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Freeze-drying
Published in S. Padma Ishwarya, Spray-Freeze-Drying of Foods and Bioproducts, 2022
Freeze-drying is the final step of the spray-freeze-drying (SFD) process. Generally, freeze-drying occurs in three stages: freezing, primary drying (sublimation drying), and secondary drying (evaporative or desorption drying) (Figure 3.1). However, unlike conventional freeze-drying, in SFD, freezing is considered as a distinct unit operation. As a comprehensive discussion on the spray-freezing operation has already been presented in the previous chapter, this chapter would focus on the primary and secondary drying stages. After spray freezing, the frozen feed droplets suspended in the cryogenic liquid are sieved and collected or separated after allowing the cryogen to boil off. Then, the separated frozen particles are freeze-dried in a drying module, under vacuum, atmospheric, or fluidized conditions, depending on which the SFD process is classified as:Vacuum spray-freeze-drying (VSFD)Atmospheric spray-freeze-drying (ASFD)Atmospheric fluidized bed spray-freeze-drying (AFBSFD)Vacuum or sub-atmospheric fluidized bed spray-freeze-drying (VFBSFD or SAFBSFD)
Drying of Solids: Principles, Classification, and Selection of Dryers
Published in Arun S. Mujumdar, Handbook of Industrial Drying, 2020
Arun S. Mujumdar, Anilkumar S. Menon
Freeze drying is a special case of drying under vacuum at a temperature below the triple point of water; here water (ice) sublimes directly into water vapor. Although the heat required for sublimation is severalfold lower than for evaporation, vacuum operation is expensive. Freeze drying of coffee, for example, costs two to three times more than spray drying. On the other hand, the product quality and flavor retention are better.
Evaluation of PCL/Chitosan/Nanohydroxyapatite/Tetracycline Composite Scaffolds for Bone Tissue Engineering
Published in Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon, Tissue Engineering Strategies for Organ Regeneration, 2020
Rashid Bin Mad Jin, Naznin Sultana, Chin Fhong Soon, Ahmad Fauzi Ismail
Freezing/freeze-drying technique involves creating a solution using polymers and solvent, quickly freezing the solution to lock liquid state structure and then remove the solvent by freeze drying. In other words, freeze drying is the process whereby solutions are completely frozen and then the frozen solvents are removed via sublimation under vacuum (Qian and Zhang 2011). This process is also known as lyophilisation. This process has been used in pharmaceutical industry to improve the stability of labile drugs, and also in tissue engineering application as it will fabricate porous materials in the process (Qian and Zhang 2011).
Novel drying techniques for controlling microbial contamination in fresh food: A review
Published in Drying Technology, 2023
Dayuan Wang, Min Zhang, Ronghua Ju, Arun S. Mujumdar, Dongxing Yu
Freeze drying is a well-known drying technique that produces high quality dried products with the advantage of retaining color, structure, flavor and nutrition. However, freeze drying is not a reliable and viable method for inactivating harmful microorganisms on food.[30] In fact, freeze drying technique is an excellent way to preserve microorganisms and is often used to drying strains and probiotics to minimize their biological activity for viability and long-term storage. Gram-positive bacteria generally survive much better than Gram-negative bacteria during freeze drying.[14] Freeze drying has the lowest temperature among nonthermal drying technologies, and its drying environment temperature is generally around −50 °C. Both freezing and low water activity can increase the resistance of cells.[10,14]
Optimal production decisions in biopharmaceutical fill-and-finish operations
Published in IISE Transactions, 2020
Tugce Martagan, Alp Akcay, Maarten Koek, Ivo Adan
Figure 1 provides a high-level overview of production steps in biomanufacturing. First, biopharmaceuticals are manufactured through a series of fermentation and purification operations. This often results in active pharmaceutical ingredients or antigens, depending on the specific application context. During manufacturing, most of the large scale industry applications use big vessels such as 1000 liter bioreactors. Therefore, the resulting product is called bulk material, and is stored in large quantities for further processing. Next, the bulk material is filled into smaller vials or other forms of packaging during fill-operations. This step typically consists of filling the bulk material into vials and capping them. However, most biopharmaceuticals contain live active ingredients (e.g., antigens), and hence vials often need to be freeze dried. Freeze-drying removes all the liquid from the filled product, such that only a so called “cookie” remains in the vial. Freeze-drying helps to maintain product stability and quality, especially during storage and shipment. The resulting product is called Finished Product Unpacked (FPU). Then, the process continues with finish-operations, where FPUs are labelled and packaged along with a leaflet of medical information. The resulting product is called Final Product Packed (FPP), as shown in Figure 1.
Encapsulation and delivery of bioactive compounds using spray and freeze-drying techniques: A review
Published in Drying Technology, 2020
Amir Rezvankhah, Zahra Emam-Djomeh, Gholamreza Askari
Drying conditions and procedure for the freeze-drying process are completely different. The freeze-drying process is affected predominantly by freezing and sublimation (drying) stages. Conventional freeze-drying (CFD) and vacuum freeze-drying (VFD) are accounted as freeze-drying methods, which in the CFD, freezing is performed at the atmospheric condition and in the VFD, the freezing is done at vacuum pressures.[119] Both have a similar stage in the dryingprocess. Dependent on the type of performed freezing, obtained micro- and nanocapsules would have different properties. To modify the operating conditions of the freezing process during freeze-drying and to enhance the stability of oil-loaded micro- and nano-capsules, vacuum at the freezing stage is applied.[119] It has been approved that VFD produces a higher quality product than CDF that can be related to the higher performance of VFD.[111] As vacuum freezing is undertaken and moisture content of a product is reduced through the action, the temperature decreases to the extent that inhibits the deteriorative reactions and microbiological growth. By vacuum freezing, a high-quality product can be produced with high retention of loaded core materials and also maintaining the nutritional characteristics, colors, aromas, tastes, and shapes of the actual food systems.[113,119]