Many people treat dehydration and freeze drying as one thing. In fact, there is a big difference between them. The following explains the specific differences between the two kinds of food preservation technology.
dehydration process
No matter what kind of food preservation method, you need to remove water. Dehydration is one of the commonly used methods. Dehydration is a way to keep food fresh for thousands of years, dating back to at least 12,000 BC. Romans and Middle Easterners used to put fruits and vegetables in a house and then roasted and smoked them to make dry food.
Modern dehydration techniques have become simple, using machines to circulate hot and cold air through the food. This removes most of the water. The temperature is controlled at a level sufficient to remove moisture, but not to cook the food. Dehydrated processed foods wilt and harden.
freeze-drying process
Freeze-drying is a relatively new modern preservation process. However, it should be known that without high-tech equipment, it is impossible to freeze-dry at home. Some reports say that freeze-drying originated in the Inca Empire. But more reliable sources show that freeze-drying was invented during World War II, when it was used to preserve plasma, drugs, and later troop food.
The lyophilization process is relatively simple. The food was placed on large shelves in the vacuum chamber. The temperature drops below freezing and then gradually rises. The water in the food is converted from solid form to gas, thus maintaining the structure and nutritional value of the food.
Main differences
Moisture-The main goal of food preservation is to remove moisture so that the food does not spoil and grow mold. Dehydration can remove 90-95% of the water, and freeze drying can remove 98099 of the water. Dehydrated food at home usually leaves 10% humidity, but professional technology is dehydrated more thoroughly, so it can have a longer shelf life.
Shelf life-Moisture removal rate directly affects shelf life. The shelf life of dehydrated foods such as dried fruits, vegetables and powders is about 15-20 years; the shelf life of dehydrated foods such as honey, sugar, salt, hard wheat and oats can be extended to more than 30 years. On the other hand, the shelf life of frozen dehydrated food is longer, such as dried fruits and vegetables can be stored for 25-30 years.
Nutritional content-Freeze-drying preserves most of the vitamins and minerals, according to research reports by American health agencies. However, compared with fresh fruits and vegetables, freeze-dried foods lack some vitamins, such as vitamin C, which decomposes faster. Dehydration does not alter dietary 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 thiamine.
Appearance vs. Structure-One of the main differences between dehydrated and freeze-dried foods is appearance. Dehydrated food will become brittle and hard, while frozen dehydrated food will become soft immediately after being placed in the mouth. Weight is another difference. Freeze-dried foods weigh much less than dehydrated foods.
Cooking-Dehydrated foods need to be eaten after cooking. Many times, they also need to use spices. This means that it takes time to cook the product in hot water and eat it after cooling. Preparing dehydrated food takes between 15 minutes and 4 hours. However, freeze-dried foods only require boiling water. Add hot or cold water and wait 5 minutes to eat.
Price-In general, dehydrated foods are cheaper than cold-dried foods. Freeze-dried and dehydrated foods have their pros and cons, and if you're on a tight budget, dehydrated foods are clearly a better choice.