This is a working overview of Primary drying, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-10-29. Anything still debated is marked as such rather than presented as settled.
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 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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
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.
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.
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.
Sitagliptin was approved by the US Food and Drug Administration (FDA) in October 2006, and is sold under the brand name Januvia. In April 2007, the FDA approved an oral combination of sitagliptin/metformin sold under the brand name Janumet. In October 2011, the FDA approved an oral combination of sitagliptin/simvastatin sold under the brand name Juvisync. The extended release version of sitagliptin/metformin was approved in February 2012.
In the bulk aqueous phase, surfactants form aggregates, such as micelles, where the hydrophobic tails form the core of the aggregate and the hydrophilic heads are in contact with the surrounding liquid. Other types of aggregates can also be formed, such as spherical or cylindrical micelles or lipid bilayers. The shape of the aggregates depends on the chemical structure of the surfactants, namely the balance in size between the hydrophilic head and hydrophobic tail. A measure of this is the hydrophilic-lipophilic balance (HLB). Surfactants reduce the surface tension of water by adsorbing at the liquid-air interface. The relation that links the surface tension and the surface excess is known as the Gibbs isotherm.
=== Pain === Ketamine infusions are used for acute pain treatment in emergency departments and in the perioperative period for individuals with refractory or intractable pain. The doses are lower than those used for anesthesia, usually referred to as sub-anesthetic doses. Adjunctive to morphine or on its own, ketamine reduces morphine use, pain level, nausea, and vomiting after surgery. Ketamine is likely to be most beneficial for surgical patients when severe post-operative pain is expected, and for opioid-tolerant patients. Ketamine is especially useful in the pre-hospital setting due to its effectiveness and low risk of respiratory depression. Ketamine has similar efficacy to opioids in a hospital emergency department setting for the management of acute pain and the control of procedural pain. It may also prevent opioid-induced hyperalgesia and postanesthetic shivering. For chronic pain, ketamine is used as an intravenous analgesic, mainly if the pain is neuropathic. It has the added benefit of counteracting spinal sensitization or wind-up phenomena experienced with chronic pain. In multiple clinical trials, ketamine infusions delivered short-term pain relief in neuropathic pain diagnoses, pain after a traumatic spine injury, fibromyalgia, and complex regional pain syndrome (CRPS).
Skittles are produced in a wide variety of flavors and colors, including sour varieties. Skittles has hinted at new flavor releases on its Facebook page, using such statuses as "Locking myself in the Rainbow kitchen until I see some results!" A 2011 posting contained confirmation of a new flavor: "Putting the last touches on a new Skittles flavor. Tweak the Rainbow." In the United States and Canada, in 2013, Skittles replaced the lime-flavored Skittles with green apple, causing a backlash from many consumers. The lime flavor became part of the Darkside packets, which were discontinued in 2015 and followed up by the Orchards packets, which were discontinued in 2017. Lime was also part of the "Long Lost Lime" packets that came out in summer 2017 and 2018. The Darkside flavor was revived in 2019. In 2021, the "All Lime" packets containing only the lime flavor were released for a limited time. In September 2021, Skittles announced that the green apple-flavored Skittles would be replaced with the original lime flavor. In 2022, Skittles Gummies were released. In October 2024, Skittles released their own version of freeze-dried Skittles called Skittles POP'd. It comes in the Original and Sour Skittles flavors.
Escherichia coli: 0.015 – 10,000 μg/mL Staphylococcus aureus: 0.06 – 128 μg/mL Streptococcus pneumoniae: 2 – 16 μg/mL Each of these concentrations is dependent upon the bacterial strain being targeted. Some strains of E coli, for example, show spontaneous emergence of chloramphenicol resistance.
Sources: en.wikipedia.org
==== Inflammation ==== When particular GPCRs are activated by their specific chemokines Gβγ directly activates PI3Kγ which is involved in the recruitment of neutrophils that contribute to inflammation. It has been discovered that the inhibition of PI3Kγ significantly reduces inflammation. PI3Kγ is the intended target molecule in the prevention of inflammation as it is the common signalling effector of many different chemokine and receptor types involved in promoting inflammation. Although PI3Kγ is the intended target there are other isoforms of PI3 which perform different functions from PI3Kγ. Since PI3Kγ is specifically regulated by Gβγ, while other isoforms of PI3 are largely regulated by other molecules, inhibiting Gβγ signalling would provide the desired specificity of a therapeutic agent designed to treat inflammation.
== Nomenclature == Alternative names for this enzyme are: human hexokinase IV, hexokinase D, and ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1 (previously 2.7.1.2). The common name, glucokinase, is derived from its relative specificity for glucose under physiologic conditions. Some biochemists have argued that the name glucokinase should be abandoned as misleading, as this enzyme can phosphorylate other hexoses in the right conditions, and there are distantly related enzymes in bacteria with more absolute specificity for glucose that better deserve the name (see for example EC 2.7.1.2). Nevertheless, glucokinase remains the name preferred in the contexts of medicine and mammalian physiology. Another mammalian glucose kinase, ADP-specific glucokinase, was discovered in 2004. The gene is distinct and similar to that of primitive organisms. It is dependent on ADP rather than ATP (suggesting the possibility of more effective function during hypoxia), and the metabolic role and importance remain to be elucidated.
