What’s Freeze Drying? What's Lyophilization? Meaning,Principle and Definition?
Lyophilization or freeze drying is a dehydration way that famous for damage-free to raw material, the fundamental principle in freeze drying is sublimation (by freezing raw material to solid phase, reduce surround pressure/Vacuum, enable the solid water/ice direct sublime to gas phase/Drying), so vacuum freeze drying also call sublimation drying.
Any 2 of the 3 water phases could flexible transformation to each other, by create a certain range pressure and temperature, here is the diagram show the relations:
How Freeze Drying Work?
Vacuum Freeze Drying, actually its working process should be Freezing>Vacuum&Drying, Freezing the material first which ensure dried products’ shape as well as the sublimation need (sublimation is solid to gas phase, No liquid phase involved). In the actual operation, the process is same, except the freeze drying recipe need study out, you could find the details technical process and how find freeze drying recipes blow.
Why Freeze Drying?
Freeze drying method is irreplaceable in dehydration industry, its protective to material physical and chemical characters is all other drying method cannot compare: well keep raw material original shape, guarantee bacteria live rate, remain nutrition etc., minimum the damage to material, we can say the only difference between original and dried products is water!
Damage Free Drying
- Freezing raw material below -20C and dried under vacuum, Shape/nutrition/color/flavor all is very close to fresh, even the dried products is better than fresh material in some aspects, such as light weight, easy transport, no special storage temperature request but can last up to 25years.
In Food Area
- Freeze dried food with its unique advantage, is very popular in activities like hiking, climbing, adventure, aerospace, meeting nutritional requirement and variety supply.
- Exclusive features: Original shape/color/taste/nutrition that could compare fresh, light weight, storage in room temperature up to 5years, excellent rehydration.
In Pharmaceutical/Biological Area
- Freezing raw material and dried in minus temperature, biological activities stop and to a dormant state, after add solvent could quick wake on, freeze dried technology guarantee bacteria live rate and ensure its effectiveness.
What Products Could Be Freeze Drying?
All most all products could success freeze drying, freeze dried products like food, fruit, vegetables, diary, pharmaceutical, chemical, biological, nutraceutical, cosmetics, floral etc.,all is made by freeze dry machine, check more of the applications.
Freeze Dried Samples:
What's Freeze Dryer?
Freeze dryer is the equipment process freeze vacuum drying/, like its name: a freeze dryer need have function of Vacuum, Freezing and Drying, so that the drying process could success, now the freeze dryer build trend small footprint, multi functions and automatic.
Freeze dryer is a system engineering, include many subsidiary system and parts, especially professional lab, commercial and industrial freeze drying equipment, they most sale higher price, because the complex structure and strict system performance request, there do have differences between food dryer and pharmaceutical dryer, however the principle requests a freeze dryer should include drying chamber, ice condenser, heating, vacuum, refrigeration, fluid recycle, control system, mechanical parts and auxiliary temperature/vacuum sensors.
The subsidiary system design and manufactured by module, could work alone, but during in freeze drying process, they link together by PLC based controller and close working with each other, efforts a success and high quality drying result.
A draft show freeze dryer structure:
①: Drying house ②: Ice condenser ③: Drying house door
④: Compressor ⑤: Vacuum pump ⑥: Plate heat exchanger
⑦: Centrifuge pump ⑧: Controller cabinet ⑨: Expansion tank
Whether food dryer or pharmaceutical dryer its general structure is same as above, but due to functions or size request, there may have differences such as chamber shape, external devices etc.
Freeze Drying Process:
Technology improved, freeze drying machines also step into automation, by input freeze drying recipe into touch screen panel or PC control software, the machine could fully automatic working till drying finish, as well as manual operation function reserved in the control system, which mainly use for freeze drying recipe research for a new products.
- Material loading on trays.
- Trays loading into drying chamber.
- Close door.
- Operate start machine.
- Primary drying.
- Secondary drying.
- Shelves temperature reduce prepare for harvest.
- Vacuum break.
- Open door.
- Trays take out.
- Harvest and packing.
- Ice condenser defrosting.
- Prepare another batch.
How Freeze Dryer Built? Main Components & Functions?
Drying house and door
- Drying house could be rectangular or cylindrical, food freeze dryer mostly choose cylindrical drying house and hemispherical door because the economic price, Pharmaceutical freeze dryer, due to rectangular shape drying house could provide excellent temperature uniformity, so most customer prefer it.
