Freeze drying

The product is first frozen, then the ice is removed in a vacuum. This method is often chosen for the light structure of berries, pieces and powders.

How it works

At reduced pressure, ice turns directly into water vapor - this is sublimation. Moisture is removed from the frozen product; Conventional freezer storage is no substitute for a controlled drying process.

History

The method has become available to small industries

Penn State describes the rise of home freeze-dryers and how they differ from conventional dehydrators: The equipment is more expensive, larger and requires more energy.

Methods are compared for specific products

A 2014 study compared freeze-dried apples with air-drying and a combination of drying. A universal winner for any fruit cannot be derived from such an experience.

What changes in the product

Lightness and shape

Freeze-dried products are usually light, retain their original shape well and are suitable for subsequent reconstitution with water. When added to a wet dessert, their original dry texture changes.

The aroma is not equal to fresh fruit

The method is capable of well preserving the character of the product, but does not promise complete coincidence with the original raw materials. The taste of the dry piece and the reconstituted portion should be assessed separately.

No guarantee of sterility

Freeze-drying is not a way to kill all dangerous bacteria. For a ready-made snack, you need products intended specifically for consumption without additional preparation.

Packaging matters a lot

After opening, the product must be protected from moisture and air. The stated period refers to the manufacturer's conditions, and not to any opened can.

Pros

• Light weight makes it easy to carry.
• Individual pieces, crumbs and powder are suitable.
• Can be reconstituted with water or used in a recipe.
• Good shape retention is useful for dessert decoration.

Limitations

• Equipment and processing costs are higher than simple air drying.
• The pieces easily lose their desired dry texture when exposed to moisture.
• Careful transportation and suitable packaging are required.
• The method does not guarantee either sterility or preservation of 100% of vitamins.

Where is it used?

• Berries and fruit pieces.
• Fruit powders and crumbs.
• Other products are based only on the manufacturer's technology.

When to choose

• You need a light dry additive to granola or decoration, which is added immediately before serving.
• The recipe requires fruit powder with a known composition.

When to choose another option

• The usual soft and viscous dried fruit is expected.
• The packaging is damaged or it is unknown how long it has been opened.

What to know before buying

• Is this really freeze-dried and not just a frozen product?
• Is there any carrier, sugar or other additives in the powder?
• Is the product suitable for consumption without cooking?
• How to store after opening and how fragile are the pieces?