Freeze-Dried vs Air-Dried Dog Food: What Is the Difference?

Written by Lucy Fitzgerald, Founder, WYLDR. Reviewed by Katie McCaul, RNutr, The Pet Diet.

The short answer: Freeze-dried food is frozen and then dried under vacuum, so the ice turns straight to vapour without heat. Air-dried food is dried using gently warmed circulating air over a long period. Freeze-dried comes out light, crisp and close to its original shape. Air-dried comes out denser and chewier. Both are shelf stable, and which is better depends on the product rather than the process.

These two words sit next to each other on shelves and are often treated as interchangeable. They are not, and the difference is easy to understand once you know what each process is doing.

How each one works

In short: Freeze-drying removes ice as vapour under vacuum. Air-drying evaporates water using warm moving air.

Freeze-drying starts with freezing. The frozen food goes under vacuum, and at that low pressure the ice turns directly to vapour and is carried away. The food never really gets warm, and because the water leaves from a solid frozen structure, the food keeps its shape.

Air-drying is closer to what it sounds like. Warmed air circulates around the food over hours, sometimes days, and the water evaporates. It is a gentle process compared with high-heat cooking, but it does use heat, and as water leaves a soft structure the food shrinks and firms up.

What that means in the bowl

In short: Freeze-dried is light, crisp and crumbly. Air-dried is denser, darker and chewier.

Pick up a freeze-dried piece and it feels almost weightless and will crumble if you squeeze it. That texture is why freeze-dried products rehydrate quickly and why they break easily in the bag.

Air-dried pieces are firmer, more like a soft jerky. They hold together better, take longer to chew, and generally do not rehydrate in the same way. For some dogs the chewiness is the appeal.

Moisture and shelf life

In short: Both formats are shelf stable. They differ in how much water is left behind, and that can affect what else a product needs in it.

Both formats take out enough water to make food keep at room temperature, but they do not leave the same amount behind. Freeze-drying generally removes more.

How much that matters in practice depends entirely on the product. Some dried products include a preservative and some do not, in both formats, and the only way to know is to read the ingredient list. We are not going to tell you what is typical of air-dried food as a category, because we do not have data on that and we are not prepared to guess about other people's products.

What we can tell you is our own. Every Dog Every Day is freeze-dried, and its ingredient list is short because taking the water out does the preserving. It does include an antioxidant, to protect the salmon oil, because removing water does nothing to stop fat oxidising and the open, porous structure of a freeze-dried bite exposes fat to more air, not less. We would rather tell you that than pretend the list is shorter than it is.

Cost, and why the packs look small

In short: Freeze-drying is slower and more energy intensive, so it usually costs more. Both look small because the water is gone.

Freeze-drying takes longer and uses specialised equipment, and that shows up in the price. Air-drying is generally cheaper to do at scale.

Both formats produce packs that look small for the price until you remember what has been taken out. A dried weight always represents a much heavier weight of original ingredients, so compare feeding amounts rather than pack sizes.

So which is better?

In short: Neither, as a category. The right question is which specific product suits your dog.

It is tempting to want a winner here, and the honest answer is that there isn't one. A well-made air-dried food with good ingredients beats a poorly made freeze-dried one, and the reverse is equally true. Format tells you about texture, handling and how a product is likely to behave in the bowl. It does not tell you whether a product is any good.

If a short, recognisable ingredient list matters to you, that is a thing to check on the pack in front of you rather than something to assume from the word on the front. Two things worth looking for: whether a preservative or antioxidant is declared, and whether a humectant such as glycerine is listed, which some dried products use to keep them soft. Neither is a mark against a product. Both are worth knowing about.

Where WYLDR fits

WYLDR's Every Dog Every Day is freeze-dried, which is why it is a five-ingredient recipe, and why the bite in your hand still looks like what went into it. That is a description of our product rather than a comment on anyone else's.

Frequently asked questions

Is freeze-dried better than air-dried for dogs?
Neither is better as a category. Freeze-drying removes more moisture at lower temperature, air-drying uses gentle warm air and produces a chewier result. The right comparison is between specific products and their ingredients.

Is air-dried dog food cooked?
Air-drying uses gently warmed circulating air rather than high-heat cooking. Whether a specific product counts as cooked depends on the temperatures used, so check with the brand if it matters to you.

Which lasts longer once opened?
Both should be resealed and kept cool and dry, and both will draw moisture back from the air once open. Follow the pack guidance rather than assuming.

Why is freeze-dried more expensive than air-dried?
The process is slower and uses more energy and more specialised equipment.

Can I rehydrate air-dried food like freeze-dried?
Air-dried food generally does not rehydrate in the same way because of its denser texture. Some products are designed to be soaked, so follow the instructions on the pack.

Sources

• Nowak, D. and Jakubczyk, E. (2020) 'The Freeze-Drying of Foods: The Characteristic of the Process Course and the Effect of Its Parameters on the Physical Properties of Food Materials', Foods, 9(10), 1488. doi: 10.3390/foods9101488.
• Barden, L. and Decker, E.A. (2016) 'Lipid Oxidation in Low-moisture Food: A Review', Critical Reviews in Food Science and Nutrition, 56(15), pp. 2467–2482. doi: 10.1080/10408398.2013.848833.