What is a freeze dryer, what are its advantages and disadvantages

If you don’t understand what a freeze dryer is, you need to learn about it immediately because it’s a versatile drying device that produces the highest quality products on the market. It can dry all products to a crisp, from those with high moisture content to those with low moisture content, from soft and mushy to firm and solid, and from thin to thick (up to 10cm). In this article, Mactech will explain this device in more detail for your reference.

Characteristics of dried products

Before delving into the explanation of what a freeze dryer is, the characteristics of dried products will be analyzed first to help readers easily understand how freeze-dried products differ from other drying methods.

There is a common perception today that dried products, whether crispy or chewy, have the easily recognizable characteristic of shrinking in shape, reducing in size, and even losing color compared to their original state. We need to pay attention to both dried and crispy products; the author is referring to crispy bananas, crispy jackfruit, and crispy sweet potatoes that are widely sold on the market at very low prices. These products are crispy fried, characterized by being hard, crunchy, with a layer of oil clinging to the product, and lacking sweetness and aroma.

Conventional dried products will shrink to varying degrees due to their natural texture. Products with high water content and a soft, mushy texture will shrink more during drying, such as strawberries, dragon fruit, mangoes, bananas, jackfruit, starfruit, and flowers. Products that are prone to discoloration after drying include green tea leaves, yellow camellias, and some vegetables and fruits. These are the easily recognizable characteristics of conventionally dried products.

However, some high-value products have the distinct characteristic of retaining their natural shape, without shrinkage or discoloration, such as cordyceps mushrooms, yellow camellias, rosebuds, and dried durian. These are products dried using freeze-drying machines.

What is a freeze dryer?

Thus, based on the analysis of the characteristics of dried products as described above, we see that freeze-dried products retain their natural shape and color, without shrinkage or deformation. This drying equipment brings high value to the production of dried goods, as natural characteristics including shape and color significantly determine market value. Freeze dryers, also known as freeze-dryers, are two common names today because the machine’s operation involves freezing the product at -30°C before the sublimation of ice occurs.

So, a freeze dryer is a product drying device based on the sublimation of ice when the drying temperature is sufficiently low (-30°C) and the drying chamber pressure reaches a vacuum level (pressure <30 Pa). During the drying process, all the water content in the product is rapidly frozen. Then, the drying chamber is vacuumed, and the ice evaporates directly without converting to liquid form. After drying, the dried product has a crispy, porous powder texture that crumbles easily when lightly squeezed. It retains its shape, does not shrink, and its color and nutritional value remain unchanged. Freeze-dried products have very high quality, therefore freeze-drying is only suitable for certain types of products including strawberries, durian, mango, kiwi, cordyceps mushrooms, shiitake mushrooms, probiotics, herbal extracts, golden camellia flowers, matcha powder, rose buds, etc.

Thus, through the basic information above, readers have understood what a freeze dryer is, its drying characteristics, and its practical applications. Customers are encouraged to contact Mactech for more detailed advice on the most suitable dryer. Thank you for reading this information.