=== Liberal Leaders in the House of Lords === Granville Leveson-Gower, 2nd Earl Granville (1859–1865) John Russell, 1st Earl Russell (1865–1868) Granville Leveson-Gower, 2nd Earl Granville (1868–1891) John Wodehouse, 1st Earl of Kimberley (1891–1894) Archibald Primrose, 5th Earl of Rosebery (1894–1896) John Wodehouse, 1st Earl of Kimberley (1896–1902) John Spencer, 5th Earl Spencer (1902–1905) George Robinson, 1st Marquess of Ripon (1905–1908) Robert Crewe-Milnes, 1st Marquess of Crewe (1908–1923) Edward Grey, 1st Viscount Grey of Fallodon (1923–1924) William Lygon, 7th Earl Beauchamp (1924–1931) Rufus Isaacs, 1st Marquess of Reading (1931–1936) Robert Crewe-Milnes, 1st Marquess of Crewe (1936–1944) Herbert Samuel, 1st Viscount Samuel (1944–1955) Philip Rea, 2nd Baron Rea (1955–1967) Frank Byers (1967–1984) Nancy Seear, Baroness Seear (1984–1989)
Under intense heat, the electrons in the metal ions or small molecules can be excited. These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present. In chemical synthesis, salts are often used as precursors for high-temperature solid-state synthesis. Many metals are geologically most abundant as salts within ores. To obtain the elemental materials, these ores are processed by smelting or electrolysis, in which redox reactions occur (often with a reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms.
Sources: en.wikipedia.org
== Evolution == Some 23-million-year-old fossils of arapaima or a very similar species have been found in the Miocene Villavieja Formation of Colombia. Museum specimens are found in France, England, the United States, Brazil, Guyana, Ecuador and Perú. This makes them some of the oldest known species of freshwater fish.
== Availability == Availability of products containing P11-4 vary by country, with some products available only to dentists, and others available to the retail public. Medical device for caries treatment and enamel regeneration:
== Sources == Bulletins of the Information Bureau of the People's Union for the Defense of the Motherland and Freedom Savinkov, Boris. The Fight Against the Bolsheviks // Russian Foreign Literature. Anthology in Six Volumes. Moscow: Kniga, 1990. Vol. 1, Book 2. The Union for the Defense of the Homeland and Freedom and the Yaroslavl Rebellion of 1918 // Proletarian Revolution, 1923, no. 10. Klementyev, V. F. In Bolshevik Moscow (1918–1920). Moscow: Russkiy Put, 1998. Korovin, V. V.; Rusanov, E. P. Boris Savinkov's Case // History of the Soviet Union, 1967, no. 6, pp. 143–155. Golinkov, D. L. The Collapse of the Enemy Underground. Moscow, 1971. Gopper, Karl. Four Collapses: Memoirs of General Gopper. Riga, 1920. Jekabsons, E.; Ščerbinskis, V. Participation of Latvians in White Military Forces During the Russian Civil War 1917–1920. Riga: Journal of the Latvian Institute of History, 1997. Shentalinsky, Vitaly. "His Among His Own. Savinkov in the Lubyanka." New World, no. 7 (1996).
Rapid evolutionary divergence, along with the multiple and parallel loss of orthologs in some lineages, can give the false appearance of the emergence of a novel gene from scratch Generally speaking, expression of young, primate-specific genes is enriched in the fetal human brain relative to the expression of similarly young genes in the mouse brain. Most of these young genes, several of which originated de novo, are expressed in the neocortex, which is thought to be responsible for many aspects of human-specific cognition. Many of these young genes show signatures of positive selection, and functional annotations indicate that they are involved in diverse molecular processes, but are enriched for transcription factors. In addition to their roles in cancer processes, de novo originated human genes have been implicated in the maintenance of pluripotency and in immune function. The preferential expression of de novo genes in the testes is also suggestive of a role in reproduction. Given that the function of many de novo human genes remains uncharacterized, it seems likely that an appreciation of their contribution to human health and development will continue to grow.
=== DNA repair === RECQL4 has a crucial role in DNA end resection that is the initial step required for homologous recombination (HR)-dependent double-strand break repair. When RECQL4 is depleted, HR-mediated repair and 5' end resection are severely reduced in vivo. RECQL4 also appears to be necessary for other forms of DNA repair including non-homologous end joining, nucleotide excision repair and base excision repair. The association of deficient RECQL4-mediated DNA repair with accelerated aging is consistent with the DNA damage theory of aging.
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
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.