If you have been reading about cake collapse 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 2026-04-19. Numbers and descriptions here follow the published literature rather than marketing material.
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 process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
| 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. |
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.
Stability programs monitor lyophilized products under defined temperature and humidity conditions over time. Real-time studies at recommended storage conditions are the reference, while accelerated studies provide early signals of degradation pathways. Because a dry cake can still undergo oxidation, hydrolysis, or aggregation, stability depends on residual moisture, excipients, and container headspace. Open questions include how best to predict long-term stability from short accelerated runs and how vial-to-vial variability affects shelf life. Current guidance treats these predictions as product-specific rather than universally generalizable.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
== Benign neoplasms (210–229) == 210 Benign neoplasm of lip, oral cavity, and pharynx 211 Benign neoplasm of other parts of digestive system 211.3 Colon Familial adenomatous polyposis 212 Benign neoplasm of respiratory and intrathoracic organs 212.0 Nasal cavities middle ear and accessory sinuses 212.1 Larynx 212.2 Trachea 212.3 Bronchus and lung 212.4 Pleura 212.5 Mediastinum 212.6 Thymus 212.7 Heart Myxoma Rhabdomyoma 213 Benign neoplasm of bone and articular cartilage 213.9 Bone and articular cartilage, site unspecified Chondroma 214 Lipoma 215 Other benign neoplasm of connective and other soft tissue 216 Benign neoplasm of skin Melanocytic nevus 217 Benign neoplasm of breast 218 Uterine leiomyoma 219 Other benign neoplasm of uterus 220 Benign neoplasm of ovary 221 Benign neoplasm of other female genital organs 222 Benign neoplasm of male genital organs 223 Benign neoplasm of kidney and other urinary organs 224 Benign neoplasm of eye 225 Benign neoplasm of brain and other parts of nervous system 226 Benign neoplasm of thyroid glands 227 Benign neoplasm of other endocrine glands and related structures 228 Hemangioma and lymphangioma, any site 228.0 Hemangioma, any site 228.1 Lymphangioma, any site 229 Benign neoplasm of other and unspecified sites
calcium gluconate 10% 10 mL or calcium chloride 10% 5 mL IV over 2 minutes sodium bicarbonate 1 meq/kg IV slow push regular insulin 5–10 U 50% glucose 1–2 ampules IV bolus kayexalate 25–50 g with sorbitol 20% 100 mL by mouth or rectum. Even so, abnormal heart rhythms may develop; electrocardiographic monitoring is advised, and specific treatment should be begun promptly.
As of 2018, research has paid insufficient attention to the potential adverse effects of carbohydrate restricted dieting, particularly for micronutrient sufficiency, bone health and cancer risk. One low-quality meta-analysis reported that adverse effects could include "constipation, headache, halitosis, muscle cramps and general weakness". In a comprehensive systematic review of 2018, Churuangsuk and colleagues reported that other case reports give rise to concerns of other potential risks of low-carbohydrate dieting including hyperosmolar coma, Wernicke's encephalopathy, optic neuropathy from thiamine deficiency, acute coronary syndrome and anxiety disorder. Significantly restricting the proportion of carbohydrate in diet risks causing malnutrition, and can make it difficult to get enough dietary fiber to stay healthy. As of 2014, it appeared that with respect to the risk of death for people with cardiovascular disease, the kind of carbohydrates consumed are important; diets relatively higher in fiber and whole grains lead to reduced risk of death from cardiovascular disease compared to diets high in refined grains.
== Hematopoiesis == The various cell types of the mononuclear phagocyte system are all part of the myeloid lineage from the CFU-GEMM (precursor of granulocytes, erythrocytes, monocytes and megakaryocytes).
Sources: en.wikipedia.org
20 July A race riot at Marine Corps Base Camp Lejeune resulted in the death of one Marine. The Navy issued the plan for Operation Duck Hook a program of massive bombing of North Vietnam commissioned by National Security Advisor Henry Kissinger.
