Colloids and Interfaces

10 pages, 3076 KiB

Open AccessFeature PaperArticle

Red Wine-Enriched Olive Oil Emulsions: Role of Wine Polyphenols in the Oxidative Stability

by Giuseppe Cinelli, Giovanni Sbrocchi, Silvio Iacovino, Luigi Ambrosone, Andrea Ceglie, Francesco Lopez and Francesca Cuomo

Colloids Interfaces 2019, 3(3), 59; https://doi.org/10.3390/colloids3030059 - 18 Sep 2019

Cited by 8 | Viewed by 3471

Abstract

The benefits associated with the consumption of red wine due to its rich pool of phenolic compounds are well-recognized, thanks to the antioxidant activity related to these kinds of molecules. However, wine drinking should be done in moderation, or is forbidden for some [...] Read more.

The benefits associated with the consumption of red wine due to its rich pool of phenolic compounds are well-recognized, thanks to the antioxidant activity related to these kinds of molecules. However, wine drinking should be done in moderation, or is forbidden for some populations for ethnic or religious reasons. One way to still enjoy the advantages of red wine is to use its dry extract. In order to test the ability of the red wine dry extract to reveal its antioxidant activity, it was solubilized in water to produce water-in-oil (W/O) emulsions based on olive oil. After the selection of the right emulsion composition, kinetics of oil oxidation were carried out in oil and emulsions in the presence of an increasing amount of red wine extract, whose presence influenced the rate of oxidation by slowing it down. This behavior was confirmed by monitoring the oxidation reaction in two ways; i.e., with the classical method that consists of the determination of the peroxide value, and with an accelerated test making use of 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN) and diphenyl1-pyrenylphosphine (DPPP). The first is a molecule that triggers the reaction at 40 °C, and the other is a molecule that by reacting with hydroperoxides becomes fluorescent (DPPP=O). Moreover, by comparing the emulsion structures observed by optical microscopy, no differences in the size of the dispersed aqueous phase were detected with the increase of the wine dry extract, which is an aspect that confirmed that the antioxidant activity was directly proportional to the wine extract concentration, and thus to the phenolic content. Full article

(This article belongs to the Special Issue Food Colloids)

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15 pages, 2607 KiB

Open AccessFeature PaperArticle

Alginate Films Encapsulating Lemongrass Essential Oil as Affected by Spray Calcium Application

by Martina Cofelice, Francesca Cuomo and Amparo Chiralt

Colloids Interfaces 2019, 3(3), 58; https://doi.org/10.3390/colloids3030058 - 04 Sep 2019

Cited by 19 | Viewed by 4313

Abstract

The necessity of producing innovative packaging systems has directed the attention of food industries towards the use of biodegradable polymers for developing new films able to protect foods and to extend their shelf-life, with lower environmental impact. In particular, edible films combining hydrophilic [...] Read more.

The necessity of producing innovative packaging systems has directed the attention of food industries towards the use of biodegradable polymers for developing new films able to protect foods and to extend their shelf-life, with lower environmental impact. In particular, edible films combining hydrophilic and hydrophobic ingredients could retard moisture loss, gas migration and ensure food integrity, reducing the necessity of using synthetic plastics. Alginate-based films obtained from emulsions of lemongrass essential oil (at 0.1% and 0.5%) in aqueous alginate solutions (1%), with Tween 80 as surfactant (0.3%), were obtained by casting and characterized as to microstructure and thermal behavior, as well as tensile, barrier and optical properties. Films were also crosslinked through spraying calcium chloride onto the film surface and the influence of oil emulsification and the crosslinking effect on the final film properties were evaluated. The film microstructure, analyzed through Field Emission Scanning Electron Microscopy (FESEM) revealed discontinuities in films containing essential oil associated with droplet flocculation and coalescence during drying, while calcium diffusion into the matrix was enhanced. The presence of essential oil reduced the film stiffness whereas calcium addition lowered the film’s water solubility, increasing tensile strength and reducing the extensibility coherent with its crosslinking effect. Full article

(This article belongs to the Special Issue Food Colloids)

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9 pages, 2359 KiB

Open AccessArticle

Automatic Single Droplet Generator with Control over Droplet Size and Detachment Frequency

by Dorota Gawel and Jan Zawala

Colloids Interfaces 2019, 3(3), 57; https://doi.org/10.3390/colloids3030057 - 22 Aug 2019

Cited by 3 | Viewed by 3340

Abstract

This paper presents a quite simple, fully automatized single droplet generator, which can be an alternative for more expensive and complicated microfluidic devices. The simple generation nozzle connected to the pressure cells and cheap peristaltic pumps, synchronized via developed software with simple GUI [...] Read more.

