Tuna Dincer - Academia.edu (original) (raw)
Papers by Tuna Dincer
Journal of Crystal Growth, Feb 1, 2009
The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrat... more The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrate crystal were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The overall growth rate of the crystal is around 50-60% of the (0 1 0) face of the crystal. The power law was applied to the growth rates of the four faces and the activation energies were calculated to be between 9.5 and 13.7 kcal/mol. This indicates a diffusion-controlled growth, but the exponents calculated are between 2.5 and 3.1 which are higher than unity. Introduction of critical supersaturation decreased the exponents to between 1.8 and 2.4. The variance of GRD for the (0 1 0) face is twice the variance of the GRD of the (11 0) and (1 0 0) faces and 10 times higher than the (11 1) face at the same supersaturations and temperatures. The GRD of the four faces were similar when expressed as a function of growth rate. However, the (0 11) face displayed lower GRD than the other faces at the same temperatures and supersaturations.
ABSTRACT Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a... more ABSTRACT Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not been any reported work on the fundamentals of lactose crystallisation and the mechanisms that operate on the molecular level. The aim of this thesis is to gain a greater understanding at the fundamental processes, which occur at the molecular level during the crystallisation of lactose, in order to improve control at a macroscopic level. The growth rates of the dominant crystallographic faces have been measured in situ, at three temperatures and over a wide range of supersaturation. The mean growth rates of faces were proportional to the power of between 2.5-3.1 of the relative supersaturation. The rate constants and the activation energies were calculated for four faces. The [alpha]-lactose monohydrate crystals grown in aqueous solutions exhibited growth rate dispersion. Crystals of similar size displayed almost 10 fold difference in the growth rate grown under identical conditions for all the faces. Growth rate dispersion increases with increasing growth rate and supersaturation for all the faces. The variance in the GRD for the (0 10) face is twice the variance of the GRD of the (110) and (100) faces and ten times higher than the (0 11) face at different supersaturations and temperatures. The influence of [beta]-lactose on the morphology of [alpha]-lactose monohydrate crystals has been investigated by crystallising [alpha]-lactose monohydrate from supersaturated DMSO ethanol solutions. The slowness of mutarotation in DMSO allowed preparation of saturated solutions with a fixed, chosen [beta]-lactose content. It was found that [beta]-lactose significantly influences the morphology of [alpha]- lactose monohydrate crystals grown from DMSO solution. At low concentrations of [beta]-lactose, the fastest growing face is the (011) face resulting in long thin prismatic crystals. At higher [beta]-lactose concentrations, the main growth occurs in the b direction and the (020) face becomes the fastest growing face (since the (011) face is blocked by [beta]-lactose), producing pyramid and tomahawk shaped crystals. Molecular modeling was used to calculate morphologies of lactose crystals, thereby defining the surface energies of specific faces, and to calculate the energies of interactions between these faces and [beta]-lactose molecules. It was found that as the replacement energy of [beta]-lactose increased, the likelihood of [beta]-lactose to dock onto faces decreased and therefore the growth rate increased. The attachment energy of a new layer of [alpha]-lactose monohydrate to the faces containing [beta]-lactose was calculated for the (010) and (011) faces. For the (0 10) face, the attachment energy of a new layer was found to be lower than the attachment energy onto a pure lactose surface, meaning slower growth rates when [beta]-lactose was incorporated into the surface. For the (011) face, attachment energy calculations failed to predict the slower growth rates of this face in the presence of [beta]-lactose. AFM investigation of [alpha]-lactose monohydrate crystals produced very useful information about the surface characteristics of the different faces of the [alpha]-lactose monohydrate crystal. The growth of the (010) face of the crystal occurs by the lateral addition of growth layers. Steps are 2 nm high (unit cell height in the b direction) and emanate from double spirals, which usually occurred at the centre of the face. Double spirals rotate clockwise on the (010) face, while the direction of spirals is counterclockwise on the (010) face. A polygonised double spiral, showing anisotropy in the velocity of stepswas observed at the centre of the prism-shaped a-lactose monohydrate crystals grown in the presence of 5 and 10 % [beta]-lactose. The mean spacing of the steps parallel to the (011) face is larger than those parallel to the (100) face, indicating higher growth rates of the (011 )face. The edge free energy of the (011) face is 6.6 times larger than the (100) face in the presence of 5% [beta]-lactose. Increase of…
Journal of Crystal Growth, Sep 1, 2014
α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variat... more α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (010) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (010) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (010) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.
