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The crystal growth of curcumin in pure 2-propanol containing two structurally related impurities, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), has been investigated by seeded isothermal desupersaturation experiments at 283, 293 and 308 K.

In many living organisms, biomolecules interact favorably with various surfaces of calcium carbonate. In this work, we have considered the interactions of aspartate (Asp) derivatives, as models of complex biomolecules, with calcite. Using kinetic growth experiments, we have investigated the inhibition of calcite growth by Asp, Asp2 and Asp3.This entailed the determination of a step-pinning growth regime as well as the evaluation of the adsorption constants and binding free energies for the three species to calcite crystals. These latter values are compared to free energy profiles obtained from fully atomistic molecular dynamics simulations. When using a flat (104) calcite surface in the models, the measured trend of binding energies is poorly reproduced. However, a more realistic model comprised of a surface with an island containing edges and corners, yields binding energies that compare very well with experiments. Surprisingly, we find that most binding modes involve the positively charged, ammonium group. Moreover, while attachment of the negatively charged carboxylate groups is also frequently observed, it is always balanced by the aqueous solvation of an equal or greater number of carboxylates. These effects are observed on all calcite features including edges and corners, the latter being associated with dominant affinities to Asp derivatives. As these features are also precisely the active sites for crystal growth, the experimental and theoretical results point strongly to a growth inhibition mechanism whereby these sites become blocked, preventing further attachment of dissolved ions and halting further growth.

In many living organisms, biomolecules interact favorably with various surfaces of calcium carbonate. In this work, we considered the interactions of aspartate (Asp) derivatives, as models of complex biomolecules, with calcite. Using kinetic growth experiments, we investigated the inhibition of calcite growth by Asp, Asp2, and Asp3.This entailed the determination of a step-pinning growth regime as well as the evaluation of the adsorption constants and binding free energies for the three species to calcite crystals. These latter values are compared to free energy profiles obtained from fully atomistic molecular dynamics simulations. When a flat (104) calcite surface is used in the models, the measured trend of binding energies is poorly reproduced. However, a more realistic model comprised of a surface with an island containing edges and corners yields binding energies that compare very well with experiments. Surprisingly, we find that most binding modes involve the positively charged ammonium group. Moreover, while attachment of the negatively charged carboxylate groups is also frequently observed, it is always balanced by the aqueous solvation of an equal or greater number of carboxylates. These effects are observed on all calcite features including edges and corners, the latter being associated with dominant affinities to Asp derivatives. As these features are also precisely the active sites for crystal growth, the experimental and theoretical results point strongly to a growth inhibition mechanism, whereby these sites become blocked, preventing further attachment of dissolved ions and halting further growth.

Correction for ‘Effects of structurally-related impurities on the crystal growth of curcumin spherulites’ by Claire Heffernan et al., CrystEngComm, 2022, 24, 5156–5169, https://doi.org/10.1039/D2CE00223J.

peer-reviewed In this work, the influence of the structurally related impurities, Demethoxycurcumin (DMC) and Bisdemethoxycurcumin (BDMC) on the primary nucleation of Curcumin (CUR) has been investigated in propan-2-ol. The induction time for nucleation was measured at different CUR driving forces and impurity concentrations 0.10 mmol.dm-3, 0.30 mmol.dm-3 and 0.60 mmol.dm-3 and the results are analysed by the classical nucleation theory (CNT). The nucleation rate for the impure systems was noticeably lower than the nucleation rate of the pure system, and the times of growth to visibility were much longer for the impure systems. The pre-exponential factors are clearly lower for the impure system compared to the pure CUR system, while the increase in the solid-liquid interfacial energy is small. DFT and Metadynamic molecular modelling reveal that the 1:1 bonding between CUR and an impurity molecule is stronger than to another CUR molecule, thus suggesting that the developing CUR nucleus has to overcome a certain energy barrier in order to remove the impurity molecules from their surface, which may explain why nucleation of CUR is more difficult in presence of the structurally related impurities; DMC and BDMC.

