Intro to Dehydrating

Four key factors effect dehydration and your success with it:

Time, Temperature, Air Circulation, Food Preparation

TIME

Drying times vary based on your location, humidity, temperature and size of item.  The general rule is that the more surface area exposed; the faster the drying time.  It is important to slice foods to the same thickness for a more consistent drying time.  A common mistake in dehydrating is thinking if you increase the temperature, you decrease the drying time.  If you increase the temperature too much, case hardening may occur.  This means the surface of the food dried to a leathery texture creating a barrier for water removal. 

TEMPERATURE

In general, food temperature is about 20 degrees cooler than air temperature.  This is due to evaporation.  As the moisture on the surface of the food evaporates, it cools the food.  We have discovered this through hours of testing and measuring the air temperature and food temperature simultaneously during the dehydration process using a Doric Tendricator with type j thermal couples. The temperature reading on the Excalibur dial refers to the food temperature.  If you set the Excalibur at 105F, you are setting it to hold the food temperature at 105 but the air temperature may get as high as 124F.

AIR CIRCULATION

The Excalibur Parallex Horizontal Air Flow was developed and patented by Excalibur.  This Air Flow combined with our heavy duty fan creates an air circulation that draws in cool air, heats the air, and distributes the air evenly over each tray.  This air flow combined with our Adjustable Hyperwave Thermostat causes the air temperature to rise rapidly to a high point, so moisture is quickly evaporated off the food’s surface.  As the temperature lowers, the dryer surface pulls moisture from the center of the food and becomes saturated again.  Because of the up and down fluctuation of air temp and constant evaporation, the food temp remains at a lower temperature.  After all the food moisture is evaporated, the food temperature will rise and equalize somewhere in the middle of the air temperature fluctuation. 

FOOD PREPARATION

Food slices should have a consistent thickness.

Blanching: Immerse cut vegetables in boiling water or expose them to steam.  The scalding action destroys naturally occurring enzymes that contribute to flavor loss, texture change and color change.  Over-blanching can cook the fruits or vegetables and soften them excessively.

Checking: Technique applied to berries with a waxy coating.  The objective is to create small disruptions in the waxy layer appearing as small cracks with a checkered appearance.  Without this, many berries will take a very long time to dehydrate.  To “check”, place berries in a strainer and dip into boiling water.  Don’t heat them too long.  An option to checking is to simply pierce the outer skin of a berry numerous times. 

Quenching / Refreshing: This is done after Blanching or Checking.  Quenching stops the action of heat on the food.  Plunge the hot food into cold water to bring down the food temperature.

IS IT DRY YET?

To determine if your food is dry, takes experimentation.  Sliced apples are firm and leathery.  Carrots are brittle.  Grapes will be soft and pliable.  If you’re not sure if your food is dry, break or tear a piece open and squeeze the flesh.  If moisture or liquid comes to the surface, return the food to the dehydrator.  It’s better to over-dry, than under-dry.  Under-drying leads to spoilage.