Food Dehydrating

by Richard Munn|Published 07-21-2006


Inuit children in front of a drying rack for salmonThe use of dehydration as a food-preserving method has been around for thousands of years. Prior to the advent of refrigeration, people only had two options - dehydration and canning. Canning requires a supply of airtight glass jars and equipment to boil those jars. Dehydration requires only a gentle source of heat. The dehydration process used by our ancestors could be a simple as hanging meat, vegetables or berries over wood frames in the sun and wind.

How does dehydration work?

Bacteria, yeasts and moulds need a food source and water to grow. When we dehydrate food, we remove most of the water and prevent this growth process. Drying also slows down the action of enzymes in the food. Enzymes are naturally present in food, causing it to ripen (and eventually spoil). By slowing down enzyme action, we help the food last longer.

Having a supply of food that requires no refrigeration to last is an obvious advantage for backcountry travellers. An added bonus is the substantial savings in weight and volume. Dried food shrinks in size, and obviously weighs less because the heaviest component (water) has been removed.

Dehydrating Food

Food can be dehydrated any number of ways, including sun-drying, oven-drying and by using a commercial

Two things are required - a heat source to dry the food; and some way of moving air over the food to remove the moist air.                                          

Sun and solar drying are slower than other methods, and may not be succesful if humidity is high. Oven drying is quick, but lacks a way of moving air over the food and is not all that energy efficient. Most people who dehydrate food in any significant quantities purchase and use a commercial food dehydrator.

                                  food dehydrator                                    

Food dehydrators generally are cylindrical in shape, and consist of a base with a heater and fan, and round trays that stack above this base. Trays are perforated to allow air movement. A lid at the top of the stack closes off the system.                                                                                             Foods that are suitable for dehydration are those that are high in water content and low in fat. This includes a wide variety of foods, including:

    • Fruits
    • Vegetables
    • Lean meats and fish
    • Sauces, purees and stews

What doesn't work? There are some foods that are not appropriate for drying, and they tend to be foods with high fat contents. Dehydration removes water, not oils and fats. If fats are present, they will eventually go rancid, even if the food itself doesn't spoil. This means we have to forgo trying to dehydrate fatty foods like some meats, cheese or sauces and stews with a high fat content. Home dehydration of dairy products is generally not an option. For example, you can't use your dehydrator to make powdered milk. Dairy dehydration requires specialized equipment.

Finally, there are some foods that have such a high moisture content that by the time that water is removed by dehydrating, there is simply nothing left. Try dehydrating watermelon and you'll end up with watermelon dust. Try celery pieces and you'll end up with tiny, hard chunks of concentrated celery that will never rehydrate (they can be ground into celery powder, though.

Weight and Space Savings

Dehydration offers substantial savings in weight and packing volume. Many fruits and vegetables consist of between 80% and 90% water, and once this water is removed by dehydration, the savings can be nothing short of amazing. For example, a ten pound bag of carrots, washed and sliced, will fit into a large mason jar after dehydration.

A large container of spaghetti sauce will dehydrate to a concentrated 'leather' which will fit into a small Ziploc bag and weigh next to nothing.

A supply of dehydrated ingredients, supplemented by soup and sauce bases available at most bulk food stores can form the basis for a number of lightweight and delicious meals.

There's another advantage of dehydrating food - the cost benefit. You can buy fruit and vegetables in season when they are at their lowest price and dry them for later use. If you know anyone with a garden, chances are they're looking for people to take those extra tomatoes and zucchinis anyway. If you've priced commercially prepared dried foods, you already understand how much money you can save by preparing your own.