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Pharmaceutical Manufacturing and Packing Sourcer

Freeze-Drying Techniques

In the freeze-drying process, water (or another solvent) is removed from a frozen product by sublimation (primary drying) at a very low temperature and low pressure. The amount of residual water, strongly bounded to the partially dried product, is then reduced to the target value by using high vacuum and moderate temperature (secondary drying). Freeze-drying is widely used in the pharmaceutical field due to the low operating temperature. Moreover, a freeze-dried product has a high surface area, and can be easily re-hydrated.

Desired product quality is obtained if product temperature is maintained below a limit value during the operation. In the case of solutes that crystallise, the limit temperature is the eutectic point of the system, in order to avoid the formation of a liquid phase and successive boiling due to low pressure. In the case of solutes that do not crystallise, the limit value corresponds to the glass transition temperature in order to avoid shrinkage or collapse of the cake structure. Cake collapse can be responsible for a higher residual water content in the final product, of a higher reconstitution time and of the loss of activity of the pharmaceutical principle; besides this, a collapsed product is often rejected because of its unattractive physical appearance.


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Prof Antonello Barresi is a certified chemical engineer; he holds a PhD from the Politecnico di Torino. He has been a visiting researcher at Yale, professor at Addis Ababa University (Ethiopia), and ‘enseignant invité’ at the University of Lyon 1 (France). He is currently a full professor at Politecnico di Torino. His main research interests in drying include: drying and freeze drying of pharmaceuticals and enzymes, lyophilisation of food and damaged paper documents; development of new sensors and control systems for freeze dryers and modelling and optimisation of freeze-drying. He is the author of about 120 papers in international journals and books, several international patents and more than 100 conference presentations.

 

Dr Davide Fissore is a certified chemical engineer; he holds a PhD from the Politecnico di Torino. He has been a visiting researcher at CPE-Lyon (France) and the University of Oviedo (Spain). He is currently Assistant Professor at the Department of Materials Science and Chemical Engineering of the Politecnico di Torino (Italy). His research activity is focused on modelling, monitoring and control of chemical processes (catalytic reactors working in unsteady-state conditions and processes of separation) and the freeze-drying of pharmaceuticals. He has authored more than 70 papers published on international journals and on proceedings of international conferences.

 

Dr Roberto Pisano graduated in Chemical Engineering in 2005 from the Politecnico of Torino (Italy) and received his PhD from the same University in 2009. His research activity is focused on modelling, monitoring and control of the process of freeze-drying of pharmaceuticals.

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Antonello Barresi
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Davide Fissore
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Roberto Pisano
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