If you have been reading about primary drying and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-11-23. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
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.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
Handling and storage practices aim to keep the cake intact and dry. Vials are typically stored upright at controlled temperatures, often between 2 °C and 8 °C or at -20 °C for longer-term use. Reconstitution involves adding a suitable diluent and gently mixing until the solid dissolves. Shaking or rapid injection of diluent can create foam or damage sensitive molecules. Once reconstituted, the product may require refrigeration and use within a defined period.
Residual moisture is a key quality attribute for lyophilized products. Water that remains after secondary drying can affect chemical stability, cake structure, and shelf life. Karl Fischer titration is a common method for measuring water content in the dried solid. The target range varies by product, but many biologics are dried to between 0.5% and 3% water by weight. Acceptable limits are set during development and confirmed by stability studies.
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 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.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
=== Hysteresis === Hysteresis, in this case, refers to the restructuring of the adhesive interface over some period of time, with the result being that the work needed to separate two surfaces is greater than the work that was gained by bringing them together (W > γ1 + γ2). For the most part, this is a phenomenon associated with diffusive bonding. The more time is given for a pair of surfaces exhibiting diffusive bonding to restructure, the more diffusion will occur, the stronger the adhesion will become. The aforementioned reaction of certain polymer-on-polymer surfaces to ultraviolet radiation and oxygen gas is an instance of hysteresis, but it will also happen over time without those factors. In addition to being able to observe hysteresis by determining if W > γ1 + γ2 is true, one can also find evidence of it by performing "stop-start" measurements. In these experiments, two surfaces slide against one another continuously and occasionally stopped for some measured amount of time. Results from experiments on polymer-on-polymer surfaces show that if the stopping time is short enough, resumption of smooth sliding is easy. If, however, the stopping time exceeds some limit, there is an initial increase of resistance to motion, indicating that the stopping time was sufficient for the surfaces to restructure.
Biuret ( BYUR-ret) is a chemical compound with the chemical formula HN(CONH2)2. It is a white solid that is soluble in hot water. A variety of organic derivatives are known. The term "biuret" also describes a family of organic compounds with the chemical formula R1R2N−C(=O)−N(R3)−C(=O)−NR4R5, where R1, R2, R3, R4 and R5 are hydrogen, organyl or other groups. Also known as carbamylurea, it results from the condensation of two equivalents of urea. It is a common undesirable impurity in urea-based fertilizers, as biuret is toxic to plants.
== Humane endpoint == A humane endpoint can be defined as the point at which pain and/or distress is terminated, minimized or reduced for an entity in a trial (such as an experimental animal), by taking action such as killing the animal humanely, terminating a painful procedure, or giving treatment to relieve pain and/or distress. The occurrence of an individual in a trial having reached may necessitate withdrawal from the trial before the target outcome of interest has been fully reached.
The poor taste and lack of sugar in modern garden and commercial tomato varieties resulted from breeding tomatoes to ripen uniformly red. This change occurred after the discovery of a mutant "u" phenotype in the mid-20th century, so named because the fruits ripened uniformly. This was widely cross-bred to produce red fruit without the typical green ring around the stem on un-crossbred varieties. Before this, most tomatoes produced more sugar during ripening, and were sweeter and more flavorful. 10–20% of the total carbon fixed in the fruit can be produced by photosynthesis in the developing fruit of the normal U phenotype. The u mutation encodes a factor that produces defective chloroplasts with lower density in developing fruit, making them a lighter green, and reducing sugar in the resulting ripe fruit by 10–15%. Perhaps more importantly, the fruit chloroplasts are remodelled during ripening into chlorophyll-free chromoplasts that synthesize and accumulate the carotenoids lycopene, β-carotene, and other metabolites that are sensory and nutritional assets of the ripe fruit. The potent chloroplasts in the dark-green shoulders of the "U" phenotype are beneficial here, but have the disadvantage of leaving green shoulders near the stems of the ripe fruit, and even cracked yellow shoulders. This is apparently because of oxidative stress due to overload of the photosynthetic chain in direct sunlight at high temperatures. Hence, genetic design of a commercial variety that combines the advantages of types "u" and "U" requires fine-tuning, but may be feasible.
