Why is sublimation drying technology the most popular today?

Different from heat and cold drying technologies, sublimation drying technology is a drying at negative temperature and vacuum pressure. The product is cooled down to a minus temperature from -25 to 45 degrees Celsius.

Sublimation drying technology – The pinnacle of quality

Sublimation drying technology helps the product to be dried but preserves the structure, color and shape of the product. One of the most important factors of the freeze-drying technique is that it does not damage the easily damaged nutrients such as vitamins, proteins, enzyme activities, pigments, and preserves the living state of microbial cells. Thus, it does not significantly affect the nutritional value and taste of the product.

The most advanced technology

In theory, the sublimation process only needs to be performed at the temperature of the three-state junction, but in practice, that condition is more stringent, usually requiring a vacuum of 0.5~1.5 mbar and a temperature of about -250C. to ensure smooth execution.

Sublimation drying chart

First, the material is frozen suddenly at the triple-point temperature, causing the water in the product to solidify, then through vacuum treatment, sublimes into vapor and then condenses. condenses into water and is discharged, the product becomes dry.

Observing the water level chart (see steam pressure curve chart) we can clearly understand the principle of sublimation.

The key principle of the vacuum freeze-drying process is to sublimate water into vapor. In the diagram, the three lines OA, OB , OC are called liquefied line, gasification line and sublimation line, representing the relationship between water vapor and temperature at 3 stages: ice-water, water-vapour. water, ice-steam. point O is called junction point, reciprocal temperature is 0.010C, vapor pressure is 6.11 mbar 4.58 mmHg，611 Pa, at this temperature 3 elements: water, ice and steam can coexist and in equilibrium.

When the temperature or pressure changes, there will be many changes or the water will melt or the solid will become a gas-sublimation. In a state of high vacuum, with the principle of sublimation, the ice in the product does not disintegrate, but directly vaporizes and escapes, reaching the purpose of drying the product.

Sublimation drying state chart

Steps of the sublimation drying process

1/ Fresh food is quickly frozen at very low temperature (-30 to -50 degrees Celsius), then put into a vacuum chamber.

2/ In a vacuum drying environment, the ice crystals in the raw materials will sublimate without going through the liquefaction phase. About 90% of the moisture in the material is removed.

Then, through the secondary drying stage, to evaporate the residual moisture, the temperature is adjusted gradually (maybe > 0 degrees Celsius). The moisture content in the raw materials is about 1~4%.

3/ Sublimation-dried food is vacuum-packed, preventing moisture & oxidation.

4/ When freeze-dried food is processed and soaked in water, it will return to its original state of flavor, nutritional content, structure and shape.

Preferably in preservation

Sublimation drying technology is a new step in the drying industry of mankind, helping people to have better ways to preserve products in terms of cost and preservation time.

Product moisture is almost completely dry, freeze-dried products can be preserved from a few tens to hundreds of years without the need for expensive cold storage methods but short preservation time.

Advantages and disadvantages of freeze drying

• The shape, color, nutrition, aroma, composition, and taste of ingredients have only changed slightly.
• The product is not contaminated, the amount of residual water is very little (1~3%), less bacteria, easy storage, convenient transportation at room temperature.
• The product structure is unchanged, easy to crush, easy to restore to its original state.
• Equipment is expensive, difficult to operate, difficult to operate at temperatures below -600C, need a vacuum with high efficiency.
• When packing, it is necessary to note that the goods are fragile, and have a very high hygroscopicity, so it is necessary to pack tightly.
• Sublimation drying has the advantage of reducing drying time by 3 times, but the specific energy cost is about 50%-60% higher than other methods.

Application of freeze drying:

• Drying mango, pineapple, jackfruit, … all kinds of fruits. Mushrooms, carrots, sweet corn, spinach, celery, peas, cabbage, shiitake, red peppers, onions, leeks, wood ear (mushrooms), coriander, asparagus.
• Beef slices, pork slices, chicken, duck meat.
• Young shrimp, squid, fry, crab, scallops.
• Tofu, miso soup, soy sauce powder, vinegar powder, tea powder, coffee powder.
• Royal jelly, flower powder, fish bone extract, garlic essential oil, reishi oil, shiitake oil, yeast, antibiotics.
•  Strawberry powder, banana powder, pineapple powder, kiwi powder.
• Microorganisms (bacteria), yeast, blood plasma used in medicine, biological specimens, antibiotics.

In addition to the sublimation dryers SUNSAY Vietnam also provides other food dryers such as cold dryers, heat dryers, agricultural dryers, .. rice dryers such as horizontal dryers.

Contact method to order dryer SUNSAY

In addition to sublimation dryers, SUNSAY Vietnam also provides other types of dryers such as: refrigeration dryers, heat dryers, rice dryers, and horizontal dryers,…

Please contact Hotline (Zalo): +84 935.995.035 or call center +84 941.108.888 or leave information in the form and we will contact you right away.

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