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1.
Sci Rep ; 14(1): 8261, 2024 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-38589622

RESUMO

In view of the health concerns associated with high sugar intake, this study investigates methods to enhance sweetness perception in chocolate without increasing its sugar content. Using additive manufacturing, chocolate structures were created from masses with varying sugar and fat compositions, where hazelnut oil served as a partial cocoa butter replacement. The study found that while variations in sugar content minimally affected the physical properties of the chocolate masses, hazelnut oil significantly modified melting behavior and consumption time. Chocolate masses with higher hazelnut oil content but similar sugar content exhibited a 24% increase in sweetness perception, likely due to accelerated tastant (i.e., sucrose) release into saliva. Multiphase structures, designated as layered, cube-in-cube, and sandwich structures, exhibited less sensory differences compared to the homogeneous control. Nonetheless, structures with hazelnut oil-rich outer layers resulted in an 11% increase in sweetness perception, even without sugar gradients. This suggests that tastant release plays a more critical role than structural complexity in modifying sweetness perception. This research highlights the efficacy of simpler multiphase structures, such as sandwich designs, which offer sensory enhancements comparable to those of more complex designs but with reduced manufacturing effort, thus providing viable options for industrial-scale production.


Assuntos
Cacau , Chocolate , Cacau/química , Sacarose , Carboidratos , Nutrientes
2.
Food Res Int ; 179: 113968, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38342524

RESUMO

The rising demand for plant-based meat analogues as alternatives to animal products has sparked interest in understanding the complex interplay between their structural and mechanical properties. The ability to manipulate the processing parameters and protein blend composition offers fundamental insights into the texturization process and holds economic and sustainable implications for the food industry. Consequently, the correlation between mechanical and structural properties in meat analogues is crucial for achieving consumer satisfaction and successful market penetration, providing comprehensive insights into the textural properties of meat analogues and their potential to mimic traditional animal produce. Our study delves into the relationship between structural and mechanical anisotropy in meat analogues produced using high moisture extrusion cooking, which involves blending protein, water, and other ingredients, followed by a controlled heating and cooling process to achieve a fibrous texture akin to traditional meat. By employing techniques such as scanning small-angle X-ray scattering, scanning electron microscopy, and mechanical testing we investigate the fibrous structure and its impact on the final texture of meat analogues. We show that textural and structural anisotropy is reflected on the mechanical properties measured using tensile and dynamic mechanical techniques. It is demonstrated that the calculated anisotropy indexes, a measure for the degree of textural and structural anisotropy, increase with increasing protein content. Our findings have significant implications for the understanding and development of plant-based meat analogues with structures that can be tuned to closely resemble the animal meat textures of choice, thereby enabling consumers to transition to more sustainable dietary choices while preserving familiar eating habits.


Assuntos
Temperatura Baixa , 60450 , Animais , Anisotropia , Culinária , Carne
3.
Curr Res Food Sci ; 7: 100580, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37811484

RESUMO

Meat-like foods based on plant protein sources are supposed to be a solution for a more sustainable sustenance of the world population while also having a great potential to reduce the impact on climate change. However, the transition from animal-based products to more climate-friendly alternatives can only be accomplished when consumers' acceptance of plant-based alternatives is high. This article introduces a novel micro-foaming process for texturized High-Moisture Meat Analogues (HMMA) conferring enhanced structural properties and a new way to tailor the mechanical, appearance and textural characteristics of such products. First, the impact of nitrogen injection and subsequent foaming on processing pressures, temperatures and mechanical energy were assessed using soy protein concentrate and injecting nitrogen fractions in a controlled manner in the range of 0 wt% to 0.3 wt% into the hot protein melt. Direct relationships between related extrusion parameters and properties of extruded HMMAs were established. Furthermore, optimized processing parameters for stable manufacturing conditions were identified. Secondly, so produced HMMA foams were systematically analyzed using colourimetry, texture analysis, X-ray micro-tomography (XRT) and by performing water and Preprint submitted to Innovative Food Science and Emerging Technologies June 17, 2023 oil absorption tests. These measurements revealed that perceived lightness, textural hardness, cohesiveness and overrun can be tailored by adapting the injected N2 concentrations provided that the gas holding capacity of the protein matrix is high enough. Moreover, the liquid absorption properties of the foamed HMMA were greatly optimized. XRT measurements showed that the porosity at the center of the extrudate strands was the highest. The largest porosity of 53% was achieved with 0.2 wt% N2 injection, whilst 0.3 wt% N2 lead to destructuration of the HMMA foam structure through limited gas dispersion and wall slip layer formation. The latter can, nonetheless, be improved by adapting the processing parameters. All in all, this novel extrusion microfoaming process opens new possibilities to enhance the structural properties of plant-based HMMA and ultimately, consumers' acceptance.

