Dry Freezer Machine

A dry freezer machine,also known as a frozen dry machine,is a device used to remove water from a material through the process of freeze-drying.This process involves freezing the material at low temperatures,followed by the application of a vacuum to sublime the ice directly from the solid state to vapor,bypassing the liquid phase.Freeze dryers are widely used in various fields,such as pharmaceuticals,biotechnology,and food processing,to preserve the structure and activity of heat-sensitive materials while extending their shelf life.The ability to maintain low temperatures and create a high vacuum environment is crucial for effective freeze-drying,ensuring the removal of water without damaging the material's integrity.

The working principle of dry freezers is based on refrigeration and drying technology. It uses a refrigerant to exchange heat with an item or air that needs to be dried, and cools the moisture in the item or air below the freezing point, making it condense into ice crystals. Subsequently, by blowing or vacuum system, the ice crystals are sublimed or evaporated, so as to achieve the purpose of drying.

Probiotics are microorganisms that are beneficial to human health and are often used to improve intestinal flora.Microencapsulation technology can help protect bacterial strains,prolong their survival time in the body,and make them less susceptible to inactivation due to the influence of the external environment.Therefore,when producing probiotic products,it is necessary to consider selecting appropriate microencapsulation technology to ensure the stability and activity of probiotics.The following application is a very good combination of microencapsulation and freeze-drying technology,proving that the bacteria are still biologically active after being embedded and dried,opening up new possibilities in the fields of fermentation technology and food transformation.

Freeze-drying,also known as freeze-drying,is a very versatile method of dehydration that is often used to preserve microorganisms,foods,or pharmaceuticals,such as protein-based drugs.It combines freezing and drying in one unique operation to create a high-quality dry end product.

Freeze-drying is often used to preserve microbial cultures because it has advantages that cannot be ignored:convenience of storage and increased possibility of mailing the microorganisms.In addition,the resulting product requires only minimal maintenance,the culture medium does not become contaminated during storage,and the microorganisms can remain viable for a long time.

However,it is known that freeze-drying technology is critical for microorganisms as it has a negative impact on their viability and physiological status.Microbial survival rates vary depending on the method and organism;however,viability levels are significantly lower than in liquid nitrogen storage2.The observed decrease in viability is mainly due to some undesirable side effects,such as the formation of intracellular ice crystals1,denaturation of sensitive proteins or some irreversible changes in the physical state of membrane lipids during the process3,5.To prevent this effect,skim milk,sucrose,glycerol,DMSO or trehalose are often used as lyoprotective substances before freezing or freeze-drying1,3.

Trehalose has been reported to have protective effects on yeast and bacteria under extreme environments such as desiccation,freezing,osmotic stress and heat shock.These protective effects are related to membrane stabilization and preservation of enzyme activity.Several hypotheses have been reported regarding the protective role of trehalose.Some reports believe that its role is to replace water molecules involved in maintaining the tertiary structure of the protein through multiple external hydrogen bonds,and other reports believe that it forms a glassy structure to ensure physical stability.

In addition to fermentation processes or food transformation,microorganisms such as Saccharomyces cerevisiae or lactic acid bacteria are of great economic importance in the field of probiotic dietary foods and feed supplements.However,these applications require maintaining cell viability during storage.By combining granulation and freeze-drying techniques,dust-free particles of uniform size and composition can be obtained.Due to the higher particle surface area,the product will have good particle flow,easier dosing and faster product reconstitution.Despite the above challenges,freeze-drying remains a convenient preservation method for yeasts,sporulating fungi,and bacteria because their long-term viability is generally maintained reasonably well and the storage and distribution requirements of the strains are simple.

Therefore,this application aims to produce Saccharomyces cerevisiae granules as a model microorganism,using an Encapsulator B-390 as a granulator to squeeze the yeast suspension into liquid nitrogen to form monodisperse spheres,and then using a freeze dryer Lyovapor ™ L – 200 for freeze drying.

