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Your Location: Home >> News >> Technical support >> Such a healthy freeze-drying method is easy to learn

Such a healthy freeze-drying method is easy to learn

Release Date: 2018/8/24 17:38:28 .
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Such a healthy freeze-drying method is easy to learn
  Freeze drying and lyophilization are synonymous. Freeze drying is a water removal process typically used to preserve perishable materials, to extend shelf life or make the material more convenient for transport. Freeze drying works by freezing the material, then reducing the pressure and adding heat to allow the frozen water in the material to sublimate.
  Freeze Drying’s 3 Primary Stages
  Freeze drying occurs in three phases, with the first and most critical being the freezing phase. Proper freeze drying can reduce drying times by 30%.
  Freezing Phase
  There are various methods to freezing the product. Freezing can be done in a freezer, a chilled bath (shell freezer) or on a shelf in the freeze dryer. Cooling the material below its triple point ensures that sublimation, rather than melting, will occur. This preserves its physical form.
  Freeze drying is easiest to accomplish using large ice crystals, which can be produced by slow freezing or annealing. However, with biological materials, when crystals are too large they may break the cell walls, and that leads to less-than-ideal freeze drying results. To prevent this, the freezing is done rapidly. For materials that tend to precipitate, annealing can be used. This process involves fast freezing, then raising the product temperature to allow the crystals to grow.
  Primary Drying (Sublimation) Phase
  Freeze drying’s second phase is primary drying (sublimation), in which the pressure is lowered and heat is added to the material in order for the water to sublimate. The vacuum speeds sublimation. The cold condenser provides a surface for the water vapor to adhere and solidify. The condenser also protects the vacuum pump from the water vapor. About 95% of the water in the material is removed in this phase. Primary drying can be a slow process. Too much heat can alter the structure of the material.
  Secondary Drying (Adsorption) Phase
  Freeze drying’s final phase is secondary drying (adsorption), during which the ionically-bound water molecules are removed. By raising the temperature higher than in the primary drying phase, the bonds are broken between the material and the water molecules. Freeze dried materials retain a porous structure. After the freeze drying process is complete, the vacuum can be broken with an inert gas before the material is sealed. Most materials can be dried to 1-5% residual moisture.
  Freeze drying method
  1. Prepare the ampoule tube, use the 2% HO to set the bubble 8 10, rinse it with tap water several times, and finally wash it with sorrow water for 1~2 times. Dry. The label with the name of the trade name and the date of the aid is placed in the Anen tube. The side with the word should be placed on the wall of the tube, and the tube 1 is stuffed with cotton and sterilized at 0.1 MPa for 30 min.
  2. Prepare skimmed milk, first boil the milk, remove the upper layer of fat, then use cotton wool to pass through the centrifuge and centrifuge for 15 minutes in a 3 000 t/min centrifuge. If not, centrifuge again until the fat is removed. So far, the milk was degreased, sterilized at 0.056 MPa for 30 min and sterilized.
  3. Prepare the bacterial suspension, use 3~4ml of sterile skim milk in the cultured mature slanted strain, gently scrape the lawn on the inclined surface with a pipette to make a dense suspension with uniform dispersion, and control the number of cells. At 10~10/ml.
  4. Dispense and use a sterile long dropper or capillary pipette to absorb the bottom of the ampoule tube that is sterilized by the bacteria and immersed in the tube. Do not stain the tube wall, 0.2 ml per tube.
  5. Pre-freeze, freeze the bacterial suspension in the ampoule into ice, and sublimate the water in a frozen state, so as to prevent the bacterial suspension from boiling during vacuum drying, and bubbles will overflow. The pre-freezing temperature should be low and the speed should be fast. It can be placed in a low-temperature refrigerator (-45~-35C) or in an anhydrous ethanol dry ice bath. If the pre-freezing temperature is higher than -25C, the suspension will be suspended. Liquid ice is not solid and easily fails when vacuum dried.
  6. Freeze and dry, cut off the cotton plug outside the ampoule tube, push the inner cotton plug to about 1cm below the tube mouth, and then connect the ampoule tube to the side tube on the branch tube with a rubber tube. The other end of the branch pipe is connected to a vacuum pump. All joints are sealed with liquid paraffin. Then put the ampoule into the saturated ice brine. When the suspension at the bottom of the bottle is completely frozen, immediately start the vacuum pump to pump air. When the appearance of the sample is basically dry, raise the branch tube and leave the ice bath at room temperature. Then the line is pumped and dried for about 1 hour.
  7. Determine the moisture, measure the residual moisture by the weight loss method, and check the degree of drying. Generally, the residual moisture is controlled to be 3% or less, and if it is higher than 3%, vacuum drying is required.
  Freeze-drying is very healthy. First, many hot substances do not degenerate or inactivate. When dried at low temperatures, some of the volatile components in the material lose little. Secondly, in the process of lyophilization, the growth of microorganisms and the action of enzymes cannot be carried out, so that the original traits can be maintained. Since the drying is carried out in a frozen state, the volume is almost constant, the original structure is maintained, and concentration does not occur. Since the moisture in the material exists in the form of ice crystals after pre-freezing, the inorganic salt-soluble substances originally dissolved in the water are uniformly distributed in the material. When sublimating, the dissolved substances dissolved in water are precipitated, which avoids the phenomenon that the inorganic salt carried by the internal moisture migration to the surface in the general drying method is precipitated on the surface to cause surface hardening. The dried material is porous and spongy. After adding water, it dissolves quickly and completely, and the original trait is almost immediately restored. Since drying is carried out under vacuum, there is very little oxygen, so some oxidizable substances are protected. Then drying can remove 95% to 99% of the water, so that the dried product can be preserved for a long time without deterioration.

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