Food Science Department Dissertations Collection Copyright (c) 2013 University of Massachusetts - Amherst All rights reserved. http://scholarworks.umass.edu/foodsci_diss Recent documents in Food Science Department Dissertations Collection en-us Tue, 26 Mar 2013 08:45:25 PDT 3600 Lactic Acid Bacteria Mediated Phenolic Bioactive Modulation From Fruit Systems For Health Benefits http://scholarworks.umass.edu/open_access_dissertations/678 http://scholarworks.umass.edu/open_access_dissertations/678 Fri, 15 Mar 2013 11:33:08 PDT Chronic oxidation linked diseases are on a rise and are one of the leading causes of death globally. Epidemiological evidence increasingly points towards consumption of fruits and vegetables as a preventive way to manage early stages of chronic oxidation linked diseases. Oxidation linked diseases are caused by excessive reactive oxygen species (ROS) generated by a disruption in cellular antioxidant homeostasis due to an overload of calories combined with stress, no excerise and a diet low in antioxidants. Phenolic compounds can not only act as antioxidants but also stimulate the activities of antioxidants enzyme through protective pathways which can help modulate cellular protection.

The aim of this dissertation was to use probiotic fermentation to enhance the phenolic and antioxidant compounds in fruit systems which can form the basis of functional food design. The potential of these food systems for disease prevention was investigated in eukaryotic systems through understanding the role of critical metabolic pathways involed in prevention of oxidation linked chronic diseases. Based on structure-function rationale, antioxidant, anti-hyperglycemia and anti-hypertensive potential of phenolic compounds in tea and the effect of extraction time and different degrees of fermentation were investigated in in vitro models. Results indicated that the most fermented teas and a longer extraction time had the highest potential. Further these extracts also had higher H. pylori inhibition potential. Probiotic fermentation of fruit juices with L. helveticus was used to mobilize phenolics and improve biological functionality by maintaining a consistent phytochemical profile. Results indicated that total phenolic and antioxidant potential decreased with feremnetation. However α-glucosidase inhibitory activity and H. pylori inhibitory potential increased with fermentation. Investigation into the mechanism of H. pylori inhibition with fermented cherry extracts revealed inhibition of proline dehydrogenase as the likely mode of action. The potential of fermented apple extracts was further investigated as a phytochemical elicitor in eliciting phenolic and antioxidant response in germinating fava bean. The results indicated a stimulation of phenolic and antioxidant response likely through the stimulation of carbon flux through glycolytic pathways. In yeast, fermented apple extracts accelerated cell death in the presence of peroxide stress in pretreatment model whereas it provided protection against oxidative stress and prevented cell death in concurrent model. Chitosan oligosachharide treatment was investigated as a potential replacement of cancer causing diphenylamine treatment for scald reduction in Cortland apples. Although the treatment did not have any effect on scald reduction, it provides better protection in storage by stimulating phenolic and antioxidant response which related to better health relevant functionality.

