The short version of cake fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-29. Anything still debated is marked as such rather than presented as settled.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
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 removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
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 usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
== Types == There are mainly two types of granules based on the presence or absence of a membrane: membrane-bound granules, and non-membrane-bound granules. Eosinophilic granules, basophilic granules, and secretory granules are examples of membrane-bound granules, while P-granules and stress granules are examples of non-membrane-bound granules.
== Causes == While the exact cause is unclear, it is believed to involve a combination of genetics and an environmental trigger such as exposure to a virus or bacterium, as is the case with many other autoimmune disorders. Around 20 autoantibodies could be involved. It can occur independently of other health problems or as a result of another connective tissue disorder. Sjögren's disease may be associated with other autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) or systemic sclerosis. The inflammation that results progressively damages the glands. Diagnosis is by biopsy of moisture-producing glands and blood tests for specific antibodies. On biopsy there are typically lymphocytes within the glands.
The Federal Research Division estimated that the 86% of the population that did not consider themselves part of one of the ethnic groups indicated by the 2006 census was divided into 49% Mestizo or of mixed European and Amerindian ancestry, and 37% White, mainly of Spanish lineage, but there is also a large population of Middle East descent; in some sectors of society there is a considerable input of German and Italian ancestry. Many of the Indigenous peoples experienced a reduction in population during the Spanish rule and many others were absorbed into the mestizo population, but the remainder currently represents over eighty distinct cultures. Reserves (resguardos) established for indigenous peoples occupy 30,571,640 hectares (305,716.4 km2) (27% of the country's total) and are inhabited by more than 800,000 people. Some of the largest indigenous groups are the Wayuu, the Paez, the Pastos, the Emberá and the Zenú. The departments of La Guajira, Cauca, Nariño, Córdoba and Sucre have the largest indigenous populations. The Organización Nacional Indígena de Colombia (ONIC), founded at the first National Indigenous Congress in 1982, is an organization representing the indigenous peoples of Colombia. In 1991, Colombia signed and ratified the current international law concerning indigenous peoples, Indigenous and Tribal Peoples Convention, 1989. Sub-Saharan Africans were brought as slaves, mostly to the coastal lowlands, beginning early in the 16th century and continuing into the 19th century. Large Afro-Colombian communities are found today on the Pacific Coast.
However, its toxicity to microorganisms is not overtly observed since the free silver ion is found in low concentrations in wastewater treatment systems and the natural environment due to its complexation with ligands such as chloride, sulfide, and thiosulfate.
The United States Food and Drug Administration and the European Medicines Agency have approved weight loss medications for adults with either a body-mass index (BMI) of at least 30, or a body-mass index of at least 27 with at least one weight-related comorbidity. This patient population is considered to have sufficiently high baseline health risks to justify the use of anti-obesity medication. The American Academy of Pediatrics had not previously supported the use of weight loss medication in adolescents but issued new guidelines in 2023, which recommend considering the use of weight loss medication in some overweight children aged 12 or older. The European Medicines Agency has approved semaglutide for children aged 12 or older who have a BMI in the 95 percentile for their age and a weight of at least 60 kilograms (130 lb). However, GLP-1 agonists may not be cost effective in this population.
Sources: en.wikipedia.org
In 2012, a laser engraved panel featuring Wheatley was launched aboard the Japan Aerospace Exploration Agency (JAXA)'s Kounotori 3 mission on its way to resupply the International Space Station. In April 2011, series of Portal-themed DLC levels were added to the game The Ball. A few Portal characters, including Chell and P-Body, feature as avatar customization items in the game Fall Guys for 5 crowns each. The portal gun is one of several weapons used alongside ones from other game and film franchises in a climactic fight for the 2021 film Free Guy which takes place within a video game. A reference to GLaDOS appears in a sub-quest in Cyberpunk 2077 as a murderous AI driving a taxi and eventually tries to kill the protagonist. In 2022, GEICO released a commercial entitled "The Gecko Visits Portal", featuring elements from the Portal games such as an unreleased test chamber shown in trailers for Portal 2, with McLain reprising her role as GLaDOS. Rocket League released free DLC that includes a variety of items from the Portal series available for vehicle customization. Evil Genius 2: World Domination includes a free Portal themed expansion pack which adds Portal-themed rooms and traps to the game. Escape Simulator features a free Portal Escape Chamber DLC in which players will need to escape from the Aperture Science Laboratories by solving various puzzles.
== Development == Formulated as the salt trelagliptin succinate, it was approved for use in Japan in March 2015. Takeda, the company that developed trelagliptin, chose to not get approval for the drug in the US and EU. The licensing rights that Takeda purchased from Furiex Pharmaceuticals for DPP-4 inhibitors included a clause specific to development of this drug in the US and EU. The clause required that all services done for phase II and phase III clinical studies in the US and EU be purchased through Furiex. Takeda chose to cease development of this drug in the US and EU because of the high costs quoted by Furiex for these services. Gliptins have been on the market since 2006 and there are 8 gliptins currently registered as drugs (worldwide). Gliptins are an emerging market and are thus being developed at an increasing rate; there are currently two gliptins in advanced stages of development that are expected to be on the market in the coming year. Gliptins are thought to have cardiovascular protective abilities though the extent of these effects is still being studied. They are also being studied for the ability that this class of drugs has at promoting B-cell survival.
Phosphomimetics are amino acid substitutions that mimic a phosphorylated protein, thereby activating (or deactivating) the protein. Within cells, proteins are commonly modified at serine, tyrosine and threonine amino acids by adding a phosphate group. Phosphorylation is a common mode of activating or deactivating a protein as a form of regulation. However some non-phosphorylated amino acids appear chemically similar to phosphorylated amino acids. Therefore, by replacing an amino acid, the protein may maintain a higher level of activity. For example, aspartic acid can be considered chemically similar to phospho-serine, due to it also carrying a negative charge. Therefore, when an aspartic acid replaces a serine, it is a phosphomimetic of phospho-serine and can imitate the protein always in its phosphorylated form. However, differences between the phosphomimetic compound and the phosphorylated residue, notably differences in Ramachandran distributions, charge states and size, can alter the protein sufficiently to result in significant differences in behavior. Phosphonate-based compounds have been used as phosphotyrosine analogues, as they are less enzyme labile and are physiologically more stable.
=== Multiple equilibria === Two or more equilibria can exist at the same time. When this is so, equilibrium constants can be ascribed to individual equilibria, but they are not always unique. For example, three equilibrium constants can be defined for a dibasic acid, H2A.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.