==== Impact of phonation ==== The viscoelastic properties of human vocal fold lamina propria are essential for their vibration, and depend on the composition and structure of their extracellular matrix. Adult vocal cords have a layered structure which is based on the layers differential in extracellular matrix distribution. Newborns on the other hand, do not have this layered structure. Their vocal cords are uniform, and immature, making their viscoelastic properties most likely unsuitable for phonation. Hyaluronic acid plays a very important role in the vocal fold biomechanics. In fact, hyaluronic acid has been described as the extracellular matrix molecule that not only contributes to the maintenance of an optimal tissue viscosity that allows phonation, but also of an optimal tissue stiffness that allows frequency control. CD44 is a cell surface receptor for HA. Cells such as fibroblasts are responsible for synthesizing extracellular matrix molecules. Cell surface matrix receptors in return, feed back to the cells through cell-matrix interaction, allowing the cell to regulate its metabolism. Sato et al. carried out a histopathologic investigation of unphonated human vocal cords. Vocal fold mucosae, which were unphonated since birth, of three young adults (17, 24, and 28 years old) were looked at using light and electron microscopy. The results show that the vocal fold mucosae were hypoplastic, and rudimentary, and like newborns, did not have any vocal ligament, Reinke's space, or layered structure. Like newborns, the lamina propria appeared as a uniform structure.
== Current Research and Future Implications == Currently, studies and experiments are being done to test for dedifferentiation-like abilities in mammalian cells, with hopes that this information can provide more insight into possible regenerative abilities in mammals. Dedifferentiation could spark innovation in regenerative medicine because it suggests that one's own cells can change cell fates, which would remove immunological response risks from treatment with allogeneic cells, or cells that are not genetically matched with the patient. A concept that has been explored for mammals is that of inducible dedifferentiation, which would make cells that do not naturally dedifferentiate be able to revert to a pluripotent or progenitor-like state. This is achieved by expressing the appropriate transcription factors in the cell and suppressing others. More information about this as well as the possible risks can be found here [1] .
Aang, in the animated series Avatar: The Last Airbender and The Legend of Korra was vegetarian. According to the show's creators, "Buddhism and Taoism have been huge inspirations behind the idea for Avatar." As shown in "The King of Omashu" and "The Headband", a notable aspect of Aang's character is his vegetarian diet, which is consistent with Buddhism, Hinduism, and Taoism. In the Brahmajala Sutra, a Buddhist code of ethics, vegetarianism is encouraged. Other fictional characters who are vegetarians include Count Duckula in Count Duckula, Beast Boy in Teen Titans and Teen Titans Go!, Lenore in Supernatural, and Norville "Shaggy" Rogers in the animated series What's New, Scooby Doo?. Before the latter animated series, Shaggy was known for having an "enormous appetite" earlier in the Scooby-Doo franchise. The decision to make Shaggy a vegetarian occurred after his voice actor, Casey Kasem, convinced the producers to do so, since he was a vegan who supported animal rights and opposed factory farming, saying he would refuse to voice Shaggy unless the character was vegetarian. An October 2019 South Park episode, "Let Them Eat Goo", featured a vegetarian character. Additionally, Steven Universe, the protagonist in the show Steven Universe and the limited epilogue series, Steven Universe Future, is a vegetarian. In the episode "Snow Day" of Steven Universe Future, Steven tells the Gems he lives with that he has been a vegetarian for a month, drinks protein shakes and mentions that he does "his own skincare routine."
=== Other uses in arts, entertainment, and media === Link (film), a 1986 horror movie featuring a super-intelligent, murderous orangutan WBT-FM, a radio station in Charlotte, North Carolina, US, that used call sign WLNK 1997–2025
Sources: en.wikipedia.org
=== In other animals === Lingual lipase – Rats and mice secrete a type of lipase (fat-digesting enzyme) from the Von Ebner's glands which are located at the back of the tongue. The analogous enzyme in humans is secreted in the stomach and called gastric lipase (LIPF).