Rectangular drying house with more reinforce rings to reduce its innerstress avoid distortion, grooves fill PUF for insulation.
Cylindrical drying house made by a steel plate go through rolling machine and welded, very less reinforce rings need, insulation layer could be PUF or rubber sponge or without.
- Shelves module include several plates, all plates are sandwich structure inner have fluid recycle channel, achieve heating or freezing function, Material could be stainless steel or aluminum alloy with anodized treatment.
Pharmaceutical freeze dryer shelf module made of stainless steel, hygienic meet GMP.
Food freeze dryer shelf module made of aluminum alloy, a better energy efficient, the shelf modules could be 2 set side by side arrangement, or 1 fixed set.
- Ice condenser could locate backside of drying chamber or beneath shelf module, coils circular inside like U shape, during the sublimation, the coils condensing vapor to ice, by this, water in raw material success removed.
Condenser beneath shelves, a higher performance guaranteed.
Condenser in backside of shelves, larger condensing capacity guaranteed.
- Refrigeration compressor could be hermetic compressor (for lab models), piston compressor or screw compressor, cooling energy mainly supply to ice condenser use for collect vapor, also could share to shelves for raw material freezing or to external material freezer room.
- Current, to achieve condenser temperature uniformity and better icing efficiency, as well as stable and reliable working, parallel compressors are more and more popular, e.g. one machine configure 2 sets 5HP compressor, system performance is better than 1 set 10HP compressor.
Piston compressor rack.
Screw compressor rack.
- Vacuum pumps create pressure in drying chamber and ice condenser, ensure the sublimation needs, smaller drying house only oil sealed rotary vane vacuum pump is needed, for larger models or lower pressure needs roots blower also need install. There are 2 most popular vacuum pump combinations:
Oil sealed vacuum pump + Roots blower is heavy duty but smaller size.
Water ring vacuum pump + 3 sets roots blower is cheaper price but trend larger volume.
- Controller is the important part in freeze dryer machine, ensure the system smooth working, as well get enough drying data for further analysis, the standard control system should have functions of: all parts working status real-time display, pressure/temperature real-time display by curve or file format, recipes management page, history data storage and export, debug page or manual operation page.
Working status display
How To Select The Right Freeze Dryer?
Freeze dryer/lyophilizer, in principle, all is special customized as per customer requirement, however factories also provide standard models for reference, after further discuss or user requirement make right solutions meet function need.
What material mainly drying?
- For example, common food drying, you could reference FDR range freeze dryer; pharmaceutical freeze drying, you could reference FDL range; Lab research, LGJ, BFD or LYO.
Estimate batch capacity require?
- Food dryer the batch input capacity could refer/equal its condenser capacity.
- Pharmaceutical drying, material depth in trays mostly around 10mm, batch processing capacity request (Liters or Kgs)/10kg could result an about shelves area(m2) needs.
- Material in vials/bottles drying, could refer technical parameters that we listed.
Why Freeze Dryer Prices Different?
You may notice that same capacity freeze dryer, different brand for sale, the prices are big different, there do have reasons:
- Main materials for drying chamber/shelves/trays and the treatment, quality?
- Main materials for ice condenser/coils and the treatment, quality?
- Drying house and condenser insulate or not?
- Main parts like compressor, vacuum pump, fluid recycle centrifuge pumps, plate heat exchanger brand and quantity? auxiliary parts brand? if all necessary parts installed?
- If all metal part well treatment? Drying chamber, ice condenser, shelves, trays carefully polish, well welded, burr remove, metal powder well cleaned after assembly. Support frame polished before painting or hot galvanization?
- Quality control for each step or only after machine assembly?
- All pipes in system well protected?
- All components carefully brand and model select? Ever make life test, performance test and parts match test?
- Machine design scientific for high performance, easy maintenance or trouble shooting?
- Pipes layout have considered the performance?
- Drying chamber and shelf module design as per temperature uniformity?
- Ice condenser coils module design for better icing efficient?
- Machine performance like shelves cooling, heating speed? lowest, highest temperature? Condenser cooling speed, lowest temperature, Pressure reduce speed and lowest vacuum?
- Dried products quality and consistency between material trays? between batches?
- Freeze drying time spend, energy consumption?
How To Find Out The Right Freeze Drying Recipe?
Freeze Drying Recipe And Optimization.
