Color Change Of Samples Research Articles

Structure and piezochromism of pyrene-1-carbaldehyde at high pressure.

The crystal structure of pyrene-1-carbaldehyde (PA), a model polyaromatic hydrocarbon, highly luminescent in the solid state and crystallizing in the triclinic system, has been re-determined at several pressures ranging from atmospheric up to 3 GPa using a diamond anvil cell. A `multi-crystal' approach was used in crystal structure determination, significantly improving completeness of X-ray diffraction data attainable for such a low-symmetry system. The crystal structure consists of infinite π-stacks of PA molecules with discernible dimers, which resemble aggregates formed by pyrene derivatives in solution as well as in the solid state. A series of measurements showed that the average inter-planar distance between individual molecules within π-stacks decreases with pressure in the investigated range. This results in piezochromic properties of PA: a significant sample color change as well as a red-shift of fluorescence with pressure, as studied with UV-vis spectroscopy. Periodic DFT calculations allowed us to relate the variations in the crystal structure with pressure to the changes in the electronic structure of this material.

Color Stability of a New Rice Husk Composite in Comparison with Conventional Composites after Exposure to Commonly Consumed Beverages in Malaysia.

Objective To evaluate the color stability of a new organic rice husk nanocomposite as compared to four conventional composites after exposure to commonly consumed beverages in Malaysia. Methods One hundred and twenty-five disk samples were prepared from a new rice husk-based composite and four other conventional methacrylate-based light-cured composites of shade A2. The samples were immersed in four commonly consumed beverages: coco-based drink, kopi, Chinese tea, and teh tarik for four weeks. The color measurements were carried out every week using the reflectance spectrophotometer according to the CIE L∗a∗b∗ color system. Color changes of samples (ΔE) in each week were calculated. Statistical analysis was carried out by performing a mixed ANOVA and Tukey's post hoc test in order to analyse the differences in ΔE. Results The findings revealed a statistically significant difference of ΔE reading (p < 0.05) among all composites immersed in all four beverages after four weeks. Rice husk composites exhibited lesser color stability as compared to Ceram.X One Universal (p < 0.001) and G-aenial Universal Flo (p < 0.001) but showed higher color stability compared to Solare-X (p < 0.001) and Neofil (p < 0.001). Coffee and Chinese tea had the most significant impact on color changes (p < 0.05) observed in all composites over four weeks of study. Conclusion Rice husk composite showed acceptable color stability. It can be considered as an alternative to conventional composites due to its eco-friendly properties.

Coating Performance on Exterior Oil-Heat Treated Wood

Thermal modification and the degree of improved properties from the treatment depend on wood species and treatment parameters. Southern yellow pine and spruce are two wood species commonly used for decking, fences, and siding in North America. This study evaluated coating performance when applied on oil-heat-treated Southern pine and spruce wood samples. Moisture content, color, and gloss changes of samples were analyzed before weathering and then after each month for the first three months and then every six months during 18 months of natural weathering exposure in Toronto, Canada. The results showed that coated heat-treated woods had lower moisture uptake, lower color change, and overall better appearance ranking than coated-untreated wood samples. Coated-spruce wood samples had lower checking and splitting, and in general, much better performance than coated-Southern pine treated samples. Notably, the average moisture content of treated spruce wood samples was significantly lower than that of Southern pine, which explains lower checking and improved coatings’ appearance.

Dyeing Parameters, Fastness and Ultraviolet Protection Properties of Nylon Dyed with Mangrove Bark Extract

Abstract Investigation of dyeing parameters (temperature, time and pH), color fastness assessments and ultraviolet protection factor (UPF) of mangrove bark extract on nylon fabric were conducted. The optimum dyeing conditions were obtained at 90°C, 60 min and pH 5, respectively. Dyeing with different metal mordants (aluminium potassium sulfate, ferrous sulfate, copper sulfate, and stannous chloride) was also investigated. The ratings of color fastness testing showed that most of color fastness properties of dyed fabrics were generally acceptable except color fastness to washing due to considerable change in color of samples after subjected to washing test. Dyed nylon fabrics showed the improvement in UV-protection property.

