Moisture Uptake Rate Research Articles

Spray‐freeze‐drying for protein powder preparation: Particle characterization and a case study with trypsinogen stability

This work investigates the use of spray freeze‐drying (SFD) to produce protein loaded particles suitable for epidermal delivery. In the first part of the study, the effects of formulation and process conditions on particle properties are examined. Aqueous solutions of trehalose produce SFD particles in the size range 20–80 μm, with a smooth, textured surface, but having high internal porosity. The latter was visualized using SEM and a novel particle embedding and sectioning technique. Use of an annealing step during the freeze‐drying cycle caused the particles to shrink, reducing hereby porosity and also the measured rate of moisture uptake into these amorphous particles. SFD pure mannitol was approximately 40% amorphous, but not hygroscopic. Incorporation of dextran 37,500 into a combined amorphous trehalose/mannitol formulation led to increased particle shrinkage and lower particle porosity on annealing. The model protein trypsinogen lost approximately 15% activity during SFD of solutions containing 50 mg/mL protein, but was only marginally aggregated (1.4%). It is suggested that trypsinogen forms an irreversible partially unfolded state or molten globule on SFD/rehydration. The pure protein was also partially inactivated without aggregation during atomization into air. Surprisingly, neither activity loss nor aggregation were detected on atomization of the protein solution into liquid nitrogen. Quench‐freezing of small droplets may reverse the partial unfolding of trypsinogen occurring on atomization into air. The origin of the trypsinogen inactivation during SFD must therefore be the subsequent freeze‐drying step of this multistep process. Isolated freeze drying of trypsinogen produces strong aggregation and equivalent inactivation. This result suggests that trypsinogen behaves differently during freeze drying from frozen droplets and from bulk solution in a vial. In the former case the protein forms an irreversible partially unfolded state, whereas in the latter case aggregates are formed. Trypsinogen inactivation during SFD could be completely prevented by the presence of trehalose in the formulation. Electron Spectroscopy for Chemical Analysis (ESCA) showed a high surface excess of the protein in the SFD particles, which was reduced on inclusion of Polysorbate 80, but not trehalose. Taken together, these results help to elucidate the complex destabilization behavior of trypsinogen during SFD. © 2002 Wiley‐Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:2122–2139, 2002

Physical chemical stability of warfarin sodium.

Crystalline warfarin sodium is an isopropanol clathrate containing 8.3% isopropyl alcohol (IPA) and 0.57% water upon receipt. The hygroscopicity and impact of moisture on IPA status as well as on the stability of the clathrate was studied at different relative humidities. The IPA loss and water uptake were simultaneous but they did not exchange at 1:1 molar ratio. At 58% relative humidity (RH) or below, the exchange process was insignificant. At 68% RH or above, the clathrate tended to lose IPA while absorbing water and reverting to the amorphous state. The rate of IPA loss and moisture uptake was a function of RH. The thermal stability of the crystalline warfarin sodium was also examined. Physical change occurred after isothermal storage for 24 hours at 80 degrees C and 11 hours at 120 degrees C. The rate of IPA loss was temperature dependent.

Effect of soil nitrogen, carbon and moisture on methane uptake by dry tropical forest soils

Methane uptake was measured for two consecutive years for four forest and one savanna sites in a seasonally dry tropical region of India. The soils were nutrient-poor and well drained. These sites differed in vegetational cover and physico-chemical features of the soil. There were significant differences in CH4 consumption rates during the two years (mean 0.43 and 0.49 mg m-2 h-1), and at different sites (mean 0.36 to 0.57 mg m-2 h-1). The mean uptake rate was higher (P < 0.05) in dry seasons than in the rainy season at all the sites. There was a significant season and site interaction, indicating that the effect of different seasons differed across the sites. There was a positive relation between soil moisture and CH4 uptake rates during summer (the driest period) and a negative relation during the rest of the year. The results suggested that seasonally dry tropical forests are a strong sink for CH4, and C and N status of soils regulates the strength of the sink in the long term.

Additives to biological substances. III. The moisture content and moisture uptake of commonly used carrier agents undergoing processing conditions similar to those used in the preparation of international biological standards

Aqueous solutions of the carbohydrates alpha alpha'-trehalose, mannitol and lactose, human serum and human albumin were freeze-dried in ampoules and part of each batch was further desiccated over phosphorus pentoxide in a manner similar to that used to prepare international biological standards and related materials. The residual moisture present in the preparations and their uptake of moisture was then measured by Karl Fischer titration. In ampoules open to atmosphere [22 degrees C, 34% relative humidity (RH)] freeze-dried serum, albumin, lactose and alpha alpha'-trehalose all exhibited hygroscopic properties, their moisture contents rising over a period of 24 h, to 10%, 8%, 8% and 7%, respectively. Mannitol when dried to low moisture levels did not exhibit hygroscopic properties, but the residual moisture in different freeze-dried batches was very variable, possibly as a result of that solid's sponge-like and/or crystalline microstructure. When exposed to the same conditions, dried materials in ampoules fitted with polythene capillary leak plugs (used routinely at this Institute during the preparation of Biological Standards) exhibited a considerably reduced rate of moisture uptake. The effect of secondary vacuum drying over phosphorus pentoxide on the moisture content of these preparations is also reported.

Blowholing in PTH Solder Fillets

This is the third paper in the series of eight, studying voids and blowholes in PTH printed circuit boards. In the previous papers the industrial significance of this problem has been established and moisture identified as the primary cause of the gassing. Now, particular attention is focused on the understanding of the mechanisms and kinetics of moisture uptake in the FR‐4 laminate. From the authors' data the rate of moisture uptake and the rate of drying of laminate can be predicted as a function of temperature and relative humidity.

