Preserving food by drying or dehydration is the oldest known method of food preservation, dating back thousands of years. Drying preserves food by removing sufficient moisture to prevent the growth of spoilage and illness-causing microorganisms.
Although drying foods in the sun is a popular method in some areas of the United States and the world, New York State does not have a suitable climate for it. Successful outdoor drying requires several days of at least 85 degrees F with humidity below 60%. Typically, in New York State when the temperature is high enough, the humidity is too high for drying food successfully.
Appropriate New York State methods include drying in a thermostatically controlled, properly vented dehydrator; conventional oven; convection oven; or microwave oven (for herbs only).
Dehydrator Drying: Commercially manufactured dehydrators come in different sizes and shapes and with varied features. They have a heat source and a method to take the warm, moist air away from the food. Dehydrators with adjustable thermostats will dry food more effectively and safely than those with only an electric heating coil. Dehydrators with a built-in fan will remove moisture more effectively than dehydrators that depend on natural convection currents.
A thermostat that controls temperatures between 85 and 160 degrees F is best because various foods require different temperatures to reach the properly dried stage. Food dried at too low a temperature may dry too slowly, giving food spoilage bacteria, yeast, and molds time to multiply. Drying at too high a temperature will result in improperly dried food because the surface hardens and does not allow the inside moisture to escape. In both cases the food may be harmful if eaten and will spoil.
Conventional Oven Drying takes more attention than dehydrator drying. An oven thermometer is used to verify a constant temperature of 140 degrees F. To assist in moving the moist air away from the food, the door should be propped open a few inches. For more effective air movement, position a fan to the side of the oven door, blowing across the opening. CAUTION – this set-up may be dangerous in a home with children and pets.
Convection Ovens have a built-in fan that circulates warm air and may be effectively used as a dehydrator, especially if the moist air can be vented. Convection ovens that have a controllable temperature starting at 120 degrees F and a continuous operation feature rather than a timer-controlled one, work best. Follow the manufacturer’s directions for specific ovens.
Microwave Oven Drying is only good for drying herbs because of ineffective air circulation that cooks food before it dries. Follow the manufacturer’s directions for specific ovens.
For more information on drying foods, register for a free webinar on “Dehydrating Fruits and Vegetables” hosted by Cornell Cooperative Extension (CCE) of Saratoga County on Friday, September 25 from 11 am – 12 noon. Details are available at CCE Herkimer County website at the events calendar. For additional food preservation resources, see the CCE of Herkimer County website at Food Preservation Resources
Article released September 21, 2020
