A practical reference on Collapse temperature: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-10-16. Anything still debated is marked as such rather than presented as settled.
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.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
| Property | Value | Notes |
|---|---|---|
| Primary phase change | Sublimation | Ice changes directly to vapor under reduced pressure |
| Typical chamber pressure | 0.01–0.5 mbar (1–50 Pa) | Below the triple point of water; product-specific |
| Typical product temperature during primary drying | −40 °C to −10 °C | Kept below collapse temperature |
| Typical residual moisture | 0.5–3% w/w | Target range varies by formulation and use |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilization is the US spelling |
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
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.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
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.
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k¢ is the capacity factor of the solute KSW is the partition coefficient of the solute between the stationary phase and the water KMW is the partition coefficient of the solute between the micelles and the water f is the phase volume ratio (stationary phase volume/mobile phase volume) n is the molar volume of the surfactant CM is the concentration of the micelle in the mobile phase (total surfactant concentration - critical micelle concentration) A plot of 1/k¢ verses CM gives a straight line in which KSW can be calculated from the intercept and KMW can be obtained from the ratio of the slope to the intercept. Finally, KSM can be obtained from the ratio of the other two partition coefficients:
Paul J. Flory – Facts. NobelPrize.org. Nobel Media AB 2019. Wed. 19 Jun 2019. <The Nobel Prize in Chemistry 1974> Somsen, Geert. Paul J Flory. Encyclopædia Britannica. June 15, 2019. Paul J. Flory | Nobel Prize-Winning American Chemist | Britannica Paul John Flory. Stanford Chemistry. [1] Archived August 9, 2022, at the Wayback Machine.
Sources: en.wikipedia.org
== Description == The emu is the second tallest bird in the world, only being exceeded in height by the ostrich; the largest individuals can reach up to 150 to 190 cm (59 to 75 in) in height. Measured from the bill to the tail, emus range in length from 139 to 164 cm (55 to 65 in), with males averaging 148.5 cm (58.5 in) and females averaging 156.8 cm (61.7 in). Emus are the fourth or fifth heaviest living bird after the two species of ostrich and two larger species of cassowary, weighing slightly more on average than an emperor penguin. Adult emus weigh between 18 and 60 kg (40 and 132 lb), with an average of 31.5 and 37 kg (69 and 82 lb) in males and females, respectively. Females are usually slightly larger than males and are substantially wider across the rump.
== Structural studies == As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1AFS, PDB: 1FJH, PDB: 1FK8, PDB: 1LWI, PDB: 1RAL, PDB: 2DKN, and PDB: 2FVL.
== Applications == In 2002, the TAP tag was first used with mass spectrometry in a large-scale approach to systematically analyse the proteomics of yeast by characterizing multiprotein complexes. The study revealed 491 complexes, 257 of them wholly new. The rest were familiar from other research, but now virtually all of them were found to have new components. They drew up a map relating all the protein components functionally in a complex network. Many other proteomic analyses also involve the use of TAP tag. A research by EMBO (Dziembowski, 2004) identified a new complex required for nuclear pre-mRNA retention and splicing. They have purified a novel trimeric complex composed of 3 other subunits (Snu17p, Bud13p and Pml1p) and find that these subunits are not essential for viability but required for efficient splicing (removal of introns) of pre-mRNA. In 2006, Fleischer et al. systematically identified proteins associated with eukaryotic ribosomal complexes. They used multifaceted mass spectrometry proteomic screens to identify yeast ribosomal complexes and then used TAP tagging to functionally link up all these proteins.
Sources: en.wikipedia.org
High Voltage Engineering Corporation (HVEC) was an American manufacturer of particle accelerators and one of the first venture capital-backed startups. HVEC originated at MIT, where physicist Robert Van de Graaff invented a high-voltage electrostatic particle accelerator and his colleague John Trump miniaturized it for cancer radiotherapy. In 1946, Trump organized a company to manufacture these machines, recruiting Van de Graaff and Denis Robinson as co-founders. Production began in a Cambridge automobile garage. The company's early medical devices gave way to large research accelerators after the Sputnik crisis increased governments' investments in nuclear physics. For two decades, HVEC accelerators were the dominant platform for nuclear physics; in the 1970s, nearly 70 percent of experimental papers relied on HVEC machines. The company built 471 accelerators between 1946 and 1981. They were installed at hospitals, universities, and national laboratories in 30 countries, and some remain in active research use. Using these instruments, HVEC subsidiaries introduced new uses of accelerator beams. Ion Physics Corporation demonstrated that ion implantation could precisely control transistor characteristics, a technique now essential to integrated circuit fabrication. Electronized Chemicals Corporation developed methods to crosslink plastics with electron beams, producing the heat-shrink tubing now ubiquitous in electrical wiring. HVEC was one of the first two startups backed by the American Research & Development Corporation, the first modern venture capital fund.
=== Economics === In the 2000s, a lawsuit was brought against the manufacturers of Toprol XL (a time-release formula version of metoprolol) and its generic equivalent (metoprolol succinate) claiming that to increase profits, lower cost generic versions of Toprol XL were intentionally kept off the market. It alleged that the pharmaceutical companies AstraZeneca AB, AstraZeneca LP, AstraZeneca Pharmaceuticals LP, and Aktiebolaget Hassle violated antitrust and consumer protection law. In a settlement by the companies in 2012, without admission to the claims, they agreed to a settlement pay-out of US$11 million.
== External links == whatisbifidusregularis.org/ – A deconstruction of the terms Bifidus Actiregularis, Bifidus Regularis, Bifidus Digestivum, L. Casei Immunitas and their variants, as well as the marketing strategy, and information about the potential health benefits of live yoghurts. Food-Info.net – How to select a probiotic Type strain of Bifidobacterium animalis at BacDive – the Bacterial Diversity Metadatabase
Some reach back even further as Wisconsin School historian Walter LaFeber in his study America, Russia, and the Cold War, first published in 1972, argued that the Cold War had its origins in 19th century conflicts between Russia and the United States over the opening of East Asia to American trade, markets and influence. LaFeber argued that the United States commitment at the close of World War II to ensuring a world in which every state was open to American influence and trade, underpinned many of the conflicts that triggered the beginning of the Cold War. Starting with Gar Alperovitz in his influential Atomic Diplomacy: Hiroshima and Potsdam (1965), revisionists have focused on the United States decision to use atomic weapons against Hiroshima and Nagasaki during the last days of World War II. In their belief, the nuclear bombing of Nagasaki and Hiroshima in effect started the Cold War. According to Alperovitz, the bombs were used not against an already-defeated Japan to win the war, but to intimidate the Soviets by signaling that the United States would use nuclear weapons to stop Soviet expansion, though they failed to do so. New Left historians Joyce and Gabriel Kolko's The Limits of Power: The World and U.S. Foreign Policy, 1945–1954 (1972) has also received considerable attention in the historiography on the Cold War. The Kolkos argued American policy was both reflexively anticommunist and counterrevolutionary.
Sources: en.wikipedia.org
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.
The process has three main stages: freezing, primary drying, and secondary drying. Freezing sets the ice structure, primary drying removes free ice, and secondary drying removes bound water. Each stage uses specific temperature, pressure, and time settings.
No, it is a drying method rather than a sterilization method. Removing water can limit microbial growth, but it does not reliably kill microorganisms. Sterility must come from separate steps such as filtration, heat treatment, or aseptic processing.
Lyophilized products should be stored in airtight containers, protected from moisture and light, at the temperature specified by the manufacturer. Many require refrigeration at 2–8 °C, while some need frozen storage. Always check the product label for specific conditions.