Guides for Success in Drying

Prepared by the Cooperative Extension Service of the University of Utah

Photo by Linda Anderson

Selecting the Right Product

• Fruits and vegetables selected for drying should be sound, fresh, and in the "peak" of condition; ripe, but still firm and at the right state of maturity.
• Wilted or inferior material will not make a satisfactory product.
• Immature fruits will be weak in color and flavor. Over-mature vegetables are usually tough and woody.
• Over-mature or bruised fruits are likely to spoil before the drying process can be accomplished.
•  Fruit and vegetables that are inferior before drying will be inferior after drying.

Speed and Enzymatic Changes

• Enzymatic changes take place rapidly in harvested food.
• Speed in both the preparation and in the drying process time is very important to a quality product.
•  Process the produce while it is still fresh.
• Vegetables should be partially cooked by steaming or scalding.
• Fruits should be steamed, sulfured, or treated by soaking in salt, sulfite, or acid solutions.

Temperature

• Heat is supplied by the sun or electrical heat.
• If the drying temperature is too low, the product will sour.
• Drying should be done as quickly as possible, at a temperature that does not seriously affect the texture, color, and flavor of the fruit or vegetable.
• If the temperature is too high or the humidity too low, there is a danger of moisture being removed too fast. This can cause a hardening of the outer cells of the product (case hardening) which prevents water vapor from diffusing from the inner cells.
• Drying is best accomplished when the process is continuous. When heat is applied intermittently, temperatures conducive to bacterial growth can develop.

Circulation of Air

• Each piece of food should have good exposure to air.
• Food should be only one layer deep with space around it. This space does not need to be large since the product will shrink during the drying process. A good flow of air is necessary.
• The air will absorb all the moisture it can hold; therefore, fresh air should be forced to circulate to remove water vapor and carry moisture away from the food being dried.
• The force of the circulating air should not be so strong that it can blow the dried food off the rack.