Quench Cooling Research Articles

Drug-Phospholipid Co-Amorphous Formulations: The Role of Preparation Methods and Phospholipid Selection.

Background/Objectives: This study aims to broaden the knowledge on co-amorphous phospholipid systems (CAPSs) by exploring the formation of CAPSs with a broader range of poorly water-soluble drugs, celecoxib (CCX), furosemide (FUR), nilotinib (NIL), and ritonavir (RIT), combined with amphiphilic phospholipids (PLs), including soybean phosphatidylcholine (SPC), hydrogenated phosphatidylcholine (HPC), and mono-acyl phosphatidylcholine (MAPC). Methods: The CAPSs were initially prepared at equimolar drug-to-phospholipid (PL) ratios by mechano-chemical activation-based, melt-based, and solvent-based preparation methods, i.e., ball milling (BM), quench cooling (QC), and solvent evaporation (SE), respectively. The solid state of the product was characterized by X-ray powder diffraction (XRPD), polarized light microscopy (PLM), and differential scanning calorimetry (DSC). The long-term physical stability of the CAPSs was investigated at room temperature under dry conditions (0% RH) and at 75% RH. The dissolution behavior of the CCX CAPS and RIT CAPS was studied. Results: Our findings indicate that SE consistently prepared CAPSs for CCX-PLs, FUR-PLs, and RIT-PLs, whereas the QC method could only form CAPSs for RIT-PLs, CCX-SPC, and CCX-MAPC. In contrast, the BM method failed to produce CAPSs, but all drugs alone could be fully amorphized. While the stability of each drug varied depending on the PLs used, the SE CAPS consistently demonstrated the highest stability by a significant margin. Initially, a 1:1 molar ratio was used for screening all systems, though the optimal molar ratio for drug stability remained uncertain. To address this, various molar ratios were investigated to determine the ratio yielding the highest amorphous drug stability. Our results indicate that all systems remained physically stable at a 1.5:1 ratio and with excess of PL. Furthermore, the CAPS formed by the SE significantly improves the dissolution behavior of CCX and RIT, whereas the PLs provide a slight precipitation inhibition for supersaturated CCX and RIT. Conclusions: These findings support the use of a 1:1 molar ratio in screening processes and suggest that CAPSs can be effectively prepared with relatively high drug loads compared to traditional drug-polymer systems. Furthermore, the study highlights the critical role of drug selection, the preparation method, and the PL type in developing stable and effective CAPSs.

Different or the same? exploring the physicochemical properties and molecular mobility of celecoxib amorphous forms

The influence of different preparation methods on the physicochemical properties of amorphous solid forms have gained considerable attention, especially with recent publications on pharmaceutical polyamorphism. In the present study, we have investigated the possible occurrence of polyamorphism in the drug celecoxib (CEL) by investigating the thermal behavior, morphology, structure, molecular mobility and physical stability of amorphous CEL obtained by quench-cooling (QC), ball milling (BM) and spray drying (SD). Similar glass transition temperatures but different recrystallization behaviors were observed for CEL-QC, CEL-BM and CEL-SD using modulated differential scanning calorimetry analysis. A correlation between the different recrystallization behaviors of the three CEL amorphous forms and the respective distinct powder morphologies, was also found. Molecular dynamics simulations however, reveal that CEL presents similar molecular conformational distributions when subjected to QC and SD. Moreover, the obtained molecular conformational distributions of CEL are different from the ones found in its crystal structure and also from the ones found in the lowest-energy structure obtained by quantum mechanical calculations. The type and strength of CEL hydrogen bond interactions found in CEL-QC and CEL-SD systems are almost identical, though different from the ones presented in the crystal structure. Pair distribution function analyses and isothermal microcalorimetry show similar local structures and structural relaxation times, respectively, for CEL-QC, CEL-BM and CEL-SD. The present work shows that not only similar physicochemical properties (glass transition temperature, and structural relaxation time), but also similar molecular conformational distributions were observed for all prepared CEL amorphous systems. Hence, despite their different recrystallization behaviors, the three amorphous forms of CEL did not show any signs of polyamorphism.

