Connect with us

Hi, what are you looking for?

Pet Food Ingredients

Freeze-Drying & Dehydrating: There’s a Difference

The terms ‘dehydrated’ and ‘freeze-dried’ are pretty often used interchangeably, but there’s more difference to them than you might think. They’re both great ways of preserving food, but that’s where the similarity ends.

The terms ‘dehydrated’ and ‘freeze-dried’ are pretty often used interchangeably, but there’s more difference to them than you might think. They’re both great ways of preserving food, but that’s where the similarity ends.

The Dehydration Process

Dehydration is the simpler of the two processes. It has been used for millennia as a method of food preservation – as early as 12,000 BC people were drying meat and fruits in the sun. These days sun drying is only used for fruit (which has to be pasteurized later.) [Source: Virginia Cooperative Extension]

Industrial dehydrators are essentially large ovens. Hot air kept around 100°F circulates throughout the chamber, slowly ridding the food of all its moisture. Foods are kept in the dehydrator for different amounts of time depending on the amount of moisture in the food. [Source: EPA]

In the end, dehydrated foods will lose about 90-95% of their moisture content. Shelf life will depend on manufacturing, but for dehydrated foods (according to the website The ReadyBlog) their shelf life averages 15-20 years.

The Freeze-Drying Process

What we think of as freeze-drying today actually dates back as far as World War II. The technology was developed to help get medicines onto the battlefield without their spoiling. [Source: How Products Are Made] Food storage actually came later.

The process starts as you might think it would, with freezing. Once that’s done the food will go through two stages of drying. The first, primary drying, utilizes something known as sublimation.

freeze_dryer

Food is placed inside a sealed dryer and the pressure is lowered, which creates a partial vacuum. Inside that vacuum the solid water (ice crystals) in the food turn directly into water vapor. The water vapor is filtered out of the freeze-drying chamber and re-freezes onto the refrigeration coils. [Source: SPScientific] (This keeps food from reabsorbing the moisture it lost.)

To remove the remaining water in the food, the drying chamber is heated up, which helps to force out any liquid water still left in the food.

At the end of this process, foods have lost between 95-99% of their moisture and (stored properly), they can last 25-30 years. [Source: The ReadyBlog]

The Nutritional Side

It’s impossible for fresh food not to lose some nutrients, whether it’s to cooking, preservation or simply time. With dehydration, contact with heat damages vitamins A & C, which are very heat sensitive. (Vitamin A is also light sensitive, which makes it important to store dehydrated foods in a dark place.)

According to the EPA, some foods can be treated with sulfur compounds such as sulfur dioxide to prevent the loss of antioxidants in the dehydration process. (Sulfur dioxide also helps with color retention.)

Freeze-dried foods minimize the loss of nutrients – primarily restricted to vitamin C.

That was the long version, but to sum-up, a chart for comparison:

comparechart_sm

Whether you choose freeze-dried or dehydrated, the benefits far outweigh any potential nutrient loss. The cooking is gentle (or non-existent) and shelf-life is extended without any additives.

 

Liane Thixton

Pet Food Safety Advocate (In Training)

18 Comments

18 Comments

  1. T Allen

    March 13, 2016 at 10:10 am

    Excellent Liane! Great description and easy to understand! Look forward to seeing more more from you!

  2. Erica

    March 13, 2016 at 12:22 pm

    Thank you Liane for the quick and easy to understand comparison !

  3. Batzion

    March 13, 2016 at 1:25 pm

    Waving hello Liane. Nice to meet you, and thank you for this info which is good as always.

  4. Lynn Utecht

    March 13, 2016 at 2:13 pm

    Very nice research! Looking forward to seeing more from you Liane!

  5. Barbara Fellnermayr

    March 13, 2016 at 4:16 pm

    Hi Liane,

    Great work. We do a cool-air dehydration process, our drying room never gets above 85 degrees. We then use dehumidifiers to remove the water from the air. It is our own process (patent pending) retains not only more nutritional value but the texture of the natural ingredients. It comes out looking like beef jerky. Dogs and even cats love it. Look forward to seeing more of your work. cheers amorepetfoods.com

    • Kathleen

      March 13, 2016 at 5:38 pm

      Yeah, but does amore use DENATURED meat? Yes I see it is human-grade, however, when meat leaves a USDA facility destined as pet food, it is required to be denatured with a denaturant such as charcoal or chemicals.

