The raw food diet has been gaining popularity. With it, a number of publications have expressed the dangers of overcooking foods. Heat sensitive vitamins and minerals diminish; protein becomes coagulated (a process where protein separates from other nutrients and turns from liquid to a solid), making it difficult to digest; and enzymes, essential in the digestion of food, are destroyed.
These, among other reasons, are why the constant consumption of cooked food is hard on the body. That is why so many people have looked towards the raw diet. However, many people are hesitant to try it. We all love the taste, and texture, of breads, crackers, bars, and other baked or cooked foods. A method that allows us to achieve these textures while still preserving most of the nutrients in food is food dehydration, or drying.
What is food dehydration?
Food dehydration is a method of food preservation. Food preservation refers to a number of processes used to keep food from spoiling. They have been used since prehistoric times, and include methods such as canning, salting, pickling, refrigeration (freezing), dehydration, freeze-drying, irradiation, pasteurization, fermentation, carbonation, and smoking. In recent years, it has also include the addition of chemical additives in chemical preservation.
The purpose of preservation is to prevent the growth of bacteria, fungi, and other microorganisms. It may also involve slowing down the oxidation of fats that cause rancidity and destroying enzymes that cause spoilage or discoloration.
Food dehydration is a method of food preservation that involves extracting moisture from food. Bacteria, yeasts, and molds need a sufficient amount of moisture to grow and thrive. Removing the water inhibits the growth of these microorganisms. It also slows down enzymatic reactions.
This process was used during the prehistoric times for sun drying seeds, and then was also used for drying fruits, vegetables, fish, eggs, rice, and meat. The dairy industry is now one of the largest processors of dehydrated food, including buttermilk, eggs, skim milk, powdered milk, etc. Many of these are dried using a spray-dry method.
Drying reduces the weight and bulk of foods, which made it an ideal method of transporting large shipments of food during World War II. Currently, dried foods are common for campers and hikers. Astronauts may use freeze-dried foods when in space.
Unlike canning and freezing, which involve extreme temperatures that can be damaging to foods, dehydration is a less damaging form of food preservation. It minimally affects the nutritional value of food. Removing the moisture from food does not affect the fibre and carbohydrates content either, but it does result in sugars, such as in fruits, being concentrated.
Some vitamin C may be lost, since it is an air-soluble vitamin and dehydration is an air-based process. It is also important to keep in mind that Vitamin A is light sensitive. Sun-drying may have some effect on the vitamin A content, but other drying techniques will not. Mineral content is also not affected.
Drying is one of the best ways to replicate the taste and textures of common foods such as bread and crackers without the dangers of destroying necessary enzymes from cooking foods at too high temperatures.
What are the different equipment for food dehydration?
There are a variety of different equipment and methods that are used for dehydration. These include tray dryers, tunnel dryers, roller or drum dryers, spray dryers, pneumatic dryers, rotary dryers, belt dryers, vacuum dryers, freeze dryers, etc.
Food dehydration was originally done outdoors by placing the food in the sun. Later, solar dehydration equipment was invented. These used racks with open areas to allow solar heat with better protection and movement of air. They have since developed into a variety of tools and equipment depending on the dehydration method you want.
The most common equipment used for drying are ovens or dehydrators. A dehydrator is a kitchen appliance that consists of a heating chamber, heating element, fan, air vents, and food trays. Heat flows through the layers of trays to absorb the moisture and dry the food evenly. The fans help circulate the air for more even drying. You can control the temperature through a thermostat or by adjusting the vents.
What is the process of food dehydration?
The process of dehydration generally uses three things: heat, dry air, and air movement.
The heat is required to draw out the moisture. You want it hot enough to force out moisture, but not so hot that the food begins to cook and the nutrients break down. The exact temperature depends on the food. Some say that the ideal is 140ºF, while others say that you need to keep temperature below 112-118ºF to keep it “raw” (to retain the most nutrient content and enzymes).
Dr. Gabriel Cousens, an American physician M.D., begins at 145ºF for a maximum of 3 hours in order to destroy and inhibit the growth of bacteria and then lowers it to around 112ºF for another several hours or more so that the most nutrients are retained. That method only works if you are using a dehydrator, which allows for more precise temperature adjustments.
Freeze-drying, another common form of food preservation that involves removing moisture, works a little differently. Instead of using heat, it involves rapidly freezing the food and then subjecting it to a high vacuum. The vacuum chamber removes the moisture and the food is sealed in an airtight container. It does not require refrigeration and the food tends to retain most of its original shape, colour, texture, and taste.
Heat-based dehydration removes approximately 80% to 90% of the moisture, while freeze-drying removes around 98% of the water. Nevertheless, the freeze drying process can be more expensive, time-consuming and labor intensive. Not all foods are suitable for freeze-drying.
3 common ways of dehydrating food at home
Three common ways of dehydrating food that can be done at home are sun drying, oven drying, and using a dehydrator.
Sun drying
Sun drying involves placing slices of fruit or vegetables on a clean rack and covering with a fine netting or screen, such as cheesecloth. You leave the food in the sun and turn once a day. This method is only suitable for drying fruits and vegetables, and cannot be used to make breads, crackers, or fruit leathers. It requires warm days with a minimum temperature of 85ºF, and low humidity with no insects.