In this work, solubility of four Active Pharmaceutical Ingredients (APIs) including Butyl Paraben, Fenoxycarb, Fenofibrate and Risperidone were predicted using Hansen Flory Huggins model using two different scenarios. In the first method, activity coefficient of APIs were obtained through fitting the experimental activity coefficients of solvents at particular temperature of 293 K, then components solubility in entire temperature range of study was predicted. In the second scenario, the model parameters were adjusted using experimental data of two selected solvents, then components solubility were predicted in other solvents. In order to check the physical meanings of obtained values, Molecular Dynamic (MD) simulations was utilized and the results were compared. Finally the predictive capabilities of two Hansen Flory Huggins models were compared to temperature-dependent NRTL-SAC model.

peer-reviewed In this work a method is developed for the extraction and purification of the three curcuminoids; Curcumin (CUR), Demethoxycurcumin (DMC) and Bisdemethoxycurcumin (BDMC) from commercially available crude curcumin. In a previous publication the extraction of pure curcumin by repeated crystallization has been described. The focus of this paper is on the following chromatographic treatment of the mother liquor from the crystallization to obtain pure DMC and BDMC, and to increase the yield of pure CUR. In the chromatographic process a mixture of chloroform and methanol is used as the mobile phase and silica gel is used as the stationary phase. Each fraction isolated in the chromatographic process was characterised by High Performance Liquid Chromatography (HPLC) and Mass Spectrometry (LC-MS) techniques, and the pure CUR, DMC and BDMC solid phases were fully characterized by powder Xray diffraction (PXRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Stability studies were performed on the purified curcuminoids where the degradation products were observed and analysed by HPLC/LC-MS. Overall, the combined purification method recovered from the crude: 88.5%, 79.7% and 68.8% of CUR, DMC and BDMC respectively, in highly pure form CUR (100%), DMC (98.6%) and BDMC (98.3%).

Purification of crude curcumin by up to four successive cooling crystallizations has been investigated for a wide variety of process conditions. For each crystallization step the influence of various processing conditions on crystal purity, polymorphic outcome, and crystal size and shape is reported. By an extensive number of experiments according to a statistical experimental design, the influence on cooling rate, seeding, seed polymorph, and agitation conditions has been identified. Slow cooling and seeding, particularly with the metastable Form II seed, significantly improves the purification. A correlation between product crystal size and purity is found. By tuning the crystallization parameters the number of recrystallization steps required to reach a certain purity can be reduced, which significantly increased the overall curcumin yield from 28% to 50%.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 07/11/2018 Using Artificial Neural Networks (ANNs), four distinct models have been developed for the prediction of solid-state properties of cocrystals: melting point, lattice energy, and crystal density. The models use three input parameters for the pure model compound (MC) and three for the pure coformer. In addition, as input parameter the model uses the pKa difference between the MC and the coformer, and a 1:1 MC–conformer binding energy as calculated by a force field method. Notably the models require no data for the actual cocrystals. In total, 61 CCs (two-component molecular cocrystals) were used to construct the models, and melting temperatures and crystal densities were extracted from the literature for four MCs: caffeine, theophylline, nicotinamide and isonicotinamide. The data set includes 14 caffein cocrystals, 9 theophylline cocrystals, 9 nicotinamide cocrystals and 29 isonicotinamide cocrystals. The model–I is trained using known cocrystal melting temperatures, lattice energies and crystal densities, to predict all three solid–state properties simultaneously. The average relative deviation for the training set is 2.49%, 6.21% and 1.88% for the melting temperature, lattice energy and crystal density, respectively, and correspondingly 6.26%, 4.58% and 0.99% for the valdation set. Model–II, model–III and model–IV were built using the same input neurons as in model–I, for separate prediction of each respective output solid–state property. For these models the average relative deviation for the traning sets becomes 1.93% for the melting temperature model-II, 1.29% for the lattice energy model-III and 1.03% for the crystal density model-IV, and correspondingly 2.23%, 2.40% and 1.77% for the respective validation sets

Surface reactions on calcite play an important role in geochemical and environmental systems, as well as many areas of industry. In this review, we present investigations of calcite that were performed in the frame of the joint research project “RECAWA” ( re activity of ca lcite– wa ter-interfaces: molecular process understanding for technical applications). As indicated by the project title, work within the project comprised a large range of length scales. The molecular scale structure of the calcite (1 0 4)–water-interface is refined based on surface diffraction data. Structural details are related to surface charging phenomena, and a simplified basic stern surface complexation model is proposed. As an example for trace metal interactions with calcite surfaces we review and present new spectroscopic and macroscopic experimental results on Selenium interactions with calcite. Results demonstrate that selenate (SeO42−) shows no significant interaction with calcite at our experimental conditions, while selenite (SeO32−) adsorbs at the calcite surface and can be incorporated into the calcite structure. Atomistic calculations are used to assess the thermodynamics of sulfate (SO42−), selenate (SeO42−), and selenite (SeO32−) partitioning in calcite and aragonite. The results show that incorporation of these oxo-anions into the calcite structure is so highly endothermic that incorporation is practically impossible at bulk equilibrium and standard conditions. This indicates that entrapment processes are involved when coprecipitation is observed experimentally. The relevance of nano-scale surface features is addressed in an investigation of calcite growth and precipitation in the presence of phosphonates, demonstrating the influence of phosphonates on the morphology of growth spirals and macroscopic growth rates. It is investigated how physical properties of limestone containing cement suspensions may influence the workability of the cement suspensions and thus the efficacy of limestone in industrial applications. The largest scale is reached in iron filtration experiments in a water-purification-pilot-plant using limestone as filter material, which appeared to be highly effective for removing iron from drinking water. Investigations presented cover a whole series of methods to study the calcite–water-interface. Many calcite related topics are addressed, demonstrating how broad the field of calcite–water-interface research is and how manifold the applications are, for which calcite–water-interface phenomena are of major relevance.

