Chapter 16

Light and Nutritious: Dehydrating Food

IN THIS CHAPTER

Discovering the secrets of successful drying

Mastering the drying process

Preserving the quality of your dried food

In the world of food preservation, sun-drying is the oldest known method. If you have the time and appropriate climate, you can use the sun to preserve your food even today (I explain how later in this chapter). Or, if you’re inclined to dry food indoors, you can use your oven or an electric food dehydrator instead.

Although canning and freezing require exact applications of processing procedures, drying food isn’t exact or precise. Don’t be surprised if you find yourself working by trial and error when it comes to knowing how long it takes for your food to reach its degree of doneness. Just follow the general guidelines provided and make adjustments. Remember, drying isn’t exact.

In this chapter, you can find basic techniques for drying food, the best drying methods, and how drying food prevents spoilage. Drying is simple and easy to do in your home. Most of the equipment and tools you need, except for an electric dehydrator, are probably just waiting for you in your kitchen.

Setting Up for Food Drying Success

Drying food is also referred to as dehydrating. The goal in this process is to remove moisture from your food. Achieving a successfully dried product requires removing 80 to 95 percent of the food’s moisture. Removing moisture inactivates the growth of bacteria and other microorganisms but doesn’t kill them.

Understanding key food drying factors

Dehydrating is all about applying gentle, constant heat to pieces of food so they dry evenly and consistently. The finished product ranges from crisp to leathery depending on the food you’re drying.

In order to end up with perfectly dried food, there are some simple rules to follow. Keep the following factors in mind, as they affect your finished product:

• Heat. The correct temperature is important in drying food. It must be high enough to force out moisture but not so high that it cooks the food. If your temperature is too high, your food exterior cooks or hardens before the interior of the food dries, trapping moisture in the food — a condition known as case hardening. If the temperature is too low or the humidity too high, then your food dries too slowly. Both of these problems may cause your food to spoil before you consume it.

  The temperature guidelines for dehydrating food are as follows: 125 degrees for vegetables, 135 degrees for fruit, and 145 degrees for meat. Always follow the instructions for the correct drying temperature for your food in your recipe or the owner’s manual for your dehydrator.

• Dry air. During the drying process, dry air absorbs moisture and leaves the food. The higher the humidity, the longer foods take to dry because of the additional moisture in the air.
• Air circulation. Circulating air carries away moisture absorbed by dry air. This keeps the humidity level constant in the drying chamber.
• Uniform size. Pieces of food that are uniform in size and thickness contain about the same amount of moisture and therefore dry in the same general time. This prevents some pieces from not being completely dried and spoiling the entire batch when stored.

Assembling the necessary equipment

After you decide which drying method you want to use (check out the upcoming section, “Choosing a Drying Method,” if you’re unsure), assemble your basic tools to aid you in completing the drying process. In addition to the basics that every kitchen should have (knives, cutting board, vegetable peeler, grater, and so on; go to Chapter 2 for a full list of basic supplies), you need to consider the following, which are particularly useful when you’re drying food:

• Blender. Use this for puréeing fruit. (For a great fruit purée recipe, head to Chapter 17.)
• Food processor. You’ll make uniform slices in the blink of an eye. You also can use a mandolin for slicing; it’s hand powered, razor sharp, and adjustable.
• Oven thermometer. For safely dehydrating food in your oven, it’s critical to know the exact temperature of your oven chamber.
• Racks and trays. Your electric dehydrator provides the correct size of trays for your unit. For oven- or sun-drying, you can use oven racks, net-covered racks, or baking sheets. Either racks with mesh bottoms or oven racks work well and provide air circulation. To prevent food from falling off the racks, tightly stretch and pin layers of cheesecloth or nylon netting over the racks. If you use baking sheets, you need to rotate the sheets and turn the food over for even drying.

