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Vacuum Drying | Can it Expedite Drying Processes?

Recently, DigiVac got speaking with some clients about whether the introduction of vacuum could potentially expedite, or speed up, drying processes. Just looking at the method, the answer would seem obvious – especially when put in comparison to simply air drying. However, we wanted to be sure and thus – this experiment was created. Before we begin discussing the experiment, however, some vacuum drying basics should be discussed beforehand.

What is Vacuum Drying?

Vacuum drying is the “science of removing moisture present in an item or substance through the use of vacuum.” This is done by placing a substance or material into a sealed container, then subjecting it to extremely low pressure to draw out and rid the substance/material of unwanted moisture.

Heat is most commonly used in the process, simultaneously applying it with the vacuum in order to remove all the water vapor. The reason for drying out a substance or material in this way is so that the water vapor that could potentially harm the product can be removed carefully, and with the lack of air in the chamber from the vacuum, it can mitigate oxidation as well.

How is Vacuum Drying Done?

The vacuum drying process is achieved with a vacuum oven, a vacuum pump, and a vacuum gauge. The vacuum oven will be the sealed container that a product or material is placed within. From there, heat is applied whilst a vacuum pump lowers the pressure. Thus, as the pressure lowers and the temperature of the heat increases, the water moisture will then evaporate – thus drying out the product. A vacuum gauge assists in monitoring pressure levels, while also potentially sending readings out to a data logger.

What Are Vacuum Drying Applications?

There are a plethora of applications that vacuum drying has potential for. Aside from cleaning and drying sterilized medical products, DigiVac recently got to experiment a bit with vacuum ovens.

In this experiment done in tandem with a client, DigiVac sought to see if there was an advantage to vacuum drying tissue samples as opposed to letting the tissue samples air dry. Read further for a full breakdown of the experiment done!

The Experiment: Vacuum Drying Will Make for Faster, More Complete Drying

Hypothesis: “We believe that the vacuum + heat + purge cycles will make for faster, more complete drying.”

Purpose: Compare whether there were benefits to using a vacuum oven to dry tissue samples as opposed to just forced air drying. Specifically, if vacuum drying offered any benefit to the time and quality of dryness.

Criteria: Before and after weight will be measured and compared, as well as a visual cross-section inspection. A moisture meter will also be used.

Sample Tissues Used: Beef Heart, Beef Kidney, and Beef Liver (the method described below was repeated for each of these samples).


  1. Label one sample (Sample B) to be tested for vacuum drying and the other (Sample A) for just heat drying.
  2. Weigh both samples and record their weight prior to losing any moisture.
  3. Place Sample A into vacuum oven, with a temperature set at 99 degrees. This will have no vacuum.*
  4. Place Sample B into a vacuum oven with the temperature set at 99 degrees, and with evacuate and purge cycles set to go off every 9 hours.
  5. Let run for 3-4 days each.
  6. Weigh both samples.
  7. Inspect both samples.

*A modification had to be made to this step during the experiment due to excessive moisture build up within the vacuum oven due to the lack of vacuum pump. Therefore, the vacuum oven holding Sample A had to be opened from time to time to release moisture + mop up excess moisture.


A total of three tests were done, with the three types of tissue samples. A few tests were done in a method resembling that of the client’s – with the samples being dried in beakers – whereas others were laid out on trays.

The samples that were dried in the beakers ended up having a layer of fat pooling at the bottom of the beaker, with water trapped beneath the fat from how the moisture was rendered out during the drying process.

However, overall, vacuum drying yielded much better results. In the test using the beef heart sample, the visual inspection for Sample B (vacuum dried) resembled that of beef jerky and was far better than that of Sample A (just heat) which resembled burnt meat. The moisture loss difference, however, was negligible.

In the test with the beef kidney on the other hand, Sample B (with vacuum) had the most moisture drawn out, even if it was trapped within the layers of fat. The beef liver tests also yielded a similar result. Additionally, not only was the drying substantially faster, but there was a deeper level of drying that was achieved overall as well.

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