This paper reports on the precipitation of CaCO3 polymorphs, having various crystal morphologies under different conditions. In particular, systems that were subject to ultrasonic irradiation were compared to the corresponding reference systems in the absence of such a treatment. The application of ultrasonic irradiation predominantly resulted in a change of particle size distribution and polymorphic composition of the precipitate, in comparison to the reference systems. Thus, it was found that the supersaturation and temperature influenced the size distribution, in both the reference and sonicated systems. A mixture of calcite, vaterite and aragonite was obtained in all reference systems, at 25 °C. At this temperature, the sonication caused the vaterite content to increase, while aragonite was not detected. In reference and sonicated systems at 80 °C, only aragonite precipitated. The results also indicate that the principle parameter responsible for the morphology of vaterite was the initial supersaturation: at higher supersaturation spherical vaterite particles precipitated, while at lower supersaturation hexagonal platelets were obtained. The morphological investigations also indicated different mechanisms of vaterite formation in the systems in which precipitation was initiated at higher supersaturation: spherulitic growth of vaterite was observed in sonicated systems, while the aggregation of primary particles was predominant in the reference systems. At lower supersaturation, the effect of c(Ca2+)/c(CO32-) on the morphology of hexagonal platelets of vaterite was observed as well. By varying the c(Ca2+)/c(CO32-), significant changes of the polymorphic composition were observed only in the sonicated systems, at 25 ˚C.

Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-L-aspartic acid (N-Sal-Asp) or N-salicyloil-L-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighbouring adsorbed salicylate molecules were also estimated.

A newly developed Biot number–Dincer number correlation was applied to determine moisture transport parameters of broccoli drying. Broccoli florets were dried in a single layer with suction flow changing the temperature and flow of drying air. Experimental dimensionless moisture content data were used to calculate the drying coefficients and lag factors, which were then incorporated into the analytical model for slab geometry. In a relatively simple manner, Biot number, effective moisture diffusivity and mass transfer coefficient were computed and ranged between 0.2272–0.3030, 3.5780 × 10−6–16.6670 × 10−6 m2 s−1 and 1.9215 × 10−4–8.7256 × 10−4 m s−1, respectively. Effective moisture diffusivities calculated by newly developed equation which incorporated lag factor and drying coefficient differed from literature values. Experimental and predicted moisture profiles showed an excellent agreement for all drying conditions with mean errors ranging from ±1.26% to ±5.57%.

The production of precipitated calcium carbonate, PCC, by a semicontinuous process of slaked lime carbonation was performed in a bench-scale chemical reactor, fully controlled by means of custom built electronics and software for the personal computer. Calcite crystals, with different characteristic morphologies (rhombohedral, truncated prismatic, scalenohedral, spheroidal or chain-like agglomerates) were produced by varying a range of process parameters, like temperature, supersaturation, gas mixture flow rate, stirring rate and mass concentration of Ca(OH)2 suspension. In order to identify the effects of the chosen process parameters on the PCC morphology and on the related specific surface area, as well as on the extent of CO2 conversion, an empirical approach based on the experimental design techniques was employed. A multiple correlation analysis of the obtained data suggests that temperature and conductivity significantly influence the PCC morphology, while CO2 conversion is principally influenced by stirring rate, conductivity and gas mixture flow rate.