Putting suggested drying strategies in play

Drying is one of the easiest ways to preserve food. Still, following a few suggestions can ensure your success:

• Pick quality food. Food of high quality that’s ripe, mature, and in top condition is the best for drying. If you dry food during the peak of its season, you get high-quality food at a lower price because the food is more abundant.
• Wash and eliminate blemishes. Always wash your food to remove dust, dirt, grime, or insects. When you clean your food, start with a clean sink and clean utensils. Any residue from previous use may cross-contaminate your food. (For detailed information on bacteria and safe food handling, check out Chapter 3.)
• Strive for uniform size. It’s important to prepare your food in a uniform size and thickness so that all the food is done at about the same time. If you have two different-sized pieces of the same fruit, spread like sizes on one tray. Because one tray of food with smaller or thinner pieces will finish drying before the other tray with larger pieces, you won’t spend time sorting through the food and disrupting the drying process.
• Place your food carefully on the drying trays. Whether you’re using an electric dehydrator, a conventional oven, or Mother Nature, make sure you arrange the food in a single layer and leave spaces between the pieces of food so that they’re not touching each other or the edge of the tray.
• Watch for spoilage while the food’s drying. The shorter the drying period, the less opportunity there is for mold to develop on your food. If mold does develop, you can kill the mold spores by removing the moldy pieces and then cleaning the area using a cloth moistened with distilled white vinegar with an acidity level of 5 percent.

• Test your food for doneness. The length of time required for dehydrating your food varies with the quality of the food, whether you’re using a pretreating method (discussed in Chapter 17), your climate and humidity, the size of the food pieces, the moisture content of the food, and the drying temperature. This all means you can’t blindly follow the recommended drying time.

  To test your food for doneness: Remove a piece from the tray and allow it to cool completely. Then check to see whether it matches the recipe’s description of how the food should look, feel, and taste when properly dried. This may sound overly simplified, but there’s nothing like using your senses.

• Store your cooled food in plastic bags, glass containers, or rigid plastic containers with airtight seals. Make sure to label the container with the contents and date. For more on storage containers and how to make your dried food last, head to the later section, “Storage Solutions: Protecting the Life of Your Dried Food.”

Choosing a Drying Method

The three approved methods for drying food are using an electric dehydrator, using a conventional oven, and drying in the sun. All three methods work well when you follow basic food-dehydrating procedures, use high-quality fresh food, and practice good sanitation when preparing the food.

Quick and consistent: Investing in an electric dehydrator

If you dry a lot of food, an electric dehydrator is a great investment (see Figure 16-1). It’s the most reliable method for achieving the most consistent results each time you dry food. This method dehydrates your food evenly and quickly, doesn’t tie up your oven, and produces great results in any weather.

FIGURE 16-1: Two examples of electric dehydrators.

An electric dehydrator dries your food by heating the air inside the chamber at a low temperature and circulating the warm air through the chamber with a fan, passing the heat evenly over your food for the entire dehydrating process. After you place your food in your dehydrator, it needs little or no attention.

To use an electric dehydrator, follow these steps:

1. Prepare your food according to the recipe and arrange it carefully on the drying trays.

2. Following the instructions for using your dehydrator, allow the food to dry for the specified period of time.

   Turn the pieces of food and rotate the trays from bottom to top to ensure even drying of all the food in the dehydrator.

3. Test your food for doneness and then label and store it in an airtight container.

Each time you use your dehydrator, review the operating instructions, including preheating the unit, filling the trays, and setting the recommended temperature and time for dehydrating your food. If you have any questions regarding the use or operation of your unit, contact the manufacturer. You can find this information in your owner’s manual or check with the store you purchased it from.

If you’re purchasing a dehydrator, carefully assess your needs. Then consider the following factors when making your final decision:

• Overall construction. Purchase a unit that’s approved for safe home use by the Underwriters Laboratory (UL). If the unit isn’t UL approved, don’t buy it — it may not be safe for use in your home. Choose one with insulated walls that’s easy to clean and has drying trays that you can move easily in and out of the dehydrator without disturbing the food.
• Capacity. Purchase a dehydrator big enough to hold the amount of food you’ll dry at one time. Typically, the most common-sized food dehydrator has four trays. Each tray holds about ¾ to 1 square foot of food. Some dehydrators expand to utilize 30 trays at one time. Snack-size dehydrators with two trays are also available.
• Heat source. Select one with an enclosed heating element. Wattage needs to accommodate about 70 watts for each tray the unit holds.

