Sublimation 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 2026-07-12 and is reviewed periodically as new material appears.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying; lyophilisation; cryodesiccation | Regional spelling and historical terms. |
| Primary drying pressure | 0.05-0.5 mbar (5-50 Pa) | Kept below the triple point of water; product-specific. |
| Shelf temperature range | -40 to +40 °C | Freezing, primary, and secondary stages use different set points. |
| Cycle duration | 12-72 hours | Depends on fill volume, formulation, and equipment. |
| Condenser temperature | -50 to -80 °C | Must remain below the product's ice temperature. |
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.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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 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.
== External links == Engineered Pathogens and Unnatural Biological Weapons: The Future Threat of Synthetic Biology . Threats and considerations Synthetic biology books popular science book and textbooks Introductory Summary of Synthetic Biology Archived 2018-04-02 at the Wayback Machine. Concise overview of synthetic biology concepts, developments and applications Collaborative overview article on Synthetic Biology Controversial DNA startup wants to let customers create creatures (2015-01-03), San Francisco Chronicle It's Alive, But Is It Life: Synthetic Biology and the Future of Creation (28 September 2016), World Science Festival
The recommended daily allowance (RDA) of methionine (combined with cysteine) for adults is set at 13–14 mg kg-1 day-1 (13–14 mg per kg of body weight per day), but some researchers have argued that this figure is too low, and should more appropriately be 25 mg kg-1 day-1. Despite the importance of sulfur, restrictions of dietary sulfur are sometimes recommended for certain diseases and for other reasons.
=== 2015 === Indian satellite pay TV provider Tata Sky launched UHD service and UHD Set Top Box on 9 January 2015. The service is 4K at 50 fps and price of the UHD box is ₹5900 for existing SD/HD customers and ₹6400 for new customers. The 2015 Cricket World Cup was telecast live in 4K for free to those who own Tata Sky's UHD 4K STB. In May 2015, France Télévisions broadcast matches from Roland Garros live in Ultra HD via the EUTELSAT 5 West A satellite in the HEVC standard. The channel "France TV Sport Ultra HD" was available via the Fransat platform for viewers in France. In May 2015, satellite operator SES announced that Europe's first free-to-air Ultra HD channel (from Germany's pearl.tv shopping channel) would launch in September 2015, broadcast in native Ultra HD via the Astra 19.2°E satellite position. In June 2015, SES launched its first Ultra HD demonstration channel for cable operators and content distributors in North America to prepare their systems and test their networks for Ultra HD delivery. The channel is broadcast from the SES-3 satellite at 103°W. In June 2015, SPI International previewed its "4K FunBox UHD" Ultra HD channel on the HOT BIRD 4K1 channel, in advance of its commercial launch on Eutelsat's HOT BIRD satellites in the autumn. In July 2015, German HD satellite broadcaster HD+ and TV equipment manufacturer TechniSat announced an Ultra HD TV set with integrated decryption for reception of existing HD+ channels (available in the Autumn) and a new Ultra HD demonstration channel due to begin broadcasting in September.
Hydrophobins are a group of small (~100 amino acids) cysteine-rich proteins that were discovered in filamentous fungi that are lichenized or not. Later similar proteins were also found in Bacteria. Hydrophobins are known for their ability to form a hydrophobic (water-repellent) coating on the surface of an object. They were first discovered and separated in Schizophyllum commune in 1991. Based on differences in hydropathy patterns and biophysical properties, they can be divided into two categories: class I and class II. Hydrophobins can self-assemble into a monolayer on hydrophilic:hydrophobic interfaces such as a water:air interface. Class I monolayer contains the same core structure as amyloid fibrils, and is positive to Congo red and thioflavin T. The monolayer formed by class I hydrophobins has a highly ordered structure, and can only be dissociated by concentrated trifluoroacetate or formic acid. Monolayer assembly involves large structural rearrangements with respect to the monomer. Fungi make complex aerial structures and spores even in aqueous environments. Hydrophobins have been identified in lichens as well as non-lichenized ascomycetes and basidiomycetes; whether they exist in other groups is not known. Hydrophobins are generally found on the outer surface of conidia and of the hyphal wall, and may be involved in mediating contact and communication between the fungus and its environment. Some family members contain multiple copies of the domain.
