Information on the Procedures, Terms, and Processes of Drying Foods
Drying food is a comparatively simple matter and definitely not rocket science. With a few tips and tricks, anyone can learn to safely dehydrate their foods. Even if only small quantities are dried at a time, the total at the end of the season will be a considerable amount of food stored for winter or long-term use.
Dehydrating is one of the easiest, least time-consuming, and most durable preserving methods you can choose. In savings of food for winter or long-term preparation by drying, the moisture content is taken out and the sugar content raised to a point where bacteria, yeast, and mold find a condition or environment where they cannot thrive sufficiently to cause the food to spoil.
The first consideration in the practice of food drying, therefore, is to decide what the best method is to get rid of the surplus moisture which is extracted from the food product stored.
The first method coming to mind, probably, would be to put it in the oven and dry it to a crisp. Experiments have shown, however, that in the drying of food products to save them, two things must be guarded against:
- If they are made too dry/cooked, the cell-structure is altered and they cannot be brought back to their original condition when wanted for use.
- If the water is extracted by heating them too suddenly, or at too high a temperature, the flavor of the food will be altered.
What your aim is then, is a method which will extract a sufficient amount of water from the product to preserve it perfectly and to do this with as little change as possible in the product itself; changing the product as little as possible physically and keeping it at as low a temperature as possible to avoid scorching, charring, or even cooking it. In this way you keep the most freshness, nutrients, and flavor. See more on nutrition here: Nutritional/Dietary Considerations of Dehydrated Food.
There is hardly a home where dehydrating cannot be used to advantage for many foods. Dried products need much less expense for containers, such as glass jars, cans, etc., than canned products because you USE less, and they need much less room for their storage. The dry products are kept in containers that could not be used for canned goods. They can be exposed to freezing without the danger of breakage and loss. Dried goods are easily transportable and lightweight, making these foods essential for travelers, campers, and backpackers, whereas canned products involve great risks, heavy weights, and expense in shipping. When storage room is at a premium and kitchen/pantry space is cramped, dried foods save the day.
The Various Methods of Drying
Success in drying, evaporating, or dehydrating vegetables or fruit will depend to a great extent on having equipment adapted to the work that is to be done. This does not mean that it is necessary to invest a considerable amount in equipment before drying is undertaken. There are now a number of machines of various sizes that cover a range of prices for home use. Many of these are not expensive, are convenient to use, and efficient.
Regardless of what method you use, it is a good idea to check the temperature of your dehydrator. For models that have a variable temperature control, this ensures you are getting a correct reading. For those with no temperature control, this will tell you what you are working with and allow you to know what foods you can safely dehydrate. A procedure on easily testing your dehydrator is found here: Checking Your Dehydrator’s Temperature.
Drying: While the drying of foods is a general term which applies to this method of keeping food products, regardless of the details of how the work proceeds, the newer terms of evaporation and dehydrating have come into use, and through common usage have come to express different methods of drying. While here they are employed with more specific meanings, the term “drying” technically refers to the practice of sun drying, or drying by exposure to the sun.
Evaporating: This refers to the method of drying by artificial heat where no air circulation is present.
Dehydrating: This refers to the method of removing the surplus moisture by artificial air-blast. Dehydrating, however, often includes evaporating, as drying by a blast or current of air is more rapid when the air is heated. The air, however, is the chief agency in removing the moisture and the temperature used is usually much less than that where evaporation alone is done, as the air current method naturally tends to keep the temperature down.
Drying in the Sun: Except where the climate is such that long periods of hot, dry weather without rain, humidity, or heavy dews are counted upon, sun drying is uncertain unless some means is taken to give protection from occasional showers and from blowing dust, insects, etc. This method can only be achieved during daylight hours and food must be brought in and safely stored at night.
Step-by-Step Process of Drying
Following is a step-by-step generic version of a dehydrating session. It will change little from what you need to do for certain foods.
- Select foods to dehydrate. Buy or grow the products as fresh, young, and tender as possible. Pick over and grade carefully; wash all products that may need it and thoroughly clean and peel or scrape root products to avoid possibility of strong acid flavor in the dry products. See more here: Cleaning Your Produce.
- Clean all surfaces and tools. Make sure all your cutting utensils and the dehydrator trays are clean and dry. Sanitize with soap and water, vinegar, and/or baking soda for scrubbing. Rinse all items thoroughly before drying.
- Prepare food for dehydration. Slice, cut, shred or purée the product, as is required.