• Fan. The fan circulates the heated air around your food. Purchase a dehydrator with a quiet fan, because it runs for long periods of time. If your unit isn’t equipped with a fan, you need to rearrange the trays more often during the dehydrating period for an even drying.

  When buying a dehydrator secondhand, always plug it in to hear how it sounds when running. The level of noise is not an indicator of quality, but a loud dehydrator needs an out-of-the-way place to run, or it’ll be too inconvenient to use.

• Thermostat. Purchase a dehydrator with an adjustable thermostat. Your temperature options need to range from 85 to 160 degrees.
• Drying trays. Check for trays that are sturdy and lightweight; made from a food-safe product like stainless steel, nylon, or plastic; and easy to clean. Some manufacturers offer dehydrator accessories like extra drying trays and trays for drying fruit leather and herbs.
• Cost. Quality dehydrator prices start as low as $70 and go up to $200 or more.
• Warranty. Check out the warranty term (one year is a good average) and any restrictions the manufacturer has for your dehydrator.

Getting results with a conventional oven

If you have an oven — gas or electric — that maintains a temperature between 130 and 150 degrees with the door propped open, you can use your oven to dehydrate food.

Your oven must maintain a temperature of 130 to 150 degrees for 1 hour to safely dehydrate food; maintaining these acceptable temperatures is difficult unless your oven can be set at less than the standard 200 degrees as the lowest temperature. The problem with higher temperatures is that they cook — they don’t dehydrate — the food. To test your oven’s temperature, put an oven thermometer in the center of the oven with the door propped open.

Oven-drying takes longer than using a dehydrator and costs more because the oven uses a greater amount of electricity than an electric dehydrator does. In addition, if you use your oven for dehydrating, it isn’t available for any other use during that time.

To dehydrate food in a conventional oven, follow these steps:

1. Preheat your oven to the temperature setting in your recipe.

   Use a separate oven thermometer to check for accuracy. Check the oven frequently to be sure the food isn’t over- or under-dried.

2. Wash and prepare your food as directed in your recipe.

3. Place your filled trays in the oven and leave the door propped open to allow moisture to escape during the specified dehydrating time.

   If you use baking sheets or other trays without holes or openings in the bottom, you must turn your food to achieve an evenly dehydrated product. After the first side of the food has absorbed all the liquid on the top of the food, turn it over and repeat this step for the other side. After this has been done on both sides, turn the food occasionally until it’s done.

4. Test your food for doneness and then label and store it in an airtight container.

Setting your trays in the sun

Sun-drying is the oldest and least expensive of the three methods, and it lets you dehydrate large quantities of food at one time. But — and these are big buts — it’s dependent on perfect weather conditions to produce a safely dehydrated product, and it can take days compared to hours in a dehydrator or a conventional oven.

Weather conditions must be perfect for sun-drying, making only a few climates suitable for this method. The ideal temperature for sun-drying fruit is 85 degrees or hotter for many consecutive days, with the humidity level low to moderate. If your temperature drops more than 20 degrees below your highest temperature during the drying period, your conditions are not suitable for this method. You also need good air circulation, a minimum of air pollution, and insect control around the food. Sun-drying is even less attractive for drying vegetables because the temperature needs to be at 100 degrees or above for a number of days, with the lowest evening temperature never dropping below 80 degrees (even at night). The humidity level also needs to be low.

Sun-drying isn’t safe for meats and fish because the low acidity level of the food, the low drying temperature, and the long drying period (requiring many days) don’t destroy the bacteria that cause your food to spoil.

