This study presents the synthesis of polymers of intrinsic microporosity and the investigation of their microporosity using gas sorption and adsorption of liquids and vapours. Microporous polymeric materials PIM-1, TAPIM-1, PIM-2 and PIM-7 were synthesised using step-growth polymerisation. The microporosity of these materials was studied using gas sorption and adsorption of molecules in the liquid phase. A procedure to validate gas sorption methods was undertaken before being used to characterise microporous materials. The sorption methodology was validated using standard reference materials (SRMs) and collaborative testing, and the PSD evaluation was validated using a well defined crystalline material. Different approaches to obtaining pore size distribution (PSD) data were dealt with. Gas sorption methods that use CO2 at 273 K and at 303 K, N2 at 77 K, H2 at77 K, and Xe (298 K) to determine PSD were compared. The Horvath-Kawazoe(HK) model was presented as the preferred model and the N2, CO2 and H2 sorption data were treated under this approach. CO2 PSD data at 273 K and at303 K was compared against N2 PSD data and a novel complementary relationship established. PIM-1 samples in film form and powder form were used to investigate the effect of sample form on the sorption properties of the material. PIM-1, PIM-2, TAPIM-1, ethano-anthracene PIM-1 copolymers, and triptycene based PIMs were used to investigate the influence of polymer structure on gas sorption properties. The free volume properties of a PIM-1 ethano-anthracene copolymer (PIM-CO1-40), was compared against PIM-1. A number of independent techniques, namely N2 sorption, Xe sorption, Positron annihilation lifetime spectroscopy (PALS), and 129Xe NMR were used to probe the free volume. The time dependence of free volume and its bearing on diffusivity of PIM-1 membranes was investigated. Water, chloroform and simple alcohols were used to investigate adsorption in the liquid and vapour phases. Interaction with PIM-1 the aromatic ether linkage and the nitrile group produced frequency shifts in ATR-FT-IR spectra. These frequency shifts were used to compare relative strengths of the hydrogen bonds.

No description available.

The aim of this research is to understand the solid state physical properties of inulin in regards to the spray-drying treatments. In this context, inulin powders were produced by pilot spray-drying a commercial inulin dispersion under various feed (Tfeed) and inlet air (Tin) temperatures. More particularly, the amorphous and crystalline properties of the powders were studied by developing different fine characterization tools, such as modulated differential scanning calorimetry or powder X-ray diffraction. When the temperature of the inulin water systems increased, the crystallinity of the powder decreased. To a smaller extent, this tendency is also observed with the increase of the inlet air temperature of the spray drier. For example, an amorphous powder is obtained with a Tfeed of 90°C whatever the Tin (comprised between 120 and 230°C); whereas for a Tfeed of 80°C, a Tin of 230°C is necessary to obtain the same result. Adsorption isotherms were established on four powders covering a large range of crystallinity (crystallinity index from 0 to 92). The Guggenheim Anderson de Boer model was fitted to the experimental data. As the water content of the powders increased, the glass transition of inulin decreased. When the Tg droped below the storage temperature (20°C for example), the powders crystallized and underwent clumping phenomenon. Under these conditions, a continuous hard mass was observed for the amorphous powders; while their semi-crystalline counterparts were agglomerated but friable. To understand these changes, a kinetic study of the physical properties evolution and stability of an amorphous powder as a function of its water content was realized. These results allowed to correlate the Tg water content relationship to the evolution of the powders behaviour, such as stickiness or hardening during storage.

Zero-valent metals such as bulk iron and zinc are known to dechlorinate toxicorganic compounds. Enhancement in reaction rates has been achieved through bimetallicnanosized particles such as nickel/iron (Ni/Fe) and palladium/iron (Pd/Fe). Batchdegradation of model compounds, trichlroethylene (TCE) and 2,2'-dichlorobiphenyls(DCB), were conducted using bimetallic Ni/Fe and Pd/Fe nanoparticles. Completedegradation of TCE and DCB is achieved at room temperature. Zero-valent iron, as themajor element, undergoes corrosion to provide hydrogen and electrons for the reductivecatalytic hydrodechlorination reaction. The second dopant metals of nickel and palladium(in nanoscale) act as catalyst for hydrogenation through metal hydride formation thatproduces completely dechlorinated final product. Different compositions of bimetallicNi/Fe and Pd/Fe nanoparticles were synthesized and their reactivity was characterized interms of reaction rate constants, hydrogen generation through iron corrosion, andproducts formation. The observed TCE degradation rate constant was two orders ofmagnitude higher than the bulk iron and nanoiron, indicating that the bimetallicnanoparticles are better materials compared to the monometallic iron systems. Longevitystudy through repeated cycle experiments showed minimum loss of activity. The surfacearea-normalized rate constant was found to have a strong correlation with the hydrogengeneration by iron corrosion reaction. A mathematical model was derived thatincorporates the reaction and Langmuirian-type sorption terms to estimate the intrinsicreaction rate constant and rate-limiting step in the degradation process. Bimetallicnanoparticles were also immobilized into the chitosan matrix for the synthesis of ananocomposite membrane reactor to achieve membrane-phase destruction of chlorinatedorganics under convective flow condition. Formation of uniformly distributed nanosizedparticles is confirmed by high resolution transmission electron microscopy. Themembrane-phase degradation results demonstrated similar trends with the previoussolution phase analysis with the observed enhanced reaction rates. The advantage of themembrane system is its ability to prevent the agglomeration of the nanoparticles in themembrane matrix, to minimize the loss of precious metals into the bulk solution phase,and to prevent the formation of precipitated Fe(III) hydroxide. These are due to thechelating effect of the amine and hydroxyl functional groups in the chitosan backbones.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.