Drying of particles (pieces) in a fluidized bed affords better quality of end products, especially for better product structure and its shorter reconstitution time. Fluid-bed drying of different fruit particles has been investigated. Starting water content varies from grape berries 81.5% and peach 87.7% to apricot 86.9%. The temperature of fluidization varies from 70 °C to 100 °C at air velocities from 0.98 m/s to 5.2 m/s. The product should be dried fruit with 10% to 14% of water content with good rehydration quality that varies from 8 to 20. Experimental data have been measured, relevant values have been calculated and a mathematical model introduced. The results have shown that drying of fruit in a fluidized bed produces dry fruit particles of improved quality in a much shorter time, with improved rehydration times and qualities, than in continuous belt-driers that are generally used.

The kinetics of scalenohedral calcite crystal growth in the presence of N-salicyloil-Laspartic (N-Sal-Asp) and N-salicyloil-L-glutamic acid (N- Sal-Glu), as selected models of antiinflammatory drug-like substances, were analyzed in order to study the molecular interactions of the selected salicylates with scalenohedral {; ; ; 2 1 4}; ; ; surfaces. The results revealed that the growth is controlled by surface reactions, proceeding at the spiral step. The presence of the additives caused the inhibition of the growth, wherein the N-Sal-Asp interacted more strongly than N-Sal- Glu. The obtained data were supported with the electrokinetic, spectroscopic and adsorption measurements. The interactions between the selected additives and the scalenohedral calcite crystals were compared with the rhombohedral modification. The stronger interactions of salicylates with scalenohedral surfaces are explained in terms of their higher reactivity and, most likely, better structural matching of their surface calcium ions with the salicylate carboxylic groups. In addition, the spontaneous precipitation of scalenohedral or rhombohedral calcite crystals in the presence of selected salicylates indicated that, under the applied conditions, the salicylate incorporation into the scalenohedral modification was significantly higher and could be related to the enhanced adsorption efficiency and the kinetics of crystal growth. 2 The obtained results can contribute to understanding the basic interactions between the model drug derivatives containing carboxylic functional groups with different mineral surfaces, as well as to the development of biocompatible calcium carbonate drug carriers.

A method for preparation of significant amount of hollow rhombohedral calcite nanoparticles, based on carbonation of calcium hydroxide suspension, is described. The mineralogical and morphological analyses of the precipitate confirmed the existence of exclusively stable polymorphic modification, calcite, with the mean particle size of about 100 nm and the diameter of the holes observed at the surfaces that are about 50 nm. The analysis of carbonation kinetics pointed out to a complex mechanism of hollow particles formation at high initial supersaturation, that assumed nucleation of amorphous precursor calcium carbonate phase and its solution mediated transformation into nanosized crystalline calcite. The holes obtained at the calcite surfaces are most probably the imprints remained after the dissolution of amorphous calcium carbonate particles.

The influence of organic additives on the crystal growth of different calcite morphologies in two crystallization processes operating under steady state and batch mode is described. The crystal growth kinetics and overgrown morphological observations of rhombohedral, scalenohedral and prismatic calcite seed crystals in the systems containing etidronic acid (HEDP) and tartaric acid (TA) were investigated. The crystallization systems were of low supersaturations (SI < 1.1) and of moderate pH (8.0). Kinetic parameters of the crystal growth in the presence of selected additives, such as reduction of the growth rates, rate constant and reduced critical supersaturation were calculated and correlated with additive concentration and different calcite seeds. The results indicate strong interactions of HEDP molecules and weak but specific interactions of TA for calcite surfaces. Interactions occur at the step edges which finally results in the expression of near-{; ; hk0}; ; faces and highly polar faces, consisting of solely Ca layer on the surface, stabilised by TA and HEDP molecules, respectively. The affinity of both additives is significantly higher for scalenohedral and prismatic calcite in contrast to rhombohedral calcite seeds. The effect of calcite seed morphology was attributed to different surface energetics of the predominant crystal faces of the studied calcite seeds.