Oven drying
Oven drying involves spreading the food in a single layer on a cookie tray and placing it into an oven preheated at the lowest setting, or about 140ºF. More than one tray of food can be dried at a time, but you want to make certain that there is at least 3 inch clearance at the top and bottom of the oven, and 2 ½ inches between trays.
If you use more than one tray, then you may need to shift trays every ½ hour. The oven door needs to be propped open 2 to 3 inches to allow proper ventilation. You may need to place a fan in front to improve air circulation.
Conventional ovens may not be able to maintain a consistent temperature, so it can be helpful to place an oven thermometer directly on the oven rack. Oven drying has a higher risk of food scorching, so you will want to check it often (at least every 2 hours) and turn pieces.
Using a dehydrator
Electric dehydrators are the most recommended for the dehydration process. They should be used in a dry, well-ventilated room. To use one, place the food in a single layer on each tray so that no pieces are touching or overlapping, and place or stack them in the heating chamber. Some dehydrators have different types of trays depending on the brand and on what food you are making. The exact temperature for dehydrating depends on the food, its size and moisture content, and what you are trying to achieve.
On some dehydrators, food on trays closer to the heat source can dry more rapidly. To prevent this from happening, the trays can be rotated throughout the drying process. As with any dehydration process, you want to check food often and turn pieces to dry more evenly.
You also want to pay close attention to temperature and air circulation. If the initial temperature is too low, or the air circulation is insufficient, then bacteria may not be properly destroyed or the food may undergo unwanted microbiological changes (such as browning). If the temperature is too high, then nutrients can be lost or moisture may be lost too quickly, resulting in the outer surface hardening and moisture not escaping from the inner tissue.
Preparing food for dehydration
Regardless of the method you choose, you want to make certain that the food is clean. You will want to wash fruits and vegetables and pat them dry before beginning the dehydration process.
Some recipes, such as those by Dr. Gabriel Cousens, involves soaking nuts and seeds, or mixing ingredients first. Fruits and vegetables can be cut into slices, rings, or pureed (if making fruit leather).
Keeping the pieces in uniform size allows for even drying. Pieces that are ⅛ to ¼ inches will also dry faster than those that are thicker. You will want to closely follow any instructions provided.
In addition, some people recommended pretreating vegetables by blanching or dipping foods.
Blanching involves briefly pre cooking food by boiling or steaming. It is used to stop enzymatic reactions that cause vegetables to mature or toughen during drying, shorten drying time, and enhance the destruction of bacteria.
Dipping foods involves dipping sliced fruit or vegetables pieces into a mixture of ascorbic acid or citric acid water to prevent them from turning brown. You can also blanch them in citric or ascorbic acid water or syrup (in the case of fruit).
However, it is important to keep in mind that extreme temperatures from boiling can also destroy the beneficial enzymes and nutrients.
Finishing the dehydration process
After drying, let foods cool before “conditioning” or testing for dryness. Foods can be conditioned by placing the dried fruits and vegetables in a large plastic or glass container so that it is about two-thirds full. Cover lightly and store in a warm, dry, well-ventilated place. Stir and shake the containers daily for four to ten days. If beads of moisture form, then return the food to the dehydrator for further drying. This process can be continued until there is no moisture.
It is important that foods are left to cool before testing for dryness or before storing since warm food can “sweat.” When dry, some foods may be pliable and leathery, while others will be hard and brittle. If you are unsure if the food is dry, then place it back into the dehydrator or oven until it looks and feels completely dry. You cannot over-dry food in a dehydrator.
Store dried food immediately after they are cooled in a sealed, air-tight container. This is important for protecting the food from insects and reabsorption of moisture. Depending on how long you plan on storing the food, you may want to seal the lids onto the containers. You may also want to label the containers with the name of the product as well as the date.
Foods can be stored in a cool, dry, dark place for up to 6 to 12 months, depending. Always check for off-smells, discoloration, and mold before consuming.
Fruits and vegetables can also be rehydrated (also known as reconstituting) by soaking them in water before being used. Although it depends on the fruit or vegetable, it is often recommended to soak them 30 minutes to 1 hour; and no more than 2 hours. Water is still essential for proper digestion and hydration for the body.
Since dehydrating removes most of the water content, it is especially important to drink plenty of fluids throughout the day.
Takeaway
Most people are familiar with dried fruits and vegetables. Raisins, a common fruit that is eaten as is or used in a variety of dishes, is an example of a partially dried fruit. You see containers of raisins and dried apricots and apples line the shelves of grocery stores. However, the process of dehydrating can be used for much more.
With the availability and convenience of the electric dehydrator, people have been experimenting with various recipes, ranging from fruit leathers, rice, risotto, bread, crackers, and biscotti cookies,to kale chips, crepes, and dog treats. Dehydration provides us with a large selection of recipes that offer a variety of flavours and textures without sacrificing as much nutrients as conventional cooking and baking.
We should try to eat as much raw and fresh fruits as possible, but food dehydration offers unlimited possibilities for healthier cooking.