This paper presents a quite simple, fully automatized single droplet generator, which can be an alternative for more expensive and complicated microfluidic devices. The simple generation nozzle connected to the pressure cells and cheap peristaltic pumps, synchronized via developed software with simple GUI (graphical user interface) implemented into the Raspberry Pi microcomputer allows precise control over the single droplet diameter and detachment frequency. The generator allows the formation of droplets of quite wide range of diameters without the need of orifice diameter replacements. Free control over time available for adsorption of surface active-substances over the surface of immobilized droplet, before its detachment from the orifice, is an advantage of the developed device. Full article

(This article belongs to the Special Issue B&D 2019)

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16 pages, 1566 KiB

Open AccessFeature PaperArticle

Spreading of Micrometer-Sized Droplets under the Influence of Insoluble and Soluble Surfactants: A Numerical Study

by Thomas Antritter, Peter Hachmann, Tatiana Gambaryan-Roisman, Bernhard Buck and Peter Stephan

Colloids Interfaces 2019, 3(3), 56; https://doi.org/10.3390/colloids3030056 - 09 Aug 2019

Cited by 1 | Viewed by 3775

Abstract

Wetting and spreading of surfactant solutions play an important role in many technical applications. In printing processes, the size of individual droplets is typically on the order of a few tens of microns. The purpose of this study is to develop a better [...] Read more.

Wetting and spreading of surfactant solutions play an important role in many technical applications. In printing processes, the size of individual droplets is typically on the order of a few tens of microns. The purpose of this study is to develop a better understanding of the interaction between spreading and surfactant transport on these small length and related time scales. Therefore, numerical simulations based on the volume-of-fluid method including Marangoni stresses and transport of an insoluble or soluble surfactant are performed. The results for an insoluble surfactant show competing effects of Marangoni flow on the one hand, and a decreasing surfactant concentration as the droplet spreads on the other hand. Even in the case of a soluble surfactant, adsorption and desorption could only partly mitigate these effects, demonstrating the importance of the sorption kinetics for fast, small scale wetting processes. Full article

(This article belongs to the Special Issue Wetting on Micro/Nano-Scale: From Fundamentals to Application)

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31 pages, 7732 KiB

Open AccessReview

Thickness and Structure of Adsorbed Water Layer and Effects on Adhesion and Friction at Nanoasperity Contact

by Chen Xiao, Pengfei Shi, Wenmeng Yan, Lei Chen, Linmao Qian and Seong H. Kim

Colloids Interfaces 2019, 3(3), 55; https://doi.org/10.3390/colloids3030055 - 06 Aug 2019

Cited by 56 | Viewed by 10329

Abstract

Most inorganic material surfaces exposed to ambient air can adsorb water, and hydrogen bonding interactions among adsorbed water molecules vary depending on, not only intrinsic properties of material surfaces, but also extrinsic working conditions. When dimensions of solid objects shrink to micro- and [...] Read more.

Most inorganic material surfaces exposed to ambient air can adsorb water, and hydrogen bonding interactions among adsorbed water molecules vary depending on, not only intrinsic properties of material surfaces, but also extrinsic working conditions. When dimensions of solid objects shrink to micro- and nano-scales, the ratio of surface area to volume increases greatly and the contribution of water condensation on interfacial forces, such as adhesion (F_a) and friction (F_t), becomes significant. This paper reviews the structural evolution of the adsorbed water layer on solid surfaces and its effect on F_a and F_t at nanoasperity contact for sphere-on-flat geometry. The details of the underlying mechanisms governing water adsorption behaviors vary depending on the atomic structure of the substrate, surface hydrophilicity and atmospheric conditions. The solid surfaces reviewed in this paper include metal/metallic oxides, silicon/silicon oxides, fluorides, and two-dimensional materials. The mechanism by which water condensation influences F_a is discussed based on the competition among capillary force, van der Waals force and the rupture force of solid-like water bridge. The condensed meniscus and the molecular configuration of the water bridge are influenced by surface roughness, surface hydrophilicity, temperature, sliding velocity, which in turn affect the kinetics of water condensation and interfacial F_t. Taking the effects of the thickness and structure of adsorbed water into account is important to obtain a full understanding of the interfacial forces at nanoasperity contact under ambient conditions. Full article