Application of active films with natural extract for beef hamburger preservation

ABSTRACT: Edible chitosan-based films, in pure form (CH100), or blended with gelatin (GEL50:CH50), with and without boldo extract (B) were prepared. The oxygen permeability of the films, as well as color changes and antioxidant and antimicrobial activities on beef hamburgers samples were evaluated. CH100+B film exhibited optimal oxygen barrier properties (6.40±0.170cc-mL/[m²-day]), and this value was significantly increased in blended films (GEL50:CH50+B = 12.99±1.50cc-mL/[m²-day]) (P&lt;0.05). All films provoked color changes in hamburger samples during storage, and the samples covered with CH100+B film showed a lower brightness and a higher redness. All films effectively protected beef hamburger from lipid oxidation, and boldo extract incorporation in pure and blended films enabled significant protection, when compared to the control sample (155.78±0.85meq O2/kg) (P&lt;0.05). Finally, all films proved to be effective in microbial growth control, suggesting that these films are an effective alternative in improving food safety and quality of fresh meat.

Assessing the impact of non-thermal and thermal treatment on the shelf-life of onion juice

Onion (Allium cepa L.) juice is a marinating agent for meat and fish marination and readily usable sauce for any meal that has onion in its formulation. This study aims to assess the microbiological and physicochemical changes in the onion juice processed by UV-C irradiation (0.5 mm sample depth, 30 min exposure time, 7.5 mW/cm&lt;sup&gt;2&lt;/sup&gt; UV incident intensity) and conventional heat treatment (74.5°C, 12 min) during its storage. Microbiological results showed processing by UV-C irradiation or heat treatment under optimum conditions extended the microbial shelf-life of untreated onion juice by minimum 6-times. Total colour change of heat-treated samples was lower than that of untreated and UV-C treated samples for 12 weeks. Also, pH, total titratable acidity, total soluble solids content, turbidity, NEBI and total phenolic content were monitored for 12 weeks. The results of this study will form scientific infrastructure for onion juice manufacturers to decide on the processing method with respect to its shelf-life.

APPEARANCE FEATURES OF CLAYEY MIXTURES HAVING FLY ASHES

The use of wastes has become very significant and widespread in terms of sustainable production of clayey mixtures, since the wastes provide many advantages. In this study, the effects of two different types of fly ash, which were wastes of Seyitomer and Cayirhan thermal power plants, on the color change of brick samples with various amount of fly ash ranging between 0 to 60% at different sintering temperatures were investigated. As a result, traditional red colored bricks could be produced with fly ash without using a separate raw material to meet the color requirements. It was found that desired colors for special architectural applications could also be achieved by using fly ash.

Porous photonic crystal structure for sensing applications

A multilayer photonic band gap structure is proposed for sensing applications in visible wavelength range. The structure is designed by introducing alternate layers of dielectric material on a glass substrate. To ease the analyte infiltration and to improve the sensitivity, porosity is introduced deliberately within each layer. Extensive analysis is carried out to optimize the number of dielectric layers, their thickness, and percentage of porosity. The transmission/reflection spectral characteristic and sensitivity of the proposed structure are analyzed by a three-dimensional finite difference time domain method. The porosity value and structural parameters are optimized to obtain highest possible sensitivity. The proposed structure exhibits a 0.05-nm shift in reflection/transmission wavelength with corresponding refractive index change of 10 − 3. Analyte can also be distinguished by seeing the sample color change with naked eyes. Thus, multiparametric characterization of the proposed structure demonstrates its potential for sensing applications.