]]> Ankolekar, Chandrakant Design and fabrication of functional lipid nanoparticles based on control of interfacial properties using biopolymers http://scholarworks.umass.edu/dissertations/AAI3545992 http://scholarworks.umass.edu/dissertations/AAI3545992 Wed, 16 Jan 2013 12:25:12 PST The main objective of this research was to better understand the formation, stability and properties of emulsions having lipid nanoparticles with tunable functional properties by controlling the composition and structure of the biopolymer interface, in order to develop better food-grade delivery systems. ^ Initially, the influence of environmental stresses (pH, heating and salts) on the physicochemical properties of cationic lactoferrin (LF)-stabilized oil-in-water emulsions was investigated. At ambient temperature, the emulsions were found to be stable at all times except when pH was close to pI. When LF-coated droplets were heated in distilled water, and then their pH was adjusted in the range 2 to 9, they were highly unstable to aggregation at pH 7 and 8. These results have important implications for the formulation and production of emulsion-based products using lactoferrin as an emulsifier. ^ Next, we studied the properties and stability of multilayer emulsions formed using the primary emulsifier lactoferrin and secondary polysaccharides like low methoxyl pectin (LMP), high methoxyl pectin (HMP) and alginate. At neutral pH, electrostatic attractions occurred between the anionic groups on the polysaccharide molecules and the cationic patches on the protein surfaces. In the absence of polysaccharide, the LF-coated droplets were highly unstable to aggregation when heated above about 60 ºC at pH 7, presumably because thermal denaturation of the adsorbed proteins increased droplet attraction. ^ Changes in the physicochemical properties and digestibility of both the primary LF and the secondary LF-polysaccharide emulsions, under simulated gastrointestinal conditions were monitored. The presence of a dietary fiber coating around the initial lipid droplets had little influence on the total extent of lipid digestion in simulated intestinal fluid (SIF), but LF-alginate emulsions had a slower initial digestion rate than the other emulsions. These results suggest that the dietary fiber coatings may become detached in the small intestine, or that they were permeable to digestive enzymes. Pepsin was found to have little influence on the physical stability or digestibility of the emulsions. ^ Next, we fabricated emulsions with oil droplets coated by sequential electrostatic deposition of cationic LF and anionic β-lactoglobulin (BLG) at pH 6.5: LF, LF-BLG, LF-BLG-LF, and LF-BLG-LF-BLG. Changes in the physicochemical properties of these systems were characterized when they were exposed to environmental stresses and simulated small intestine conditions. LF-coated droplets were stable throughout the entire pH range which was attributed to strong steric repulsion. All the nanolaminated droplets were unstable to aggregation at pH 5, which is between the isoelectric points of BLG and LF. ^ Finally, a "premix" approach was utilized to fabricate interfacial coatings around the lipid droplets, instead of the LbL approach. This method involved mixing BLG and LF prior to emulsion formation and the influence of environmental stresses on the properties of these emulsions was examined. Droplets coated by BLG were unstable to aggregation near their isoelectric point (pH ≈ 5), whereas those coated by LF were stable across the whole pH range. The stability of emulsions to pH induced aggregation improved as the ratio of LF-to-BLG in the mixed systems was increased. Lipid droplets coated by either LF or BLG were unstable to aggregation at high salt concentrations (500 mM NaCl, pH 6.5), but those stabilized by mixed protein coatings (LF and BLG) were stable, which was attributed to an increase in interfacial thickness and steric repulsion. Droplets coated by BLG were stable to droplet aggregation after thermal treatment (30 to 90 oC, 0 mM, NaCl pH 7), whereas those coated by LF were highly unstable when heated above their thermal denaturation temperature. The thermal stability of the droplets decreased as the amount of LF in the mixed systems increased. (Abstract shortened by UMI.)^

]]> Tokle, Tanushree Strategies to Improve the Performance of Antioxidants in Oil-in-Water Emulsions http://scholarworks.umass.edu/open_access_dissertations/655 http://scholarworks.umass.edu/open_access_dissertations/655 Wed, 12 Dec 2012 07:58:28 PST Due to the limited number of approved antioxidants for food applications, several alternative strategies to improve antioxidant performance have been developed by focusing on synergistic antioxidant interactions. Susceptibility to lipid oxidation in food systems is the result of the summation of antioxidative and prooxidative mechanisms. Understanding the sometimes paradoxical behavior of antioxidants and prooxidants is a vital key to design synergistic antioxidant systems suitable for particular foods. This research focused on 3 main strategies to improve the performance of antioxidant activity in oil-in-water emulsions.

The first part of this research has been focused on inhibition of lipid oxidation by a combination of the modification of liposomal surfaces by chitosan-coating techniques along with addition of rosmarinic acid esters of varying polarity. Repelling metal ions away from the interface of positively charged liposomes can inhibit lipid oxidation (induced by Fe2+), and also reduce antioxidant loss by Fe3+ reduction. As a result, lipid oxidation can be inhibited synergistically because of a reduction in the prooxidant activity of iron.

