Inom dagens tillverkande företag pågår en allt större konkurrens om att vinna marknadens kunder. En av de främsta konkurrenskrafterna är korta ledtider. Som ett led i detta har vetenskapliga filosofier och metoder inom Lean blivit allt mer förekommande inom verksamheterna. Teorierna handlar om att skapa effektiva processer och att producera rätt produkt, till rätt kvalitet inom rätt tid. Under de senaste åren har en ökad medvetenhet för inköp-och orderhanteringens betydelse trätt fram. Enligt tidigare forskning kan en effektiv inköps-och orderhanteringsprocess bidra till att den totala tillverkningsprocessens ledtid effektiviseras. Sekventiella arbetsprocesser är vanligt förekommande trots att administrativa handläggningsaktiviteter ofta kan utföras parallellt, detta medför en onödig fördröjning av ledtiden. Studiens syfte är undersöka hur orderhanteringsprocessen ledtid kan reduceras. En ledtidsreducering baserat på att finna icke värdeskapande aktiviteter och problemområden inom och åtgärda dessa med hjälp av lämpliga åtgärdsmetoder.   Arbetet är en fallstudie som utförts på teknikutvecklingsföretaget Syntronic. Arbetets empiriska studie gjordes genom intervjuer, observationer och dokument. För att underlätta analysarbetet användes ett fiskbensdiagram för att finna orsakerna till problemområden och icke värdeskapande aktiviteter i processen. För att förtydliga processflödet och vart i processen de identifierade problemområdena uppstod kartlades observationen genom en värdeflödesanalys. Arbetets litteraturstudie bestod av teorier kring orderhantering, effektivisering, ledtider och Lean.   Analysarbetet gav upphov till att bristande kommunikation, avsaknad av standardiserat arbetssätt, bristande planering, bristande affärssystem samt bristande helhetssyn var orsakerna till den ineffektiva orderhanteringsprocessen. Studien resulterade i att lämpliga förbättringsåtgärder och arbetsmetoder kunde urskiljas. Metoder inom Lean som 5S, Kaizen och TQM (Total Quality Management) ansågs kunna lämpa sig för fallstudien. Analysarbetet inspirerade även till att utveckla förslag till en ny arbetsmetod: 5S Administration Plus. Arbetsmodellen talar för vikten att standardisera arbetsrutiner, följa upp och utvärdera för att bibehålla förbättringsarbetet.   Studiens teoretiska bidrag talar för hur kombinationen av metoder inom Lean kan tillämpas som effektiviseringsverktyg i en administrativ orderhanteringsprocess. Det praktiska bidraget svarar på studiens syfte och frågeställning angående hur orderhanteringsprocessen kan effektiviseras.

This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry. / Whole document restricted, but available by request, use the feedback form to request access.

This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry. / Whole document restricted, but available by request, use the feedback form to request access.

Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry. / Whole document restricted, but available by request, use the feedback form to request access.

This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry. / Whole document restricted, but available by request, use the feedback form to request access.

Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

This thesis relates the physicochemical properties of phenolic compounds to their antioxidant activities. It focuses on the partitioning of phenolic compounds between hydrophilic and lipophilic environments and the relevance this has to their in vivo health effects. Data in the literature was lacking so the phase partition coefficients (log P) of 53 phenolic antioxidants were measured by reversed-phase HPLC and calculated by log P prediction software. There was a very strong linear correlation between measured and calculated values (r=0.91). The importance of log P in determining antioxidant assay values was then tested by developing an assay system capable of measuring activities of both hydrophilic and lipophilic antioxidants. This Lipid Peroxidation Inhibition Capacity Assay (LPIC), based on using liposomes to simulate a cell membrane environment, was then used to measure the activity of antioxidants with a broad range of structures. The activities were correlated against log p, the difference of heat of formation (∆Hf) and half-wave potential (Ep/2) and used to derive a predictive model to calculate the LPIC activity. There was a highly significant linear correlation between the calculated and measured values. The LPIC activities also correlated well to published LDL inhibition activities but not to measured ORAC activities. These findings suggested that behaviours of antioxidants in the small unilamellar vesicles of the LPIC assay were similar to that in the LDL assay but not to the aqueous phase based ORAC assay. The LPIC assay may therefore be a better indicator of potential health benefits of antioxidants in the human body than the ORAC assay. The possible mechanistic reasons are that it may better reflect ability to prevent the oxidation of LDL blood stream particles that leads to cardiovascular disease and also takes into account the importance of membrane solubility which can raise the cellular concentration and thus potential to protect cells from oxidative damage. KEYWORDS: LPIC, LDL; Antioxidant; Phytochemical; Polyphenolic; Phenolic acid; Flavonoids; log P; Partition Coefficient; Liposome; Lipid bilayer; Lipid Membrane; ORAC; Comet assay; Flow Cytometry. / Whole document restricted, but available by request, use the feedback form to request access.