesecloth or a second elevated screen over the food helps keep away birds. You can also “line dry” apple rings or light pieces of fruit or vegetables by threading a food safe thread through the foods with a sterilized needle or simply through the ring. Sun drying is not recommended for meat for safety reasons. Fruit is best for sun drying.
Oven Drying: is best for those who do not dehydrate very often and are only drying a small amount of food. Your oven should have a range of 120-150 degrees or lower. Ovens that have a higher minimum temperature are not ideal. Do not use a convection oven for drying, as it will not carry moisture away. Note that the oven is much less cost effective to operate than an electric dehydrator, so if you plan on dehydrating more than once or twice a year, it is best to invest in a dehydrator. Foods dried in an oven need to be turned over if using a cookie sheet. Dehydrating them on a ventilated roasting rack might produce better results. Sometimes cracking the oven door is necessary to release moisture as it is lifted from the foods.
Electric & Solar Dehydrators: are perhaps the best option for producing the most consistent results and drying many foods at once. Both can by built by hand or purchased. Purchased dehydrators usually come with instruction booklets, but it is helpful to take notes and make adjustments as you experiment. See how to Choose an Electric Dehydrator below. Electric and solar dryers work well for all kinds of foods. Electric dryers are the most popular because of their convenience and year-round usability. I use both!
Vine Drying: is best for hard bean varieties. Leave mature bean pods to dry on the vine until the beans rattle in their shell. De-shell and complete the drying process using the sun or oven method.
Choose an Electric Dehydrator
Better quality dehydrators will save you money in the long run, as they will work more efficiently and last longer. Look for:
- Horizontal airflow instead of vertical, where the fan and heating element are on the sides of the unit. (This creates more even drying, less mixing of flavors if drying several foods at once, and it does not drip juices onto the heating unit and fan.)
- Service guarantee
- Adjustable thermostat with a range of 85-160 degrees
- A timer that turns off the unit for you
- 4-10 removable mesh drying trays (choose an appropriate size for your needs)
Dry Fruit
Use seasonal, raw, organic fruits at their peak of ripeness. Melons, citrus flesh, and avocados do not dry well.
Prep: Wash well, prep, and try to get fruit pieces as even as possible.
Peel: apples, bananas, pears, pineapples, citrus peel (no white part)
Core: apples, pears, pineapples
Evenly chop or slice (¼-½”): apples, banana, pears, pineapple, strawberries
Halve and pit: apricots, cherries, nectarines, peaches, plums
De-stem: blueberries, grapes, strawberries
Crack: coconuts (drain, scoop flesh out)
Grate: coconut flesh
Leave whole: berries (except strawberries), figs, prune plums
Pre-Treat: If desired, you can pre-treat light colored fruits before drying to reduce oxidation/browning by creating an acidic dipping solution:
- 1 quart water per 1 cup of lemon or lime juice. Soak a maximum of 10 minutes.
- 1 quart water per 1 tablespoon ascorbic acid (vitamin C powder) or ½ tablespoon each ascorbic acid and citric acid blend (like produce protector). Soak a maximum of 30 minutes.
Choose one of these solutions for dipping sliced apples, apricots, bananas, nectarines, pears, or peaches (optional).
Blanch: If desired, fruits that have a waxy skin like blueberries, cranberries, grapes, and plums can be dropped in boiling water briefly for 30-60 seconds. This splits or “checks” the skins and helps with the drying process. If desired, peaches with thick skins can be blanched for 1 minute, then dipped in cold water and peeled before pitting, slicing, and drying.
Invert halved fruits such as apricots and plums by popping the skin side inward to expose more of the flesh.
Dry all fruits at 135 -140F. Cherries can be dried higher at 165 for the first few hours and at 135 -140 for the remainder. Dry fruits with skins peel side down. Fruit is dried when 80-85% of the moisture content is removed. Fruits can take up to 24 hours to dry. Most fruits will still be pliable or leathery. Strawberries can be almost crisp. Cut open a finished piece to check that there are no moisture pockets.
Store: Completely cool dried fruit. Pack loosely in dry, airtight glass or plastic containers. Keep in a cool, dry place (50-60F is best). Letting dry fruit sit for several days will help evenly distribute moisture. Most fruit will last for 6 months to 1 year. If you see signs of mold or excess moisture seeping from the fruit or clinging to the jar, dispose of that batch.
Dry Vegetables
Use seasonal, raw, organic vegetables at their peak of freshness.
Prep: Wash well and prep if needed to remove stems, ends, bruises, peels, seeds, etc. Slice or dice into small even pieces (about ¼“), the more uniform and smaller the better to keep drying time short. Shuck corn, but keep on the cob. Blanch tomatoes in boiling water for 30 seconds and then in cold water to remove the skins. Rinse sliced potatoes to remove the starch.
Steam: prepped vegetables briefly for about 3-6 minutes (depending on the vegetables and the cut) until they are softer, but still crisp. Beets may take longer. Steam corn on the cob, and then cut off. Do not steam popping corn varieties. These you will dry while on the cob.
Dry vegetables at 125F. Vegetables are dried when 95% of the moisture content is removed. (Popping corn should have 90% removed and can be dried at 130F. Tomatoes are dried at 145F.) Dehydrating vegetables can take 4-14 hours on average. Most vegetables will be crisp, brittle, and/or shriveled. Beets, okra, and sweet peppers will be leathery.
Store: Completely cool dried vegetable. Pack loosely in dry, airtight glass or plastic containers. Keep in a cool, dry place (50-60F is best). Most dry vegetables will last for 6 months to 1 year. If you see signs of mold or excess moisture, dispose of that batch.
