Food preservation methods have come a long way from traditional techniques such as salting and sun-drying. In today’s world, where convenience and nutrition are key factors for consumers, two contemporary methods are often compared: freeze-drying and dehydration. Both processes serve the essential purpose of extending the shelf life of food by removing a significant portion of its moisture content, which inhibits the growth of microorganisms and slows down food degradation. However, there are key differences that make their finished products distinct. So, what is the difference between freeze-dried and dehydrated food?
Let’s find out.
WHAT IS FREEZE DRYING AND DEHYDRATING?
Freeze-drying, scientifically known as lyophilization, is a food preservation method that involves freezing food and then removing its moisture content while it is still in a frozen state. The process consists of three main stages: freezing, primary drying, and secondary drying.
In the first stage, the food is frozen, locking in its structure and nutritional content. Then, in the primary drying phase, the pressure and temperature are lowered, causing the frozen water in the food to sublimate directly into water vapor. This gentle process prevents the food from undergoing significant damage. Lastly, during the secondary drying phase, the food is slightly warmed to remove any remaining moisture, leaving behind a lightweight, shelf-stable freeze- dried food.
I have discussed freeze drying in more detail in a separate post, which you can access here: The Process Of Freeze Drying Food
Dehydration is a similar method to freeze drying. However, it primarily involves the removal of moisture from food through the application of heat and airflow. The process aims to reduce the water content in the food without freezing.
In the process of dehydration, food items are first prepared by slicing, dicing, or even pureeing to facilitate the removal of moisture effectively. Then, these prepared foods are placed in a dehydrator, an oven, or even exposed to the sun, where heat and airflow gradually draw out the moisture. The heat causes the water within the food to evaporate, while the airflow carries it away. The result is dehydrated food that is less prone to spoilage and is more suitable for long-term storage.
THE DIFFERENCES BETWEEN FREEZE DRIED AND DEHYDRATED FOOD
Freeze drying and dehydrating are both methods of preserving food by removing moisture. But freeze-dried and dehydrated foods differ in several ways.
Shelf life
Freeze-drying involves taking most of the moisture out of the food. This creates an environment where the growth of bacteria, yeasts, and molds—things that make food go bad—is significantly slowed down. This careful process gives freeze-dried products a really long shelf life, with some lasting up to 25 years or more.
On the other hand, dehydrated food does a good job too, lasting around 15 years or even more. However, it might not stay good for as long as freeze-dried food. The reason is that the dehydration process, while effective, might leave a bit of moisture behind, even though it’s not much. The good news is that the technology of today has improved a lot. Back in the old days, dehydration would leave about 30% moisture in the food. Today, dehydrated food contains around 2 % to 3% moisture.
This leftover moisture could still make the shelf life a bit shorter compared to freeze-drying, where they get rid of almost all the moisture. This little difference highlights why freeze-dried foods can last so impressively long. Thus, it makes them a top choice for anyone who wants their food to stay good for an extra-long time. In the world of keeping food fresh, freeze-drying is like a chef carefully crafting a dish to last, standing out for its ability to make food last longer than the usual methods.
Nutritional value
When it comes nutrition, freeze-drying stands out because it naturally keeps a higher percentage of nutrients that were in the fresh food. Here’s how it works: they freeze the food and then take out the ice, keeping the structure and all the nutrients intact. This means that freeze-dried food holds onto more of its color, flavor, and all the good-for-you stuff. One study found that freeze-drying strawberries zero loss in vitamin C as well as phenolics.
Now, dehydrated food is no slouch either. It manages to keep a good chunk of its nutritional value. However, there’s a bit of a trade-off. During the dehydration process, where the food gets dried out with heat, some of the vitamins and minerals might take a hit. It’s like they’re saying, “Okay, I’ll stick around, but I might lose a bit of my sparkle.” The extent of this nutrient retention can depend on what kind of food we’re talking about and how it’s processed.
You might also like: How Nutrient Loss Occurs In Fruits and Vegetables
Vitamin C is sensitive to heat, and its content in fruits and vegetables can decline during the dehydration process. Foods rich in vitamin C, such as citrus fruits and berries, may experience some loss. B-vitamins, including B1 (thiamine), B2 (riboflavin), B3 (niacin), and B6 (pyridoxine), are water-soluble and can be susceptible to degradation during dehydration. These vitamins are often found in grains, legumes, and vegetables.
So, freeze-drying and dehydration—both heroes in their own right—have their unique ways of dealing with nutrition. Freeze-drying goes for the gold, keeping things vibrant and nutritious, while dehydration, while still doing a good job, might have a bit of a trade-off.
Applications
Both freeze-dried and dehydrated foods find various applications, but their uses differ based on factors such as weight, texture, and rehydration time. Freeze-dried foods, because of their light and airy texture, are popular among hikers, campers, and backpackers. The lightweight nature of freeze-dried products makes them convenient for carrying during outdoor activities. Additionally, freeze-dried foods often require less time to rehydrate compared to their dehydrated counterparts, making them a quick and convenient option.
Instant coffee is often produced through the freeze-drying process. The result is a coffee that allows for a rapid and straightforward rehydration when hot water is added. The freeze-drying method preserves the coffee flavor and aroma effectively, and the resulting granules quickly dissolve in water.
On the other hand, dehydrated foods are widely used in home kitchens and food storage. Their affordability and ease of use make them a popular choice for those who want to preserve seasonal fruits, vegetables, and herbs for later use in cooking and baking. Dehydrated foods are also common in the production of snacks like dried fruits and jerky.