- Pretreat food. Blanch, steam-blanch, roast, or spritz with bottled lemon juice (or other acidic dip), as required, and place in trays ready for drying. (Putting on gloves to handle your foods keeps the oils in your hands from adulterating your foods.) Use mesh or solid tray inserts for foods that need them.
- Preheat dehydrator to the proper temperature for the food being dehydrated (usually about 15-30 minutes).This ensures the dehydrator is already up to the proper temperature and begins drying the food right away.
- Dry for the required length of time. Check the level of dryness during the dehydrating process and move the trays around so everything dries as evenly as possible if needed. Examinations should be frequent and occasional turning of food may be necessary.
– Be sure to keep sun–dried products carefully protected from dust or moths. The product is taken in each night before sunset and put out each morning after the dew is off. There should be a protecting cover of light cheese cloth (mosquito netting is not fine enough) which should be kept over the product to prevent moths or other insects from depositing their eggs, so that a large part or all the product is spoiled afterward while in storage.
– In evaporating by heat, care is taken to avoid too high a temperature, as this may cause the freshly cut surfaces to seal up, so that the pieces do not dry out evenly (see case hardening).
- Periodically test your food by taking a few pieces out and allowing them to cool on a plate. This will be your best indicator of dryness. When foods are hot they will not crisp up to show the level of dryness.
- Rotate trays during the drying process, if needed, to make sure there is even drying of food.
- Remove food from dehydrator when it is completely dried. Experience only, in this as in many other things, will teach you just when the right condition or degree of dryness is obtained.
– One of the tests to show when this condition is reached is to snap one of the pieces and see if it is impossible to press any of the juice from the freshly cut end.
– The natural “ grain ” of the vegetable or fruit should also have disappeared.
– Keeping a Dehydrator Journal is a good way to help yourself remember what your previous drying sessions have yielded.
Make sure all food is completely dry. If there’s any moisture left in it the food will spoil and can quickly become moldy.
- Conditioning. Loosely store your food in a container (such as a Mason jar or other see-through airtight glass container) where you can observe it for a time to make sure it is fully dry (see Conditioning Dried Foods). If necessary, re-dry all parts that seem to still be too moist.
– If the product has been sun-dried, it is sterilized before being stored by heating to a temperature of about 140°F/60°C.
– If dried by artificial heat and/or air current, the product can be heated again for a short time (about 1 hour at the same temp as dehydration occurred) after conditioning, as an added precaution.
- Storing food. At the end of conditioning, if your food is sufficiently dried, you can repackage if necessary and store away permanently in your pantry or long-term storage.
– It is advisable not to have the package so large that the contents, after it is once opened, will not be used in a comparatively short time.
– Label everything carefully with food name, date of storage, and any special information on its preparation.
– Labeling is important; it is not always easy to distinguish what dried products you have. Have the labels ready to tag everything as it is stored; and until you are familiar with the work of drying or dehydrating, it will be well to put on the labels data as to the length of time the product was dried, etc., as a guide for future work.
- Periodically check your dried foods after storing. Products which seem perfectly dry when put away, sometimes will be moist after they are put into the containers so that they will begin to mold and almost immediately spoil. As a precaution against this, a sample of all products put away is examined carefully about twenty-four hours after being packed; if there is any sign of moisture still present, the batch is put back in the dehydrator for further drying.
Drying Instructions for Foods
Many foods can be dehydrated at home, but a few do not work safely in home drying. See more here: What CAN You Dehydrate at Home?
The various fruits and vegetables may be dried according to the printable Dehydrator Chart directions.
For more detailed directions on each food, see our link here. We will be adding to this listing as we finish articles on the many foods you can dehydrate.
- Living/Raw Foods 105°F / 40°C
- Herbs/Flowers (leaves/stems) 95°F/ 35°C
- Spices (roots/tubers) 110°F/40°C
- Raising Bread 110°F / 40°C (box dehydrator models like Excalibur only)
- Making Yogurt 115°F / 45°C (box dehydrator models like Excalibur only)
- Vegetables 125°F / 50°C
- Fruits 125°F / 50°C to 135°F/55°C
- Fruit Roll-ups/Leathers 135°F /55°C to 145°F/65°C
- Cooked Rice & Grains 145°F/65°C
- Fish 155°F / 70°C
- Beef 160°F / 70°C
- Poultry 165°F / 75°C
- Beef Jerky 160°F / 70°C
The recommended times given in instruction manuals and online resources are approximate, as the time required will vary. The product should be carefully watched during the process of drying, and kept drying until it is in the right condition, regardless of the length of time it has been under processing.
