Thermoanalytical Techniques for the Investigation of the Freeze Drying Process and Freeze-Dried Products

Kett, Vicky L.; Mcmahon, Debra; Ward, Kevin

doi:10.2174/1389201054022850

Cited by 13 publications

(5 citation statements)

References 132 publications

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“…The collapse temperature (Tc) in the freeze drying application is specific for each substance and it is the temperature above which the collapse of the frozen structure occurs. This irreversibly leads to the failure of the material and to defect formation (Kett et al 2005; Bellows and King 1972; Abdelwahed et al 2006). During gelation, hydrocolloids generate a network, specific for each gelling agent, in which water is embedded.…”

Section: Resultsmentioning

confidence: 99%

Role of the Drying Technique on the Low-Acyl Gellan Gum Gel Structure: Molecular and Macroscopic Investigations

Cassanelli

Prosapio

Norton

et al. 2018

Food Bioprocess Technol

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The effect of three drying processes (freeze, oven and supercritical CO 2 drying) on CP Kelco low-acyl gellan gum gel was investigated, highlighting the role of the water removal mechanism (i.e. sublimation, evaporation and solvent replacement/extraction) and the process parameters on the gel structure, rather than focusing on the drying kinetics. It is the first time that a research paper not only compares the drying methods but also discusses and investigates how the molecular and macroscopic levels of gellan gum are affected during drying. Specifically, the dried gel structures were characterised by bulk density and shrinkage analyses as well as scanning electron microscope (SEM) and micro-computed tomography (μCT) microscopy. Micro-differential scanning calorimetry (μDSC) was used in a novel way to investigate the effect of the drying technique on the polymer disorder chains by partial melting of the gel. The resulting water uptake during rehydration was influenced by the obtained dried structure and, therefore, by the employed drying process. It was found that freeze-dried (FD) structures had a fast rehydration rate, while both oven-dried (OD) and supercritical CO 2 -dried (scCO 2 D) structures were slower. After 30 min, FD samples achieved a normalised moisture content (NMC) around 0.83, whereas OD and scCO 2 D samples around 0.33 and 0.19, respectively. In this context, depending on the role of the specific hydrocolloid in food (i.e. gelling agent, thickener, carrier), one particular dried-gel structure could be more appropriate than another. Graphical abstract From left to right: unprocessed hydrogels; μ-CT images of dried gels and unprocessed hydrogel; DSC curves after drying process

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Section: Resultsmentioning

confidence: 99%

Role of the Drying Technique on the Low-Acyl Gellan Gum Gel Structure: Molecular and Macroscopic Investigations

Cassanelli

Prosapio

Norton

et al. 2018

Food Bioprocess Technol

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“…Drying of proteins for pharmaceutical applications can impact their conformation, and hence, reduce the potency of the drug. [ 146 147 ] DSC has been used to gauge different drying techniques for potential pharmaceutical applications. Techniques such as spray drying, lyophilization, super critical fluid technology, and many others have been proven challenged to maintain protein stability under high temperature, freezing, and dehydration.…”

Section: Drug Stabilitymentioning

confidence: 99%

Differential scanning calorimetry: An invaluable tool for a detailed thermodynamic characterization of macromolecules and their interactions

2011

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Differential Scanning Calorimetry (DSC) is a highly sensitive technique to study the thermotropic properties of many different biological macromolecules and extracts. Since its early development, DSC has been applied to the pharmaceutical field with excipient studies and DNA drugs. In recent times, more attention has been applied to lipid-based drug delivery systems and drug interactions with biomimetic membranes. Highly reproducible phase transitions have been used to determine values, such as, the type of binding interaction, purity, stability, and release from a drug delivery mechanism. This review focuses on the use of DSC for biochemical and pharmaceutical applications.

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“…Water freezes beyond the eutectic temperature, and as the solution becomes more saturated, the viscosity increases, slowing down ice crystallization until freezing stops. This phenomenon is called glassification or vitrification [25,40], and the corresponding temperature is called the glass transition temperature [41]. This temperature marks the point between a viscous liquid and a rigid glass.…”

Section: Solidifactionmentioning

confidence: 99%

“…The glass consists of concentrated solutes and unfrozen water. The high viscosity limits the movement to a few millimeters per year [41].…”

Section: Solidifactionmentioning

confidence: 99%

Effect of the Freezing Step on Primary Drying Experiments and Simulation of Lyophilization Processes

Juckers

Knerr²,

Harms³

et al. 2023

Processes

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Lyophilization is a widely used preservation method for thermosensitive products. It consists of three process steps: freezing, primary and secondary drying. One of the major drawbacks is the long processing time. The main optimization effort was put into the primary drying phase since it is usually the longest phase. However, the freezing step is of immense importance for process efficiency and product quality. The lack of control during freezing comprises a challenge for process design and tech transfer. In this study, four different freezing steps (shelf-ramped freezing with and without holding step, precooled shelves and an ice fog method for controlled nucleation) are used and their impact on primary drying experiments and simulations is shown. Only the ice fog method is able to control the nucleation temperature leading to low dry layer resistances with low deviations. During the primary drying simulations, the control of the nucleation temperature drastically increases the precision and accuracy of the product temperature prediction. For optimal primary drying design and model predictive control, the nucleation temperature is strongly recommended to be controlled inside a Process Analytical Technology (PAT) concept to achieve reliable and reproducible process conditions.

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Thermoanalytical Techniques for the Investigation of the Freeze Drying Process and Freeze-Dried Products

Cited by 13 publications

References 132 publications

Role of the Drying Technique on the Low-Acyl Gellan Gum Gel Structure: Molecular and Macroscopic Investigations

Role of the Drying Technique on the Low-Acyl Gellan Gum Gel Structure: Molecular and Macroscopic Investigations

Differential scanning calorimetry: An invaluable tool for a detailed thermodynamic characterization of macromolecules and their interactions

Effect of the Freezing Step on Primary Drying Experiments and Simulation of Lyophilization Processes

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