Visualization of Ice Crystal Behavior in Mouse Oocytes During High-Speed Quench Cooling and Ice Inhibition by Antifreezing Hydrogels.

Oocyte vitrification has become a widely adopted method in clinical practice. However, the solidification behavior and its impact on oocytes during the ultrarapid cooling process remain poorly understood. In this study, we established a system and methodology to observe crystallization behavior in oocytes during quench cooling and warming. Subsequently, the threshold concentration of cryoprotective agents (CPAs) required for oocyte vitrification was determined through a visualization method. The results demonstrated that the ice front could not be observed in the image sequence when using 16.5% DMSO +16.5% EG during high-speed quench cooling (2821.58°C/min). Finally, oocytes were encapsulated with an antifreezing hydrogel (7.5% EG +7.5% DMSO +0.5% alginate) and subjected to high-speed quench cooling. No ice crystals appeared in the antifreezing hydrogel-encapsulated oocytes at a low concentration of osmotic CPA (2.4 M). This research opens up new possibilities for oocyte vitrification with a reduced concentration of CPA.

Unveiling polyamorphism and polyamorphic interconversions in pharmaceuticals: the peculiar case of hydrochlorothiazide.

Polyamorphism has been a controversial and highly debated solid-state phenomenon in both material and pharmaceutical communities. Although some evidence of this fascinating phenomenon has been reported for several inorganic systems, and more recently also for a few organic compounds, the occurrence of polyamorphism is poorly understood and the molecular-level organization of polyamorphic forms is still unknown. Here we have investigated the occurrence of polyamorphism and polyamorphic interconversions in hydrochlorothiazide (HCT), using both experimental and computational methods. Three distinct HCT polyamorphs, presenting distinct physical and thermal stabilities as well as distinct relaxation properties, were systematically prepared using spray-drying (SD), quench-cooling (QC) and ball milling (BM) methods. HCT polyamorph II (obtained by QC) was found to be more physically stable than polyamorphs I and III (obtained by SD and BM, respectively). Furthermore, polyamorphs I and III could be converted into polyamorph II after QC, while polyamorph II did not convert to any other polyamorph after SD or BM. Molecular dynamics simulations show that HCT dihedral angle distributions are significantly different for polyamorphs I and II, which is postulated as a possible explanation for their different physicochemical properties.

Thermal destruction of PFAS during full‐scale reactivation of PFAS‐laden granular activated carbon

AbstractGranular activated carbon (GAC) is the most widely used and well‐established treatment technology for the removal of per and polyfluoroalkyl substances (PFAS) contaminants from drinking water and wastewater. After the GAC has reached the end of its useful service life and become “spent carbon,” it is common practice in industry to thermally treat it in a process known as reactivation. The reactivation process volatilizes and destroys adsorbed contaminants at high temperatures and restores the GAC to a near‐virgin state so that it can be reused. Since the advent of PFAS regulatory actions, questions have arisen about the effectiveness of the reactivation process for the destruction of PFAS given their high thermal stability and the lack of documented study on this new topic. In light of this, a thorough program of testing was carried out at a full‐scale GAC reactivation facility during the reactivation of a load of GAC known to contain adsorbed PFAS. The facility employs a multihearth Herreschoff furnace and a downstream abatement train that includes a thermal oxidizer, spray quench cooler, dry injection scrubber, and baghouse. All inputs and outputs of the system were tested for targeted PFAS compounds and fluoride (total and as hydrogen fluoride). Under typical operating conditions, the system demonstrated both full removal of PFAS compounds from GAC and >99.99% destruction of PFAS compounds through the furnace and abatement system. Additional key findings include: (1) a large portion of the PFAS destruction occurs in the furnace, before the thermal oxidizer; (2) the fluoride mass balance was close to 61.4%; and (3) emission levels were significantly lower than available public data for PFAS manufacturing emissions.

