What foods can and cannot be freeze-dried?

What is freeze-drying?

Freeze-drying, also known as lyophilization, is a process that removes moisture from food under low temperature and vacuum conditions through “ice sublimation,” maintaining the food’s basic structure.

Why freeze-dry?

Freeze-drying better preserves nutrients, texture, and shape, and allows for long-term storage. Because the water is removed, the product’s weight is reduced. Since freeze-dried products, when rehydrated, are closer to their fresh state, they are ideal for high-quality food for outdoor activities and emergency situations.

However, freeze-drying is not suitable for all foods. Due to the high cost of freeze-drying equipment, the long processing time, and the need to keep freeze-dried food dry for storage, freeze-dried products are expensive. Some abundant, readily available, and non-seasonal foods do not need to be freeze-dried. Some freeze-dried products may experience slight changes in color and texture. Therefore, not all products are suitable for freeze-drying.

What is suitable for freeze-drying?

Foods that are low in fat and sugar and can be completely frozen are best suited for freeze-drying, such as fruits, vegetables, meats, cooked foods, dairy products, and liquids like coffee.

Fruits that can be freeze-dried include strawberries, apples, bananas, blueberries, and mangoes. Common examples include dried mangoes, dried strawberries, and durian chunks. This process can effectively preserve the food’s shape and texture.

Vegetables that can be freeze-dried include okra, corn, and carrots. Freeze-dried vegetables can be used as snacks.

Meats that can be freeze-dried include beef, chicken, and fish. Many pet foods now contain freeze-dried chicken and beef.

Cooked foods that can be freeze-dried include rice, noodles, stews, and soups. These freeze-dried instant meals can be taken on camping or hiking trips; simply add hot water for a quick meal.

Liquids that can be freeze-dried include milk, yogurt, fruit smoothies, coffee, and fruit juices. Yogurt can be freeze-dried into yogurt chunks for snacks. Many coffees now use freeze-drying technology to make the coffee powder instantly soluble.

What is not suitable for freeze-drying?

Foods high in fat, high in syrup, pure oils, alcoholic beverages, and foods with complex emulsified structures are not suitable for freeze-drying.

High-fat foods:Fats are prone to oxidation or clumping, such as fatty meat and bacon.

High-sugar or syrup-based foods:These are difficult to freeze completely and are prone to collapse and sticking during freeze-drying. Examples include honey and syrup, which tend to collapse during freeze-drying.

Pure oil-based foods:Edible oils, butter, lard, etc., cannot form a stable freeze-dried structure.

Alcohol-containing foods:Alcohol has a low freezing point, making alcohol-containing liquids unsuitable for freeze-drying. Examples include spirits, wine, fruit wine, and alcoholic beverages.

Foods with complex emulsified structures:Cream sauces, mayonnaise, salad dressings, and thick sauces may experience structural damage, separation, and oil leakage after freeze-drying.

Заключение

Freeze-dried foods do not require refrigeration and can be stored for up to 20 years under sealed, moisture-proof conditions. However, the freeze-drying process involves vacuum, low temperature, and sublimation control, and improper operation can easily lead to: structural collapse, excessively high moisture content, and changes in taste or color. It’s advisable to try a small batch before large-scale freeze-drying. The freeze-drying time may vary for fruits with different water content; larger fruits or vegetables can be cut into smaller pieces before freeze-drying. Freeze-drying machines are suitable for food processing, home food storage, pet food, pharmaceuticals, biological research, and emergency food reserves.