4.
NPJ Sci Food ; 7(1): 42, 2023 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-37596255

RESUMO

Additive manufacturing (AM) is creating new possibilities for innovative tailoring of food properties through multiscale structuring. This research investigated a high-speed inkjet-based technique aimed to modify sweetness perception by creating dot patterns on chocolate surfaces. The dots were formulated from cocoa butter with emulsified water droplets containing the sweetener thaumatin. The number and surface arrangement of dots, which ranged from uniformly distributed patterns to concentrated configurations at the sample's center and periphery, were varied while maintaining a constant total amount of thaumatin per sample. A sensory panel evaluated sweetness perception at three consumption time points, reporting a significant increase when thaumatin was concentrated on the surface. Specifically, an amplification of sweetness perception by up to 300% was observed, irrespective of dot pattern or consumption time, when compared to samples where thaumatin was uniformly distributed throughout the bulk. However, when thaumatin was concentrated solely at the sample center, maximum sweetness perception decreased by 24%. Conclusively, both the proximity of thaumatin to taste receptors and its spatial distribution, governed by different dot arrangements, significantly influenced taste responsiveness. These findings present a more effective technique to substantially enhance sweetness perception compared to traditional manufacturing techniques. This method concurrently allows for sensorial and visual customization of products. The implications of this study are far-reaching, opening avenues for industrially relevant AM applications, and innovative approaches to study taste formation and perception during oral processing of foods.

5.
J Colloid Interface Sci ; 630(Pt A): 731-741, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36274408

RESUMO

The crystallization behavior of lipids is relevant in many fields such as adipose tissue formation and regeneration, forensic investigations and food production. Using a lipid model system composed of triacylglycerols, we study the formation of crystalline structures under laminar shear flows across various length scales by polarized light-, scanning electron-, and atomic force microscopy, as well as laser diffraction spectroscopy. The shear rate during crystallization γ̇cryst influences the acyl-chain length structure and promotes domain growth into the flow direction thereby transforming the crystallites from oblate into prolate particles. Concentration dependent aggregation of crystallites into clusters is the rate limiting step for floc and floc network formation. At high γ̇cryst, fast crystallite cluster formation at smaller equilibrium diameters is promoted. The high crystallite cluster concentration induces their aggregation into flocs which form weak networks. At low γ̇cryst, floc generation is limited by the low amount of crystallite clusters leading to slow growth of larger flocs and forming of strong networks. The findings in this work have potential implications ranging from the design of injectable soft tissue fillers for adipose tissue regeneration, to the crystalline network formation in microorganism derived lipids, up to a more energy-efficient production of chocolate confectionery.


Assuntos
Cristalização , Microscopia de Força Atômica , Triglicerídeos/química
6.
Soft Matter ; 18(6): 1183-1193, 2022 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-35037667

RESUMO

The rheology of triacylglycerol (TAG) crystal-melt suspensions (CMSs) consisting of anhydrous milk fat (AMF), cocoa butter (CB), and palm kernel oil (PKO) as function of crystallization shear rate cryst and crystal volume fraction ΦSFC is investigated by in-line ultrasound velocity profiling - pressure difference (UVP-PD) rheometry. Measurements up to ΦSFC = 8.8% are presented. Below the percolation threshold Φc, no yield stress τ0 is observed and the viscosity η scales linearly with ΦSFC. Above Φc, a non-linear dependency of both τ0 and η as function of ΦSFC is apparent. For AMF and CB, the increase in cryst leads to a decrease in η and τ0 as function of ΦSFC, whereas for PKO based CMSs the opposite is the case. Scanning electron microscopy (SEM) and polarized light microscopy (PLM) relate these rheological findings to the microstructure of the investigated CMSs by taking the effective aspect ratio aeff and the concept of the effective crystal volume fraction ΦeffSFC into account. Foam formation by dynamically enhanced membrane foaming (DEMF) is performed directly after crystallization and reveals that depending on the CMS rheology and crystallite-, crystallite cluster- and crystal floc microstructure, a wide range of gas volume fractions between 0.05-0.6 are achievable.