Second, understanding non-linear antioxidant behavior (the cut-off effect) of antioxidant esters in oil-in-water (O/W) emulsions was also studied to determine how the distributions and locations of antioxidants impacted their antioxidant activity. Antioxidant activity of rosmarinic acid was improved by esterification with alkyl chain lengths between 4 to 12 carbons due to increased ability to partitioning at the interface in oil-in-water emulsions. Surfactant micelles which could increase or decreased the concentration of the antioxidants at the emulsion droplet interface altered antioxidant activity.

In the last part of this research, rosmarinic acid and its esters were found to be an excellent tool for studying how antioxidant location could impact its ability to interact with α-tocopherol in O/W emulsions. Synergistic, additive, and antagonistic effects were observed in the combinations between the rosmarinate esters with α-tocopherol. Increases in alkyl chain lengths of rosmarinic acid have influenced both the partitioning of the rosmarinate esters as well as their ability to they interact with α-tocopherol at the interface of oil-in-water emulsions. Fluorescence quenching and EPR studies showed that water soluble rosmarinic acid (R0) exhibited more interactions with á-tocopherol than any of the esters (R4-R20). Synergistic antioxidant interactions between rosmarinic acid and α-tocopherol could not be explained by electron transfer mechanisms, but formation of caffeic acid from rosmarinic acid. Due to the thermodynamic infeasibility and the fact that increases in α-tocopherol degradation rates, α-tocopherol could not be regenerated efficiently by rosmarinic acid. This formation of caffeic acid was proposed to be responsible of the synergistic activity of R0 and α-tocopherol since the formation of an additional antioxidant could further increase the oxidative stability of the emulsion.

]]> Panya, Atikorn Fabrication, Characterization and Utilization of Filled Hydrogel Particles as Food Grade Delivery Systems http://scholarworks.umass.edu/open_access_dissertations/652 http://scholarworks.umass.edu/open_access_dissertations/652 Wed, 12 Dec 2012 07:43:56 PST Filled hydrogel particles consisting of emulsified oil droplets encapsulated within a hydrogel matrix were fabricated based on the phase separation of proteins and polysaccharides through aggregative and segregative mechanisms. A 3% (wt/wt) pectin and 3% (wt/wt) caseinate mixture at pH 7 separated into an upper pectin-rich phase and a lower casein-rich phase. Casein-coated lipid droplets added to this mixture partitioned into the lower casein-rich phase. When shear was applied, an oil-in-water-in-water (O/W1/W2) emulsion consisting of oil droplets (O) contained within a casein-rich dispersed phase (W1) suspended in a pectin-rich continuous phase (W2) was formed. Acidification from pH 7 to 5 promoted adsorption of pectin onto casein-rich W1 droplets, forming filled hydrogel particles. Particles were then cross-linked using transglutaminase.

Particles were assessed for stability to changes in pH, increasing levels of salts (sodium chloride and calcium chloride), and susceptibility to lipid oxidation. Both cross-linked and not cross-linked particles were stable at low pH (pH 2-5). At high pH, cross-linked particles maintained their integrity while not cross-linked particles disintegrated. Particles were stable to sodium chloride (0-500 mM). Calcium chloride levels above 4 mM resulted in system gelation. The rate of lipid oxidation for 1% (vol/vol) fish oil encapsulated within filled hydrogel particles was compared to that of oil-in-water emulsions stabilized by either Tween 20 or casein. Emulsions stabilized by Tween 20 oxidized faster than either filled hydrogel particles or casein stabilized emulsions, while filled hydrogel particles and casein stabilized emulsions showed similar oxidation rates. Using an in-vitro digestion model, the digestion of lipid encapsulated within filled hydrogel particles was compared to that of a casein stabilized oil-in-water emulsion. Results showed similar rates of digestion for both hydrogel and emulsion samples.