Journal of Crystal Growth, Sep 1, 1999
In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of ... more In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of β-lactose on the morphology of α-lactose monohydrate crystals. DMSO was used as the solvent as it greatly reduces the rate of mutarotation of α-lactose to β-lactose. It is shown that as the β-content of the solution increases, the crystal shape starts increasing in the
International Dairy Journal, Mar 1, 2014
Although research on sonocrystallisation of lactose has been reported in the literature (yield an... more Although research on sonocrystallisation of lactose has been reported in the literature (yield and crystal size), the effect of ultrasound variables on nucleation and growth rate of lactose have not been studied. In this study, lactose crystallisation with ultrasound was investigated and compared to mechanical agitation using the induction time method at 22 °C. Ultrasound had a significant effect in reducing induction times and narrowing the metastable zone width but had no effect on individual crystal growth rate or morphology. A rapid decrease in induction time was observed up to 0.46 W g-1 power density. Sonication up to 3 min decreased the induction time but no further reduction was observed beyond 3 min. It was not possible to generate the nucleation rates achieved by sonication using agitation alone. One minute sonication at 0.46 W g-1 power density followed by continuous stirring was found to be the optimum under the experimental conditions tested.
Journal of Crystal Growth, Apr 1, 2009
The growth rates of the (0 1 0) face of a-lactose monohydrate crystals were measured at 30, 40 an... more The growth rates of the (0 1 0) face of a-lactose monohydrate crystals were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The mechanisms of growth were investigated. Spiral growth was found to be the mechanism of growth up to a critical relative supersaturation (sÀ1) crit =1.9 at 30 1C. Above the critical relative supersaturation, the crystal growth mechanisms were predicted to change. All growth models fit equally well to the growth rates. No twodimensional nucleation was observed above critical supersaturation by AFM. On the other hand increased step height and roughness on the edges of steps were observed. It was concluded that the growth mechanism of the (0 1 0) face of a-lactose monohydrate crystal is spiral growth. A parabolic relationship was obtained below critical supersaturation followed by a linear relationship with relative supersaturation.
International Dairy Journal, 2014
Although research on sonocrystallisation of lactose has been reported in the literature (yield an... more Although research on sonocrystallisation of lactose has been reported in the literature (yield and crystal size), the effect of ultrasound variables on nucleation and growth rate of lactose have not been studied. In this study, lactose crystallisation with ultrasound was investigated and compared to mechanical agitation using the induction time method at 22 °C. Ultrasound had a significant effect in reducing induction times and narrowing the metastable zone width but had no effect on individual crystal growth rate or morphology. A rapid decrease in induction time was observed up to 0.46 W g-1 power density. Sonication up to 3 min decreased the induction time but no further reduction was observed beyond 3 min. It was not possible to generate the nucleation rates achieved by sonication using agitation alone. One minute sonication at 0.46 W g-1 power density followed by continuous stirring was found to be the optimum under the experimental conditions tested.
Ultrasonics Sonochemistry, Nov 1, 2014
Whey concentrated to 32% lactose was sonicated at 30°C in a non-contact approach at flow rates of... more Whey concentrated to 32% lactose was sonicated at 30°C in a non-contact approach at flow rates of up to 12 L/min. Applied energy density varied from 3 to 16 J/mL at a frequency of 20 kHz. Sonication of whey initiated the rapid formation of a large number of lactose crystals in response to acoustic cavitation which increased the rate of crystallisation. The rate of sonocrystallisation was greater than stirring for approximately 180 min but slowed down between 120 and 180 min as the metastable limit was reached. A second treatment with ultrasound at 120 min delivering an applied energy density of 4 J/mL stimulated further nuclei formation and the rate of crystallisation was maintained for >300 min. Yield on the other hand was limited by the solubility of lactose and could not be improved. The crystal size distribution was narrower than that with stirring and the overall crystal size was smaller.