Sorption Behaviour of Selected Dairy Powder Mixtures: A Study of The Effects of Composition and Mixing Methods Abstract As water mediates physico-chemical reactions (i.e. Maillard reactions, phase changes of sugars and minerals, protein conformational changes), water-powder interactions during storage are critical for dairy powder stability. Therefore, the mechanisms of moisture adsorption from the environment and water distribution among components in the dry state need to be investigated, especially in mixed systems. In order to achieve this goal, the research reported in this thesis had two key objectives. The first was to examine the effect of the sorption properties and phase changes of individual components in relation to the sorption properties of the mixed system. This was achieved by adding three level concentrations of lactose and mineral rich dairy powder (10, 20 and 30%) to Milk Protein Concentrate containing 85% of protein (MPC-85). The second objective was to examine the effect of mixing methods on the sorption behaviour of mixed systems, by applying two different mixing methods, solution mixing and mechanical mixing (particulate mixing). In the solution mixing method, the components were mixed in the same water and then spray dried. In the mechanical mixing method, two individual powder components were physically mixed. For both mixed systems, the kinetics of moisture adsorption were determined at 4 different equilibrium relative humidity levels (22.5, 43.2, 65.4 and 84.3%) and the final equilibrium moisture contents were determined at 8 different equilibrium relative humidity levels (11.3, 22.5, 32.8, 43.2, 52.9, 65.4, 75.3 and 84.3%) at 25°C. The effect of lactose addition to the MPC powder tended to retard the moisture sorption of the mixtures. The increase of concentration level of the lactose that was introduced to the MPC system, through either solution or mechanical mixing, resulted in less moisture adsorption when compared to MPC itself (p-value<0.05). This effect tended to be greater with the increase in relative humidity. A similar effect was observed for MPC/mineral rich milk calcium powder (MC) mixtures. The application of different mixing methods modified the equilibrium moisture content of MPC/Lactose mixtures, even though both mixing methods resulted in similar monolayer moisture value. The monolayer moisture values calculated for both mixing methods were significantly lower than their theoretical values (p-value< 0.05). This suggested that a lactose-protein interaction might exist in both powders prepared by solution and mechanical mixing. Even though the interaction itself is hypothetical, the effect of interaction could be reflected by significant different adsorption rate (p-value < 0.05) of powders produced by different mixing method. A similar type of interaction might exist for the solution mixed MPC/MC system, even though different results were obtained for MPC/MC mixtures prepared by mechanical mixing. The addition of lactose to MPC tended to slow the rate of moisture adsorption. This deceleration might have been contributed to by a reduction of the protein hydration sites by the association of lactose molecules to these sites. In contrast to the MPC/lactose system, the addition of mineral rich MC powder to MPC did not significantly change the rate of adsorption (p-value<0.05). Different mixing methods were found to change the rate of moisture adsorption for the MPC/Lactose systems (p-value<0.05). Even though the mechanically mixed powder adsorbed faster than that of solution mixed powder and X-Ray measurement indicated lactose crystal formation, a drop of moisture during the sorption study was not observed. This suggests that water released during crystallisation might be adsorbed by protein. Meanwhile, the application of two different mixing methods did not modify adsorption rate of MPC/MC system, except for samples stored at RH 84.3%. At this environment, mechanically mixed MPC/MC powders were adsorbed more slowly than the solution mixed powder (p-value<0.05). It might reflect powder compaction or a collapse of the porous structure, leading to limited moisture transfer at the interface. Lactose proportions and different mixing methods influenced the glass-rubber transition temperature (Tg-r) of the MPC/Lactose mixtures. An increase in the proportion of lactose tended to depress Tg-r of the mixtures (p-value<0.05). The Tg-r of the mechanically mixed powder was lower than that of solution mixed powder, presumably on account of the Tg-r for mechanically mixed powder being dominated by phase separated sugar components. Meanwhile, the Tg-r of MPC/MC mixtures was not influenced by either MC proportion or mixing method, particularly for samples stored at below RH 65.4%. The XRD-pattern suggested that the crystal formed during storage of MPC/Lactose mixtures was α-lactose monohydrate. As confirmed by XRD, a drop in moisture for the mixture corresponded to the presence of a peak in the XRD pattern, except for mechanically mixed powder. In this type of powder, even though a peak was detected, a moisture drop was not observed. Within the sensitivity limits of XRD, a crystalline form was not observed for MPC/MC mixtures.