Attempts to fabricate particles using free oil (rather than emulsified oil) were unsuccessful and resulted in the formation of large non-encapsulated oil droplets (d ~10 μm). By controlling particle concentrations of biopolymer, water, and oil, it was possible to fabricate particles that were highly resistant to gravitational separation which was attributed to the equivalent density of the continuous and particle phases. Results highlight the potential applications and versatility of this delivery system.

]]> Matalanis, Alison M. Minor components and their roles on lipid oxidation in bulk oil that contains association colloids http://scholarworks.umass.edu/dissertations/AAI3518215 http://scholarworks.umass.edu/dissertations/AAI3518215 Mon, 24 Sep 2012 11:00:20 PDT The combination of water and surface active compounds found naturally in commercially refined vegetable oils have been postulated to form physical structures known as association colloids. This research studied the ability of 1,2-dioleoyl-sn-glycerol-3-phosphocholine (DOPC) and water to form physical structures in stripped soybean oil. Interfacial tension and fluorescence spectrometry results showed the critical micelle concentration (CMC) of DOPC in stripped soybean oil was 650 and 950 µM, respectively. Light scattering attenuation results indicated that the structure formed by DOPC was reverse micelles. The physical properties of DOPC reverse micelles were determined using small-angle X-ray scattering (SAXS) and fluorescence probes. These studies showed that increasing the water concentration altered the size and shape of the reverse micelles formed by DOPC. ^ The impact of DOPC reverse micelles on the lipid oxidation of stripped soybean oil was investigated by following the formation of primary and secondary lipid oxidation products. DOPC reverse micelles had a prooxidant effect, shortening the oxidation lag phase of SSO at 55 °C. It also was not able to change the lipid oxidation of stripped soybean oil compared with DOPC reverse micelles at same concemtration ( i.e., 950 µM). 1,2-dibutyl-sn-glycerol -3-phosphocholine (DC4PC) which has the shorter fatty acid than DOPC was not able to form association colloids and did not impact lipid oxidation rates. This indicated that the choline group of the phospholipid was not responsible for the increased oxidation rates and suggested that the physical structure formed by DOPC was responsible for the prooxidant effect. ^ The impact of the DOPC reverse micelles on the effectiveness and physical location of the antioxidants, α-tocopherol and Trolox was also studied. Both non-polar (α-tocopherol) and polar (Trolox) were able to inhibit lipid oxidation in stripped soybean oil in the presence of DOPC reverse micelles. Trolox was a more effective antioxidant than α-tocopherol. Fluorescence steady state and lifetime decay studies suggested that both α-tocopherol and Trolox were associated with DOPC reverse micelle in bulk oil. Trolox primarily concentrated in the water pool of reverse micelle since it quenched NBD-PE fluorescence intensity with increasing concentrations. A portion of α-tocopherol was also associated with the aqueous phase of the DOPC reverse micelles but this was likely at the oil-water interface since α-tocopherol is not water soluble. ^ The addition of ferric chelator, deferoxamine (DFO) to stripped soybean oil significantly prevented the lipid oxidation caused by DOPC reverse micelles as the lag phase was extended from 2 to 7 days. DFO was also found to increase the antioxidant activity of both Trolox and α-tocopherol. Trolox and α-tocopherol were found to be rapidly decomposed by high-valence Fe(III) while low-valence-state (Fe (II) was much less reactive. Fe(III) was also consumed by both hydrophilic Trolox and lipophilic α-tocopherol presumably though reduction to Fe (II). DOPC reverse micelles were able to decrease antioxidants-iron interactions as evidence by a decrease in antioxidant depletion by iron and a decrease in iron reduction by the antioxidants. These results suggested that the ability of DFO to increase the antioxidant activity of α-tocopherol and Trolox was due to its ability to decrease free radical production and not its ability to decrease direct iron-antioxidant interactions. ^ Overall, the results presented in this dissertation show phospholipids and water can form reverse micelles in edible oils. These reverse micelles increase lipid oxidation rates by increasing the prooxidant activity of iron. Free radical scavenging antioxidants can inhibit oxidation promoted by the reverse micelles with polar Trolox being more effective than non-polar α-tocopherol presumably because Trolox is more highly associated with the reverse micelle. The reverse micelles produced by DOPC protected α-tocopherol and Trolox from direct degradation by iron. The knowledge gained from this study will improve our understanding of the mechanism of lipid oxidation in bulk oils which will hopefully provide new technologies to improve the oxidation stability of edible oils. For example, it may be able to use oil refining technologies to remove prooxidative minor components that for physical structure in bulk oils.^

