Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Structural Changes in Fasted State Dietary Mixed Micelles Upon Solubilization of Beta-Carotene(2022) Bayramoğlu, BesteIt was aimed to investigate the structural changes taking place in duodenal mixed micelles (MM) at fasted state with the incorporation of fatty acids (FA) and the morphological transformations in these MMs upon solubilization of β-carotene (BCR) through coarse-grained (CG) molecular dynamics (MD) simulations. All simulations were performed with GROMACS 2019 simulation package using the Martini force field. Lauric acid (LA), stearic acid (SA) and linoleic acid (LNA) were used to explore the effects of FA chain length and unsaturation. Micelle swelling was observed with the incorporation of all FAs. The increase in size was in line with increasing FA chain length and unsaturation. MMs incorporating LA and SA were ellipsoidal in shape, while polyunsaturated LNA resulted in a worm-like MM. Upon solubilization of BCRs, swelling was observed only in the MMs with long-chain SA and LNA. No micelle growth was observed in the plain and LA MMs despite their smaller sizes. This was attributed to their low-density hydrophobic cores, which allowed a condensation effect induced by the interactions between BCRs and POPC tails. It is inferred that when the micelle is large enough to solubilize BCRs, whether or not swelling will take place depends on the core density. The increase in micelle size was very small in the MM incorporating LNA compared to that in the MM with SA, which was accompanied by an elliptical-to-cylindrical shape transformation. This was due to the fluid nature of the worm-like LNA micelle, which readily allowed the solubilization of 3 BCRs within its core. By resolving the internal structures of BCR incorporated MMs, this study gives valuable insight into the effects of FA chain length and unsaturation on the solubilization behavior of dietary MMs. The results are expected to give direction to the development of rational design strategies for effective BCR delivery systems.Research Project Yarı mamul taze meyve ve sebzeler için katmanlı depozisyon yöntemi ile yeni nesil ince yenilebilir kaplamaların geliştirilmesi(2016) Bayramoğlu, Beste; Üney, Sinem; Koca, NazanBu çalışmanın amacı kitozan ve sodyum kazeinat kullanılarak katmanlı depozisyon ile çok katmanlı (LbL) yenilebilir kaplamaların elde edilmesidir. pH, adsorpsiyon süresi ve katman sayısının film oluşumuna etkileri incelenmiştir. Film oluşumu UV-Vis spektrofotometre ve yüzey plazmon rezonansı (YPR) ile ‘yerinde’ takip edilmiştir. Sonuçlar, LbL kaplama oluşumunun sadece her iki polielektrolitin de ortalama yük yoğunluğuna sahip olduğu pH birleşiminde (5,5-5,5) gerçekleştiğini göstermiştir.Article Citation - WoS: 22Citation - Scopus: 27Layer-By Assembly of Lysozyme With Iota-Carrageenan and Gum Arabic for Surface Modification of Food Packaging Materials With Improved Barrier Properties(Elsevier, 2022) Koca, Nazan; Bayramoğlu, BesteThe study aimed to investigate the surface modification of biaxially oriented polypropylene (BOPP) by layer-by-layer (LbL) assembly of lysozyme (LZ) with two different polysaccharides, iota-carrageenan (IC) and gum arabic (GA), for food packaging applications. The effects of solution pH, adsorption time, elimination of intermediate drying steps were investigated. The LbL film growth was monitored up to 10 deposition steps by UV–Vis spectroscopy and in situ surface plasmon resonance (SPR). The most successful processing conditions for both types of coatings were pH 7–7 combination with intermediate drying and 20 min adsorption time. SPR pointed out a ‘dissolution/reconstruction’ mechanism in film formation. The thickness and surface morphology of the coatings were characterized by Atomic force microscopy (AFM). The surface roughnesses of LZ/IC coatings were higher than that of LZ/GA coatings indicating a denser matrix in the latter. Deposition of 5 bilayers of LZ/IC and LZ/GA on BOPP resulted in 66.15% and 56.89% reduction in oxygen transmission rate (OTR) of the film, respectively. The corresponding reductions in water vapor transmission rate (WVTR) were 28% and 33.52%, respectively. Elimination of intermediate drying steps resulted in less overall deposition, rougher surfaces, diminished oxygen and water barrier properties. The edible LbL coatings obtained in this study possess good gas barrier properties, which is very promising for their use in the preservation of fresh/fresh-cut produce in combination with modified atmosphere packaging applications. The results promise reduced use of plastic films in food packaging.Article Citation - WoS: 11Citation - Scopus: 11Molecular Dynamics Simulations of Duodenal Self Assembly in the Presence of Different Fatty Acids(Elsevier, 2022) Tunçer, Esra; Bayramoğlu, BesteA comprehensive understanding