Freeze drying recipe is the basic before you start lyophilization, as know, because of the high machine investment, high energy consumption, and slow drying rate arising from inefficient heat transfer, freeze dried products cost is more higher than other drying method, one excellent freeze drying curve could help you save energy cost every day.
Freeze Dryer recipes (Cycle optimization) is, therefore, crucial, especially for food products produced on a large scale, where the cost factor increases significantly with time spent in the freeze dryer. A fully optimized freeze dryer recipe uses only the energy and time required, resulting in shorter process time and higher product throughput. Most importantly, it ensures optimum product quality and consistency between batches.
For example, you could start optimization from the basic recipe below:
End temperature set +40C, create conditions for harvest, the time could set a bit longer if you are not sure if material have dried.
During freeze drying process, operator could check real-time temperature and vacuum displayed on screen, proper make a recipe update, the controller system will automatic execute the latest one.
Also, could export and analysis freeze drying data on computer after drying finish, could proper make adjustment of previous recipe, the recipe optimization work may last months, till fully optimized.
How To Reduce Freeze Drying Cost?
As mentioned above: because of the high machine investment, high energy consumption and slow drying speed, freeze drying cost higher than other drying method, however, the advantage of freeze drying and freeze dried products also is incomparable, it’s totally organic without additives, especially the excellent nutrition supply and amazing taste make more and more people willing to pay it. As well, the technology progress, freeze drying cost have reduce a lot and continue.
Freeze drying cost structure:
- Good quality machines always guarantee the stable production, reliable brand parts, state of art workmanship, scientific design is involved.
- When freeze drying system have failure, it may take days even weeks fix it up, during the period, you production lose, labor cost, orders and delivery time, even raw material may waste.
- To avoid machine failure, various matters need attention: good machine quality, regular maintenance, also an experienced operator could alert the abnormal in time avoid lose.
- Such as compressor, vacuum pump oil regular change, transmission part regular check or change, system cleaning etc., regular maintenance could reduce system downtime in some aspects.
- Such as electric cost, water for tray/drying house cleaning each batch.
- Also, the excellent freeze drying recipe surely could help you save energy each batch.
Precautions When Use Freeze Dryer
Under vacuum condition, the raw material is very sensitive, its drying speed and drying quality influence by a lot factors, especially new users are confusion and make mistakes when use a freeze dryer:
1, Mixing Raw Material
Freeze dry many raw materials in same time is not a good idea, there have potential risks of:
- Bacteria cross contamination.
- Smells/odor pollution.
- An inconstant lyophilization result, since each raw material character different cause drying time different.
So, if you want a constantly and high efficiency freeze drying, please don't mix products in freeze dryer chamber.
2, Trying Dry High Sugar, High Fat Products
- These products are not freeze dry well, no matter how long you take, they are still sticky because block vapor sublimation channel, not easy to clean the trays, like pure honey, without additive or attenuation, it’s very hard to dry.
3, Freeze Drying Large Pieces Products
- Large volume products like large pieces meat, entire apples, pears etc. Could only cause times longer drying time than cut to pieces, and the drying protocol is hard to handle.
- The most economical way to drying is slice or cut to pieces, recommend thickness <10mm, evenly put in trays, of course berry products like strawberry, blueberry could drying without cut.
4, Not Using A Liner In The Trays
- Commercial and industrial large scale freeze dryer machine, plastic wrap is recommend for raw material loading, it could help a lot whether in harvest process or cleaning process.
- Products direct load in trays, when harvest, they may not easy come off the trays and harvest take some time, during the period, dried products will start absorb moisture from air, as well, the trays surface leave colors and flavors, is not good for another product.
5, High Shelf Temperature Set
- Expect a quick drying by set higher shelf temperature is not right, the reason because large heating energy give in a short time may cause frozen material melt(glass transition), with sugar or something together will block the vapor escape channel, freeze drying will fail. Step back, too much vapors in short time will out of condenser collect capacity, vapor go to vacuum pump will broke it.
6, Loading Too Much In Trays
- The recommend loading weight is heaviest water in raw material should less than condenser capacity, otherwise they cannot complete dry. But this is not the only consideration, loading weight and drying time relation are delicate, find out the most economic drying solution(material thickness/weight in trays cause shortest drying time) could help you save energy every batch. Also remember, the each trays load volume(material evenly stacking) need similar.
At last, its better consult us before you purchase freeze dryer, we are professional supplier and manufacturer in China!
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