Freeze dryer, drying equipment that keeps original shape and color

Not all products need a freeze dryer, but there are many products that need a freeze dryer to be able to dry according to customer requirements. So what is this device and what is the drying principle that is so important, Mactech will analyze the basic information so that customers can better understand this device.

Some products from freeze dryers

Drying products such as drying fruits, drying agricultural products, drying food, drying medicinal herbs, drying seafood, drying special products… when encountered in practice, it is impossible to list all the specific products and different drying requirements from customers. However, in terms of the characteristics of dried products, they can be divided into 3 requirements: 1 is popular dried products, 2 is dried products at a good quality level and 3 is high-end dried products.

Freeze dryer is a high-end drying equipment to create high-end dried products. When your production facility needs to create different products on the market to create great value, meeting high-end needs, using a freeze dryer is very suitable. Below are typical products for readers to distinguish.

The most outstanding feature of the dried product from the freeze dryer (which is freeze drying) is the shape of the dried product, keeping the natural shape of the product almost intact. That is the top priority feature, the basic factors such as keeping color, keeping flavor, keeping nutrients are just the following factors because the most important thing of freeze drying is keeping the natural shape. The freeze drying method is the next step of development of the freeze dryer and vacuum dryer to further improve the quality of the dried product. The image above is strawberries dried by freeze dryer, with the characteristics of keeping the shape, keeping the color, ….

Freeze dryers are suitable for many products such as fruits, medicinal herbs, vegetables and food, but in reality, only a few products need to use this device. The main reason is that the drying time is long and the machine is very expensive, not suitable for small and medium-sized production facilities today. Therefore, only for products that are really necessary such as drying fruits to keep their original shape, specifically dragon fruit, pineapple, strawberry, kiwi, persimmon, custard apple, avocado, durian… and some types of flowers that are difficult to dry such as yellow camellia, yellow chrysanthemum, jasmine, rose buds. In general, products that are difficult to dry by other methods need freeze drying.

Principle of freeze drying machine

So why does the freeze-drying method meet the criteria of keeping the shape of the product even though it is very soft and difficult to dry such as durian, custard apple, ripe avocado? That is due to the mechanism of freezing the product at extremely low temperatures so that the water content in the frozen food has small crystals. When the entire amount of water in the product has frozen according to the technical requirements of the method, the freeze-drying process will begin.

The structure of the product when frozen will be similar to the honeycomb shape below, the fiber part of the food will form a skeleton like a honeycomb, and the frozen water content will be like honey.

When the sublimation process begins, the ice crystal component in the product will turn into gas to permeate out of the product thanks to the vacuum pressure in the drying chamber. The process of transforming from ice crystal to gas without going through the liquid state is called sublimation. That is the principle used in the freeze dryer, when the positions in the product where ice crystals occupy space have been completely vaporized, it will leave a honeycomb-like structure inside the product, so the shape of the dried product is kept intact.

The diagram above shows the boundary of the state change between solid – liquid – gas under different conditions of temperature and pressure. When the temperature is below 0oC and the pressure is below 0 atm, the change will go from solid to gas without going through the liquid state. The drying conditions of the product in the freeze dryer will be somewhere below the intersection of the 3 black lines on the diagram, usually at a cold temperature of minus 30^oC to minus 40^oC. The process of freeze drying any product will have to go through many stages of temperature and pressure changes, so this is a very complicated drying method, usually only applied to products that require drying to maintain their natural shape.

Freeze dryer application

Freeze dryers are much more advanced drying equipment than other dryers such as hot air dryers and cold dryers. Freeze drying can be applied to dry most types of products such as fruits, foods, vegetables, meat, fish, medicinal herbs, starch, and milk powder. However, for each specific product, with the scale of production, with the value of the product on the market, which dryer brings the highest economic efficiency is the matter of concern.

In fact, the current freeze-drying method is only applied to dry soft, mushy, watery fruits to keep the shape of the natural product, along with special products such as water powder, essential oils, food powder, spirulina powder. In general, other drying methods do not meet the requirements, so freeze-drying is used.

Contact Mactech Vietnam

For more details on the products that best suit the product to be dried and the appropriate investment level, customers should contact Mactech directly via the hotline on this website.