If you’re willing to deal with the variances in weather conditions and the lengthy dehydrating time, follow these step-by-step instructions:

1. Wash and prepare your food as specified in your recipe.
2. Line your drying trays or racks with a double layer of cheesecloth or nylon netting.

3. Place your food on the trays and cover them with a single layer of cheesecloth or nylon netting to protect the food from insects and dust.

   Stretch the cover tightly over the trays, but don’t let it touch the food.

4. Place your filled trays on benches or tables in full sunlight and check regularly.

   Check your trays at different times of the day, keeping them in full sun at all times. If your nighttime temperature varies more than 20 degrees from the temperature at the hottest part of the day, move your trays to a warmer area (indoors or in an enclosed patio area) for the evening, returning them outside when they can be in full sunlight. Relocate the trays if it rains, regardless of the temperature.

   If you use baking sheets or other trays without holes or openings in the bottom, then you must turn your food to achieve an evenly dried product. After the first side of the food has absorbed all the liquid on the top of the food, turn it over and repeat this step for the other side. After this has been done on both sides, turn the food daily until it’s done.

5. Check your food daily for evidence of mold (refer to the section, “Putting suggested drying strategies in play,” earlier in this chapter).

6. Test your food for doneness and then label and store it in an airtight container.

   If one day is hot and sunny, but the next is cloudy, you have a problem because mold can develop on partially dehydrated foods before the weather turns back to hot and sunny again. In this situation, you need to use an alternative to sun-drying to finish the foods.

Storage Solutions: Protecting the Life of Your Dried Food

You’ll receive many months of rewarding flavor from your dried foods when they’re protected from air, moisture, light, and insects. Generally speaking, food that is dehydrated and stored properly can be kept from six months to one year.

Cooler air provides a longer shelf life for your food. The best storage temperature is 60 degrees or colder. This will maintain your food for at least one year. Temperatures between 80 and 90 degrees preserve the quality of your dehydrated food for only about three to four months.

Check your unused dried food from time to time for any visible moisture or spoilage. If the food has signs of moisture, such as droplets of liquid in the containers, then the food isn’t completely dehydrated. Use it immediately or repeat the dehydrating process and repackage it.

Desiccant packets are available to buy in many big-box stores and online. Adding one of these small packets to each jar before sealing will absorb any little bit of moisture still in the jar as well as help keep it dry during storage.

Suitable storage containers include the following:

• Glass. Home-canning jars with two-piece caps (see Chapter 2) are a perfect choice for storing dehydrated food. Wash them with hot, soapy water and rinse them well or wash them in a dishwasher. Dry and cool your jars completely before filling them and adding the two-piece caps. Reusing glass jars with lids also works well. Remove the cardboard liner that sometimes lines the underside of the plastic lid before washing and filling it with herbs.
• Plastic. Heavy-duty (freezer) plastic bags with locking zipper-style seals work well. After placing your dehydrated food in the bag, roll the bag to remove any extra air and press the seal together, making the bag airtight.
• Metal. If you buy coffee in cans, line the inside of a clean can with heavy plastic wrap, place your food inside, and add the tight-fitting lid.
• Vacuum sealers. If you own one of these units, now’s the time to use it. Check your owner’s manual for operating instructions and start packaging your dehydrated food.
• Vacuum sealer attachment. This tube-and-cap item fits over the flat lid of your glass jar and removes the air inside. There is no need for a metal ring, and the food remains fresh until you unseal the lid. Simply use the vacuum sealer attachment to reseal it again.

Always label your container with the type of food it contains and the date of processing. If you measure your food before placing it into the storage container or bag, also list the amount.

Because some pieces of fruit contain more moisture than others, be sure all your fruit is dehydrated to the same extent before you store it. Try this tip from the Oregon State Extension Office: Fill a plastic or glass container about ⅔ full with cooled, dehydrated fruit. Cover or seal tightly. Shake the container daily for two to four days. The excess moisture in some of the fruit will be absorbed by the drier pieces. Vegetables dry almost completely, so you don’t have to do this with them.