July 14, 2017

What is Freeze Drying?

Freeze drying is the process of removing liquid from an item, such as food, to help shelf life, reduce weight, and preserve quality.

Freeze drying begins with freezing the item and subjecting it to vacuum pressure to remove the solvent content (usually water) from the item. The product is then heated, which allows the solvent to evaporate through a process known as sublimation.

This allows a product to be preserved for many years without compromising its quality (if the item is sealed in packaging that keeps oxygen, moisture, and light out). For example, in the case of freeze dried food, a food item’s texture, flavor, and nutritional content remain intact. Freeze-drying also greatly reduces the weight of the food, making it easier to transport and store.

How to freeze dry food

How does freeze drying work?

Freeze drying for food specifically is a step-by-step process that includes:

  1. Freezing the product – The product is frozen solid.
  2. Applying vacuum pressure to the product – The product is placed in a vacuum, which causes the solvent to sublimate.
  3. Heating the product – Applying heat accelerates the sublimation process.
  4. Condensation – The vaporized solvent is removed and converted back into a solid state, completing the separation process.

For most foods, the finished product is one that can be brought back to it’s normal state by just adding water.

The freeze drying process across industries

Freeze drying isn’t just limited to food. Here are a few other products that can also be freeze dried:

  • Pharmaceutical – The pharmaceutical industry frequently uses freeze drying to prolong the shelf life of wound dressings, drugs and more.
  • Biotechnology and biomedical – Freeze drying has been used on vaccines, bacterial cultures, blood plasma, purified proteins and enzymes.
  • Nutraceutical – Antioxidants, aloe vera, echinacea, and similar products that have been extracted from foods and plants for their health benefits can also be freeze dried.
  • Floral – Floral bouquets can be freeze dried to commemorate a wedding day. Freeze dried flowers are also used for culinary and decorative purposes.

Lyophilization vs. freeze drying

What’s the difference between lyophilization and freeze drying? There is none — both terms refer to the same process.

The formal term “lyophilization” became popular in the 1960s to describe the porous nature of freeze-dried products and their ability to quickly reabsorb a solvent (typically water) to return to their original state.

The word “lyophilization” is more commonly used in the biomedical, biotechnology, and pharmaceutical industries, while “freeze-drying” is the norm when referring to food products.

The scientific process of freeze drying

The process begins with freezing the item. Next, the product is placed under vacuum pressure to evaporate the ice in a process known as sublimation. This allows the ice to directly transform from a solid to a gas, bypassing the liquid phase.

Heat is then applied to aid in the sublimation process. Finally, low temperature condenser plates remove the vaporized solvent to complete the freeze-drying process.

The OFD Difference

As you can see, freeze-drying is a process that’s used across a wide variety of industries. With so many options to choose from, what makes OFD’s freeze-drying process stand above the rest?

  • Our history. We’ve been in business for more than 50 years and have created products for the U.S. military, NASA, outdoor enthusiasts, popular private label food brands, and the biomedical and pharmaceutical industries. Learn more about our brands.
  • Our reach. OFD is the largest freeze dryer in North America. Thanks to our size, we’re able to maximize our production with our packaging capabilities and automated lines.
  • Our quality. We take every step to make sure our products exceed our consumers’ expectations on every level. From taste to texture to convenience, our freeze dried food products deliver exceptional quality. Our facilities are regularly inspected by the FDA and USDA, and are SQF level II approved.

If you have any further questions about the freeze drying process or the results, reach out to us by filling out the contact form on our homepage or calling us at 541.926.6001.

Watch the video below for more information on the freeze drying process.