Air drying is achieved by hanging food in a dry breezy place. Humidity, insects, leaves, dirt and other particulate matter are enemies of air drying and could create mold and food spoilage. Air drying should be done over two to three days and the food should not be left outside overnight exposing it to animals and morning moisture.
Ascorbic acid is a sugar acid with antioxidant properties. Ascorbic acid is white to light yellow crystals or powder, and dissolves in water. One common type of ascorbic acid is vitamin C.
Blanching Blanching occurs when vegetables are exposed to boiling water or steam for a brief period of time, typically four to six minutes. Water blanching is immersing the vegetables into boiling water, steam blanching obviously works off the steam generated by the boiling water and does not require dipping the vegetables into the boiling water. Blanching inactivates enzymes in vegetables that could otherwise cause chemical reactions within the food and post dehydration spoilage. Dried vegetables that have been blanched will have better color and flavor than non-blanched dried vegetables. Fruits are not blanched before dehydration.
Case Hardening Case hardening is a result of partially dehydrated food that. Case hardened food has the outermost portion of the food dried while the interior remains moist. This situation typically results when too high of a drying temperature is used. Case hardened foods will spoil due to microbial growth. Moisture from the interior of the food will migrate to the exterior.
Enzymes Enzymes are largely proteins, complex chains of amino acids, which catalyze or increase the rate of chemical reactions. As it relates to food, enzymes can accelerate and cause food spoilage.
Horizontal Air Flow Food Dehydrators Horizontal air flow food dehydrators have their heating element and fan located on one side of the dehydrator. The drying trays that hold the food are arranged like drawers inside the food dehydrator. A horizontal air flow dehydrator typically has a more even distribution of temperature across the drying trays resulting in more consistent food dehydration. Typically, horizontal air flow dehydrators are better at dehydrating different types of food at the same time as the horizontal air current mixes the food flavors less than vertical air flow dehydrators. Lastly, horizontal air flow dehydrators better prevent food juices from dripping down onto the heating element, thus making cleaning easier.
Oven Drying Oven dehydration involves drying food at temperatures between 130 and 150 degrees Fahrenheit (54 to 65 degrees Celsius) in your home appliance. With oven dehydration, you simply place food items on the wire racks in your oven, set the heat and leave the oven door slightly ajar to let moisture out. Oven dehydration’s drawbacks include: a) inefficient energy use given the oven’s size and cost, b) the danger inherent in leaving the oven door open while it is in use, c) the lack of air movement which is a component of food dehydration and moisture removal and d) many older ovens cannot set temperatures below 200 degrees Fahrenheit (93 degrees Celsius).
Pre-treating FruitsPre-treating fruits before dehydration involves dipping the fruit in a acidic solution dip (citrus fruit juice or ascorbic acid) or a sodium sulfite dip. Pre-treating helps keep dried fruits from darkening during drying and storage and also helps speed the dehydration of fruits with skins, such as grapes and cherries. Pre-treating fruits also helps retain and adds vitamin C to and within the fruit.
Shelf Life Shelf life is the period of time that food or other perishable items are given before they are considered unsuitable for consumption or use. Shelf life, as it pertains to dehydrated food, is the recommended time that products can be stored and retain their taste, nutrition, freshness and intended use (to be eaten and enjoyed!).
Sodium Sulfite Sodium sulfite is a water soluble compound of sodium and is used as a preservative to prevent dried fruit from discoloring or browning.
Solar DryingSolar dehydration is a variation of sun dehydration in which the sun’s rays are collected inside a specially designed unit with adequate vents for the removal of moist air. Due to the enclosed unit, the temperature inside a solar dehydration unit is usually 20 to 30 degrees warmer than in open sunlight which results in a shorter drying time. Solar dehydration has advantages over sun dehydration, including more focused, higher temperatures, and thus shorter drying times, and protection from insects and other wind borne matter. However, inclement weather, limited ideal hot and dry weather climates and a lack of control over the weather are the main problems with both sun dehydration and solar dehydration.
Sun DryingAs the name implies, sun drying is taking advantage of the sun’s free, renewable energy source for food dehydration. Sun dehydration requires a location that has several consecutive hot days of 90 to 95 degree Fahrenheit weather (32 to 35 degrees Celsius) and low humidity. Unfortunately, only a few areas in the United States, primarily the southwest, consistently have this type of climate. As with air drying, humidity, insects, leaves, dirt and other particulate matter are enemies of sun drying and could create mold and food spoilage.
Thermostat A thermostat is a device used to regulate the temperature of a heating or cooling system so that the system's temperature is maintained near a desired chosen temperature. The thermostat does this by switching heating or cooling systems on or off as needed to maintain the correct temperature.
Total Drying Area The total drying area of a food dehydrator is measured in square feet and is equal to: a) the number of drying trays multiplied by b) the size of the drying trays. For example, if a dehydrator had a total of four 12 inch by 12 inch drying trays (1 square foot each), the total drying area would be four square feet.
Vertical Air Flow Food DehydratorsVertical air flow food dehydrators have their heating element and fan located at the base of the dehydrator. The drying trays that hold the food are stacked on top of the base. Because the drying trays and food are stacked on top of the heating element, drying temperatures can vary between the top and bottom food drying trays. Vertical air flow dehydrators may require a swapping of top and bottom drying trays, during the dehydration process, so that an even drying effect is achieved across all the food and drying trays.
Water Content Water content is the percentage of a food’s weight that is water. The water content of most fruits and vegetables is 80% to 95% of their overall weight.
Watts The energy consumed or used by a food dehydrator is measured in watts, similar to that of the light bulb. If a 100 watt light bulb is turned on for two hours, the energy used is 200 watt hours. The same applies to a 100 watt food dehydrator used for two hours. The watt power of a food dehydrator should be considered in relation to the number of food drying trays and size of the dehydrator. More drying trays and larger dehydrator dimensions should require more watts used by the dehydrator to ensure adequate dehydration.
Published 4/28/2009 12:00:00 AM