Raloxifene HCl – quercetin co-amorphous system: preparation, characterization, and investigation of its behavior in phosphate buffer

Purpose Raloxifene HCl (RLX), a practically insoluble drug used in the treatment of osteoporosis in post-menopausal women; was modified at its molecular level to enhance its solubility using co-amorphous technology. Methods In this study, RLX was co-amorphized with Quercetin (QCT; a nutraceutical flavonoid) using solvent evaporation (SE), quench cooling (QC), and ball milling (BM) techniques. The prepared co-amorphous systems (CAMs) were characterized using XRD, DSC, and FT-IR. For the simultaneous analysis of RLX and QCT, an RP-HPLC method was developed to quantify the drugs in the prepared systems. Behavior in aqueous media was investigated by studying amorphous and equilibrium solubility, and drug release of RLX using USP phosphate buffer pH 6.8. Results Solvent evaporation (RQ(SE)) was able to produce a homogeneous system, where quench cooling showed thermal degradation of the drug, and ball milling was not able to amorphize the blend. From the DSC results, it was found that RQ(SE) was able to increase the glass transition temperature by 40 °C. It was observed that the solubility of RLX reduced, as RLX formed phosphate aggregates in the buffer media which further formed complexes with QCT; this was determined by investigating the residual particles from solubility studies. Though the solubility was reduced, drug release of RQ(SE) exhibited improvement in concentration by 2.3 times. Conclusions RQ(SE) formed a stable CAM; though the solubility of RLX in presence of QCT reduced, from the drug release study, it was apparent that the co-amorphous technique improved the concentration of RLX.

Rewetting Delay Time During Jet Impingement Quench Cooling of Hot Curved Surfaces

Rewetting a hot dry surface is the establishment of wet contact between the hot surface and a liquid at a lower temperature. Rewetting occurs after destabilizing a vapor film that exists between the hot surface and the liquid. Situations involving rewetting heat transfer are encountered in a number of postulated accidents in Canada Deuterium Uranium (CANDU) reactors, such as rewetting of a hot dry calandria tube in a critical break loss-of-coolant accident (LOCA). It is also encountered in improving metals’ mechanical properties in metallurgical industries. One of the important parameters in rewetting cooling is the rewetting delay time, which is the time interval from starting to cool the surface by the liquid to the establishment of the wet contact. Determining the rewetting delay time is very important for limiting the extent of core damage during the early stages of reactor severe accidents and is essential for predicting the period after which the coolant effectively cools an overheated core. If the rewetting delay time is relatively long, an escalation in the calandria surface temperature can occur, and if the temperature was not reduced by the establishment of the wet contact, this may lead to failure of the fuel channel. Although there is increasing interest in literature in estimating the rewetting delay time of hot flat surfaces, very limited studies exist on rewetting of curved surfaces, such as tubes. In this study, experimental tests were carried out to measure the rewetting delay time at the stagnation point of hot horizontal tubes cooled by a vertical rectangular water jet. The tubes were heated to initial temperatures between 400°C and 740°C, then rapidly cooled to the jet temperature. The two-phase flow behavior was visualized using high-speed imaging, and the moment at which the vapor film collapses was captured. In addition to studying the effect of initial surface temperature on the delay time, effects of water subcooling in the range 15°C to 80°C and jet velocity in the range 0.17 to 1.43 m/s were studied and a correlation for the delay time was developed and validated. The delay time was found to strongly increase by increasing initial surface temperature and surface curvature and by decreasing water subcooling and jet velocity. The effects of solid material and tube wall thickness were also studied.

