Primary drying raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-01-24 and is reviewed periodically as new material appears.
Lyophilization is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid that can be reconstituted later.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
| Property | Value | Notes |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
Cardiomyocites sheets have also been successfully implanted with an observed contractile function as a result of inter-cellular communication between the host and graft. However, from a practical point of view, such approach lacks of translational character as all studies share the lack of reproducibility, i.e. a construct of similar characteristics of the native tissue does not guarantee the same results. Another approach resides in the use of hydrogels. Natural hydrogels such as Matrigel, collagen and fibrin have been used as entrapment matrices, wherein the cells to be injected are embedded. However the associated high pressure of injection is associated with a high mortality rate for the cells thereby negatively impacting the benefit ratio of this approach. Furthermore, from a technical point of view, due to the polydispersity of these natural hydrogels, purification is a requisite but very difficult step. Synthetic hydrogels, such as polyethylene glycol, polylactic acid, polylactic acid-co-glycolic acid, polycaprolactone, polyacrylamide and polyurethane have been proposed. Metalloproteinase-sensitive polyethylene is of particular interest. Indeed, this polymer modulates its mechanical and biophysical properties accordingly to enzymatic activities associated with cardiomyogenic differentiation of implanted cells. To date, no hydrogel matrix is FDA-approved for stem cell therapy use despite a large number of biomaterials currently commercially available.
Some have argued that it has common features with other self-diagnosed "mystery syndromes" such as Morgellons or multiple chemical sensitivity, while others, including some in the biomedical research community, have concluded based on the available evidence that it represents a real and serious condition. There is no known underlying biological mechanism for the proposed syndrome, and its incidence is unclear. A lack of clear diagnostic criteria and the variable reporting fraction in different healthcare settings make the problem challenging to evaluate. In 2016 Merck was a defendant in approximately 1,370 product liability lawsuits which had been filed by customers alleging they had experienced persistent sexual side-effects following cessation of treatment with finasteride. Most cases had been settled by 2018, when Merck paid a lump sum of US$4.3 million to be distributed. As of September 2019, 25 cases remained outstanding in the United States. In 2019, Reuters reported that faulty redactions in court documents revealed allegations from plaintiffs that Merck had known of persistent side effects in their original clinical trials but chose not to disclose them in warning labels.
Church's Texas Chicken is an American fast food restaurant chain that specializes in Southern fried chicken and is headquartered in Atlanta, Georgia. The chain was founded as Church's Fried Chicken To-Go by George W. Church Sr. in April 1952, in San Antonio, Texas, across the street from The Alamo. Church's Texas Chicken trades as Texas Chicken or Church's Chicken in many countries. The chain is owned by an American private equity firm known as High Bluff Capital Partners. As of 2017, Church's Texas Chicken had more than 1,700 franchised and company-owned locations in 26 countries.
Sources: en.wikipedia.org
The original design of the NanoSIMS instrument was conceived by Georges Slodzian at the University of Paris Sud in France and at the Office National d'Etudes et de Recherches Aérospatiales. There are currently around 60 NanoSIMS instruments worldwide.
Ambala district: Centre of Excellence for Litchi, announced in FY2025-26. Yamunanagar district: Centre of Excellence for strawberry, announced in FY2025-26. Karnal district: Centre of Excellence for Vegetables, Gharaunda, established 7.01.2011. Karnal district: Potato Technology Centre, Shamgarh, established 06.04.2016. Kurukshetra district: Centre for Subtropical Fruits, Ladwa, established 06.04.2016. Kurukshetra district: Horticulture Integrated Bee Keeping, Ram Nagar, post office Chaduni Jattan, established 10.11.2017. Rohtak district: Hi-tech Greenhouse Seedling Centre, established 17.12.2013. Jhajjar district: Center of Excellence for Flowers, Munimpur, established 2022. Gurugram district: Hi-tech Greenhouse Seedling Centre, established 17.12.2013. Nuh district: Center of Excellence for Onions, Pinangwan, established 2022. Palwal district: Integrated Horticulture Development, Centre, Hodal, established 13.10.2018. Mahendergarh district: Integrated Horticulture Development Centre, Sundrah village on Ateli-Kanina road, established 01.09.2019. Bhiwani district: Centre of excellence for semi-arid horticulture, Gignaw, established 2022. Hisar district: Multi Crops Demonstration Centre, Barwala, established 2022. Hisar district: Date Palm and Guava Demonstration Centre, announced in FY2025-26. Fatehabad district: Guava Demonstration Centre at Government Garden Nursery on Uklana road, Bhuna, established 27.10.2020. Sirsa district: Centre of Excellence for fruits (Citrus & Pomegranate), Mangiana, established 22.06.2013.