Always dry your foods until no moisture remains regardless of any recommended times. For the most part, you cannot over dry your foods. To understand more about dehydration times, read When is it Fully Dehydrated?
Do not turn off your dehydrator, especially when you are experiencing high humidity, and leave the food to sit overnight. Either wrap it up and refrigerate or keep the dehydrator running.
Just as you should not leave foods out on your countertop for more than 2 hours unheated or unrefrigerated, the same applies to dehydrating. Food that stays out for more than 2 hours will re-absorb moisture and can be subject to bacteria and mold and should be discarded. Dehydrating—a combination of heat with air flow—prevents this process from happening.
You cannot always see or smell bacterial contamination. Mold that appears to be growing only on the surface may grow invisible roots into softer foods. Do not rely on a visual inspection or “smell test” to tell you whether or not a food is safe. It’s not worth the risk – food poisoning can be much, much worse than an upset stomach.
Explanation of Terms Used in Dehydrating
Acid Dip: See “Dipping”.
Blanching: A cooking process wherein the food substance, usually a vegetable, is plunged into boiling water, removed after a brief, timed interval, and finally plunged into ice water or placed under cold running water (shocking or refreshing) to halt the cooking process. Blanching stops the food’s enzyme action, preserves color, and destroys any microorganisms present on the vegetables surface reducing your risk of food poisoning. See more here: Pretreatment Methods for Dehydrating, Preparing Fruit for Dehydration.
Blender (Liquidiser): An appliance used to mix, purée, or emulsify food and other substances. A stationary blender consists of a blender jar with a rotating metal blade at the bottom, powered by an electric motor in the base. Some powerful models can also grind your foods to powders. Generally, a blender’s main function is to blend or mix soft foods and liquids, while a food processor’s is to chop, shred, grate, slice or mix either soft or hard foods. See more here: Equipment Labor-Savers for Dehydrating.
Case Hardening: This occurs when the outside of the food hardens and moisture remains trapped on the inside. This moisture is then unable to dry because it is encased in a hard shell. This usually occurs when the heat is too high, in hopes of a faster drying time. See more here: What is Case Hardening?
Checking Fruits: Some fruits (like blueberries, grapes, and cranberries) need special preparation because of their thick skins. This is called “checking” or “crazing”. To prepare these fruits, you will blanch, pierce, or freeze them to crack their thick skins. See more here: Preparing Fruit for Dehydration.
Chiffonade: A chopping technique in which herbs or leafy green vegetables (such as spinach and basil) are cut into long, thin strips. This is accomplished by stacking leaves, rolling them tightly, then slicing the leaves perpendicular to the roll. See more here: Hack for Dehydrating Greens & Herbs.
Chopper: Some food choppers are small, such as the hand-slap, spring-type blade choppers where you usually have to downsize vegetable portions accordingly, they’re useful and practical kitchen tools. Whether large or small, they generally have a similar function – to chop, dice, or slice, coarse or fine. Chopping foods such as onions, celery, garlic, and carrots is much faster and easier with this appliance. See more here: Equipment Labor-Savers for Dehydrating.
Coffee/Spice Grinder: Most coffee or spice grinder will allow you to finely powder your foods. Because of the low flat blade, these machines are excellent for making powders from your dried fruits and vegetables. Alternatives to using this appliance are a mortar and pestle set, or a high-powdered blender such as a VitaMix, NutriBullet, or Blendtec. See more here: Equipment Labor-Savers for Dehydrating.
Conditioning: After the product is dried to as nearly the condition wanted as possible, it will be found in most cases that the degree of dryness obtained will not be absolutely uniform throughout the batch. To make certain that all parts are dry enough, and to make the degree of moisture as uniform as possible it is conditioned by keeping the product in see-through containers for a 7-10 days, and occasionally turning it over. If the product is not sufficiently dried out, as is sometimes the case, it is returned to the dehydrator for further treatment. See more here: Conditioning Dried Food, an Essential Step.
Containers: Containers in which the finished dried product is stored and kept for future use may be glass Mason jars, other glass jars, or specially prepared bags like Food Saver-type or Mylar. These containers do not have to be, as in canning, absolutely air-tight unless you are storing long-term. See more here: Storage Considerations for Dried Foods, Storing Fruit & Vegetable Powders.
Crazing Fruits: See Checking Fruits.
Cubing & Shredding: Vegetables which are not suitable for slicing are prepared by cutting into small cubes, or in some cases are cut into fine shreds. Some vegetables have to be partly cooked before drying, or in some cases, prepared by pulping or passing them through the food processor, chopper, or mandoline, to prepare them for drying.
