Combined freeze-drying

Autissier A, Le Visage C, Pouzet C, Chaubet F, Letoumeur D. Fabrication of porous polysaccharide-based scaffolds using a combined freeze-drying/cross-linking process. Acta Biomater 2010 6 3640-8. 

H. Tai and A. L. Underwood, Infrared Spectrophotometry of Sulfate Ion. Combining Freeze-Drying with Potassium Bromide Disk Technique, Anal. Chem. 29, 1430, 1957. 

C. Isolation and purification of XK-62-2 100 g of the white powder obtained in the above step B are placed to form a thin, uniform layer on the upper part of a 5 cm0X 150 cm column packed with about 3 kg of silica gel advancely suspended in a solvent of chloroform, isopropanol and 17% aqueous ammonia (2 1 1 by volume). Thereafter, elution is carried out with the same solvent at a flow rate of about 250 ml/hour. The eluate is separated in 100 ml portions. The active fraction is subjected to paper chromatography to examine the components eluted. XK-62-2 is eluted in fraction Nos. 53-75 and gentamicin Cja is eluted in fraction Nos. 85-120. The fraction Nos. 53-75 are combined and concentrated under reduced pressure to sufficiently remove the solvent. The concentrate Is then dissolved in a small amount of water. After freeze-drying the solution, about 38 g of a purified preparate of XK-62-2 (free base) is obtained. The preparate has an activity of 950 units/mg. Likewise, fraction Nos. 85-120 are combined and concentrated under reduced pressure to sufficiently remove the solvent. The concentrate is then dissolved in a small amount of water. After freeze-drying the solution, about 50 g of a purified preparate of gentamicin Cja (free base) is obtained. 

Bj Pivaloyloxymethyl D(—)-Ot-aminobenzylpenicillinate. hydrochloride To a solution of pivaloyloxymethyl D(—)-a-azidobenzylpenicillinate (prepared as described above) in ethyl acetate (75 ml) a 0.2 M phosphate buffer (pH 2.2) (75 ml) and 10% palladium on carbon catalyst (4 g) were added, and the mixture was shaken in a hydrogen atmosphere for 2 hours at room temperature. The catalyst was filtered off, washed with ethyl acetate (25 ml) and phosphate buffer (25 ml), and the phases of the filtrate were separated. The aqueous phase was washed with ether, neutralized (pH 6.5 to 7.0) with aqueoussodium bicarbonate, and extracted with ethyl acetate (2 X 75 ml). To the combined extracts, water (75 ml) was added, and the pH adjusted to 25 with 1 N hydrochloric acid. The aqueous layer was separated, the organic phase extracted with water (25 ml), and the combined extracts were washed with ether, and freeze-dried. The desired compound was obtained as a colorless, amorphous powder. 

To prepare the mild-alkali-extract, dry watermelon cell walls were suspended in a solution of 0.1 N NaOH, and allowed to react with stirring at room temperature for 15 minutes. A pH of 13, as indicated by pH paper, was kept constant during this period by addition of 0.1 N NaOH. To ensure complete reaction, the treatment was continued overnight at 4 °C. The soluble portion was separated by centrifugation at 10,000 RPM for 20 minutes in a Sorval GSA rotor. The insoluble portion was washed twice with water. The supernatants were combined and, after neutralization to pH 7.0 with acetic acid, dialyzed against distilled water and freeze dried. 

Stir with 1000ml 50mM CDTA at pH 6.5 for 6h at 20-22X. Filter on G3 glass filter, wash residue with water, centrifuge filtrate at SOOOrpm for 20min, dialyse, concentrate. Reextract the residue under the same conditions and freeze-dry the combined filtrates CDTA-Fraction... 

Flavonoids may be extracted from fresh or frozen plant tissues or from herbarium material, although freeze-dried material may also be utilized [34]. It is very important to ensure that the matoial to be extracted is finely divided, whether by cutting or emshing, to ensure proper extraction. Extraction can be carried out successively with methanol containing some 10% of wate and thm with a 1 1 mixture of methanol and water. Each extraction should be carried out for a period of about 2 h, shaking or stirring to facilitate the process. The extracts are then combined for chromatographic separation. 

In paired comparison tests two different samples are presented and one asks which of the two samples has most of the sensory property of interest, e.g. which of two products has the sweetest taste (Fig. 38.3). The pairs are presented in random order to each assessor and preferably tested twice, reversing the presentation order on the second tasting session. Fairly large numbers (>30) of test subjects are required. If there are more than two samples to be tested, one may compare all possible pairs ( round robin ). Since the number of possible pairs grows rapidly with the number of different products this is only practical for sets of three to six products. By combining the information of all paired comparisons for all panellists one may determine a rank order of the products and determine significant differences. For example, in a paired comparison one compares three food products (A) the usual freeze-dried form, (B) a new freeze-dried product, (C) the new product, not freeze-dried. Each of the three pairs are tested twice by 13 panellists in two different presentation orders, A-B, B-A, A-C, C-A, B-C, C-B. The results are given in Table 38.3. 