Sources: en.wikipedia.org
Narrated by Stephen Rashbrook, produced by Nick Catliff, directed by Henry Singer, made by Lion Television and Sandpaper Films. Shown on Monday 7 February 2000 on The Nature of Things in Canada 27 September Near Miss, about ATC, the 1960 New York mid-air collision in December 1960; around 7,500 aircraft visit the three airports each day; LaGuardia Airport has two conjoined runways that operate in a strange mixed way; on 3 April 1998 there was a near miss; USAir Flight 5050 in September 1989; Colombian Avianca Flight 52 in January 1990 approached John F. Kennedy International Airport when running out of fuel, when a 4-hour flight turned into 6 hours due to weather. Narrated by Jack Davenport, directed by Jeremy Llewellyn-Jones, produced by Emma Bowman, made by Windfall Films and The Learning Channel (TLC). On All 4 4 October Curing the Incurable, the strange teratoma cells; Paul R. Sanberg of the University of South Florida; Irving Weissman of Stanford University; pathologist John Goepel; Peter Andrews (biologist); neurosurgeon Douglas Kondziolka of the University of Pittsburgh Medical Center, and stereotactic surgery; John Sinden of ReNeuron; Ann Tsukamoto of CytoTherapeutics. Narrated by David Malone, made by Boa Picture Company 20 December Talking with Aliens, an Equinox Special, with zoologist Denise L. Herzing, made by Pioneer Films
Cyclotides have been reported to have a wide range of biological activities, including anti-HIV, insecticidal, anti-tumour, antifouling, anti-microbial, hemolytic, neurotensin antagonism, trypsin inhibition, and uterotonic activities. An ability to induce uterine contractions was what prompted the initial discovery of kalata B1. The potent insecticidal activity of cyclotides kalata B1 and kalata B2 has prompted the belief that cyclotides act as plant host-defence agents. The observations that dozens or more cyclotides may be present in a single plant and the cyclotide architecture comprises a conserved core onto which a series of hypervariable loops is displayed suggest that cyclotides may be able to target many pests/pathogens simultaneously.
The linea alba (Latin for: white line) is a fibrous midline structure of the anterior abdominal wall situated between the two recti abdominis muscles (one on either side). The umbilicus (navel) is present on the linea alba through which foetal umbilical vessels pass before birth. The linea alba is formed by the union of aponeuroses (of the muscles of the anterior abdominal wall) that collectively make up the rectus sheath. The linea alba attaches to the xiphoid process superiorly, and to the pubic symphysis inferiorly. It is narrow inferiorly where the two recti abdominis muscles are in contact with each other posterior to it, and broadens superior-ward from just inferior to the umbilicus. The name means white line as it is composed mostly of collagen connective tissue, which has a white appearance.
In New Zealand, it was applied to the kawakawa (Piper excelsum), which is endemic to New Zealand and nearby Norfolk Island and Lord Howe Island. It was exploited by the Māori based on previous knowledge of the kava, as the latter could not survive in the colder climates of New Zealand. The Māori name for the plant, kawakawa, is derived from the same etymon as kava, but reduplicated. It is a sacred tree among the Māori people. It is seen as a symbol of death, corresponding to the rangiora (Brachyglottis repanda), which is the symbol of life. However, kawakawa has no psychoactive properties. Its connection to kava is linked to its similarity in appearance and bitter taste. Other names for kava include ʻawa (Hawaii), ʻava (Samoa), yaqona or yagona (Fiji), sakau (Pohnpei), seka (Kosrae), and malok or malogu (parts of Vanuatu).
Peukert wrote: "Eclectic as regards ideas, but up to date in its attitude to technology, National Socialism laid claims to offer a "conclusive" new answer to the challenges and discomforts of the modern age". Peukert wrote that: "The much heralded Volksgemeinschaft of the National Socialists in no way abolished the real contradictions of a modern industrial society; rather these were inadvertently aggravated by the use of highly modern industrial and propaganda techniques for achieving war readiness. In fact, the long-term characteristics of a modern industrial society, which had been interrupted by the world economic crisis, continued to run their course". Reflecting the influence of functionalist historians like Martin Broszat and Hans Mommsen, Peukert wrote the inability to achieve the idealized volksgemeinschaft of their dreams left the National Socialists increasingly frustrated and led them to lash out against groups considered to be enemies of the volksgemeinschaft as a way of compensation. Peukert argued that for the National Socialists "it was more important to travel hopefully than to arrive", as for the Nazis had no solutions to the problems of classical modernity other than a creating a sense of movement towards the vague goal of the utopian society that was to be the volksgemeinschaft. Peukert wrote the "violent answers" of the Nazis to the "contradictions of modernity" were not the basis of a successful social order, and as such the dynamism of the Nazi movement was primarily negative and the "movement" had a strong self-destructive streak.
Sources: en.wikipedia.org
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.
Reduced pressure lowers the boiling point of water and allows ice to sublime at temperatures below freezing. It also helps remove water vapor from the product toward the condenser. The exact pressure is chosen to stay below the triple point of water.
No. Materials with low solids content or high volatile solvents may form weak or collapsed cakes. Some proteins and cells require stabilizers to survive freezing and drying stresses. Feasibility depends on formulation and process design.
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.