7.
Acta Biomater ; 130: 32-53, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34077806

RESUMO

Fluid interfaces, i.e. the boundary layer of two liquids or a liquid and a gas, play a vital role in physiological processes as diverse as visual perception, oral health and taste, lipid metabolism, and pulmonary breathing. These fluid interfaces exhibit a complex composition, structure, and rheology tailored to their individual physiological functions. Advances in interfacial thin film techniques have facilitated the analysis of such complex interfaces under physiologically relevant conditions. This allowed new insights on the origin of their physiological functionality, how deviations may cause disease, and has revealed new therapy strategies. Furthermore, the interactions of physiological fluid interfaces with exogenous substances is crucial for understanding certain disorders and exploiting drug delivery routes to or across fluid interfaces. Here, we provide an overview on fluid interfaces with physiological relevance, namely tear films, interfacial aspects of saliva, lipid droplet digestion and storage in the cell, and the functioning of lung surfactant. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe therapies and drug delivery approaches targeted at fluid interfaces. STATEMENT OF SIGNIFICANCE: Fluid interfaces are inherent to all living organisms and play a vital role in various physiological processes. Examples are the eye tear film, saliva, lipid digestion & storage in cells, and pulmonary breathing. These fluid interfaces exhibit complex interfacial compositions and structures to meet their specific physiological function. We provide an overview on physiological fluid interfaces with a focus on interfacial phenomena. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe novel therapies and drug delivery approaches targeted at fluid interfaces. This sets the scene for ocular, oral, or pulmonary surface engineering and drug delivery approaches.


Assuntos
Preparações Farmacêuticas , Lágrimas , Sistemas de Liberação de Medicamentos , Reologia
8.
Materials (Basel) ; 14(9)2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33946697

RESUMO

An open-porous protein sponge with mixed wettability is presented made entirely from whey proteins and with promising applications in biomedicine, pharmaceutical, and food industry. The fabrication relies on an additive-free, clean and scalable process consisting of foaming followed by controlled microwave-convection drying. Volumetric heating throughout the matrix induced by microwaves causes fast expansion and elongation of the foam bubbles, retards crust formation and promotes early protein denaturation. These effects counteract collapse and shrinkage typically encountered in convection drying of foams. The interplay of high protein content, tailored gas incorporation and controlled drying result in a dried structure with dual-scale porosity composed of open macroscopic elongated foam bubbles and microscopic pores in the surrounding solid lamellae induced by water evaporation. Due to the insolubility and mixed wettability of the denatured protein network, polar and non-polar liquids are rapidly absorbed into the interconnected capillary system of the sponge without disintegrating. While non-watery liquids penetrate the pores by capillary suction, water diffuses also into the stiff protein matrix, inducing swelling and softening. Consequently, the water-filled soft sponge can be emptied by compression and re-absorbs any wetting liquid into the free capillary space.

9.
Curr Res Food Sci ; 4: 182-190, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33889851

RESUMO

Crust treatments, namely edible bread coatings, enzymatic crust modification and chemical crust modification, were introduced with the intention to minimize bread water loss during ambient storage. It was observed that compared to the treated bread, the untreated bread had significantly higher weight loss and crumb firmness after 14 days of ambient storage. A large array of materials was tested, among which hydrophobic coatings were shown to have the highest moisture barrier efficiency. In particular, the 20% candelilla wax coating (solution of 20% candelilla wax in sunflower oil), 20% beeswax coating (solution of 20% beeswax in sunflower oil) and HPMC oleogel coating (coating containing hydroxypropyl methyl cellulose oleogel) were proved to be most effective, thanks to their low affinity with water and low water vapor permeability. The application of the 20% candelilla wax coating resulted in reductions of the bread weight loss from about 30 to 13% and the crumb firmness from above 500 to 34 â€‹N after a storage period of 14 days. In addition, it was noted that the enzymatic and chemical crust modifications yielded moderately good results, but showed a significantly altered appearance of the bread crust.