Effect of Moisture on the Physical and Chemical Stability of Granulations and Tablets of the Angiotensin Converting Enzyme Inhibitor, Enalapril Maleate

Granulations and tablets of enalapril maleate in a lactose matrix were stored in open petri dishes at a range of relative humidities and respective moisture uptakes measured, Extrapolation of the moisture uptake rates measured at the exaggerated humidities yielded a critical humidity, i.e. humidity where the moisture uptake rate is zero and, therefore, least detrimental to the product.Enalapril maleate was reasonably stable at the storage conditions. The hardness of the tablets decreased at all humidities except when stored with silica-gel. The disintegration times were unaffected except at very high humidities. The dissolution profiles of the tablets remained unchanged.

Weighing Technique for Determining Bacterial Dry Mass Based on Rate of Moisture Uptake

Weights were recorded at 30-s intervals timed from initial exposure of dried cells to atmosphere. Linear regressions of data over 3 min gave moisture-free dry mass estimates.

Multisalt Preservatives and the Treated Wood/Water Relationship

SYNOPSIS Multisalt preservative-treated and untreated wood blocks were exposed to moist soil to determine the hygroscopicity and hence the fixation of the preservatives. The effects of companion cations and anions of the formulation salts on the hygroscopicity of the preservatives in the treated wood were studied. Other factors affecting the hydrophylic character of wood were also studied. It was found that the rate of moisture uptake from wet soil, with moisture contents above the critical moisture content2 for wood could be reduced substantially by treatment of the blocks with specially selected formulations of copper-chrome-arsenate (CCA) applied by means of special treatments. It is proposed that the retardation in moisture uptake is caused by a layer of insoluble salt on the cell walls of the treated wood.

Selected physical properties of glucose syrup fractions obtained by reverse osmosis

SummaryA series of glucose syrups were prepared by the reverse osmosis fractionation of a commercial 43 D.E. glucose syrup and the carbohydrate composition of each determined by a paper chromatography technique. These fractions were dried to zero moisture content and the hygroscopicity of each determined.The method of drying of the fractions was found to influence the rate of moisture uptake but not the final moisture content in each sample and the presence of inorganic salts in a sample caused an elevation of rate of absorption of moisture and also final moisture content.An increase in time to reach an equilibrium moisture content was noted as dextrose equivalent increased.Five commercial glucose syrups were compared with glucose syrup fractions of similar dextrose equivalent, and found to be more hygroscopic in all but one sample.Samples of dextrose and maltose were also studied and were found to have abnormal moisture absorption curves if not dried correctly.

NITROGEN EXTRACTABILITY AND MOISTURE ADSORPTION CHARACTERISTICS OF SUNFLOWER SEED PRODUCTS

Diffusion‐extracted (DE) sunflower meal and protein isolate were compared with untreated samples for their nitrogen extractability and moisture adsorption. Nitrogen extractability values of 90% were found at pH 7 or above in the untreated meal, whereas a maximum solubility of only 70% was achieved at pH 9.0 in the DE meal prepared at 60°C. DE meal prepared at 80°C had low solubility over a pH range of 1–11 which indicated substantial denaturation of the sunflower proteins. The untreated isolate showed a sharp minimum solubility point in contrast to the law solubility of the DE isolate over a pH range of 3–7. Moisture adsorption values for the samples held at 5, 20 and 30°C indicated little difference in moisture contents at relative humidities of 11–55%. At higher levels, however, the untreated meal adsorbed more moisture than the DE meal. A reverse trend was noticed for the isolates as the moisture content of the DE isolate was higher than the untreated sample. The rate of moisture uptake by sunflower kernels was slower than that observed with rapeseed or soybean meats and lower total moisture contents were observed after a 4 hr soaking period.

Moisture uptake by surface-applied superphosphate and movement of the phosphate and sulphate into the soil

Capillary uptake of soil water appeared to be more important than hygroscopic uptake of moisture by monocalcium phosphate in the wetting of surface-applied superphosphate particles. For hygroscopic uptake of water a relative humidity greater than 89% was found necessary, but particles on the soil surface are exposed to atmospheric humidity which is frequently well below 89%. This may prevent uptake of moisture from soils of low moisture content. The rate of moisture uptake from the vapour phase by superphosphate increased directly with increase in relative humidity above 89%. The rate of uptake was also influenced by temperature and surface area of the particle. Capillary uptake of soil water was influenced by soil moisture content, density of the particles, and the degree of contact between soil and particle. Movement of phosphate from the moist particle into the soil was rapid but the rate was affected by soil moisture, temperature, contact with the soil, and certain physical properties of the particle. In contrast to phosphate, movement of sulphate into the soil was slow because of the low solubility of calcium sulphate, and was greatly influenced by particle size. Leaching by rainfall may be an important factor in the movement of sulphate from coarse particles.

Moisture Levels in Frozen Poultry as Related to Thawing Losses, Cooking Losses, and Palatability: 2. Turkey Fryer-Roasters

QUESTIONS concerning moisture absorption by poultry carcasses in washing and chilling have been much discussed by processors and regulatory officials in recent years. Standards which set limits on the retention of water have now been established by the United States Department of Agriculture, but these are subject to continuing review as additional data become available through research and the experiences of industry.Factors affecting the rate of moisture up-take by chicken broilers and the fate of the water absorbed have been studied by a number of investigators as reviewed by Kotula et al. (1960) and Froning et al. (1960). Less information is available relative to the turkey. The work of Spencer et al. (1956) is the only extensive study reported, and this does not include the effect of moisture level on palatability.The purpose of the investigation reported below was to expand our information on moisture absorption and retention by …