This is a working overview of collapse temperature, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
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 |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
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.
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.
=== Other species === FPR receptors are widely distributed throughout mammalian species with the FPR1, FPR2, and FPR3 paralogs, based on phylogenetic analysis, originating from a common ancestor, early duplication of FPR1, and FPR2/FPR3 splitting with FPR3 originating from the latest duplication event near the origin of primates. Rabbits express an ortholog of FPR1 (78% amino acid sequence identity) with high binding affinity for FMLP; rats express an ortholog of FPR2 (74% amino acid sequence identity) with high affinity for lipoxin A4.
Portugal's culture has developed due to the influence from various civilisations that have crossed Europe, especially the Mediterranean. Later, during the period of Portugal's engagement in the Age of Discovery, cultural elements from outside of Europe were introduced and became a central element of Portuguese national identity. Portugal is known for its heritage and architecture, sacred sites, festivities, poetry, its music (especially the fado), and cuisine (including its wine). As of 2026, UNESCO inscribed 17 properties in Portugal on the World Heritage List. Portugal's national day is on 10 June, celebrated as the Dia de Portugal, de Camões e das Comunidades Portuguesas (Portugal, Camões, and Portuguese Communities Day).
=== Leaves === The leaves are generally simple, elongated, entire (smooth and even), linear, oval to filiform (threadlike), mostly with parallel veins, but occasionally net-veined. They are alternate (single and alternating direction) and spiral, but may be whorled (three or more attached at one node, e.g. Lilium, Fritillaria), cauline (arranged along the aerial stem) or sheathed in a basal rosette. They are rarely petiolate (stalked), and lack stipules. The aerial stem is unbranched.
endoplasmic reticulum (ER) The irregular network of unit membranes, continuous with the outer nuclear membrane, that extends from the nucleus into the cytoplasm in most eukaryotic cells, where it serves important packaging and transport functions for newly synthesized macromolecules. The membranes interweave to form a mesh of tubular channels and flattened sacs called cisternae which house a variety of enzymes that perform post-translational modifications including tagging proteins for sorting. The outer surfaces of so-called rough endoplasmic reticulum are studded with attached ribosomes that serve as sites of protein synthesis, whereas smooth endoplasmic reticulum, lacking ribosomes, functions in the synthesis of lipids and steroid hormones and in the detoxification of metabolic wastes. Generally both types of ER occur together, though some cell types are characterized by different proportions of rough and smooth ER, depending on the activities of the cell.
Low complexity regions in proteins can be computationally detected from sequence using various methods and definitions, as reviewed in. Among the most popular methodologies to identify LCRs is by measuring their Shannon entropy. The lower the value of the calculated entropy, the more homogeneous the region is in terms of amino acid content. In addition, a Neural Network webserver, LCR-hound has been developed to predict the function of an LCR, based on its amino acid or di-amino acid (bigram) content. Compression-based tools have also been used to perform such analysis providing higher sensitivity while mitigating the risk of overestimation inherent in other methods.
Sources: en.wikipedia.org
==== Mayhew's leaked letter ==== By now the political row was being discussed in the media, partly because of the lack of other news in December. Cuckney wrote to Thatcher, at her behest, asking for reassurance that the Sikorsky deal would not damage Westland's business prospects in Europe. Heseltine was not satisfied with Thatcher's draft reply when he saw it and consulted Sir Patrick Mayhew (Solicitor-General and acting attorney-general as Sir Michael Havers was ill) on the grounds that the government might be legally liable for any incorrect advice. Heseltine supplied extra material about the risk of losing European business, which Thatcher did not include in her reply to Cuckney. Heseltine then wrote to David Horne of Lloyds Merchant Bank, who was advising the European consortium (in reply to planted questions from Horne which had been dictated to him over the phone by one of Heseltine's staff), giving him the advice which Thatcher had declined to include in her letter to Cuckney (that the Sikorsky deal would be "incompatible with participation" in European helicopter projects). Heseltine's letter was also leaked to the press. This was a blatant challenge to Thatcher's authority as Heseltine had not consulted Downing Street, the Department of Trade and Industry or Mayhew before writing to Horne. Thatcher discussed sacking Heseltine with close colleagues over Christmas; but, as she later admitted in her memoir, refrained from doing so as he was too popular and important as a political figure.
=== Biologically-derived units === The extremely strong complexation between avidin and biotin is instrumental in blood clotting, and has been used as the recognition motif to construct synthetic systems. The binding of enzymes with their cofactors has been used as a route to produce modified enzymes, electrically contacted enzymes, and even photoswitchable enzymes. DNA has been used both as a structural and as a functional unit in synthetic supramolecular systems.