Sources: en.wikipedia.org
==== Satiety ==== As a peptide hormone, CCK mediates satiety by acting on the CCK receptors distributed widely throughout the central nervous system. The mechanism for hunger suppression is thought to be a decrease in the rate of gastric emptying. CCK also has stimulatory effects on the vagus nerve, effects that can be inhibited by capsaicin. The stimulatory effects of CCK oppose those of ghrelin, which has been shown to inhibit the vagus nerve. The effects of CCK vary between individuals. For example, in rats, CCK administration significantly reduces hunger in adult males, but is slightly less effective in younger subjects, and even slightly less effective in females. The hunger-suppressive effects of CCK also are reduced in obese rats.
=== Amphetamines === Substituted amphetamines are a chemical class of stimulants, entactogens, hallucinogens, and other drugs. They feature a phenethylamine core with a methyl group attached to the alpha carbon resulting in amphetamine, along with additional substitutions.
=== Disadvantages === While molecular farming is one application of genetic engineering, there are concerns that are unique to it. In the case of genetically modified (GM) foods, concerns focus on the safety of the food for human consumption. In response, it has been argued that the genes that enhance a crop in some way, such as drought resistance or pesticide resistance, are not believed to affect the food itself. Other GM foods in development, such as fruits designed to ripen faster or grow larger, are believed not to affect humans any differently from non-GM varieties. In contrast, molecular farming is not intended for crops destined for the food chain. It produces plants that contain physiologically active compounds that accumulate in the plant's tissues. Considerable attention is focused, therefore, on the restraint and caution necessary to protect both consumer health and environmental biodiversity. The fact that the plants are used to produce drugs alarms activists. They worry that once production begins, the altered plants might find their way into the food supply or cross-pollinate with conventional, non-GM crops. These concerns have historical validation from the ProdiGene incident, and from the StarLink incident, in which GMO corn accidentally ended up in commercial food products. Activists also are concerned about the power of business. According to the Canadian Food Inspection Agency, in a recent report, says that U.S. demand alone for biotech pharmaceuticals is expanding at 13 percent annually and to reach a market value of $28.6 billion in 2004.
His government established a centralised totalitarian state, withdrew from the League of Nations, and dramatically increased Germany's rearmament. A government-sponsored programme for economic renewal focused on public works, the most famous of which was the Autobahn. In 1935, the regime withdrew from the Treaty of Versailles and introduced the Nuremberg Laws which targeted Jews and other minorities. Germany also reacquired control of the Saarland in 1935, remilitarised the Rhineland in 1936, annexed Austria in 1938, annexed the Sudetenland in 1938 with the Munich Agreement, and, in violation of the agreement, occupied Czechoslovakia in March 1939. Kristallnacht (Night of Broken Glass) saw the burning of synagogues, the destruction of Jewish businesses, and mass arrests of Jewish people. In August 1939, Hitler's government negotiated the Molotov–Ribbentrop Pact that divided Eastern Europe into German and Soviet spheres of influence. On 1 September 1939, Germany invaded Poland, beginning World War II in Europe; Britain and France declared war on Germany on 3 September. In spring 1940, Germany conquered Denmark and Norway, the Netherlands, Belgium, Luxembourg, and France. The British repelled German air attacks in the Battle of Britain in the same year. In 1941, German troops invaded Yugoslavia, Greece and the Soviet Union, and Germany declared war on the United States.
Markers for CAFs are notably similar to those of surrounding tumour-associated cells but at the same time, display massive heterogeneity of behaviour, appearance and genotype. In 2017 Swedish researchers tried to classify molecularly distinct fibroblasts into groups depending on their differential expression of markers. They found overlapping expression patterns which supported the idea that there are transitional states and even identified pluripotency in some patients’ activated fibroblasts (suggesting progenitor cells). Pleotropic functions (e.g. tumour-promoting and tumour-inhibiting) require cell plasticity. While there are positive markers for CAFs, there are also negative markers namely; cytokeratin and CD3, as CAFs do not have epithelial and endothelial characteristics.