=== Separation Processes === King wrote the book Separation Processes in 1971. In the book, King presented that each of the separation processes (distillation, extraction, absorption, etc.) is a special case of a unified technology that can be described by a general set of quantitative principles. Before that, the standard separation operations were considered to be separate topics within the category of unit operations, with separate methodologies. The book was revised for a second edition in 1980. After the book went out of print, King secured the copyright back from McGraw-Hill and put it on eScholarship, where it is available open-access.
Sources: en.wikipedia.org
== Research and pipeline == In 2025, Novo tested whether semaglutide helped slow progression for Alzheimer's disease. However, on November 24, 2025, the company announced that the studies failed to find any effect of the drug on cognition and functioning in people with mild cognitive impairment or with dementia. Novo was researching pulmonary delivery systems for diabetic medications, and in the early stages of research into autoimmune and chronic inflammatory diseases, using technologies such as translational immunology and monoclonal antibodies. In September 2014, the company announced a decision to discontinue all research in inflammatory disorders, including the discontinuation of R&D in anti-IL-20 for the treatment of rheumatoid arthritis. In September 2018, it was reported that the company would lay off 400 administrative staff, laboratory technicians and scientists, in Denmark and China in order to concentrate research and development efforts on "transformational biological and technological innovation".
De novo nucleation by the Arp2/3 complex, formins, and Spire that forms a trimer Barbed-end uncapping by the removal of barbed-end-capping proteins (CapZ, Hsp70, EPS8) Barbed-end uncapping by actin-binding-proteins that sever actin filaments Elongation Facilitated in vivo by polymerization promoters and barbed-end capping inhibitory proteins. The elongation phase begins when the concentration of short, F-actin polymers is significantly larger than at equilibrium. At this point, both termini accept the addition of new monomers (although primarily at the "barbed end") and the actin microfilament lengthens. Termination Involves the degradation of polyphosphoinositides and reactivation of "barbed end" capping proteins Hsp70 and CapZ, thereby reinitiating barbed-end capping and greatly diminishing elongation. Despite the presence of active capping proteins, certain inhibitors including profilin, formins, ENA and VASP promote elongation. These inhibitors may function in a variety of different methods, however, most employ the inhibition of subunit depolymerization and actin-depolymerizing actin-binding-proteins. Branching amplification Consists of the nucleation of new actin microfilaments from the existing sides of F-actin. The cell employs Arp2/3 complex to temporarily bind to existing polymers at a 70° angle. The Arp2/3 complex then elongates into a filamentous branch that proves essential for intracellular reorganization through cytoskeletal changes.
Pharmacy automation involves the mechanical processes of handling and distributing medications. Any pharmacy task may be involved, including counting small objects (e.g., tablets, capsules); measuring and mixing powders and liquids for compounding; tracking and updating customer information in databases (e.g., personally identifiable information (PII), medical history, drug interaction risk detection); and inventory management.
=== Characteristics in patients === There is a relationship between the subcutaneous dose of calcitonin and peak plasma concentrations. Following parenteral administration of 100 IU calcitonin, peak plasma concentration lies between about 200 and 400 pg/ml. Higher blood levels may be associated with increased incidence of nausea, vomiting, and secretory diarrhea.
Sources: en.wikipedia.org
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.