Journal of Crystal Growth, 2009
α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variat... more α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (010) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (010) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (010) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.
Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a signific... more Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not b...
Handbook of Ultrasonics and Sonochemistry, 2015
Handbook of Ultrasonics and Sonochemistry, 2016
Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a signific... more Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not b...
Journal of Crystal Growth, 1999
In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of ... more In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of β-lactose on the morphology of α-lactose monohydrate crystals. DMSO was used as the solvent as it greatly reduces the rate of mutarotation of α-lactose to β-lactose. It is shown that as the β-content of the solution increases, the crystal shape starts increasing in the
Journal of Crystal Growth, 2009
The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrat... more The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrate crystal were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The overall growth rate of the crystal is around 50-60% of the (0 1 0) face of the crystal. The power law was applied to the growth rates of the four faces and the activation energies were calculated to be between 9.5 and 13.7 kcal/mol. This indicates a diffusion-controlled growth, but the exponents calculated are between 2.5 and 3.1 which are higher than unity. Introduction of critical supersaturation decreased the exponents to between 1.8 and 2.4. The variance of GRD for the (0 1 0) face is twice the variance of the GRD of the (11 0) and (1 0 0) faces and 10 times higher than the (11 1) face at the same supersaturations and temperatures. The GRD of the four faces were similar when expressed as a function of growth rate. However, the (0 11) face displayed lower GRD than the other faces at the same temperatures and supersaturations.
Journal of Crystal Growth, Feb 1, 2009
The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrat... more The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrate crystal were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The overall growth rate of the crystal is around 50-60% of the (0 1 0) face of the crystal. The power law was applied to the growth rates of the four faces and the activation energies were calculated to be between 9.5 and 13.7 kcal/mol. This indicates a diffusion-controlled growth, but the exponents calculated are between 2.5 and 3.1 which are higher than unity. Introduction of critical supersaturation decreased the exponents to between 1.8 and 2.4. The variance of GRD for the (0 1 0) face is twice the variance of the GRD of the (11 0) and (1 0 0) faces and 10 times higher than the (11 1) face at the same supersaturations and temperatures. The GRD of the four faces were similar when expressed as a function of growth rate. However, the (0 11) face displayed lower GRD than the other faces at the same temperatures and supersaturations.
ABSTRACT Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a... more ABSTRACT Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not been any reported work on the fundamentals of lactose crystallisation and the mechanisms that operate on the molecular level. The aim of this thesis is to gain a greater understanding at the fundamental processes, which occur at the molecular level during the crystallisation of lactose, in order to improve control at a macroscopic level. The growth rates of the dominant crystallographic faces have been measured in situ, at three temperatures and over a wide range of supersaturation. The mean growth rates of faces were proportional to the power of between 2.5-3.1 of the relative supersaturation. The rate constants and the activation energies were calculated for four faces. The [alpha]-lactose monohydrate crystals grown in aqueous solutions exhibited growth rate dispersion. Crystals of similar size displayed almost 10 fold difference in the growth rate grown under identical conditions for all the faces. Growth rate dispersion increases with increasing growth rate and supersaturation for all the faces. The variance in the GRD for the (0 10) face is twice the variance of the GRD of the (110) and (100) faces and ten times higher than the (0 11) face at different supersaturations and temperatures. The influence of [beta]-lactose on the morphology of [alpha]-lactose monohydrate crystals has been investigated by crystallising [alpha]-lactose monohydrate from supersaturated DMSO ethanol solutions. The slowness of mutarotation in DMSO allowed preparation of saturated solutions with a fixed, chosen [beta]-lactose content. It was found that [beta]-lactose significantly influences the morphology of [alpha]- lactose monohydrate crystals grown from DMSO solution. At low concentrations of [beta]-lactose, the fastest growing face is