Cut-Resistant Protective Gloves: Ideal for protecting your hands (which are your best tools in the kitchen) while cutting, slicing, peeling, and grating. If you have a mandoline slicer, these are a must to protect against injury. See more here: Equipment Labor-Savers for Dehydrating.
Desiccants: Packets used for storage of dried foods, used to cut moisture condensation and allows the stored item to stay dry even during humid, damp conditions. These packets are mainly used for items that are opened on a frequent basis, for short-term storage. See more here: Oxygen Absorbers & Desiccant Packs, Mystery Solved!
Dipping: Treating food, usually fruit, with an acid substance (like lemon juice, ascorbic acid, or citric acid), to fix the color and flavor. See more here: Pretreatment Methods for Dehydrating, Preparing Fruit for Dehydration.
Dry Oven Canning: The process of heating jars in the oven for canning, canning dry goods (such as flour, beans, oats, and dehydrated foods) in an oven, or using jars to bake is unsafe and not recommended. See more here: Using the Oven for Dry Canning—Is it Safe?
Drying: Drying out the food product in the equipment prepared to use either sun heat, artificial heat, or air-blast.
Food Processor: While there are combination blender/processor units on the market, a blender and food processor are two distinct counter appliances. (Many blenders designed with chopping accessories, make a sort of hybrid and these fit in either appliance class.) Generally, a food processor’s main function is to chop, shred, grate, slice or mix either soft or hard foods, while a blender’s is to blend or mix soft foods and liquids. A food processor, has a wider work bowl and very sharp blade designed more for chopping foods, and can usually do various other processing tasks depending on the types of accessories (slicing/shredding disks) that are included with the unit. Food processors generally do not make good grinders for powdering foods unless they have a separate attachment to do so. See more here: Equipment Labor-Savers for Dehydrating.
Mandoline Slicer: Wonderful for achieving uniform cuts of many different sizes. Sharp surgical grade stainless steel blades allow you to slice different thicknesses, julienne, shred, cube, and create fantastic French fry shapes depending on the blade attachments that come with the unit. I highly recommend buying cut-resistant gloves when you buy a mandoline. See more here: Equipment Labor-Savers for Dehydrating.
Mortar and Pestle: A mortar and pestle is a non-electric device used since ancient times to prepare ingredients or substances by crushing and grinding them into a fine paste or powder. The mortar is a bowl, typically made of hard wood, ceramic or stone. The pestle is a heavy and blunt club-shaped object, the end of which is used for crushing and grinding. The substance to be powdered is placed in the mortar and ground, crushed, or mixed using a pestle.
Oxygen Absorbers: A packet used in food storage that removes oxygen allowing the food to keep fresher for a longer time. These packets are mainly used for long-term storage. See more here: Oxygen Absorbers & Desiccant Packs, Mystery Solved!
Preparing: Getting the vegetables ready for drying by carefully sorting; discarding all that are old and tough or injured, carefully washing and/or scrubbing, etc. Pretreat if necessary to keep nutrients and color. See more here: Preparation is Key.
Puréeing: A purée (or mash) is cooked food (usually vegetables or legumes) or raw food (usually fruits) that has been ground, pressed, blended or sieved to the consistency of a soft creamy paste or thick liquid. Purées of specific foods are often known by specific names, e.g., mashed potatoes or applesauce. See more here: Pretreatment Methods for Dehydrating, Preparing Fruit for Dehydration.
Slicing: This is an important part of fixing vegetables by the drying method. They are cut into thin pieces or small parts to dry out evenly. Were the attempt made to dry them in large sections, they would merely wilt or shrivel on the surface, while the interior would be little changed. In fact, one of the chief reasons for the existence of the skin on most fruits and vegetables is to prevent evaporation. The vegetables are sliced thin, but not too thin. The usual thickness of 1/4 inch is about right for most foods. This will be thin enough to expose a large amount of surface to the air to dry, without giving a product that cannot be handled without sticking together and being in general messy. When sliced too thin or cut into too small pieces, the product is likely to lose its flavor and fail to come back when re-soaked for use, so that it may be used to advantage in cooking. See more here: Preparation is Key.
Vacuum Sealer: A vacuum sealing machine keeps food fresh by removing the air surrounding the food we wish to store and helps to preserve it. A machine that has attachments for Mason Jars can vacuum out the air and keep dehydrated foods from degrading in storage. These machines are perfect for those who want to store their food in bags as well. See more here: Equipment Labor-Savers for Dehydrating.
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