]]> Chen, Bingcan Minor Components and Their Roles on Lipid Oxidation in Bulk Oil That Contains Association Colloids http://scholarworks.umass.edu/open_access_dissertations/540 http://scholarworks.umass.edu/open_access_dissertations/540 Wed, 29 Aug 2012 09:23:52 PDT The combination of water and surface active compounds found naturally in commercially refined vegetable oils have been postulated to form physical structures known as association colloids. This research studied the ability of 1,2-dioleoyl-sn-glycerol-3-phosphocholine (DOPC) and water to form physical structures in stripped soybean oil. Interfacial tension and fluorescence spectrometry results showed the critical micelle concentration (CMC) of DOPC in stripped soybean oil was 650 and 950 microM, respectively. Light scattering attenuation results indicated that the structure formed by DOPC was reverse micelles. The physical properties of DOPC reverse micelles were determined using small-angle X-ray scattering (SAXS) and fluorescence probes. These studies showed that increasing the water concentration altered the size and shape of the reverse micelles formed by DOPC.

The impact of DOPC reverse micelles on the lipid oxidation of stripped soybean oil was investigated by following the formation of primary and secondary lipid oxidation products. DOPC reverse micelles had a prooxidant effect, shortening the oxidation lag phase of SSO at 55 °C. It also was not able to change the lipid oxidation of stripped soybean oil compared with DOPC reverse micelles at same concemtration ( i.e., 950 microM). 1,2-dibutyl-sn-glycerol-3-phosphocholine (DC4PC) which has the shorter fatty acid than DOPC was not able to form association colloids and did not impact lipid oxidation rates. This indicated that the choline group of the phospholipid was not responsible for the increased oxidation rates and suggested that the physical structure formed by DOPC was responsible for the prooxidant effect.

The impact of the DOPC reverse micelles on the effectiveness and physical location of the antioxidants, alpha-tocopherol and Trolox was also studied. Both non-polar (alpha-tocopherol) and polar (Trolox) were able to inhibit lipid oxidation in stripped soybean oil in the presence of DOPC reverse micelles. Trolox was a more effective antioxidant than alpha-tocopherol. Fluorescence steady state and lifetime decay studies suggested that both alpha-tocopherol and Trolox were associated with DOPC reverse micelle in bulk oil. Trolox primarily concentrated in the water pool of reverse micelle since it quenched NBD-PE fluorescence intensity with increasing concentrations. A portion of alpha-tocopherol was also associated with the aqueous phase of the DOPC reverse micelles but this was likely at the oil-water interface since alpha-tocopherol is not water soluble.

The addition of ferric chelator, deferoxamine (DFO) to stripped soybean oil significantly prevented the lipid oxidation caused by DOPC reverse micelles as the lag phase was extended from 2 to 7 days. DFO was also found to increase the antioxidant activity of both Trolox and alpha-tocopherol. Trolox and alpha-tocopherol were found to be rapidly decomposed by high-valence Fe(III) while low-valence-state (Fe (II) was much less reactive. Fe(III) was also consumed by both hydrophilic Trolox and lipophilic alpha-tocopherol presumably though reduction to Fe (II). DOPC reverse micelles were able to decrease antioxidants-iron interactions as evidence by a decrease in antioxidant depletion by iron and a decrease in iron reduction by the antioxidants. These results suggested that the ability of DFO to increase the antioxidant activity of alpha-tocopherol and Trolox was due to its ability to decrease free radical production and not its ability to decrease direct iron-antioxidant interactions.