Co-formability, solubility enhancement and stability of olanzapine co-amorphous systems produced with different co-formers

Introduction Strategies to address the problem of poorly water-soluble drugs encompass the conversion of a crystalline drug into an amorphous form to promote its apparent solubility and dissolution. Co-amorphous systems (CAMs) incorporate low molecular mass molecules (co-formers), which are mixed with the drug to form one single phase [1,2]. The aim of this study is to understand the capability of different co-formers (amino, carboxylic and sulphonic acids), in the production of CAMs with olanzapine by ball milling, solvent evaporation and quench cooling. Materials and methods Mixtures (2 g) of olanzapine (OLZ) and each co-former [l-aspartate (ASP); l-tryptophan (TRY); l-arginine (ARG); l-proline (PRO); citric acid (CIT); tartaric acid (TAR); oxalic acid (OXA); saccharine (SAC); potassium acessulfame (ACE); cyclamic acid (CYC)] in 1:1 molar ratios were submitted to ball milling (BM), solvent evaporation (SE) and quench cooling (QC). CAMs were evaluated for the OLZ solubility increase, co-formability and storage stability over time, by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and Fourier-transform infra-red spectroscopy (FTIR). Results The BM technique presented the most promising results followed by QC and SE (Table 1), since more CAMs were produced. All the sulphonic acids (SAC, CYC and ACE) formed CAMs regardless of the technique used, presenting complete amorphization probably due to their higher ability to produce intermolecular interactions, like hydrogen-bonding, thus increasing the stability of CAMs (more than 8 weeks at 25 °C/11 and 53% RH). Conversely, amino acids were the least efficient in producing CAMs. Crystalline OLZ presented low solubility (40.1 mg/L) in water and a general increase in the solubility of the CAMs was observed. Carboxylic acids (TAR, CIT, OXA) achieved the biggest increase (up to 269 times, BM with TART) followed by sulphonic acids (up to 199 times, SE with SAC), unveiling the possibility of improved dissolution profiles and bioavailability. Discussion and conclusions: The study has shown the possibility of converting a crystalline drug into an amorphous entity, particularly when in presence of co-formers which stabilise the amorphous structures formed. In fact, with sulphonic acids, both SE and BM, achieved complete amorphization and successfully stabilised the CAMs obtained. Due to the noteworthy increase in solubility, resulting from co-amorphization, this technique is considered to be adequate to process active compounds with poor water solubility, such as OLZ. Table 1. Comparison of the of co-amorphization ability using different techniques and co-formers. Mixtures QC SE BM OLZ:PRO Yesa No No OLZ:ARG No No No OLZ:TRY No No Yesa OLZ:SER No No No OLZ:ASP No No Yesa OLZ:CIT Yesa No Yesb OLZ:TAR Yesa No Yesb OLZ:OXA Yesa No No OLZ:SAC Yesb Yesb Yesb OLZ:CYC No Yesb Yesb OLZ:ACE Yesb Yesb Yesb aIncomplete amorphization; bcomplete amorphization.

Prediction and Experimental of Yield Strengths of As-Quenched 7050 Aluminum Alloy Thick Plates after Continuous Quench Cooling

The aim of this study was to predict the yield strength of as-quenched aluminum alloys according to their continuous quench cooling path. Our model was established within the framework of quench factor analysis (QFA) by representing a quenching curve as a series of consecutive isothermal transformation events and adding the yield strength increments after each isothermal step to predict the yield strength after continuous quench cooling. For simplification; it was considered that the effective hardeners during quenching were the nanosized solute clusters formed at low temperatures, whereas the other coarse precipitates were neglected. In addition, quenching tests were conducted on aluminum plates with different thicknesses. The predictions were compared with the experimental measurements, and the results showed that the predictions fit the measurements well for the 40- and 80-mm-thick plates but overestimated the as-quenched yield strength at the mid-thickness of the 115-mm-thick plates.

Could the small molecules such as amino acids improve aqueous solubility and stabilize amorphous systems containing Griseofulvin?