(This article belongs to the Special Issue Surface Forces, Adhesion, and Friction)

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14 pages, 3489 KiB

Open AccessFeature PaperArticle

One- and Two-Dimensional NMR in Studying Wood–Water Interaction at Moisturizing Spruce. Anisotropy of Water Self-Diffusion

by Victor V. Rodin

Colloids Interfaces 2019, 3(3), 54; https://doi.org/10.3390/colloids3030054 - 02 Aug 2019

Cited by 3 | Viewed by 3797

Abstract

This paper examines how wetting the surface of wood affects characteristics of wood materials. An important question is how moisturizing wood has an effect on diffusion parameters of water, which will change conditions of the technological treatment of material. A fibrous structure of [...] Read more.

This paper examines how wetting the surface of wood affects characteristics of wood materials. An important question is how moisturizing wood has an effect on diffusion parameters of water, which will change conditions of the technological treatment of material. A fibrous structure of wood can result in different diffusivities of water in the perpendicular direction and along the wood fibers. The work explores how 1- and 2-dimensional NMR with pulsed field gradients (PFG) highlights an anisotropic diffusion of water when moisturizing spruce wood. The methods applied: T₂-relaxation (CPMG) measurements with the application of inverse Laplace transform (ILT), cross-relaxation experiments (Goldman–Shen pulse sequence), 1D PFG NMR on oriented wood pieces or applying gradients in various orientation, and 2D diffusion-diffusion correlation spectroscopy (DDCOSY) with two pairs of colinear gradient pulses. The results showed anisotropic restricted diffusion correlating the size of tracheid cells. The experimental 2D diffusion-diffusion correlation maps were compared with model calculations based on parameters of 2D experiment on spruce and the theory of 2D DDCOSY with ILT. Moisturizing spruce wood resulted in anisotropic diffusion coefficient which can be monitored in 2D NMR to discover different diffusion coefficients of water along the axis of wood fibers and in orthogonal direction. Full article

(This article belongs to the Special Issue Wetting on Micro/Nano-Scale: From Fundamentals to Application)

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12 pages, 7440 KiB

Open AccessFeature PaperArticle

Spreading and Imbibition of Vesicle Dispersion Droplets on Porous Substrates

by Abhijeet Kumar, Jochen Kleinen, Joachim Venzmer, Anna Trybala, Victor Starov and Tatiana Gambaryan-Roisman

Colloids Interfaces 2019, 3(3), 53; https://doi.org/10.3390/colloids3030053 - 21 Jul 2019

Cited by 11 | Viewed by 3546

Abstract

Vesicles have recently found widespread use in applications such as conditioning of textiles, paper and hair, as well as transdermal drug delivery. The mode of treatment in several such cases involves the application of droplets of aqueous dispersions of vesicles onto dry porous [...] Read more.

Vesicles have recently found widespread use in applications such as conditioning of textiles, paper and hair, as well as transdermal drug delivery. The mode of treatment in several such cases involves the application of droplets of aqueous dispersions of vesicles onto dry porous substrates like paper and textiles. One of the factors which affects the performance of such treatments is the rate at which the droplets spread and imbibe on the porous substrate. Depending upon the specific purpose of the treatment either a fast or slow droplet spreading kinetics could be desired. Therefore, it is important to have a good understanding of the droplet spreading process and the factors which influence it. In this work, an experimental investigation of the simultaneous spreading and imbibition of vesicle dispersion droplets on cellulose filter papers is carried out. Two different types of vesicles which are composed of similar lipid molecules but exhibit contrasting lipid bilayer phase behavior are used. Two different grades of filter papers with comparable porosities but different thicknesses are used as porous substrate. It is found that the droplet spreading behavior is of the “complete wetting” type on the thicker porous substrate, whereas it is of the “partial wetting” type on the thinner substrate. Furthermore, it is observed that the spreading of droplets containing vesicles with liquid-crystalline phase bilayers occurs faster than that of vesicles with solid-gel phase bilayers. The secondary radial penetration which commences after the initial droplet spreading is complete is also investigated and discussed. Full article

(This article belongs to the Special Issue Colloids and Interfaces in Printing Technology)

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Colloids Interfaces, Volume 3, Issue 3 (September 2019) – 7 articles

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