      • Barbara Fellnermayr

        March 13, 2016 at 8:34 pm

        No, Amore only uses Human Grade meat. Most of our meats come direct from local farms. I won’t buy pet food grade meats, because they are not meat, they are leftovers. My staff and I all buy meat from the company as it is better than the meats we can buy at the grocery store. Certified organic beef, free range chicken, wild pacific salmon filets.

      • barbara m.

        March 15, 2016 at 2:16 pm

        If you want to bone up on the facts of denaturing, please check out Mollie’s Poisoned Pets article, “Pet food’s Darkest Secret”: http://poisonedpets.com/pet-foods-darkest-secret-denatured-condemned-and-inedible-material/ . I’ve heard that she may be writing another one, which promises to be more gross.

        • Barbara Fellnermayr

          March 15, 2016 at 3:40 pm

          Hi Barbara,

          We are in Canada and don’t follow the same rules as applied by the USDA. My meats are the same as those delivered to high quality restaurants and grocery stores. The certified organic beef comes from Blue Goose Cattle Company, they even have their own abbatoir.

        • Barbara Fellnermayr

          March 15, 2016 at 3:48 pm

          The reason the meat is denatured is that it is pet food grade not human grade. They want to ensure that these substandard meats don’t end up in the human food supply chain by unscrupulous meat vendors. Another reason to buy direct from the farmers!

          • Susan Thixton

            March 15, 2016 at 4:29 pm

            Actually many human grade quality meat ingredients are denatured solely because they are shipped to pet food. USDA regulation requires it. Which causes a problem for consumers. USDA has thus far refused to participate in pet food regulatory discussions (with FDA and AAFCO). If we could get them into the conversation, we could perhaps stop the denaturing of human grade ingredients being sent to pet food. Condemned ingredients should be destroyed – not denatured and sent into the animal food/pet food system.

          • Mollie Morrissette

            March 17, 2016 at 3:20 pm

            Actually – as long as it is human edible (not condemned and/or inedible) there is no law that requires a human edible meat or poultry product to be denatured before transporting. There would be no reason to denature a human-edible product.

            Forgive me Susan, my Mom made me answer you – she was confused…

          • Susan Thixton

            March 18, 2016 at 8:30 am

            I know you’ve read all of the USDA law – multiple times (ugh) – my response was based on information from multiple manufacturers, what’s being done to their product, what effort they have to go through to not get denatured meat.

  6. barbara m.

    March 14, 2016 at 7:19 pm

    Great post. These processes are something I’ve been wondering about. Maybe someday you can do one on HPP. Thanks.

    • Barbara Fellnermayr

      March 14, 2016 at 7:53 pm

      I have an article on HPP for anyone that is interested. I would post it on this site but am not sure that is allowed.

      • Lisa Southern

        March 17, 2016 at 2:26 pm

        I’m interested!

  7. BC Henschen

    March 15, 2016 at 11:58 am

    Making us proud Liane.

Leave a Reply

Cancel reply

Your email address will not be published. Required fields are marked *

Learn More

Human Grade & Feed Grade
Do you know what the differences are between Feed Grade and Human Grade pet food? Click Here.

 

The Regulations
Pet Food is regulated by federal and state authorities. Unfortunately, authorities ignore many safety laws. Click Here to learn more about the failures of the U.S. pet food regulatory system.

 

The Many Styles of Pet Food
An overview of the categories, styles, legal requirements and recall data of commercial pet food in the U.S. Click Here.

 

The Ingredients
Did you know that all pet food ingredients have a separate definition than the same ingredient in human food? Click Here.

Click Here for definitions of animal protein ingredients.

Click Here to calculate carbohydrate percentage in your pet’s food.

 

Sick Pet Caused by a Pet Food?

If your pet has become sick or has died you believe is linked to a pet food, it is important to report the issue to FDA and your State Department of Agriculture.

Save all pet food – do not return it for a refund.

If your pet required veterinary care, ask your veterinarian to report to FDA.

Click Here for FDA and State contacts.

The List

The Treat List

Special Pages to Visit

Subscribe to our Newsletter
Click Here

Pet Food Recall History (2007 to present)
Click Here

Find Healthy Pet Foods Stores
Click Here

About TruthaboutPetFood.com
Click Here

Friends of TruthaboutPetFood.com
Click Here

You May Also Like

Pet Food News

Attention all freeze dried and dehydrated pet food manufacturers: do the right thing...put an alert on your label.