Griseofulvin (GSF) is an antifungal drug that has low aqueous solubility and low oral bioavailability. Amorphous systems are capable to promote rapid drug dissolution, usually affording concentrations above drug solubility in the gastrointestinal tract (supersaturation) in order to promote better absorption. Thus, the aim of this work was to evaluate the ability of amino acids, as hydrophilic carriers, to improve drug kinetic solubilization and to stabilize GSF supersaturated solutions, as well as to stabilize GSF amorphous systems at solid-state. The effect of 5 amino acids on GSF precipitation behavior was investigated by solvent shift method. Amorphous systems were developed by ball milling (GSF + amino acid 1:1 M ratio) and Quench Cooling (to obtain GSF QC) techniques. The samples were characterized by solid-state techniques, submitted to in vitro kinetic solubility studies and evaluated under stability tests. Aspartic acid, methionine, valine and tryptophan demonstrated similar anti-precipitant abilities in phosphate buffer pH 6.5. However, in FaSSIF biorelevant medium, tryptophan was only one able to slow down the drug precipitation. The characterization of milled samples showed that an amorphous system was obtained just using the combination of the drug with tryptophan (GSF-TRYP BM). At the higher dose tested (0.850 mmol L−1) during in vitro kinetic solubility studies, this amorphous system increased the AUC in FaSSGF (88.6%) and FaSSIF (58.2%) media when compared to GSF QC. Thus, the ability of this amino acid to inhibit GSF precipitation appears to be dependent on its concentration in solution and could be optimized. During the stability study, TRYP inhibited GSF recrystallization in the solid-state for a period of 12 months, whereas GSF QC recrystallized in 1 week.

Quench Cooling Performance–Hardness Correlation for AISI 1045 and 1090 Steels

Abstract Heat transfer and microstructure evolution during quenching of AISI 1045 and 1090 steels in vegetable oils was investigated. To simulate the industrial quench heat treatment, reference probes made of medium and high carbon steels were quenched, and heat flux transients were estimated by taking into account the phase transformation. The cooling curves obtained with reference probes made from AISI 1045 and AISI 1090 steels showed kinks indicating enthalpy change accompanied with phase transformations during continuous cooling. This was reflected in the estimated heat flux curves. The section thickness effect on heat flux transients was examined by using probes of diameters 25 mm and 50 mm. The cooling rates measured at various locations across the section diameter of reference probes were related to the hardness using the quench factor technique. The heat transfer characteristics of the quench media, the evolved microstructure, and the resulting hardness were in complete agreement.

Influences of Quench Cooling Rate on Microstructure and Corrosion Resistance of Al-Cu-Mg Alloy Based on the End-Quenching Test

To investigate the effects of the quench cooling rate on corrosion resistance of Al-Cu-Mg alloy, an end-quenching test was conducted and the microstructures at different cooling rates were observed by SEM and TEM. Additionally, the corrosion resistance was characterized by an intergranular corrosion test and electrochemical test. Moreover, the finite element method was applied to simulate the end quenching process. The results indicate that the actual end quenching process can be approximated as one-dimensional heat transfer, and the cooling rate varies at different cooling distances. By affecting the microstructures, decreasing the cooling rate leads to a decline in the corrosion properties. Low cooling rates coarsen the constituent particles and grain boundary particles, resulting in a wide precipitation-free zone and an increase in the intensity of corrosion reactions. A high cooling rate concentrates on the intragranular precipitant, which can reduce the pitting depth and represents a conversion from localized corrosion to general corrosion.