Dry Meats/Jerky
Use lean cuts of meat like flank, round, sirloin tip, and sometimes rump. Beef is the easiest to dry, but turkey is also popular.
Prep: Lightly freeze to making slicing easier. Slice in ½” thick strips. Slice with the grain (for chewy jerky) and against the grain (for a tender jerky).
Cure the meat by rubbing salt or a salted seasoning into the meat before drying or cover with a liquid meat marinade overnight in the refrigerator and then drain before drying.
Heat: An important step of the process is to bring the jerky to 160F either before drying or immediately after. If using a marinade, bring the meat in the marinade to a boil for 5 minutes before draining and drying. Or dry first and then transfer to a preheated oven at 275F for 10 minutes.
Dry using an electric dehydrator. Sun drying is not recommended because of increased risk of spoilage before it is fully dry. Dry meat at 145F until it is leathery and bends, but does not break. Blot fat droplets that may appear while drying with a paper towel.
Store: Completely cool dried vegetable. Pack loosely in dry, airtight glass or plastic containers. Keep in a cool, dry place (50-60F is best). Most dry vegetables will last for 6 months to 1 year. If you see signs of mold or excess moisture, dispose of that batch.
Dry Herbs
See the article Cooking Herbs for detailed growing, harvesting, and drying instructions. Shade drying in small bundles or bouquets that are hung upside down is the best method. Laying sprigs of herbs flat on an elevated screen in the shade is also good. Warm or hot weather with low humidity or inside near an oven or stove are good environments.
The Scientific Method: Calculate the Correct weight of Dehydrated Foods
If you are more scientifically minded or just wary about drying your foods properly, there is a calculation to help determine if the correct amount of moisture has been taken from the food to fully preserve it. Properly dried vegetables will have 95% of the water weight removed and fruit will have 80% removed. The first thing you have to figure out is how much water weight your food has. Take the percentage from the Water Content Chart below of the food you are using and multiply this by the fresh weight to get the water weight. For example: 10 (pounds of prepped apples) X .84 (the percent of water weight in apples)=8.4 (pounds of water in your apples)
The Formula:
(fresh starting weight of the food) – (water weight that should be removed) = (correct dry weight of the final dry product)
Fresh weight is the weight of the prepped product after peeling, coring, etc. (i.e. 10 pounds of prepped apples)
Water weight removed should be 95% for vegetables and 80% for fruits. To find this multiply the pounds of water weight in your food (calculated first) by 80% if it is a fruit and 95% if it is a vegetable to get the amount of water weight you should remove. (i.e. 8.4 pounds of water in your apples X .80 = 6.72 pounds of water should be removed)
Dry weight is whatever your final product weighs. Compare this to the value you get in the calculation to see if enough water was removed during the dehydration process. (i.e. 10 pounds apples – 6.72 pounds water removed = 3.28 dry pounds)
Rehydrate Dried Foods
Dehydrated herbs, meats, and most fruits are eaten in their dry state. However, you can rehydrate dried fruits and vegetables and use them as you would fresh foods by one of two methods: 1) by first soaking in cold or hot water and then adding to dishes or 2) by adding directly to dishes as they cook (usually liquid based such as soups or stews). See Rehydrating Tips.
Fruit: For immediate use, pour boiling water over the dried fruit pieces (just enough to cover). Let it sit 10 minutes. Or cover with water and let sit overnight. Or cover with a milk, juice, or yogurt and let sit in the refrigerator overnight (for use in muesli).
Vegetables: For immediate use, pour boiling water over the dry vegetables pieces using equal water to the amount of veggies. Cover. Let it sit anywhere from 10 minutes to several hours, depending on the cut of vegetable. Add to cooked dishes during the cooking process, using the soaking water if desired. Or add directly to soups or stews when you add the water.
Water Content Chart (% of water weight in fresh foods)
*Percentages taken from Blue Book, guide to preserving.
Fruits
Apples=84
Apricots=85
Bananas=76
Blueberries=83
Cherries, sweet/sour=80/84
Coconut meat=51
Grapes=81
Nectarines=82
Peaches=89
Pears=83
Pineapples=86
Plums=87
Prune plums=79
Strawberries=90
Vegetables
Asparagus=92
Beets=87
Carrots=88
Corn, sweet/popping=73
Green beans=90
Mushrooms=90
Okra=89
Onions/leeks=89
Peas=78
Peppers, sweet/hot=93
Potatoes=80
Pumpkin=90
Rutabagas=87
Summer squash=94
Sweet potatoes/yams=71
Tomatoes=94
Turnips=92
Tips
Rehydrating:
- Vegetables take longer to rehydrate than fruit because they only have 5% residual moisture after drying whereas fruit has 15-20%
- Rehydration time is quickened by the following factors: soft water, boiling water before covering, smaller cut pieces.
- Add salt or sugar after rehydrating because they can slow the process.
Soaking:
- Grains, small beans, and nuts that have been soaked overnight or sprouted can then be dehydrated for later uses.
Safety:
- Use clean, food-safe materials for drying foods. Stainless steel, food-grade plastic, Teflon coated fiberglass and any natural fiber is best. Avoid screen materials made of copper, aluminum, and cadmium- or zinc-coated metals. (Mainly these are known to have undesirable effects on the drying process, such as discoloration and reduced vitamin content.)
- Discard any stored dried foods that show moisture or mold forming on the surface. Glass jars are the best for checking for moisture and mold.
Names: dry grapes are called raisins and dry plums are called prunes. Not all plum varieties are used to make prunes.
Resources
Ball Blue Book, guide to preserving (100th Anniversary Edition)