Overall, the results presented in this dissertation show phospholipids and water can form reverse micelles in edible oils. These reverse micelles increase lipid oxidation rates by increasing the prooxidant activity of iron. Free radical scavenging antioxidants can inhibit oxidation promoted by the reverse micelles with polar Trolox being more effective than non-polar alpha-tocopherol presumably because Trolox is more highly associated with the reverse micelle. The reverse micelles produced by DOPC protected alpha-tocopherol and Trolox from direct degradation by iron. The knowledge gained from this study will improve our understanding of the mechanism of lipid oxidation in bulk oils which will hopefully provide new technologies to improve the oxidation stability of edible oils. For example, it may be able to use oil refining technologies to remove prooxidative minor components that for physical structure in bulk oils.

]]> Chen, Bingcan Effects of Free Fatty Acids, Mono- and Diacylglycerols on Oxidative Stability of Soybean Oil-In-Water Emulsions http://scholarworks.umass.edu/open_access_dissertations/376 http://scholarworks.umass.edu/open_access_dissertations/376 Fri, 19 Aug 2011 09:13:48 PDT Even though edible oils undergo refining processes to remove undesirable components, commercial oils still contain small amounts of minor components that can contribute to either prooxidant and antioxidant pathways which ultimately affect the quality of the oils. The objective of this research was to determine the role of free fatty acids and mono- and diacylglycerols on the oxidative stability of oil-in-water emulsions.

Free fatty acids acted as a strong prooxidants in stripped soybean oil-in-water emulsions. Concentrations as low as 0.1% of the lipid accelerated lipid oxidation rate by both shortening the lag phase of lipid hydroperoxide and hexanal formation. The results showed that the most likely mechanisms for the prooxidant activity of free fatty acids is through their ability to increase the negatively charge on emulsion droplets that in turn could attract the cationic transition metals to the emulsion droplet surface where they can interact with lipid and thus promote oxidation. The prooxidant activity of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic < linoleic < oleic. Surprisingly, an increase in the degree of unsaturation of the free fatty viii acids lowered the ability of the free fatty acids to promote oxidation which may be due to their differences in geometric shape thus influencing their ability to access the emulsion droplet interface and increase the negative charge. Overall, free fatty acids are strong prooxidants in oil-in-water emulsions. This prooxidant activity is dependent not only on their concentration but also on the molecular structure of the fatty acid.

Addition of mono- and diacylglycerols in oil-in-water emulsions showed an antioxidative effect in both non-stripped and stripped soybean oil. Addition of 1-monooleoylglycerol only had a small impact on the oxidative stability of non-stripped soybean oil-in-water emulsions but did inhibit lipid oxidation in emulsions prepared with stripped soybean. Much stronger antioxidant activity was observed upon the addition of 1,2-dioleoyl-sn-glycerol to both non-stripped and stripped soybean oil-in-water emulsions. Both lipid hydroperoxide and hexanal formation decreased with increasing 1,2-dioleoyl-sn-glycerol concentrations with 2.5% 1,2-dioleoyl-sn-glycerol almost completely preventing hydroperoxide and hexanal production over the course of the study. Overall, these results suggest that diacylglycerols could be an effective antioxidant in oil-in-water emulsions which possibility due to their ability to form a liquid crystal phase which could form a physical barrier that decreases interactions between unsaturated fatty acids in the emulsion droplet core and prooxidants or oxygen in the aqueous phase of the emulsion. However, the antioxidant mechanism of diacylglycerols is not currently understood and needs further investigation.