As shown in Figure 2.25, it is more efficient to use a backing pump combined with one or two roots blowers (Fig. 2.27). The backing pump requires only 40 m3/h capacity, combined with a roots pump of 200 m3/h. This system evacuates the 1000 L also in 8 min down to 0.01 mbar, but below 0.1 mbar the system has a capacity of 200 m3/h or 2.2 10 3 g/s at 0.05 mbar. Such a pumping system is preferable for freeze drying compared with a large two-stage pump alone. 

Fouarge and Dewulf [3.45] reported about the freeze drying of poly (isohexylcyanocrylat) nanoparticles, which were loaded with dehydroemetine (DHE). The load of absorbed DHE was uniform and reproducible. The stability remained good during 24 months, and the acute toxicity of DHE was reduced by combination with nanoparticles, as was the radical concentration. 

Poulsen, M. P. Economy of combined freeze and air drying. International Institute of Refrigeration <1IR> Paper 314, (Conference Montreal 1991)... 

Microwave-assisted (0.1 or 0.2 Wg-1) convection drying was also applied to osmotically dehydrated blueberries, leading to dried berries that were comparable to freeze-dried ones in much shorter time (Venkatachalapathy and Raghavan, 1998). Frozen blueberries were also dried in a microwave and spouted bed combined dryer (MWSB) after a pretreatment using ethyl oleate and a NaOH dipping solution followed by sucrose osmotic treatment (Feng et al., 1999). Osmotic dehydration prevented the blueberries from... 

The starch fraction was washed initially with 0.02% NaOH, the extract being added to the protein solution (Figure 2). The starch was then slurried in distilled water, separated by sedimentation, and dried at 30°C. The combined protein extracts were adjusted to pH 4.5 with IN HC1 and the whey separated from the curd by centrifugation in the basket centrifuge (1100 x g). The protein curd was washed twice with water adjusted to pH 4.5, then resuspended at pH 7.0 using IN NaOH. The proteinate was freeze-dried. 

Preparation of Aqueous Extract of Cotton Dust. Cotton cardroom dust was collected from V-cell filters in a commercial textile mill. A typical extraction was carried out by manually kneading 50 g of dust with 500 ml of deionized water for 5 min at 25°c and removing the liquor by centrifugation. The process was repeated twice with 250 ml of deionized water each time. The combined supernatant was filtered through filter paper by gravity and the filtrate (of final pH 8.3 without addition of buffer) was freeze-dried to yield fraction 1 (f-1). The major portion of f-1... 

Preparation of Aqueous Extract of Cotton Bract. Field-dried cotton bract, 10 g, picked directly from plants in a field near Lake Providence, Louisiana, was ground with mortar and pestle, extracted twice with 100 ml of deionized water at pH 7 for 30 min each time at 250c with stirring. The extracts were combined and the solution was filtered the filtrate was freeze-dried. This bract extract (bAg) was also used to immunize rabbits. Additional bAg was further purified by treatment with 85% methanol in a similar manner as with cotton dust. 

The hydration state of risedronate sodium was monitored continuously in a fluidized bed dryer and correlated to data on the physical stability of tablets made from the monitored material [275]. The final granulation moisture was found to affect the solid-state form, which in turn dictated the drug s physical stability over time. The process of freeze-drying mannitol was monitored continuously with in-line Raman and at-line NIR spectroscopies [276]. The thin polymer solvent coatings, such as poly(vinyl acetate) with toluene, methanol, benzene, and combinations of the solvents, were monitored as they dried to generate concentra-tion/time profiles [277]. 

Donsi, G., Ferrari, G. and Di Matteo, P, Utilization of combined processes in freeze-drying of shrimps. Food Bioprod. Proc., 79 (2001) 152-159. 

In some cases, a combination of spray precipitation (see Sect. 22.5.6) and freeze-drying is recommended. For example, one can spray the polymer solution into a mortar, the bottom of which is covered with pieces of solid carbon dioxide the size of a hazel nut. The pieces are then ground more finely, the mortar placed in a desiccator and evacuated with an oil pump. The polymer solution can also be sprayed into a liquid cooled to low temperature, the liquid being immiscible with the solvent of the polymer, e.g., spraying an aqueous solution into cold ether. The polymer then precipitates in the form of a light flaky snow decantation of the ether is followed by evacuation as described above. 

In order to accelerate sample preparation, new extraction methodologies such as accelerated solvent extraction (ASE) and MAE, based on the use of elevated temperature and pressure to heat the mixture sample-solvent, have been recently developed and applied for PAH extraction from meat [695] and vegetables [696-698]. Garda Falcon et al. [699] used microwave treatment with hexane to accelerate PAH extraction from freeze-dried foods. The fat extracted in this way underwent microwave assisted saponification with ethanolic KOH. Hernandez-Borges et al. [700] combined microwave-assisted hydrolysis and extraction to isolate organic pollutants from mussels, while... 

Two of the more recent such approvals are that of Ovitrelle and Luveris. Ovitrelle is the trade name given by Serono to its recombinant hCG-based product. The producer is an engineered CHO cell line that has been co-transfected with the genes coding for both the hCG a- and P-subunits. Downstream processing entails a combination of several chromatographic and ultrafiltration steps and the final product is presented in freeze-dried form. Each vial of product contains 285 fig of active substance (hCG) and the product has been assigned a 2 year shelf-life. It is reconstituted with water for injections (WFI) immediately before use. 

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