Food dehydration is one of the oldest unit operations used by the food processing industry. Food dehydration is a process of reducing moisture of food to low levels for improved shelf life by adding one or more forms of energy to the food. However, it does not include removal of moisture from food by mechanical pressing or concentration of liquid foods. Most commonly, heat is added to the food by hot air, which also carries the moisture away from the food. The process of food dehydration involves simultaneous transfer of mass and heat within the food and the medium used to transfer energy to the food. In food dehydration methods that supply energy to the food, using media other than hot air, air or some other gas may be required to move moisture away from the food.

Copyright © 2016 Elsevier Inc. All rights reserved.

 

Dehydration methods

There are several methods often used to dehydrate foods. Methods vary in terms of the way that they dry foods, the amount of time required, and the type of equipment needed.

Here are some of the most popular methods

 

Sun drying

Sun drying is one of the oldest and most simple methods used to dehydrate foods.

It involves laying foods, such as fruits like figs or mangos, on a mesh screen or tray made with wooden dowels. Then, you cover the food with a second screen to deter pests and insects.

Food can be dried in any sunny area with low humidity and a minimum temperature of 86° F (30° C). If using this method, it’s also important to avoid screens made with hardware cloth, as these may oxidize and leave residue on your food. However, keep in mind that foods like fruits may take several days to fully dry when using this method.

 

Air drying

Like sun drying, air drying is a dehydration method that’s so simple that it doesn’t require any special equipment. Similar to sun drying, air-drying places food in the shade instead of the sun.

This can help protect foods from the sun’s powerful rays, making it a good option for leafy greens, herbal teas, and spices.

 

Solar drying

Solar dehydrators are powered by the sun, which can help dehydrate your foods without using any electricity.

Solar dehydrators often appear similar to a tabletop greenhouse. They can be purchased or made at home using materials that are readily available from your local hardware store.

 

Oven drying

Your oven can be used to dry foods when you keep it temperature around 140° F (60° C).

Though oven drying can take around 6-10 hours depending on the specific food, this method may be beneficial for people who don’t want to purchase any additional appliances.

Make sure your oven can be set to a temperature of 140° F (60° C) or less, as higher temperatures will cook food instead of drying it.

Additionally, be sure to prop the door open while dehydrating foods, which allows extra moisture to escape during the drying process.

 

Electric dehydrators

Electric dehydrators are one of the most efficient and convenient methods used for drying foods.

These appliances are usually equipped with a timer and temperature gauge, along with fans to evenly distribute heat.

They also typically have multiple trays, allowing you to dehydrate several types of food simultaneously. While these electric dehydrators may be the most efficient dehydration method, they’re not your best bet if you’re on a budget.

 

 

Benefits and uses

Food drying is often used to extend the shelf-life of ingredients and help them last longer.

By reducing the moisture content of foods, this process can prevent the growth of harmful contaminants, including types of bacteria and fungi that may make you sick   This can be particularly beneficial for seasonal foods like fruits and vegetables by increasing their availability throughout the year — even in remote locations where they don’t grow

This method of food preservation also reduces the weight and bulk of foods, which can decrease packaging, handling, and transportation costs for manufacturers                            It also alters the taste and texture of food products, often giving dried foods like fruits a sweeter, more concentrated flavor.

While this may have both pros and cons, these foods can supply a variety of vitamins, minerals, and antioxidants if you enjoy them in place of sugary sweets or other processed foods

 

 

Best foods to dehydrate

Many foods can be dehydrated — including fruits, vegetables, meats, yogurt, and even pet food.

You can even dehydrate jams and sauces to free up storage space and help them last longer in the pantry.

However, keep in mind that foods that are high in fat or oil do not dehydrate well, as the fat can go rancid. Therefore, avoid drying foods like peanut butter or avocados and be sure to trim meat to remove any fat before dehydrating.

While nonfat dairy products can technically be dehydrated, it’s not recommended and may be associated with a higher risk of foodborne illness.

Additionally, note that raw meat and poultry should be steamed, roasted, or cooked to an internal temperature of at least 160° F (71° C) and 165° F (74° C) to prevent foodborne illness even before drying .

Here are a few ideas for foods that you can try dehydrating:

• Fruits: apples, bananas, apricots, cherries, grapes, mangos, peaches
• Vegetables: carrots, beets, broccoli, cabbage, mushrooms, eggplant, zucchini
• Lean meats: beef, chicken, fish, jerky
• Sauces and syrups: jam, pizza sauce, maple syrup, spaghetti sauce, barbecue sauce,
• molasses
• Herbs: basil, dill, rosemary, oregano, thyme, sage, mint, lavender, marjoram

 

Storage and shelf life

Exposure to heat and moisture may decrease the shelf-life of your dried foods.

For this reason, dried foods should be stored in an airtight container and placed in a cool and dry area .

The shelf-life for these foods can range from a few months to several years, depending on the specific ingredients and how you store the food.

Here is the recommended shelf-life for a few dried foods, according to the United States Department of Agriculture (USDA) :

• Homemade jerky: 1-2 months if stored in the pantry or refrigerator
• Dried fruit: 6 months if stored in the refrigerator or pantry, 1 month if stored in the pantry after opening
• Dried herbs: 1-2 years
• Dried mushrooms: 1-2 years if stored in the pantry, 3 months if stored in the panty after opening

 

SUMMARY

• Dehydrated foods should be stored in an airtight container in a cool, dry area. The shelf-life for these items depends on several factors and may range from several months to several years.

Downsides

 

While dried foods can definitely be a healthy addition to a nutritious and well-rounded diet, they come with a few downsides that you should consider.

First, note that dried foods contain a similar set of nutrients as fresh foods, yet are packaged in a smaller and more condensed forms.

This can make it easier to overeat, which may lead to you consuming more calories, sugar, or sodium

Furthermore, dehydration could lead to some slight changes in the nutritional value of your foods. This may reduce the amount of certain vitamins and minerals, such as vitamin C and beta-carotene

Finally, keep in mind that moisture is removed from foods during the dehydration process.

It’s estimated that around 20-30% of your daily water intake comes from food sources, including foods with a high water content like fruits and vegetables

For this reason, it’s important to ensure you’re drinking plenty of water or enjoying a variety of fresh fruits and vegetables. Eating dried foods requite you to drink more water to meet your hydration needs.

 

 

The bottom line

 

Dehydrating foods can be an easy and effective way to prolong the shelf-life of ingredients, maximize storage space, and enjoy your favorite foods all year long.

There are a variety of foods that can be dried, as well as many different methods that can be used.

However, keep in mind that dehydrating foods decreases the water content of your foods, may make it easier to overeat, or may slightly alter the nutritional value for some foods.

At any rate, enjoy your dried foods in moderation.