Microparticles containing yeast can be easily prepared using the Microcapsule Granulator B-390 and freeze-dried using the LyovaporTM L-200.The nozzle diameters of B-390 are 300 μm and 1000 μm respectively,and the diameters of the particles produced are 700 μm and 1500 μm respectively.The size and shape of the beads did not change after freeze-drying.The particles have good fluidity,making it easy to control the dosage,and they dissolve quickly after being mixed with water.Freeze-dried microorganisms can still maintain good vitality during storage and can successfully grow after rehydration.

In this application,the combination of granulation embedding and freeze-drying showed very good experimental results.It can open up new possibilities in the fields of fermentation processes and food transformation,facilitating the production of cultured starter cultures with easily controlled and reconstituted dosages;in addition,dust-free and free-flowing powders can be obtained in the field of probiotics and food supplements,while ensuring the uniformity of product particle size and composition.

 The role of the refrigerant

To achieve refrigeration cycle:refrigerant is the key substance to achieve refrigeration cycle in freezer dryers.By absorbing heat in the evaporator,it cools the compressed air,thus achieving the purpose of removing water.

Protection of refrigeration system:refrigerant can also play a role in protecting the refrigeration system,effectively reducing the failure rate and operating costs of equipment.

 The working process of the refrigerant in the frozen dryer

Compression process:The refrigeration compressor inhales the low-pressure (low-temperature) refrigerant in the evaporator into the compressor cylinder,the refrigerant steam is compressed,and the pressure and temperature rise at the same time.

Condensing process:high-pressure and high-temperature refrigerant steam is pressed to the condenser,in the condenser,the refrigerant steam with a higher temperature and the cooling water or air with a lower temperature for heat exchange,the refrigerant heat is taken away by the water or air and condensed,and the refrigerant steam becomes a liquid.

Throttling process:This part of the liquid is then transported to the expansion valve,the expansion valve throttling into low temperature and low pressure liquid and into the evaporator.

Evaporation process:The low-temperature and low-pressure refrigerant liquid in the evaporator absorbs the heat of the compressed air and vaporizes(commonly known as"evaporation"),and the compressed air condenses out a large amount of liquid water after cooling.

Cycle process:the refrigerant steam in the evaporator is sucked away by the compressor,so that the refrigerant completes the four processes of compression,condensation,throttling and evaporation in the system,forming a cycle.

 The requirements of the refrigerated dryer for the refrigerant

Good heat exchange performance:the refrigerant needs to have good heat exchange performance in order to effectively absorb the heat in the compressed air in the evaporator and cool the compressed air.

Chemical stability:The refrigerant needs to be chemically stable and will not react chemically with other substances in the system to ensure the stable operation of the system.

Environmental protection:With the improvement of environmental awareness,the environmental protection requirements for refrigerant are also getting higher and higher.Therefore,when choosing a refrigerant,it is necessary to consider whether it is harmful to the environment.

The refrigerant of dry freezer machine is the key component of the refrigeration system, and its performance directly affects the refrigeration effect and energy efficiency of the freezer. The following is a detailed introduction to the dry freezer machine:

Common refrigerant types

R22:

High refrigeration efficiency, stable operation, is the common refrigerant in the early dry freezer.

However, due to its larger greenhouse effect and more serious impact on the environment, it is being gradually phased out.

R404A and R507A:

Both are mixed refrigerants, with excellent refrigeration performance and environmental protection performance.

It has been widely used in many new dry freezers.

R134a:

It has low greenhouse effect and stable cooling performance.

It has been used in some high-end dry freezers.

CO2:

With the characteristics of zero emission and high efficiency refrigeration, it has been widely used in green and low carbon dry refrigerators.

Especially in cases where ultra-low temperature freezing is required, CO2 refrigerants perform well.

 

 

Refrigerant service life and maintenance

01.

Service life

The service life of the refrigerant depends on a number of factors, including ambient temperature, frequency of use, equipment manufacturing quality, etc. Generally speaking, the refrigerant service life of dry refrigerators is about 8 to 10 years, but the specific time may vary depending on the actual situation.

02.

Maintenance

In order to extend the service life of the refrigerant and maintain the performance of the dry freezer, regular maintenance and maintenance are required. Including checking the leakage of refrigerant, cleaning the condenser, replacing the air filter, etc.

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