Precipitated calcium carbonate (PCC) was prepared by means of semicontinuous carbonation of Ca(OH)(2) suspension, at 35 and 45 degrees C and in the presence of non-ionic dextran and dextran sulfate. The carbonation process was regulated at different predetermined values of electrical conductivity, that corresponded to different concentrations of dissolved Ca(OH)(2): 0.5 mS cm(-1) < kappa(25) < 5.0 mS cm(-1). The results of physical-chemical characterization of the product showed that calcite was the only polymorphic modification obtained in the whole range of experimental conditions investigated. In addition, it was found that morphology, crystal size distribution and specific surface area of PCC strongly depended on the electrical conductivity / concentration of dissolved Ca(OH)(2), at which the process was performed: predominantly scalenohedral crystals of higher surface area (about 5 m(2) g(-1)) were produced at higher electrical conductivity, while at lower electrical conductivity predominantly rhomohedral calcite crystals of relatively low specific surface area were obtained. In the system of the highest electrical conductivity, kappa(25) = 5.0 mS cm(-1), and at 35 degrees C, the addition of non-ionic dextran significantly influenced the process by preventing the regulation. The crystals that appeared were in the form of irregular aggregates of high specific surface area, S approximate to 29 m(2) g(-1). FT-IR and TG analyses indicated that the non-ionic dextran was adsorbed onto the calcite surface, most probably by relatively strong and specific interactions between oxygen from the hydroxyl groups of dextran molecules and calcium ions from the crystal surface. On the contrary, the anionic dextran (dextran sulfate) exerted minor effects in the course of semicontinuous carbonation process and in the properties of the final product, PCC. However, the analysis of the precipitate indicated that dextran sulfate was adsorbed at the surfaces, most probably by the weak and non-specific electrostatic interactions.

Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content ( $$ Q_{{{\text{H}}_{\text{2}} {\text{O}}}} $$ ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and $$ Q_{{{\text{H}}_{\text{2}} {\text{O}}}} $$ influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples.

Ovim pregledom izdvojeni su interesantni planovi pokusa za primjenu u industriji kako bi se istaknula njihova učinkovitost kod reduciranja broja potrebnih pokusa i povećanja kvalitete informacija. Opisani su potpuni i djelomični faktorijalni planovi pokusa, zatim metoda odzivne plohe i pripadajući planovi za opis nelinearnih odziva, kao i upotreba računalom generiranih planova pokusa. Opisana je Taguchijeva metoda planiranja pokusa pogodna za primjenu u proizvodnji i kontroli kvalitete. Diskutirana je upotreba analize varijance u prehrambenom inženjerstvu, kao osnovna statistička metoda za analizu osjetljivosti čimbenika, kao i upotreba višestruke linearne regresije za analizu osjetljivosti, modeliranje i optimiranje procesa., The experimental design techniques useful for industrial applications are reviewed. The full and fractional factorial designs and also response surface methodology with associated designs for describing the nonlinear responses, as well as computer-aided designs, are briefly described. Taguchi method, suitable for use in production and quality engineering, is also described. The use of analysis of variance, basic statistical methods for determining the significant factors, as well as use of multiple linear regression for correlation analysis, process modeling and optimization, are described and discussed.

The influence of sodium stearate (NaSt) on the precipitation of calcium carbonate during the semicontinuous process of slaked lime carbonation was studied in the systems in which process parameters, like concentration of total dissolved calcium, temperature, CO(2) flow rate and initial addition rate of slaked lime, were controlled. It was found that calcite was the only calcium carbonate polymorph that appeared under the investigated experimental conditions, while FT-IR spectroscopy and thermogravimetric analysis of samples confirmed the presence of stearate on the surface of precipitated calcium carbonate (PCC). Specific surface area of PCC increased with increasing stearate content: the highest value, s = 52.8 m(2) g(-1), was obtained at t = 20 degrees C, c(tot) = 17.0 mmol dm(-3) and the stearate content of m(NaSt)/m(CaO) = 0.03. It was also found that hydrophobic calcite crystals in the form of rhombohedral and scalenohedral morphology can be produced at m(NaSt)/m(CaO)0.01. The exception is the case of nanosized PCC production, when much higher concentration of NaSt is needed, m(NaSt)/m(CaO) = 0.22. Minimal amount of stearate necessary to build up the monolayer and corresponding cross sectional area of one stearate molecule were estimated for the obtained calcite morphologies.

Mechanical properties of cereal (starch-based) extrudates are perceived by the final consumer as criteria of quality. We investigate one of the important characteristics of extrudates, mechanical hardness, which is one of the main texture parameters. Texture quality has an influence on taste sensory evaluation, and thus on the acceptability of the product. Characteristics that have great influence on acceptability are crispness, elasticity, hardness and softness. These attributes are narrowly related to, and affected by, the process parameters. A 2-level– 4-factor factorial experimental design was used to investigate the influence of temperature of expansion, screw speed, feed moisture content and feed rate, and their interactions, on the mechanical hardness of extrudates. Feed moisture content, screw speed and temperature are found to influence, while feed rate does not have significant effect on extrudate hardness. Mechanical properties of specimens were measured by means of compression testing, based on the concept of nominal stress, using a universal testing machine and special grips that were constructed for this purpose.