Freeze Drying, Air Drying and REV™ Drying. Which dehydration process is best?

processing advantages

Tired of waiting hours for your freeze-dried product to complete it’s drying cycle? Rapid drying methods are becoming the process of choice for manufacturers looking to increase output. This is especially true when a product’s colour, flavour and nutritional content must be maintained for commercial viability. With consumers becoming increasingly aware of what they are eating, product quality cannot be sacrificed during the drying process.

In this article, drying times, nutrient retention, and basic processing advantages are compared for conventional drying methods (freeze drying and air drying) and REV™ (vacuum microwave drying).


The REV drying process is extremely quick compared to conventional drying methods such as air drying or freeze drying. Faster processes allow manufactures to increase throughput and potentially reduce operating costs.

Pineapples, as shown in the data table below, can be dried in 2.5 hours using the REV process.  By comparison, the freeze drying process for the same pineapple pieces takes upwards of 72 hours to dry to the same specifications. That’s a reduction of 70 hours between the two processes.

The added benefit is that the REV process does not require any lacerations of non-porous fruits and vegetables that are needed for the freeze drying process.

The REV drying process is best paired with air drying pre-treatment for many fruit and vegetable products as noted in the following tables.

Table Below: Drying time comparison table for Air Drying, Air Drying + REV drying and Freeze Drying of pineapples.

Estimated Reading Time:

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PDF – Freeze Dry versus REV™ Dry 

About the Data Set

The data set was produced and presented as a technical poster at IFT Expo.



MOISTURE control

REV technology is a uniform, volumetric drying process that provides precise moisture control during the entire drying process.

Drying occurs from the inside out which means that whether you stop at 20% moisture or 1% moisture, your product will be consistently dry all the way through. This allows for a range of product textures from chewy to crunchy that is currently unavailable with freeze drying.

Table Below: Comparison of Freeze Drying and REV Drying Processes

COLOUR, FLAVOUR & nutrients

REV drying keeps your fruits and vegetables looking natural. The process is incredibly gentle due to moderate temperatures and an oxygen-free drying environment. This gentle process also retains Ascorbic Acid (vitamin C) and is comparable to the retention rates found with freeze drying.

Table Below: Ascorbic Acid (Vitamin C) Retention for Pineapples


REV drying occurs under vacuum and at a pressure where water boils at 25° C.

Unless specifically desired, temperatures stay at a moderate level to prevent cooking and allow the cell-structures of the product to remain intact which keeps colours, flavours, and nutrients. Antioxidant retention is another indicator of product quality and is on par for pineapples as shown in the table below.

Table Below: Antioxidant Activity table comparing the results for pineapples dried using conventional methods and REV.

Product Data Sets

The following tables show processing data for blueberries, strawberries, and pineapples dried using air drying, freeze drying and REV drying methods.

REV dried results

The REV drying process outperforms freeze drying with faster processing times. This results in an increase in throughput and a potential reduction in production costs. The added ability to retain natural colours, flavours, and nutrients allow companies to add high-margin, premium ingredients and snacks to their product catalogues.

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