Sources: en.wikipedia.org
== Background == Traditionally, most meat was shipped as primal cuts from the slaughterhouse to the butcher. Meat was then cut to commonly used cuts and packaged at the store or was custom cut for consumers. Case-ready meat is cut and packaged at central regional facilities and sent to retail stores ready for placement in refrigerated display cases. Local butchering, cutting, trimming, and overwrapping the meat at retail stores is greatly reduced. Advantages of the centralized master-packager preparation include: efficiency of centralized operations, tight quality control, close control of sanitization, specialized packaging, etc.
A partial vacuum may be generated by increasing the volume of a container. To continue evacuating a chamber indefinitely without requiring infinite growth, a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded again. This is the principle behind a positive displacement pump, for example the manual water pump. Inside the pump, a mechanism expands a small sealed cavity to reduce its pressure below that of the atmosphere. Because of the pressure differential, some fluid from the chamber (or the well, in our example) is pushed into the pump's small cavity. The pump's cavity is then sealed from the chamber, opened to the atmosphere, and squeezed back to a minute size. More sophisticated systems are used for most industrial applications, but the basic principle of cyclic volume removal is the same:
Schymanski has developed a subset of PubChem for exposomics, PubChemLite, which can be annotated to increase ability of researchers to identify unknown environmental compounds. Within this field, Schymanski is working to automate the identification of a group of fluorinated compounds called ‘per- and poly-fluoroalkyl substances’ (PFASs) in order to increase the ability of researchers to find unknown PFAS in the environment. Schymanski is an advocate for open science and data sharing. Within the NORMAN network, a collaborative activity across Europe, North America, and Asia, Schymanski worked in 2011 with the team that established NORMAN MassBank, which was a community-driven project to gather information about small molecules. In 2015, Schymanski expanded this type of data with the NORMAN Suspect List Exchange. Schymanski has also worked to develop computational tools that allow the processing of complex high resolution mass spectrometry data and sought to establish standards to consider the quality of the mass spectrometry data. Schymanski's 2014 publication in Environmental Science & Technology establishes a means to estimate confidence in the quality of unknown organic compound identifications (now known as "Schymanski Confidence") and, as of 2021, has over 1000 citations. In 2018, Schymanski considered this paper her greatest achievement because it established the standard for compound identification in metabolomics and encouraged community conversation about future of these tools.
When asked at trial why she had not spoken against the ongoing physical, emotional, and sexual abuse she had endured for seven years before running away from home when she was aged 15, Anna Marie emphasised that, as a child and adolescent, she had not known any other normality, adding, "[My father and stepmother] were all I had." Fred's younger brother, John, hanged himself in the garage of his Gloucester home in November 1996. At the time of his suicide, he had been awaiting the jury verdict in his trial for the alleged multiple rapes of his niece, Anna Marie, and another underage girl at Cromwell Street in the 1970s. The Wests' son Stephen is also known to have made a suicide attempt by hanging in 2002. In 2004 he was jailed for nine months for having unlawful sex with a 14-year-old girl on multiple occasions. Another of the West children, Barry, took his own life via a suspected drug overdose in October 2020 at the age of 40. For several years prior to his death, he is known to have battled a drug addiction and psychiatric problems as a result of the abuse he had endured and witnessed, including the murder of his sister Heather, as a child. The Wests' house in Cromwell Street was demolished in October 1996, with every piece of debris destroyed to discourage potential souvenir hunters. It had been referred to in the press as the "House of Horrors." The site was later redeveloped into a public pathway. As of May 2026, Rose remains incarcerated at New Hall jail, in Wakefield, West Yorkshire, where she maintains her innocence.
Carbamazepine and its bio-transformation products have been detected in wastewater treatment plant effluent and in streams receiving treated wastewater. Field and laboratory studies have been conducted to understand the accumulation of carbamazepine in food plants grown in soil treated with sludge, which vary with respect to the concentrations of carbamazepine present in sludge and in the concentrations of sludge in the soil. Taking into account only studies that used concentrations commonly found in the environment, a 2014 review concluded that "the accumulation of carbamazepine into plants grown in soil amended with biosolids poses a de minimis risk to human health according to the approach."
Sources: en.wikipedia.org
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
Sealed vials or containers should be kept at the temperature specified by stability data, often controlled room temperature or 2–8 °C. Moisture and oxygen barriers are important because both can degrade sensitive materials. Opened containers may need immediate use or protection from ambient humidity.