the (011) face resulting in long thin prismatic crystals. At higher [beta]-lactose concentrations, the main growth occurs in the b direction and the (020) face becomes the fastest growing face (since the (011) face is blocked by [beta]-lactose), producing pyramid and tomahawk shaped crystals. Molecular modeling was used to calculate morphologies of lactose crystals, thereby defining the surface energies of specific faces, and to calculate the energies of interactions between these faces and [beta]-lactose molecules. It was found that as the replacement energy of [beta]-lactose increased, the likelihood of [beta]-lactose to dock onto faces decreased and therefore the growth rate increased. The attachment energy of a new layer of [alpha]-lactose monohydrate to the faces containing [beta]-lactose was calculated for the (010) and (011) faces. For the (0 10) face, the attachment energy of a new layer was found to be lower than the attachment energy onto a pure lactose surface, meaning slower growth rates when [beta]-lactose was incorporated into the surface. For the (011) face, attachment energy calculations failed to predict the slower growth rates of this face in the presence of [beta]-lactose. AFM investigation of [alpha]-lactose monohydrate crystals produced very useful information about the surface characteristics of the different faces of the [alpha]-lactose monohydrate crystal. The growth of the (010) face of the crystal occurs by the lateral addition of growth layers. Steps are 2 nm high (unit cell height in the b direction) and emanate from double spirals, which usually occurred at the centre of the face. Double spirals rotate clockwise on the (010) face, while the direction of spirals is counterclockwise on the (010) face. A polygonised double spiral, showing anisotropy in the velocity of stepswas observed at the centre of the prism-shaped a-lactose monohydrate crystals grown in the presence of 5 and 10 % [beta]-lactose. The mean spacing of the steps parallel to the (011) face is larger than those parallel to the (100) face, indicating higher growth rates of the (011 )face. The edge free energy of the (011) face is 6.6 times larger than the (100) face in the presence of 5% [beta]-lactose. Increase of…
Journal of Crystal Growth, Sep 1, 2014
α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variat... more α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (010) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (010) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (010) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.
Journal of Crystal Growth, Sep 1, 1999
In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of ... more In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of β-lactose on the morphology of α-lactose monohydrate crystals. DMSO was used as the solvent as it greatly reduces the rate of mutarotation of α-lactose to β-lactose. It is shown that as the β-content of the solution increases, the crystal shape starts increasing in the
International Dairy Journal, Mar 1, 2014
Although research on sonocrystallisation of lactose has been reported in the literature (yield an... more Although research on sonocrystallisation of lactose has been reported in the literature (yield and crystal size), the effect of ultrasound variables on nucleation and growth rate of lactose have not been studied. In this study, lactose crystallisation with ultrasound was investigated and compared to mechanical agitation using the induction time method at 22 °C. Ultrasound had a significant effect in reducing induction times and narrowing the metastable zone width but had no effect on individual crystal growth rate or morphology. A rapid decrease in induction time was observed up to 0.46 W g-1 power density. Sonication up to 3 min decreased the induction time but no further reduction was observed beyond 3 min. It was not possible to generate the nucleation rates achieved by sonication using agitation alone. One minute sonication at 0.46 W g-1 power density followed by continuous stirring was found to be the optimum under the experimental conditions tested.
Journal of Crystal Growth, Apr 1, 2009
The growth rates of the (0 1 0) face of a-lactose monohydrate crystals were measured at 30, 40 an... more The growth rates of the (0 1 0) face of a-lactose monohydrate crystals were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The mechanisms of growth were investigated. Spiral growth was found to be the mechanism of growth up to a critical relative supersaturation (sÀ1) crit =1.9 at 30 1C. Above the critical relative supersaturation, the crystal growth mechanisms were predicted to change. All growth models fit equally well to the growth rates. No twodimensional nucleation was observed above critical supersaturation by AFM. On the other hand increased step height and roughness on the edges of steps were observed. It was concluded that the growth mechanism of the (0 1 0) face of a-lactose monohydrate crystal is spiral growth. A parabolic relationship was obtained below critical supersaturation followed by a linear relationship with relative supersaturation.
