The freezable water contents of samples obtained from previously chilled semimembranous muscle of middle-aged beef carcasses after a 24 h cooling period a room at in 5±1‡C were determined by differential scanning calorimetry (DSC) at −5, −10, −15, −20, −30, −40, −50 and −65‡C. This was accomplished by freezing the samples at the above-mentioned temperatures, followed by thawing to 35‡C, and measuring the melting peaks of freezable water. The areas of these peaks were determined by using the peak integration method programs through a computer linked to the DSC, and they were then used to determine the latent heat of melting (δHm) in kJ kg−1 at each freezing temperature. The resultant latent heat of melting per sample was divided by the latent heat for pure water to determine the amount of freezable water present in these samples. This amount of freezable water was divided by the total water content of the meat sample to determine the percentage of freezable water in the sample. The percentage of freezable water was subtracted from 100 to determine the percentage of bound water present in the sample.
Several drug substances or excipients are hygroscopic. The uptake or loss of water of such substances is generally difficult
to control during processing or storage of drug products. DSC instruments with sub-ambient temperature equipment allow the
determination of the amount of freezable water by measuring the corresponding melting enthalpy.
The determination of freezable water adds valuable information complementary to TG analysis for understanding the processing
and storage of raw materials and drug products. Several substances were tested as is, without treatment, after storage at
92% r.h. and after equilibration with water. The results of these experiments showed that it was possible to demonstrate defined
hydrate formation, to determine the upper level of binding of water in amorphous substances and to confirm reversible hydrate
formations demonstrated by temperature resolved X-ray diffraction.
Authors:Garry Kerch, Alexander Glonin, Janis Zicans, and Remo Merijs Meri
. During bread storage, moisture migrated from the crumb to the crust, which was associated with the firming of the crumb. It was found that freezablewater content and total water content in bread crumb decrease during staling more rapidly in the presence
Authors:D. Giron, Ch. Goldbronn, M. Mutz, S. Pfeffer, Ph. Piechon, and Ph. Schwab
Manufacturing processes may involve the presence of water in the crystallization of the drug substance or in manufacturing
or in the composition of the drug product through excipients. Dehydration steps may occur in drying, milling, mixing and tabletting
processes. Furthermore, drug substances and drug products are submitted to different temperatures and relative humidities,
due to various climatic conditions giving rise to unexpected hydration or dehydration aging phenomena. Therefore the manufacture
and the characterization of hydrates is part of the study of the physical properties of drug substances.
Several hydrates and even polymorphic forms thereof can be encountered. Upon dehydration crystal hydrates may retain more
or less their original crystal structure, they can lose crystallinity and give anamorphous phase, they can transform to crystalline
less hydrated forms or to crystalline anhydrous forms.
The proper understanding of the complex polyphasic systemhydrates–polymorphs–amorphous state needs several analytical methods.
The use of techniques such as DSC-TG, TG-MS, sorption-desorption isotherms, sub-ambient experiments, X-ray diffraction combined
with temperature or moisture changes as well as crystal structure and crystal modelling in addition to solubilities and dissolution
experiments make interpretation and quantitation easier as demonstrated with some typical examples.
Authors:Jiří Kučerík, Petra Bursáková, Alena Průšová, Lucie Grebíková, and Gabriele Ellen Schaumann
. Subsequently, the pans were hermetically sealed. DSC was performed using the TA Instruments Q200 equipped by a rapid cooling system (RCS) in order to study the melting process of ice formed by freezablewater. An empty hermetically sealed pan was used as
Authors:D. Champion, C. Loupiac, D. Russo, D. Simatos, and J. M. Zanotti
state diagram [ 12 ], is the temperature of the crossover between the ice melting and glass transition curves at . Actually, in the temperature range where is expected to occur, DSC curves of carbohydrate solutions containing freezablewater show a
The differences in bound water content of beef semimembranous muscle samples obtained from previously chilled (24 h at +4°C)
middle-aged beef carcasses were determined by the use of DSC. Initially, samples obtained from fresh, unprocessed meat were
frozen at −40, −50 or −65°C to determine their melting peaks for freezable water (free water) content with the use of DSC.
The samples were then subjected to an environment with an ambient temperature of −30, −35, −40 or −45°C, with no air circulation,
or with an air circulation speed of 2 m s−1, until a thermal core temperature of −18°C was attained; this was followed by thawing the samples until a thermal core temperature
of 0°C was reached. This process was followed by subjecting the samples to the ambient temperatures mentioned above, to accomplish
complete freezing and thawing of the samples, with DSC, and thereby determination of the freezable water contents, which were
then used to determine the peaks of melting. The calculated peak areas were divided by the latent heat of melting for pure
water, to determine the freezable water contents of the samples. The percentage freezable water content of each sample was
determined by dividing its freezable water content by its total water content; and the bound water content of each sample
was determined by subtracting the percentage free water content from the total. In view of the fact that the free water content
of a sample is completely in the frozen phase at temperatures of −40°C and below, the calculations of free and bound water
contents of the samples were based on the averages of values obtained at three different temperatures.
Authors:A. Yaghmur, A. Aserin, I. Tiunova, and N. Garti
The five-component system is quite unique since it allows formation of reverse micelles with hydrophilic ethoxylated alcohol in the presence of ethanol and it facilitates dilution by water/propylene glycol (1,2-propanediol, PG) aqueous phase, all the way from a water-in-oil (W/O) microemulsion via a bicontinuous phase to an oil-in-water (O/W) microemulsion.The surfactant/alcohol/PG can strongly bound water in the inner phase so that it freezes below –10°C and acts in part as bound water and in part as non-freezable water. Upon dilution to >30 mass% aqueous phase (water/PG at constant mass ratio of 1/1) the system becomes bicontinuous and the aqueous layers are composed again from bound water. Even after complete inversion to O/W microemulsions the water in the continuous phase is strongly interacting with the PG/surfactant and remains bound or non-freezable. Water/PG/ethanol have a strong effect on the head groups (freezing below -10°C) and also on the hydrophobic tails (recrystallizing and melting) at lower temperature when dilution exceeds 45 mass% water/PG (1/1).No free water was detected neither in the W/O microemulsion's inner droplet domains nor when the microemulsion was either bicontinuous or when it was inversed to O/W. Continuous phase of resulting O/W microemulsion apparently is based on water/PG at a mass ratio of 1/1.
Authors:X.-Z. Lan, Z.-C. Tan, Q. Shi, and Z.-H. Gao
A novel gelling method was studied to stabilize phase change material Na2HPO4 · 12H2O with amylose grafted sodium acrylate. Gelled Na2HPO4 · 12H2O shows stable heat storage performance prepared at optimized conditions: 2.7mass/mass% sodium acrylate, 0.4 mass/mass% amylose,
0.05–0.09 mass/mass% N, N′-methylenebisacrylamide, 0.05–0.09 mass/mass% K2S2O8 and Na2SO3 (mass ratio 1:1), at 50 °C. Na2HPO4 · 12H2O was dispersed in gel network as tiny crystals less than 0.1 mm. Melting points were in the range 35.4 ± 2 °C. Short-term
thermal cycling proves the effectiveness of the novel method for eliminating phase separation in the gelled salt. Adiabatic
calorimetric measurement of heat capacities shows two phase transitions, which correspond to melting of Na2HPO4 · 12H2O and freezable bond water in gel, respectively. Heat of fusion of pure Na2HPO4 · 12H2O was determined as 260.9 J g−1. Distribution of extra water is: free water:freezable water:nonfreezing water = 0:0.85:0.15.