]]> Waraho, Thaddao Characterization of Listeria monocytogenes biofilm formation: A molecular approach by target gene knockout and mariner-based transposon mutagenesis http://scholarworks.umass.edu/dissertations/AAI3427506 http://scholarworks.umass.edu/dissertations/AAI3427506 Tue, 24 May 2011 15:18:22 PDT The food-borne pathogen Listeria monocytogenes can attach to environmental surfaces and form biofilms which can be a source of food contamination, yet little is known about the molecular mechanisms of its biofilm development. The overall objective of this study was to identify the genetic requirements of biofilm formation by L. monocytogenes.^ In-frame deletion mutants of a putative mutarotase gene (lmo2476/lin2619 ) were constructed to investigate its influence on Listeria biofilm formation. No biofilm phenotype changes were observed between the wild type and the corresponding mutants, indicating that the putative mutarotase gene was not involved in Listeria biofilm formation under the conditions tested.^ A mariner-based transposon mutagenesis was performed to generate mutants of L. monocytogenes. A mutant library consisting of 6,500 colonies was screened for reduced biofilm formation. A total of 24 distinct loci were identified, 18 of which, to our knowledge, have not been previously reported to function in the biofilm formation of L. monocytogenes.^ A putative DNA translocase gene, lmo1386, was further characterized. The mutant was complemented, and the complemented mutant restored its biofilm phenotype. The lmo1386 mutants showed reduced initial attachment abilities, and had higher numbers of elongated cells when grown in a nutrient TSBYE broth. However, the exact mechanisms of how lmo1386 affects biofilm formation remain to be elucidated.^ The inhibitory effects of EDTA against biofilm formation of L. monocytogenes were investigated. EDTA at a concentration of 0.1 mM efficiently inhibited biofilm formation of L. monocytogenes without affecting its planktonic growth. EDTA functions in the early stage by affecting the initial attachment of L. monocytogenes cells to surfaces, though the mechanisms remain unclear.^ The role of extracellular DNA (eDNA) in the formation of L. monocytogenes biofilm was determined indirectly by treatments of DNase I. Our data adds to the knowledge that eDNA plays an essential role in attachment and maintenance of L. monocytogenes biofilm. The pre-formed biofilms on the wells of microtiter plates could be efficiently removed by DNase I, suggesting a potential use of DNase I to eradicate the existing L. monocytogenes biofilms.^

]]> Chang, Yuhua Fabrication of Protein-Polysaccharide Particulates through Thermal Treatment of Associative Complexes http://scholarworks.umass.edu/open_access_dissertations/145 http://scholarworks.umass.edu/open_access_dissertations/145 Fri, 04 Dec 2009 08:53:54 PST Mixed solutions of β-lactoglobulin and anionic polysaccharides, specifically pectin, were formed into associative complexes through pH reduction from neutral conditions. Thermal treatment of these associative complexes was investigated as a function of biopolymer composition, heating conditions, pH, and ionic strength. Thermal treatment of β-lactoglobulin-pectin complexes at pH 4.5 – 5.0 was found to create protein-based particulates of consistent and narrow size distribution (diameter ~ 150 – 400 nm). These particulates were relatively stable to further pH adjustment and to high levels of salt (200 NaCl). Particle characteristics were maintained after re-suspending them in aqueous solutions after they have been either frozen or lyophilized. Thermal analysis of β- lactoglobulin-pectin complexes using calorimetry (DSC) and turbidity-temperature scanning indicated that the denaturation of β-lactoglobulin was unaffected by pectin, but protein aggregation was limited by the presence of pectin. Biopolymer particles formed using two different methods were compared: Type 1 – forming β-lactoglobulin nanoparticles by heating, then coating them with pectin; Type 2 – forming particles by heating β-lactoglobulin and pectin together. Type 2 particles had smaller diameters and had better pH and salt stability than Type 1 particles. It was proposed that Type 2 particles had a pectin-saturated surface that limited their aggregation, whereas Type 1 particles had “gaps” in the pectin surface coverage that led to greater aggregation. Finally, the possibility of controlling the size and concentration of biopolymer particles formed by heating β-lactoglobulin-pectin complexes by controlling preparation conditions was studied. Biopolymer particle size and concentration increased with increasing holding time (0 to 30 minutes), decreasing holding temperature (90 to 70 ºC), increasing protein concentration (0 to 2 wt%), increasing pH (4.5 to 5.0), and increasing salt concentration (0 to 50 mol/kg). The influence of these factors on biopolymer particle size was attributed to their impact on protein-polysaccharide interactions, protein denaturation, and protein aggregation kinetics. The knowledge gained from this study will facilitate the rational design of biopolymer particles with specific physicochemical and functional attributes that can be used in the food and other industries, e.g., for encapsulation, texture modification, optical properties modification.