10.
Foods ; 9(12)2020 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-33260871

RESUMO

Wheat bran consumption is associated with several health benefits, but its incorporation into food products remains low because of sensory and technofunctional issues. Besides, its full beneficial potential is probably not achieved because of its recalcitrant nature and inaccessible structure. Particle size reduction can affect both technofunctional and nutrition-related properties. Therefore, in this study, wet milling and cryogenic milling, two techniques that showed potential for extreme particle size reduction, were used. The effect of the milling techniques, performed on laboratory and large scale, was evaluated on the structure and physicochemical properties of wheat bran. With a median particle size (d50) of 6 µm, the smallest particle size was achieved with cryogenic milling on a laboratory scale. Cryogenic milling on a large scale and wet milling on laboratory and large scale resulted in a particle size reduction to a d50 of 28-38 µm. In the milled samples, the wheat bran structure was broken down, and almost all cells were opened. Wet milling on laboratory and large scale resulted in bran with a more porous structure, a larger surface area and a higher capacity for binding water compared to cryogenic milling on a large scale. The extensive particle size reduction by cryogenic milling on a laboratory scale resulted in wheat bran with the highest surface area and strong water retention capacity. Endogenous enzyme activity and mechanical breakdown during the different milling procedures resulted in different extents of breakdown of starch, sucrose, ß-glucan, arabinoxylan and phytate. Therefore, the diverse impact of the milling techniques on the physicochemical properties of wheat bran could be used to target different technofunctional and health-related properties.

11.
Langmuir ; 36(26): 7566-7572, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32520568

RESUMO

Crystalline glycerides play an important role in the formation of multiphase systems such as emulsions and foams. The stabilization of oil/water interfaces by glyceride crystals has been extensively studied compared to only few studies which have been dedicated to oil/air interfaces. This study investigates the crystallization and network formation of tripalmitin (TP) and monopalmitin (MP) at the middle-chain triglyceride (MCT) oil/air interface. TP crystals were found to crystallize in the bulk before aggregating as large rectangular crystal conglomerates at the MCT oil/air interface. This leads to the slow formation of a plastic deformable, macroscopic crystal layer with high interfacial rheological moduli. MP crystals form directly at the MCT oil/air interface resulting in a comparatively fast formation of an elastic deformable network. Crystals with tentacle-like morphology were found to be responsible for the network elasticity. In this work, we show how interfacial crystallization dynamics and mechanical strength can be linked to the molecular structure and crystallization behavior of glyceride crystals.

12.
Food Funct ; 11(3): 2040-2047, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-32186301

RESUMO

The enzyme laccase is a copper-containing oxidoreductase with the ability to oxidize a wide range of substrates, such as ferulic acid. Thus, the ferulic acid-containing sugar beet pectin (SBP) can be cross-linked through laccase-mediated oxidation. As cross-linking increases viscosity, it could be applied to stabilize SBP-containing foams. In this study, laccase-mediated cross-linking of SBP was investigated under conditions of a high-pressure foaming process. Shear, presence of CO2, and pressure were simulated in a rheometer equipped with a high-pressure cell. At rest, addition of laccase to SBP solution led to the formation of a stiff gel. Application of shear upon mixing of laccase and SBP solution decreased the storage modulus with increasing shear duration and shear rate. This can be attributed to the formation of a fluid gel. However, when shear was stopped before all available ferulic acid groups were cross-linked, a stronger and more coherent network was formed. Pressure exerted by CO2 did not affect cross-linking. Additionally, this approach was tested in a stirred high-pressure vessel where SBP was foamed through CO2 dissolution under pressure and shear followed by controlled pressure release. While pure SBP foam was highly unstable, addition of laccase decelerated collapse. Highest stability was reached when laccase and SBP were mixed prior to depressurization. At the point of foam formation, the continuous phase was thereby viscous enough to increase foam stability. At the same time, continuation of cross-linking at rest caused gel templating of the foam structure.


Assuntos
Pectinas/química , Beta vulgaris/química , Dióxido de Carbono , Reagentes de Ligações Cruzadas/química , Lacase/metabolismo , Oxirredução , Pressão , Reologia
13.
Food Funct ; 10(8): 4854-4860, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31328195

RESUMO

Chia seeds and their mucilage gels provide a nutritionally and functionally promising ingredient for the food and pharmaceutical industry. Application and utilization of the gel remain limited due to the tightly adhesion of the mucilage to the seeds, which affects the organoleptic properties, control of concentration and structuring possibilities. To exploit the full potential of chia mucilage gels as a functional ingredient calls for separation and purification of the gel. Herein, the gel was extracted by centrifugation and characterized rheologically and microscopically to link the viscoelastic properties to the structural properties. Subsequently, the gel was dried employing three different methods for facilitated storage and prolonged shelf life. The dried gels were readily soluble and its viscoelastic properties were fully regenerated upon rehydration demonstrating its potential to envisage industrial applications. The viscoelastic chia mucilage demonstrated shear-thinning behavior with complete relaxation upon stress removal. The gel's elasticity was enhanced with increasing mucilage concentration resulting in a highly tunable system. The extractable and rehydratable functional chia gel is a viable candidate as additive for the development of products requiring specific viscoelastic properties. Addition of the gel enhances the nutritional profile without interfering with the organoleptic properties.


