Vacuum drying

Water is removed in a chamber with reduced pressure. A vacuum helps dry under other temperature conditions, but does not replace heating and control of readiness.

How it works

Reducing pressure makes it easier for water to evaporate at a lower temperature than at normal pressure. The heat is still supplied; the result depends on pressure, temperature and steam removal.

History

Finding the right regime for berries

A 2019 paper from La Serena University examined vacuum drying of maqui berries at different temperatures. The researchers assessed composition and quality indicators, not just weight loss.

Development of moisture removal

The 2023 apple slice study used a cooled surface inside a vacuum chamber to condense steam. This is an example of how dryer design changes the outcome.

What changes in the product

Thermal effect can be changed

Reduced pressure allows you to select a mode for sensitive raw materials. However, vacuum drying varies in temperature and duration; the word "vacuum" does not mean the absence of thermal changes.

Color and recovery depend on mode

In the apple experiment, modification of the steam exhaust affected color, texture, and water absorption. These results apply to the samples studied and not to all store-bought dried fruit.

Vacuum packaging is a different operation

A normal product can be evacuated during packaging without drying it out. Therefore, a tight bag in itself does not confirm vacuum drying and does not make a wet product suitable for storage without refrigeration.

Pros

• Lower evaporation temperatures can be used.
• The chamber allows you to set the pressure and processing mode.
• Suitable for developing fruit ingredients with the desired color and structure.

Limitations

• A special chamber, pump and energy supply are needed.
• Insufficient steam removal can slow down the process.
• The name cannot predict softness, crunch, or longevity of flavor.
• The method does not eliminate the need to check the composition.

Where is it used?

• Berries, for example in research - poppies.
• Apple slices.
• Fruit ingredients as part of a combined technology.

When to choose

• There is a sample or description of the texture suitable for your baked goods and desserts.
• The manufacturer discloses the drying method, and not just the type of bag.

When to choose another option

• Vacuum packaging is given as proof of special drying.
• You are promised unchanged vitamins without analyzing the product.

What to know before buying

• Was the product vacuum dried or just vacuum packed?
• Was there any pre-freezing?
• Did you use syrup and additional drying?
• What are the storage conditions for closed and opened packaging?