Home > Science Fact Finder > Food and Nutrition - How Is Food Freeze-Dried?

1. Printable Version
2. Download PDF
3. Cite this Page

How is food freeze-dried?

The freeze-drying food preservation process, first developed in the 1950s, can be used on 600 different foods. It is a two-step process involving rapid freezing and subsequent dehydration (removal of moisture). Rapid freezing helps preserve the nutrients and flavor of a food.

The freeze-drying process begins when food is placed between two cold hollow plates that contain a refrigerant liquid, in a tightly sealed chamber. While the food is being fast-frozen, a high-powered pump creates a vacuum in the chamber. Then the refrigerant liquid in the hollow plates is replaced with warm gas, which converts the ice in the food directly into water vapor. This dehydration process takes 20 hours. The food must then be packaged to seal out oxygen and moisture, either of which would cause the food to decay.

Any food, raw or cooked, which can withstand freezing may be freeze-dried. When properly...

Join eNotes

The above is a free excerpt. Get total access to this content with the:

eNotes Pass

1. Dairy Products
   1. What is the temperature to which milk must be heated to be pasteurized?
   2. Is there a difference in nutritional value between brown-shelled eggs and white-shelled eggs?
   3. How does butter differ from margarine and oleo?
   4. How do you make clarified butter?
   5. How do the holes form in Swiss cheese?
2. Fruits And Vegetables
   1. What is the difference between a fruit and a vegetable?
   2. Is the tomato a fruit or a vegetable?
   3. What are some common varieties of apples?
   4. What is a legume?
   5. What is a star fruit?
   6. What is an ugli?
   7. Will an orange ripen after it is picked?
3. Meats And Miscellaneous Foods
   1. What are the leanest red meats?
   2. How hot must the temperature of meat be to ensure that it is safe to eat?
   3. Which fish have the most nutrients and are the least susceptible to contamination?
   4. What are sweetbreads?
   5. What is a prawn?
   6. Where did bagels originate, and why are genuine bagels boiled before baking?
   7. Where did pizza originate?
   8. How does popcorn pop?
   9. What is Indian corn?
   10. Who invented peanut butter?
   11. How is tofu made?
   12. How are truffles found?
   13. What are the different kinds of sugar?
   14. How much maple syrup does a maple tree make?
   15. What are rose hips?
   16. How is garlic used?
   17. What plant is the source for natural vanilla flavoring?
4. Nutrition
   1. What are good sources of vitamins?
   2. What are good sources of the major dietary minerals?
   3. What are RDAs (Recommended Dietary Allowances)?
   4. What is the food guide pyramid recommended by the U.S. Department of Agriculture?
   5. What is the difference between essential and nonessential amino acids?
   6. How are food calories measured?
   7. What is the difference between an herb and a spice?
   8. What is the daily recommended allowance of salt and cholesterol in the diet?
   9. Why is salt added to ice in an ice cream freezer?
   10. What terms are allowed under Food and Drug Administration rules to describe the fat content of foods?
   11. How much junk food does the average American eat in a year?
5. Beverages
   1. How many glasses of water should humans drink every day?
   2. Why does water not put out an oil fire?
   3. What is the formula for Coca-Cola™?
   4. What is the beverage known as Moxie™?
   5. What is wassail?
   6. Who drinks the most coffee in the world?
   7. How much caffeine is in coffee, tea, and cocoa?
   8. How is coffee decaffeinated?
   9. What are the ingredients in beer?
6. Food Processing
   1. Why does the smoking of meat act as a preservative?
   2. When were frozen foods first available commercially?
   3. How is food freeze-dried?
   4. What is MSG?
   5. What was the first genetically altered whole food?
   6. Why is flour bleached?