Assuntos
Extratos Vegetais/química , Mucilagem Vegetal/química , Salvia/química , Aditivos Alimentares/química , Aditivos Alimentares/isolamento & purificação , Géis/química , Géis/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Mucilagem Vegetal/isolamento & purificação , Reologia , Sementes/química , Viscosidade
14.
J Agric Food Chem ; 66(46): 12353-12360, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30403137

RESUMO

Enzymatic browning primarily affects fruits and vegetables but also occurs in wheat-based food. Herein, the browning behavior in wheat pastry dough was investigated aiming toward a targeted inhibitory treatment without influencing the pastry dough properties such as workability or taste. Dough discoloration is attributed to several subsequent enzyme-substrate reactions, which can selectively be inhibited by food additives. In most cases, an effective and lasting inhibition is only guaranteed by compounds acting upon multiple inhibition pathways. Despite their effectiveness, the unlimited use of commercial inhibitors is nondesirable due to necessary labeling, thus sustainable and natural inhibitors usually occurring as conventional food ingredients are of interest. It is shown that white wine combined with lemon juice revealed itself as an ideal combination for prevention of enzymatic browning in pastry dough.


Assuntos
Farinha/análise , Aditivos Alimentares/química , Manipulação de Alimentos/métodos , Proteínas de Plantas/antagonistas & inibidores , Triticum/química , Triticum/enzimologia , Citrus/química , Cor , Sucos de Frutas e Vegetais/análise , Cinética , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Vinho/análise
15.
J Food Sci Technol ; 55(8): 3077-3084, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30065417

RESUMO

Reduced elasticity and high stickiness of gluten-free bread doughs are major issues regarding the industrial breadmaking process. In this work, we compared traditional batch mixing with a revised continuous extrusion process and extensively study the rheological properties of both doughs. Shear viscosities were measured offline with a capillary rheometer and inline at the extruder die over a large range of apparent shear rates. Data were corrected for entrance effects, wall slip and non-Newtonian flow behaviour. Good agreement between inline and offline measured viscosities were supplemented by amplitude and frequency sweep tests. The results highlight that this extrusion process fostered the production of gluten-free bread dough. We demonstrated that extrusion processing support the combined mixing, kneading, and moulding of gluten-free dough in one single unit. This fundamental study linked physical dough characterization with applied engineering and yielded the understanding and processing of corresponding products.

16.
Langmuir ; 34(37): 10932-10942, 2018 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-30130966

RESUMO

Cellulose nanocrystals (CNCs) are an emerging natural material with the ability to stabilize fluid/fluid interfaces. Native CNC is hydrophilic and does not change the interfacial tension of the stabilized emulsion or foam system. In this study, rodlike cellulose particles were isolated from hemp and chemically modified to alter their hydrophobicity, i.e., their surface activity, which was demonstrated by surface tension measurements of the particles at the air/water interface. The buildup and mechanical strength of the interfacial structure were investigated using interfacial shear and dilatational rheometry. In contrast to most particle or protein-based interfacial adsorption layers, we observe in shear flow a Maxwellian behavior instead of a glasslike frequency response. The slow and reversible buildup of the layer and its unique frequency dependence indicate a weakly aggregated system, which depends on the hydrophobicity and, thus, on the contact angle of the CNC particles at the air/water interface. Exposed to dilatational flow, the weakly aggregated particles cluster and form compact structures. The interfacial structure generated by the different flow fields is characterized by the contact angle, immersion depth, and layer roughness obtained by neutron reflectometry with contrast variation while the size and local structural arrangement of the CNC particles were investigated by AFM imaging.

