Many people think of dehydration and freeze-drying as the same thing. Actually, they are not. They are very different from each other.
The following explains exactly what the differences are between these two food preservation techniques.
Regardless of the type of food preservation used, water needs to be removed. And dehydration is the most common of these methods.
Dehydration is a food preservation method that has been used for thousands of years, dating back to at least 12,000 BCE. The Romans and Middle Easterners used to put fruits and vegetables in a house and then roast and smoke them to make dry food.
Modern dehydration techniques have become simple, using machines to circulate hot and cold air through food. This removes most of the moisture. The temperature is controlled to a level sufficient to remove the moisture, but not to cook the food. The dehydrated food wilts and hardens.
Freeze-drying is a relatively new modern preservation process. However, it should be known that it is not possible to freeze-dry your own food at home without highly technical equipment.
Some reports say that freeze-drying originated in the Inca Empire. However, more reliable sources indicate that freeze-drying was invented during World War II when it was used to preserve blood plasma, drugs, and later troop food.
The freeze-drying process is relatively simple. Food is placed on a large shelf in a vacuum chamber. The temperature is lowered to below freezing and then gradually increased. The water in the food is converted from a solid form to a gas, thus preserving the structure and nutritional value of the food.
Key Difference Between Freeze-Dried and Dehydrated
The main goal of food preservation is to remove water, so that food does not spoil and grow mold. Dehydration removes 90-95% of the water, while freeze-drying removes 98099% of the water.
Dehydrating food yourself at home usually leaves 10% moisture, but professional techniques dehydrate more thoroughly and therefore provide a longer shelf life.
Moisture removal rate directly affects shelf life. Dehydrated foods such as dried fruits, vegetables, and powders have a shelf life of approximately 15-20 years; dehydrated foods such as honey, sugar, salt, durum wheat, and oats have a shelf life that can extend to 30+ years. On the other hand, frozen dehydrated foods have a much longer shelf life, such as dried fruits and vegetables that can last 25-30 years.
Freeze-drying retains most vitamins and minerals, according to a study by the American Institutes of Health. However, compared to fresh fruits and vegetables, freeze-dried foods lack some vitamins, such as vitamin C, which breaks down more quickly.
Dehydration does not alter food fiber or iron content. However, dehydration breaks down vitamins and minerals during the preservation process, so the nutritional value is not as good as freeze-dried foods. Dehydration tends to cause loss of vitamins A and C, niacin, riboflavin, and thiamin.
Appearance and Structure
One of the main differences between dehydrated and freeze-dried foods is appearance. Dehydrated foods become crisp and hard, while freeze dehydrated foods soften immediately in the mouth.
Weight is another difference. Freeze-dried foods weigh much less than dehydrated foods.
Dehydrated foods need to be cooked and eaten. Many times, they also need to be seasoned. This means taking the time to cook the product in hot water, cooling it, and then serving it. It takes between 15 minutes and 4 hours to prepare dehydrated foods. Freeze-dried foods, however, only require boiling water. Add hot or cold water and wait a minimum of 5 minutes before eating.
Overall, dehydrated foods are cheaper than cold-dried foods. There are pros and cons to both freeze-dried and dehydrated foods, and if you are on a tight budget, dehydrated foods are clearly the better choice.