Interdependence of particle properties and bulk powder behavior of indomethacin in quench-cooled molten two-phase solid dispersions

Solid dispersions (SDs) hold a proven potential in formulating poorly water-soluble drugs. The present paper investigates the interfacial phenomena associated with the bulk powder flow, water sorption, wetting and dissolution of the SDs prepared by a modified melt and quench-cooling (QC) method. Poorly water-soluble indomethacin (IND) was QC molten with solubilizing graft copolymer (Soluplus®) or polyol sugar alcohol (xylitol, XYL). The interfacial interactions of SDs with air/water were found to be reliant on the type (amorphous/crystalline) and amount of the carrier material used. The final SDs were composed of fused agglomerates (SOL) or large jagged particles (XYL) with good wetting and powder flow properties. The initial dissolution of IND was accelerated by both carrier materials studied. The QC molten SDs with amorphous Soluplus® significantly improved the dissolution rate of IND at pH 6.8 (79.9 ± 0.2% at 30 min) compared to that of pure crystalline drug. The substantial improvement in the dissolution rate of IND was in connection with the amorphous state of the drug being stabilized by Soluplus® in the QC molten SDs. However, it is evident that a strong H-bond formation between the components in some regions of the QC molten SDs can limit the dissolution of IND. The QC molten two-phase SDs with a polyol carrier (XYL) showed rapid and continuous drug release without reaching a plateau.

Extractive Sampling of Gas and Particulates from the Reactor Core of an Entrained Flow Biomass Gasifier

With the purpose of demonstrating a process for pressurized entrained flow gasification for pulverized biomass, the aim with this work was to characterize the conditions inside the gasifier. To gain a broader understanding, it was important to extract both gases and particulate matter from the hot reaction zone. The objectives were, therefore, to (1) develop a sampling system capable of extracting both gas and particulates from the gasifier, (2) study the production of particulate matter as well as its composition and size distribution as a function of different operating conditions, and (3) extract time-resolved data for the syngas species (CO, CO2, and CH4) in order to study the compositional variance. The results indicated that the syngas heating value was lower at the sampling position in the gasifier compared to the heating value measured downstream of the quench cooler. The difference was most probably an effect of ongoing gasification of carboneous solids downstream of the sampling position in the ...

A gas phase method for the generation of aqueous submicron suspensions of poorly water soluble organic substances

This work presents a novel process for the production of vapor-borne submicron organic particles and their transfer into an aqueous environment. A mixture of water and the organic substance is totally evaporated in a micro-structured evaporator. In a second step, the hot vapor mixture is rapidly cooled down inside a quench cooler so that the organic component gets into a supersaturated state and fine particles are formed due to homogenous nucleation. The rapid cooling is realized by the injection of liquid water into the hot vapor atmosphere. The liquid water evaporates and thereby cools down the vapor mixture. Water as one component of the vapor mixture remains in the vapor phase and acts as a carrier for the generated organic particles. The generation of the aqueous suspension is realized by the total condensation of the water vapor atmosphere directly after the quench cooler. The condenser is continuously supplied with surfactant solution. This prevents agglomeration as soon as the particles get transferred from the vapor into the liquid environment. The process has been realized successfully in a lab-scale plant. First results with Tocopheryl acetate and Myristyl myristate as model substances are presented in this work.

Effect of Rapid Compression on the Crystallization Behaviour of Polyethylene

The crystallization behaviour of PE samples with different molecular weight was investigated through two different processes, concerning rapid compression (RC) and quench cooling (QC). The scanning electron micrographs, wide angle X-ray diffraction and Raman results showed that all the recovered samples were composed of spherulites. For the QC process, the effect of molecular weight on the spherulites morphologies was slight, but for the RC process, with increased molecular weight (MW), the growth rate as well as the final average diameter of the spherulites decreased remarkably. Additionally, for samples with the same MW, the mass fraction of the rigid amorphous phase of RC samples was lower. Furthermore, the crystallinity distributions in the longitudinal and latitude directions of the RC samples were both more uniform than those of the QC samples, implying that in the RC process, the pressure distribution was quite uniform and there was no pressure decay.