Ketone bodies can be used as fuels, yielding 22 ATP and 2 GTP molecules per acetoacetate molecule when oxidized in the mitochondria. Ketone bodies are transported from the liver to other tissues, where acetoacetate and beta-hydroxybutyrate can be reconverted to acetyl-CoA to produce reducing equivalents (NADH and FADH2), via the citric acid cycle. Ketone bodies cannot be used as fuel by the liver, because the liver lacks the enzyme β-ketoacyl-CoA transferase, also called thiolase. Acetoacetate in low concentrations is taken up by the liver and undergoes detoxification through the methylglyoxal pathway which ends with lactate. Acetoacetate in high concentrations is absorbed by cells other than those in the liver and enters a different pathway via 1,2-propanediol. Though the pathway follows a different series of steps requiring ATP, 1,2-propanediol can be turned into pyruvate.
Actinides easily react with halogens forming salts with the formulas MX3 and MX4 (X = halogen). So the first berkelium compound, BkCl3, was synthesized in 1962 with an amount of 3 nanograms. Like the halogens of rare earth elements, actinide chlorides, bromides, and iodides are water-soluble, and fluorides are insoluble. Uranium easily yields a colorless hexafluoride, which sublimates at a temperature of 56.5 °C; because of its volatility, it is used in the separation of uranium isotopes with gas centrifuge or gaseous diffusion. Actinide hexafluorides have properties close to anhydrides. They are very sensitive to moisture and hydrolyze forming AnO2F2. The pentachloride and black hexachloride of uranium were synthesized, but they are both unstable. Action of acids on actinides yields salts, and if the acids are non-oxidizing then the actinide in the salt is in low-valence state:
Mental disorders are diagnosed in accordance with diagnostic manuals such as the International Classification of Diseases (ICD), edited by the World Health Organization (WHO), and the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association (APA). The fifth edition of the DSM (DSM-5) was published in May 2013. However, its release coincided with a statement by then-NIMH (National Institute of Mental Health) director Thomas Insel noting that the manual lacks validity compared to other medical specialties due to the absence of objective laboratory measures (biomarkers) for diagnosis. Treatment may include psychotropics (psychiatric medicines), psychotherapy, substance-abuse treatment, and other modalities such as interventional approaches, assertive community treatment, community reinforcement, and supported employment. Treatment may be delivered on an inpatient or outpatient basis, depending on the severity of functional impairment or risk to the individual or community. Research within psychiatry is conducted by psychiatrists on an interdisciplinary basis with other professionals, including clinical psychologists, epidemiologists, nurses, social workers, and occupational therapists. Psychiatry has been controversial since its inception, facing criticism both internally and externally over its medicalization of mental distress, reliance on pharmaceuticals, use of coercion, influence from the pharmaceutical industry, and its historical role in social control and contentious treatments.
=== New Granada (Colombia) === Sailing southeast, the sloop entered the Gulf of Batabano, passing Isla de Pinos and navigating the challenging Jardines y Jardinillos archipelago, a region earlier named by Columbus. Humboldt measured latitudes and studied water characteristics, noting the solitude of the area, which was once frequented by fishermen. The journey was slow, with stops for geological and botanical observations. The crew’s cruelty toward wildlife disturbed Humboldt. After several days, the ship entered open water and was driven off course by winds toward the Cayman Islands before resuming its route to the Colombian coast. On March 24, the ship arrived in the Gulf of Santa Marta, enduring rough weather before seeking shelter near the Rio Sint. The travelers landed in a remote area, where locals regarded them with suspicion. Humboldt met a fellow German among palm wine workers, who offered insights about the climate but little else. After collecting botanical specimens, the travelers faced further storms at sea, nearly capsizing before finally finding shelter. Humboldt attempted to make astronomical observations to determine longitude but was prevented by the captain due to difficult terrain. An encounter with escaped enslaved people left Humboldt reflecting on the region’s hardships and the blunted sympathy caused by slavery. Arriving in Cartagena, Humboldt and Bonpland spent six days confirming geographical data and exploring the area. Cartagena, a key Spanish colonial port, faced challenges in defending its harbor.
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.
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.