If you have been reading about Sublimation 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 2026-03-06. Numbers and descriptions here follow the published literature rather than marketing material.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture and oxygen exposure. The container closure system matters because stoppers and seals can allow moisture ingress over time. Storage conditions are selected from stability studies that track potency, cake appearance, and reconstitution behavior. Many freeze-dried materials are kept at controlled room temperature, while some require refrigeration or protection from light.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | Porous cake or plug | Uniform structure suggests the drying cycle preserved the matrix. |
| Reconstitution time | Usually under 2 minutes | Depends on cake porosity, diluent volume, and excipient composition. |
| Water content range | 0.5–3% w/w | Common specification range; exact limits are product-specific. |
| Headspace oxygen | <1% v/v | Inert gas backfill reduces oxidation of sensitive materials. |
| Storage temperature | 2–8 °C or controlled room temperature | Choice depends on accelerated and real-time stability results. |
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.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
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.
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.
Sinecatechins (Veregen) was the first botanical drug approved in the US in 2006; a green tea extract, for genital warts Crofelemer (Mytesi), approved by the FDA in 2012, an extract of "dragon's blood" sap of the Croton lechleri plant, for diarrhea in people with HIV/AIDS Nabiximols (USAN, trade name Sativex) is a specific extract of Cannabis approved as a botanical drug in the United Kingdom as a mouth spray for people with multiple sclerosis, who can use it to alleviate neuropathic pain, spasticity, overactive bladder, and other symptoms; it was developed by the UK company GW Pharmaceuticals Menerba is a botanical drug candidate consisting of 22 herbs that have been used historically in traditional Chinese medicine that act as a selective estrogen receptor modulator. As of 2015 the FDA had approved Bionovo's chemical manufacturing and controls and Menerba was in a Phase III clinical trial as a potential treatment to relieve hot flashes associated with menopause.
== Awards and honors == 2024 York U Alumni Award for Outstanding Achievement 2020 Lifetime Achievement Award in Plasma Spectrochemistry 2019 HUPO Award (Human Proteome Organization) 2014 Fellow of the American Institute for Medical and Biological Engineering 2011 University of Toronto Inventor of the Year Award for Biomedical and Life Sciences 2011 Thermo Fisher Scientific Spectroscopy Award 2004 Elsevier / Spectrochimica Acta Atomic Spectroscopy Award for the most important paper published in Spectrochimica Acta Part B in 2002 (Title: Reaction cells and collision cells for ICP-MS: a tutorial review) in co-authorship with Dmitry Bandura and Vladimir Baranov 2003 W.A.E. McBryde medal from the Canadian Chemical Society of the Chemical Institute of Canada 2001 Manning Innovation Award, Award of Distinction Dr. Scott Tanner, together with Dr. Vladimir Baranov, received the Manning Award of Distinction from the Manning Innovation Awards Foundation for the remarkable invention of the ICP-MS Dynamic Reaction Cell (Collision/reaction cell). 1999 Pittcon Editors' Awards Perkin-Elmer Sciex for their ELAN 6100 DRC (Dynamic Reaction Cell) ICP-MS system. Fellow of the Royal Society of Chemistry (UK) Fellow of the American Institute for Medical and Biological Engineering (AIMBE)
This trend, along with advice from the Food and Drug Administration's attorneys that it could not win a First Amendment case on the issue, prompted the administration to issue new rules for television commercials in 1997. Instead of including the "brief summary" that took up a full page in magazine ads and would take too long to explain in a short television advertisement, drug makers were allowed to refer viewers to print ads, informative telephone lines, and websites, and to urge people to talk to their doctors if they wanted additional information. Schering-Plough invested US$322 million in Claritin direct-to-consumer advertising in 1998 and 1999, far more than any other brand. Spending on direct-to-consumer advertising by the pharmaceutical industry rose from US$360 million in 1995 to US$1.3 billion in 1998, and by 2006, was US$5 billion.
== Harvesting and cultivation == The berries of A. chilensis are collected from wild plants from December to March of each year by families, mainly Mapuche, who collect their harvest near the Andes Mountains. The harvesting process involves collecting the side branches of trees, shaking them to separate the berries and leaves from the branches, and then employing a mechanical process to separate the berries from the leaves. In the Juan Fernandez Islands, the Juan Fernandez Women's Group has led efforts to reduce the presence of the species by encouraging local women to harvest to berries and create products for sale with them. The stored fruits are sold in local markets, with prices ranging from $6.5 to $15 per kilogram ($2.9 to $6.8/lb). The average area yield is about 220 kilograms (490 lb) per hectare annually, with an estimated yearly total of only 90 short tons (180,000 lb), due to remote access and difficulty of transportation. Aristotelia chilensis is planted in home gardens and is not grown on an orchard scale. Most of the fruits on the market have been gathered from the wild. Maqui is frost sensitive and fairly tolerant of seaside conditions. It prefers a well-drained soil in full sun, with some protection against cold, drying winds. The soil should be slightly acidic, with moderate fertility. Aristotelia chilensis can be planted in USDA zones 8 to 12. It is cultivated in Spain, and in milder, moister areas of Britain, where winter freezes cause dieback, thereby stimulating growth of more shoots in spring.
Sources: en.wikipedia.org
=== Biosynthesis === Ricin is synthesized in the endosperm of castor oil plant seeds. The ricin precursor protein is 576 amino acid residues in length and contains a signal peptide (residues 1–35), the ricin A chain (36–302), a linker peptide (303–314), and the ricin B chain (315–576). The N-terminal signal sequence delivers the prepropolypeptide to the endoplasmic reticulum (ER) and then the signal peptide is cleaved off. Within the lumen of the ER the propolypeptide is glycosylated and a protein disulfide isomerase catalyzes disulfide bond formation between cysteines 294 and 318. The propolypeptide is further glycosylated within the Golgi apparatus and transported to protein storage bodies. The propolypeptide is cleaved within protein bodies by an endopeptidase to produce the mature ricin protein that is composed of a 267 residue A chain and a 262 residue B chain that are covalently linked by a single disulfide bond.
==== Ohio ==== In 2008, Ohio's Department of Agriculture (ODA) banned the use of labeling in dairy products as rBST-free because it was deemed misleading to consumers. However, the International Dairy Foods Association and the Organic Trade Association claimed ODA's ban was a violation of the first amendment by not allowing consumers to decide whether they deem the milk was safe and filed suit against the bill. "The district court granted summary judgment in favor of Ohio, concluding that using 'rBST' as a label was inherently misleading because it implies a compositional difference between those products that are produced with rBST and those that are not."
Note: For purposes of this table, genes are defined as orphan genes (when species-specific) or TRGs (when limited to a closely related group of species) when the mechanism of origination has not been investigated, and as de novo genes when de novo origination has been inferred, irrespective of method of inference. The designation of de novo genes as "candidates" or "proto-genes" reflects the language used by the authors of the respective studies.
Sources: en.wikipedia.org
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.
It usually appears as a uniform porous plug or cake that fills the container without excessive shrinkage. Color should match the specification, and there should be no meltback or visible foreign matter. Minor cracking may be acceptable if the product still meets moisture and potency limits.
Water content is a key stability parameter because excess water can promote hydrolysis, aggregation, or cake collapse. It also affects reconstitution and product weight. Each product has a target range, and methods such as Karl Fischer titration are used to verify it.
Primary drying removes ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, often under the same vacuum. The two stages differ in the water state being removed.