of dietary mixed micelle formation in the presence of lipid digestion products is crucial for an effective design of nutraceutical delivery systems. This study aimed to investigate the duodenal self-assembly of bile lipids and fatty acids (FA) with different characteristics via coarse-grained molecular dynamics (MD) simulations. The results show that increase in FA chain length and unsaturation degree lead to micelles with lower/higher fractions of FAs/bile salts (BS), lower core and surface packing densities, decreased ordering of lipid tails, thus more fluid internal structures. Our findings provide molecular insight into the instability of intestinal colloidal structures composed of long unsaturated FAs. We show the correlation between FA unsaturation degree and lipid packing density is a significant factor in determining the intermicellar BS concentrations. Overall, this study advances the knowledge in the field by establishing a more integral relationship between the FA characteristics and micelle structural properties over a wider range of FA types through MD simulations.Article Citation - WoS: 11Citation - Scopus: 12Characterization of the Self-Assembly and Size Dependent Structural Properties of Dietary Mixed Micelles by Molecular Dynamics Simulations(Elsevier Ltd., 2019) Tuncer, Esra; Bayramoğlu, BesteThe bile salts and phospholipids are secreted by the gallbladder to form dietary mixed micelles in which the solvation of poorly absorbed lipophilic drugs and nutraceuticals take place. A comprehensive understanding of the micellization and structure of the mixed micelles are crucial to design effective delivery systems for such substances. In this study, the evolution of the dietary mixed micelle formation under physiologically relevant concentrations and the dependence of structural properties on micelle size were investigated through coarse grained molecular dynamics simulations. The MARTINI force field was used to model cholate and POPC as the representative bile salt and phospholipid, respectively. The micellization behavior was similar under both fasted and fed state concentrations. Total lipids concentration and the micelle size did not affect the internal structure of the micelles. All the micelles were slightly ellipsoidal in shape independent of their size. The extent of deviation from spherical geometry was found to depend on the micellar POPC/cholate ratio. We also found that the surface and core packing density of the micelles increased with micelle size. The former resulted in more perpendicular alignments of cholates with respect to the surface, while the latter resulted in an improved alignment of POPC tails with the radial direction and more uniform core density.Article Citation - WoS: 23Citation - Scopus: 22Modeling of Polystyrene Under Confinement: Exploring the Limits of Iterative Boltzmann Inversion(American Chemical Society, 2013) Bayramoğlu, Beste; Faller, RolandWe explore the limits of a purely structure based coarse-graining technique, the iterative Boltzmann inversion (IBI), in the coarse-graining of a confined concentrated polystyrene solution. In the first place, some technical considerations and challenges encountered in the course of the optimization process are represented. The concepts of the choice of the initial potentials and the cross-dependency of the interactions as well as the order of optimization are discussed in detail. Furthermore, the transferability of a previously developed CG confined polystyrene solution model, the "parent CG confined model", to different degrees of confinement at constant concentration and temperature is examined. We investigate if a CG force field developed for a confined polymer solution by IBI is sensitive to changes in the degree of localization or arrangement of polymers near the surfaces although the concentration is kept constant. For this purpose, reference atomistic simulations on systems of different confinement levels have been performed. The differences in the structure and dynamics of the chains are addressed. Results are compared with those of an unconfined (bulk) system at the same concentration. The chain dimensions and orientations as a function of the distance from the surfaces are also reported. To the best of our knowledge, this is the first computational study that investigates the structural behavior of polymers in close proximity of the surfaces in a concentrated polymer solution rather than in a melt. Transferability of the parent CG confined model is tested by employing the parent force field in CG simulations of the reference systems. Results indicate that the degree of arrangement of monomers and solvent molecules near the surfaces is an important factor that needs to be paid attention to when considering the application of a CG force field developed by IBI to different degrees of confinement.