Facing the Sulfuric Acid Aerosol Problem in Flue Gas Cleaning: Pilot Plant Experiments and Simulation

Experimental and simulation results of sulfuric acid aerosol formation during absorption of sulfuric trioxide in a wet flue gas scrubber (quench cooler) are presented. The complete characterization of the volatile aerosol with respect to number concentration and droplet size distribution is only possible by combining experimental and theoretical methods. Both experiments performed in a pilot plant and simulation results, reveal high number concentrations. A simulation tool predicts the formation of very small droplets that remain even submicron after coagulation in typical residence times of scrubbing systems and thus are difficult to precipitate. Copyright 2013 American Association for Aerosol Research

Numerical modeling of counter-current condensation in a Black Liquor Gasification plant

Pressurized Entrained flow High Temperature Black Liquor Gasification is a novel technique to recover the inorganic chemicals and available energy in black liquor originating from kraft pulping. The gasifier has a direct quench that quickly cools the raw syngas when it leaves the hot reactor by spraying the gas with a water solution. As a result, the raw syngas becomes saturated with steam. Typically the gasifier operates at 30 bar which corresponds to a dew point of about 235 °C and a steam concentration in the saturated syngas that is about 3 times higher than the total concentration of the other species in the syngas. After the quench cooler the syngas is passed through a counter-current condenser where the raw syngas is cooled and most of the steam is condensed. The condenser consists of several vertical tubes where reflux condensation occurs inside the tubes due to water cooling of the tubes on the shell-side. A large part of the condensation takes place inside the tubes on the wall and results in a counterflow of water driven by gravity through the counter current condenser. In this study a computational fluid dynamics model is developed for the two-phase fluid flow on the tube-side of the condenser and for the single phase flow of the shell-side. The two-phase flow was treated using an Euler–Euler formulation with closure correlations for heat flux, condensation rate and pressure drop inside the tubes. The single-phase model for the shell side uses closure correlations for the heat flux and pressure drop. Predictions of the model are compared with results from experimental measurements in a condenser used in a 3 MW Black Liquor Gasification development plant. The results are in good agreement with the limited experimental data that has been collected in the experimental gasifier. However, more validation data is necessary before a definite conclusion can be drawn about the predictive capability of the code.

Physicochemical Properties of Amorphous Roxithromycin Prepared by Quench Cooling of the Melt or Desolvation of a Chloroform Solvate

Roxithromycin is a poorly soluble antibacterial drug. The aim of this study was to prepare and characterize an amorphous form of roxithromycin. The amorphous form was prepared by desolvation of its chloroform solvate, and by quench cooling a melt of the crystalline monohydrated solid. The X-ray powder diffraction pattern of the desolvated chloroform solvate was indistinguishable from that of the glass prepared by melting, which indicated that it was amorphous. The roxithromycin glass was determined to be a fragile glass, but due to its high Kauzmann temperature (approximately 8°C), it should remain fairly stable upon refrigeration or even at room temperature. It was also determined that this glass remains stable in the presence of moisture with no indication of crystallization.

Influence of Water Quench Cooling on Degassing and Aroma Stability of Roasted Coffee

Coffee roasting experiments with air cooling versus water quench cooling were carried out on laboratory scale with a fluidized-bed hot air roasting system (200 g batch size) and on production scale with a rotating bowl roaster (320 kg batch size). Two series of coffees with different water contents resulted, which were stored at 25 degrees C under normal atmospheric conditions. Carbon dioxide desorption was followed and stability of selected aroma compounds was tested with headspace solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and stable isotope labeled compounds as internal standards. Degassing is faster in water-quenched coffees with higher moisture content, but pore size distribution in the different coffee samples did not correlate with degassing behavior. Bean firmness, which increases with increasing moisture content, might have an influence on degassing. Air- and water-quenched coffees exhibit similar stability of most aroma compounds despite different degassing behavior. However, evolution of dimethyl trisulfide was different in coffees with increased water content. This suggests higher thiol oxidation rates, a factor that is cited to be related to a faster loss of freshness attributes.