The influence of the freezing process on vapour transport during sublimation in vacuum-freeze-drying of macroscopic samples

Kochs, M.; Körber, Ch.; Heschel, I.; Nunner, B.

doi:10.1016/s0017-9310(05)80159-0

Cited by 56 publications

(23 citation statements)

References 20 publications

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“…77 In freeze drying, it is assumed that pores appearing after the sublimation step at low pressure are "phantoms" of ice crystals in the frozen sample; this technique has the advantage of being easy to carry out. 78 Ice crystallization studies in biology have used thin water/ice layers that overcome the limitations of fixation and sectioning in transmitted light microscopy. Measured thickness of specimens is in the order of 100 μm for solutions and suspensions in flat glass capillary tubes.…”

Section: Observing and Measuring Ice Morphologymentioning

confidence: 99%

Ice Morphology: Fundamentals and Technological Applications in Foods

2009

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Freezing is the process of ice crystallization from supercooled water. Ice crystal morphology plays an important role in the textural and physical properties of frozen and frozen-thawed foods and in processes such as freeze drying, freeze concentration, and freeze texturization. Size and location of ice crystals are key in the quality of thawed tissue products. In ice cream, smaller ice crystals are preferred because large crystals results in an icy texture. In freeze drying, ice morphology influences the rate of sublimation and several morphological characteristics of the freeze-dried matrix as well as the biological activity of components (e.g., in pharmaceuticals). In freeze concentration, ice morphology influences the efficiency of separation of ice crystals from the concentrated solution. The cooling rate has been the most common variable controlling ice morphology in frozen and partly frozen systems. However, several new approaches show promise in controlling nucleation (consequently, ice morphology), among them are the use of ice nucleation agents, antifreeze proteins, ultrasound, and high pressure. This paper summarizes the fundamentals of freezing, methods of observation and measurement of ice morphology, and the role of ice morphology in technological applications.

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Section: Observing and Measuring Ice Morphologymentioning

confidence: 99%

Ice Morphology: Fundamentals and Technological Applications in Foods

2009

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“…The ice crystals formed typically have the shape of columns, dendrites, or ''ice fingers''. [17,18] The ice crystals were subsequently sublimated at $ À25 8C by exposing our samples to a reduced pressure of 100 Pa. A series of polymeric foams were prepared using mass ratios of Ludox TM-40 colloidal silica nanoparticles and poly(vinyl laurate) particles of 0, 0.22, 0.38, 0.46 and 0.69, respectively, at corresponding overall solid contents of the waterborne mixtures of colloids of 9.3, 12.1, 13.0, 13.6, and 19.7 wt%. Field-emission-gun scanning electron microscopy (FEG-SEM) analysis at room temperature of the fabricated materials is shown in Figure 1A-E.…”

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Conducting Nanocomposite Polymer Foams from Ice‐Crystal‐Templated Assembly of Mixtures of Colloids

et al. 2009

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“…This is because the bulk density of the LM product depends on the freezing step. Freezing determine the dimension and the shape of the ice crystals that form the structure of the frozen LM product (Kochs et al, 1993;Nakagawa et al, 2006;Searles et al, 2001). Regardless of the concentration of mannitol solution, the LM powders were solids occupying approximately the volume of the former solution.…”

Section: Density Porosity and Cohesivitymentioning

confidence: 99%

Influence of mannitol concentration on the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol

Kaialy

Mawlud

2016

International Journal of Pharmaceutics

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Mannitol is a pharmaceutical excipient that is receiving increased popularity in solid dosage forms. The aim of this study was to provide comparative evaluation on the effect of mannitol concentration on the physicochemical, mechanical, and pharmaceutical properties of lyophilised mannitol. The results showed that the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol powders are strong functions of mannitol concentration. By decreasing mannitol concentration, the true density, bulk density, cohesivity, flowability, netcharge-to-mass ratio, and relative degree of crystallinity of LM were decreased, whereas the breakability, size distribution, and size homogeneity of lyophilised mannitol particles were increased. The mechanical properties of lyophilised mannitol tablets improved with decreasing mannitol concentration. The use of lyophilised mannitol has profoundly improved the dissolution rate of indomethacin from tablets in comparison to commercial mannitol. This improvement exhibited an increasing trend with decreasing mannitol concentration. In conclusion, mannitols lyophilised from lower concentrations are more desirable in tableting than mannitols from higher concentrations due to their better mechanical and dissolution properties. Abbreviations∆H0, Endothermic enthalpy of CM melting; ∆Hs, Endothermic enthalpy of LM melting; ANOVA, One-way analysis of variance; API, Active pharmaceutical ingredient; c.opt, Optimal concentration; CI, Carr's index; CM, Commercial mannitol; Cman, Concentration of mannitol; d10%, particle size at 10% volume distribution; d50%, particle size at 50% volume distribution; d90%, particle size at 90% volume distribution; Db, Bulk density, DE, Dissolution efficiency; DSC, Differential scanning calorimeter; Dt, tap density; EB, Ease of breakage; Eq, Equation; FT-IR, Fourier transform infrared; GI, Gastro intestinal; HSD, Honestly Significant Difference; I, Relative intensity; Iamorphous, the input to the intensity from the amorphous region; Icrystalline, the input to the intensity from the crystalline region; LM, Lyophilised mannitol; MDR, Mean dissolution rate; MDT, Mean dissolution time; P, Statistical probability; PXRD, Powder X-ray diffraction; Q10min, The mean percentage of drug dissolved in the first 10 min; Q30min, The mean percentage of drug dissolved in the first 30 min; Q4min, The mean percentage of drug dissolved in the first 4 min; Q50min; The mean percentage of drug dissolved in the first 50 min; RDB, Relative degree of breakage;

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The influence of the freezing process on vapour transport during sublimation in vacuum-freeze-drying of macroscopic samples

Cited by 56 publications

References 20 publications

Ice Morphology: Fundamentals and Technological Applications in Foods

Ice Morphology: Fundamentals and Technological Applications in Foods

Conducting Nanocomposite Polymer Foams from Ice‐Crystal‐Templated Assembly of Mixtures of Colloids

Influence of mannitol concentration on the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol

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