17.
Food Funct ; 9(5): 2951-2961, 2018 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-29744494

RESUMO

Ever-growing demand for gluten-free products calls for the development of novel food processing techniques to widen the range of existing baked goods. Extensive research has been targeted towards recipe optimization, widely neglecting the tailoring potential of process-induced structuring of gluten-free raw materials. Herein, we address this shortcoming by demonstrating the potential of rubbery milling for the generation of structure and techno-functionality in breads obtained from a variety of rice flour types. Moisture and temperature induced state transitions during milling were exploited to tailor the physicochemical properties of the flour. Moisture addition during conditioning of the different rice varieties and milling in the rubbery state considerably decreased starch damage due to more gentle disintegration. The degree of starch damage dictated the water absorption capacity of the rice flour types. Flour types with reduced starch damage upon milling offered lower dough densities, yielding bread loafs with a higher volume and better appearance. The choice of rice variety enables fine-tuning of the final product quality by influencing the dough viscoelasticity, which defines the final loaf volume. Whole grain rice flour dramatically increased the loaf volume, whilst simultaneously offering nutritional benefits. Combining the proposed functionalised flour types with current and future advances in product recipes paves the way towards optimised gluten-free goods.


Assuntos
Pão/análise , Farinha/análise , Manipulação de Alimentos/métodos , Glutens/análise , Oryza/química , Culinária , Temperatura Alta
18.
ACS Appl Mater Interfaces ; 10(21): 17571-17581, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29708724

RESUMO

The use of oil-in-water emulsions for controlled lipid release is of interest to the pharmaceutical industry in the development of poorly water soluble drugs and also has gained major interest in the treatment of obesity. In this study, we focus on the relevant in vitro parameters reflecting gastric and intestinal digestion steps to reach a reliable in vitro-in vivo correlation for lipid delivery systems. We found that (i) gastric lipolysis determines early lipid release and sensing. This was mainly influenced by the emulsion stabilization mechanism. (ii) Gastric mucin influences the structure of charge-stabilized emulsion systems in the stomach, leading to destabilization or gel formation, which is supported by in vivo magnetic resonance imaging in healthy volunteers. (iii) The precursor structures of these emulsions modulate intestinal lipolysis kinetics in vitro, which is reflected in plasma triglyceride and cholecystokinin concentrations in vivo.


Assuntos
Lipídeos/química , Digestão , Emulsões , Humanos , Lipólise , Estômago
19.
ACS Appl Mater Interfaces ; 10(10): 8926-8936, 2018 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-29460620

RESUMO

Hydrogels delivering on-demand tailorable optical properties are formidable smart materials with promising perspectives in numerous fields, including the development of modern sensors and switches, the essential quality criterion being a defined and readily measured response to environmental changes. Lanthanide ion (Ln3+)-chelating bicelles are interesting building blocks for such materials because of their magnetic responsive nature. Imbedding these phospholipid-based nanodiscs in a magnetically aligned state in gelatin permits an orientation-dependent retardation of polarized light. The resulting tailorable anisotropy gives the gel a well-defined optical signature observed as a birefringence signal. These phenomena were only reported for a single bicelle-gelatin pair and required high magnetic field strengths of 8 T. Herein, we demonstrate the versatility and enhance the viability of this technology with a new generation of aminocholesterol (Chol-NH2)-doped bicelles imbedded in two different types of gelatin. The highly magnetically responsive nature of the bicelles allowed to gel the anisotropy at commercially viable magnetic field strengths between 1 and 3 T. Thermoreversible gels with a unique optical signature were generated by exposing the system to various temperature conditions and external magnetic field strengths. The resulting optical properties were a signature of the gel's environmental history, effectively acting as a sensor. Solutions containing the bicelles simultaneously aligning parallel and perpendicular to the magnetic field directions were obtained by mixing samples chelating Tm3+ and Dy3+. These systems were successfully gelled, providing a material with two distinct temperature-dependent optical characteristics. The high degree of tunability in the magnetic response of the bicelles enables encryption of the gel's optical properties. The proposed gels are viable candidates for temperature tracking of sensitive goods and provide numerous perspectives for future development of tomorrow's smart materials and technologies.

20.
J Vis Exp ; (131)2018 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-29364235

RESUMO

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln3+) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln3+ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies' dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 °C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.


Assuntos
Elementos da Série dos Lantanídeos/química , Magnetismo/métodos , Fosfolipídeos/química , Birrefringência , Quelantes/química , Imageamento por Ressonância Magnética/métodos , Fosfolipídeos/síntese química
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