]]> Jones, Owen Griffith Development of Structured Delivery Systems Using Nanolaminated Biopolymer Layers http://scholarworks.umass.edu/open_access_dissertations/89 http://scholarworks.umass.edu/open_access_dissertations/89 Tue, 01 Dec 2009 13:52:58 PST The objectives of this study were to carry out research to better understand of the formation, stability and properties of multilayer emulsions containing nano-laminated biopolymer coatings, and to utilize this information to develop food-grade delivery systems. The effect of various preparation parameters on the formation and stability of multilayer emulsions was investigated: droplet concentration; mean droplet diameter; droplet charge; biopolymer concentration. β-lactoglobulin (β-Lg) stabilized emulsions (0.5 – 10 wt% oil) containing different pectin concentrations (0 to 0.5 wt%) were prepared at pH 7 (where lipid droplets and pectin molecules were both anionic) and pH 3.5 (where lipid droplets were cationic and pectin molecules anionic) and “stability maps” were constructed. At pH 3.5, pectin adsorbed to the droplet surfaces, and the emulsions were unstable to bridging flocculation at intermediate pectin concentrations and unstable to depletion flocculation at high pectin concentrations. At certain droplet and pectin concentrations stable multilayer emulsions could be formed consisting of protein-coated lipid droplets surrounded by a pectin layer. An in situ electro-acoustic (EA) technique was introduced to monitor the adsorption of charged polysaccharides onto oppositely charged protein-coated lipid droplets. The possibility of controlling interfacial and functional characteristics of multilayer emulsions by using mixed polysaccharides (pectin/carrageenan or pectin/gum arabic) was then examined. Emulsions containing different types of polysaccharides had different interfacial characteristics and aggregation stabilities: carrageenan had the highest charge density and affinity for the protein-coated lipid droplets, but gave the poorest emulsion stability. The possibility of assembling protein-rich coatings around lipid droplets was examined using the electrostatic deposition method, with the aim of producing emulsions with novel functionality. Protein-rich biopolymer coatings consisting of β-Lg and pectin were formed around lipid droplets using the electrostatic deposition method. The composite particles formed had relatively small diameters (d < 500 nm) and were stable to gravitational separation. They also remained stable after they were heated above the thermal denaturation temperature of the globular protein and had better stability to aggregation at high salt concentrations (50 – 200 mM NaCl) than conventional emulsions stabilized by only protein. The effect of a polysaccharide coating on the displacement of adsorbed globular proteins by non-ionic surfactants from lipid droplet surfaces was examined to simulate situations where competitive adsorption occurs. Oil-in-water emulsions stabilized by β- Lg were prepared containing either no pectin (1º emulsions) or different amounts of pectin (2º emulsions). At pH 3.5, where pectin forms a coating around the β-Lg stabilized lipid droplets, the amount of desorbed protein was much less for the 2º emulsion (3%) than for the 1º emulsion (39%), which indicated that the pectin coating inhibited protein desorption by surface active agents. Knowledge gained from this research will provide guidelines for rationally designing emulsion-based delivery systems that are resistant to environmental stresses or with controlled release properties. These delivery systems could be used to encapsulate, protect and release functional components in various industrial products, such as foods, pharmaceuticals, cosmetics, and personal care products.

]]> Cho, Young-Hee