== Mechanism == The basis of many functional gastrointestinal disorders is distension of the intestinal lumen. Such luminal distension may induce pain, a sensation of bloating, abdominal distension and motility disorders. Therapeutic approaches seek to reduce factors that lead to distension, particularly of the distal small and proximal large intestine. Food substances that can induce distension are those that are poorly absorbed in the proximal small intestine, osmotically active, and fermented by intestinal bacteria with hydrogen (as opposed to methane) production. The small molecule FODMAPs exhibit these characteristics. Ingestion of certain short-chain carbohydrates, including lactose, fructose and sorbitol, fructans and galactooligosaccharides, can induce gastrointestinal discomfort similar to that seen in IBS. Dietary restriction of short-chain carbohydrates is associated with improvement of symptoms. These short-chain carbohydrates (lactose, fructose and sorbitol, fructans and GOS) behave similarly in the intestine. Firstly, being small molecules and either poorly absorbed or not absorbed at all, they drag water into the intestine via osmosis. Secondly, these molecules are readily fermented by colonic bacteria, so upon malabsorption in the small intestine they enter the large intestine where they generate gases (hydrogen, carbon dioxide and methane). The dual actions of these carbohydrates cause an expansion in volume of intestinal contents, which stretches the intestinal wall and stimulates nerves in the gut.
The new ATSDR analysis derives provisional Minimal Risk Levels (MRLs) of 3 × 10−6 mg/kg/day for PFOA and 2 × 10−6 mg/kg/day for PFOS during intermediate exposure. The European Food Safety Authority opinion sets a provisional tolerable weekly intake (TWI) of 6 × 10−6 mg/kg body weight per week for PFOA.
Sources: en.wikipedia.org
=== Role of the extracellular matrix and its components === Another difference between the healing of embryonic and adult wounds is due to the role of fibroblast cells. Fibroblasts are responsible for the synthesis of the ECM and collagen. In the fetus, fibroblasts are able to migrate at a faster rate than those found in the adult wound. Fetal fibroblasts can also proliferate and synthesize collagen simultaneously, in comparison to adult fibroblasts where collagen synthesis is delayed. It is this delay in both collagen deposition and migration, which is likely to contribute to formation of a scar in the adult. Proteins and cell surface receptors found in the ECM differ in fetal and adult wound healing. This is due to the early up regulation of cell adhesion proteins such as fibronectin and tenascin in the fetus. During early gestation in the fetal wounds of rabbits, the production of fibronectin occurs around 4 hours after wounding, much faster than in adult wounds where expression of fibronectin does not occur until 12 hours post wounding. The same pattern can be seen in the deposition of tenascin. It is this ability of the fetal fibroblast to quickly express and deposit fibronectin and tenascin, which ultimately allows cell migration and attachment to occur, resulting in an organised matrix with less scarring. Another major component of the ECM is hyaluronic acid (HA), a glycosaminoglycan. It is known that fetal skin contains more HA than adult skin due to the expression of more HA receptors.
Second Cup Coffee Co. is a Canadian specialty coffee retailer operating more than 345 cafes across the country. Its headquarters are in Mississauga, Ontario. Its stores sell hot and cold beverages, pastries, snacks, pre-packaged food items, hot and cold sandwiches, and drinkware, including mugs and tumblers. Second Cup sales continue to compete with Starbucks, Tim Hortons and McDonald's, which also feature espresso-based specialty drinks. Since its inception, Second Cup has expanded its franchises to the United States, Morocco, Saudi Arabia, Bahrain, Kuwait, Oman, Qatar, Lebanon, Jordan, Egypt, the United Arab Emirates, Iraq, Syria, Yemen, Cyprus, Azerbaijan, Angola, Lithuania, and Romania. It also opened a store in Pakistan in 2013, in the United Kingdom in 2014, in the Philippines in 2015, and in Poland in 2016.
Throughout Belize's history, Guatemala has claimed sovereignty over all or part of Belizean territory. This claim is occasionally reflected in maps drawn by Guatemala's government, showing Belize as Guatemala's twenty-third department. The Guatemalan territorial claim involves approximately 53% of Belize's mainland, which includes significant portions of four districts: Belize, Cayo, Stann Creek, and Toledo. Roughly 43% of the country's population (≈154,949 Belizeans) reside in this region. As of 2020, the border dispute with Guatemala remains unresolved and contentious. Guatemala's claim to Belizean territory rests, in part, on Clause VII of the Anglo-Guatemalan Treaty of 1859, which obligated the British to build a road between Belize City and Guatemala. At various times, the issue has required mediation by the United Kingdom, Caribbean Community heads of government, the Organization of American States (OAS), Mexico, and the United States. In April 2018, Guatemala's government held a referendum to determine if the country should take its territorial claim on Belize to the International Court of Justice (ICJ) to settle the long-standing issue. Guatemalans voted 95% yes on the matter. A similar referendum was to be held in Belize in April 2019, but a court ruling led to its postponement. The referendum was held in May 2019, and 55.4% of voters opted to send the matter to the ICJ. Both countries submitted requests to the ICJ (in 2018 and 2019, respectively) and the ICJ ordered Guatemala's initial brief be submitted by December 2020 and Belize's response by 2022.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
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.