International Dairy Journal, 2014
Although research on sonocrystallisation of lactose has been reported in the literature (yield an... more Although research on sonocrystallisation of lactose has been reported in the literature (yield and crystal size), the effect of ultrasound variables on nucleation and growth rate of lactose have not been studied. In this study, lactose crystallisation with ultrasound was investigated and compared to mechanical agitation using the induction time method at 22 °C. Ultrasound had a significant effect in reducing induction times and narrowing the metastable zone width but had no effect on individual crystal growth rate or morphology. A rapid decrease in induction time was observed up to 0.46 W g-1 power density. Sonication up to 3 min decreased the induction time but no further reduction was observed beyond 3 min. It was not possible to generate the nucleation rates achieved by sonication using agitation alone. One minute sonication at 0.46 W g-1 power density followed by continuous stirring was found to be the optimum under the experimental conditions tested.
Ultrasonics Sonochemistry, Nov 1, 2014
Whey concentrated to 32% lactose was sonicated at 30°C in a non-contact approach at flow rates of... more Whey concentrated to 32% lactose was sonicated at 30°C in a non-contact approach at flow rates of up to 12 L/min. Applied energy density varied from 3 to 16 J/mL at a frequency of 20 kHz. Sonication of whey initiated the rapid formation of a large number of lactose crystals in response to acoustic cavitation which increased the rate of crystallisation. The rate of sonocrystallisation was greater than stirring for approximately 180 min but slowed down between 120 and 180 min as the metastable limit was reached. A second treatment with ultrasound at 120 min delivering an applied energy density of 4 J/mL stimulated further nuclei formation and the rate of crystallisation was maintained for >300 min. Yield on the other hand was limited by the solubility of lactose and could not be improved. The crystal size distribution was narrower than that with stirring and the overall crystal size was smaller.
Journal of Crystal Growth, 2009
α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variat... more α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (010) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (010) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (010) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.
Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a signific... more Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not b...
Handbook of Ultrasonics and Sonochemistry, 2015
Handbook of Ultrasonics and Sonochemistry, 2016
Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a signific... more Lactose is the major carbohydrate in milk. The presence of lactose in whey constitutes a significant pollution problem for dairy factories. At the same time, there is an increasing market for high quality crystalline lactose. The main problem of lactose crystallisation, compared to sucrose, which is also a disaccharide, is that it is very slow, unpredictable and cannot easily be controlled. Compared to sucrose crystallisation, which has been extensively studied, lactose crystallisation lacks the fundamental research to identify the mechanisms of growth and effect of additives. An important difference from most other crystal growth systems is that ([alpha]-lactose hydrate crystals never grow from a pure environment; their growth environment always contains beta lactose. [alpha]-lactose monohydrate crystallises much more slowly because of the presence of [beta]- lactose in all solutions. Although there have been some studies on growth rates and the effect of additives, there has not b...
Journal of Crystal Growth, 1999
In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of ... more In this study, the dimethyl sulfoxide (DMSO)–lactose system has been used to study the effect of β-lactose on the morphology of α-lactose monohydrate crystals. DMSO was used as the solvent as it greatly reduces the rate of mutarotation of α-lactose to β-lactose. It is shown that as the β-content of the solution increases, the crystal shape starts increasing in the
Journal of Crystal Growth, 2009
The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrat... more The growth rates and growth rate dispersion (GRD) of four different faces of a-lactose monohydrate crystal were measured at 30, 40 and 50 1C in the relative supersaturation range 0.55-2.33 in aqueous solutions. The overall growth rate of the crystal is around 50-60% of the (0 1 0) face of the crystal. The power law was applied to the growth rates of the four faces and the activation energies were calculated to be between 9.5 and 13.7 kcal/mol. This indicates a diffusion-controlled growth, but the exponents calculated are between 2.5 and 3.1 which are higher than unity. Introduction of critical supersaturation decreased the exponents to between 1.8 and 2.4. The variance of GRD for the (0 1 0) face is twice the variance of the GRD of the (11 0) and (1 0 0) faces and 10 times higher than the (11 1) face at the same supersaturations and temperatures. The GRD of the four faces were similar when expressed as a function of growth rate. However, the (0 11) face displayed lower GRD than the other faces at the same temperatures and supersaturations.