Chemical sensor using metal-organic complex: Preparation, characterization and application for highly selective detection of cyanide ions in mixed aqueous-organic media

In this study, a novel metal-organic hybrid material (MO1) was designed and synthesized for the detection of CN− ions. The spectral analyses by FT-IR, 1H NMR, 13C NMR, CHN and TGA satisfactorily confirmed the structure of MO1. The sensor MO1 was applied as colorimetric probe for sensing of cyanide ions in aqueous solutions of dimethyl sulfoxide. MO1 with electron withdrawing group at organic ligand showed high selectivity for detection of cyanide over other interfering anions. Interaction of MO1 with cyanide provides obvious colorimetric change from red to violet, enabling easy detect with the naked eye. In addition, the sensing details were evaluated using UV–vis spectroscopy. Furthermore, the detection limit of chemosensor toward CN‾ ions was found to be 5.52 μM. Moreover, probe MO1 can be used for selective sensing of cyanide based on the obvious color changes in real samples.

Stability, physical properties and acceptance of salad dressings containing saffron (Crocus sativus) or pomegranate juice powder as affected by high shear (HS) and ultrasonication (US) process

The influence of preparation method, high shear (HS) or ultrasonic (US) homogenization on stability, physical and sensory attributes of salad dressings containing saffron and pomegranate juice has been investigated upon 6 months of ambient storage. Emulsified dressings were evaluated for stability, microstructure, viscoelastic properties, and acceptance. All samples processed by HS showed higher apparent viscosity, yield stress (τ0), storage and loss moduli (G′, G″), particle diameters, yellow-blue color (b values) and lower lightness (L) compared to their US counterparts. Ambiguous results depending on added constituents (saffron or pomegranate juice) were obtained regarding long term stability and red-green color (a), whereas total color change (TCD) of samples was unaffected. Pomegranate dressings prepared with HS exhibited enhanced viscoelastic character and high stability during storage (Back scattering variation, dBS ∼ 1%). US samples were equally accepted as their HS counterparts by panelists for most sensory attributes, but sonication clearly improved the color likeness of samples containing pomegranate by 51%. Saffron addition significantly improved the taste of the dressings.This study shows that ultrasonication may be used to ameliorate color attributes related to pomegranate juice addition homogenizating successfully these products without detrimental effects on their long-term stability i.e. product syneresis.

Impact of steaming on the chemical composition of maple wood

Chemical changes resulting from the thermal treatment of maple wood (Acer platanoides L.) through various steaming techniques were evaluated. Main wood components were isolated and characterized from the maple wood samples after steaming. Then, the isolated holocellulose and dioxane lignin were analyzed using ATR-FTIR spectroscopy. The effects of an increase in temperature and extension of the steaming period were seen primarily in the holocellulose and extractives contents, and less in the cellulose and lignin components. Certain steaming methods resulted in an increase in chemical composition, while others saw a decrease. The cellulose content of steamed maple wood was not considerably altered; however, the cellulose crystallinity did increase. The slight changes observed in this study can be attributed to several concurrent effects. While the lignin content in steamed maple wood showed only minimal changes, there were several changes in the structure of the lignin macromolecule. Demethoxylation, the decrease in the ratio of syringyl-propane to guaiacyl-propane units, and the formation of new alpha-C=O bonds were also observed. The hydrothermal treatment of wood also resulted in color changes of wood samples; the intensity of the change depended on the intensity of the treatment.

Effect of Differing Ingredients and Packaging Technologies on the Color of High-Pressure Processed Ground Beef

High-pressure processing (HPP) is a nonthermal pasteurization technique to control pathogens, like Escherichia coli. However, color changes in raw beef induced by HPP restrict its use within the beef industry. The objectives of this study were to investigate the effects of adding curing agents (nitrite) and packaging with or without reducing compounds (ascorbic acid/erythorbate) on color retention in high-pressure processed ground beef. Color was measured (CIE L∗a∗b∗) before HPP and on days 3, 7, 12, 14, 19, and 21 after HPP. Statistical analysis (SAS GLIMMIX) was run to identify the main effects of adding curing agents, packaging, and reducing agents on color retention. HPP resulted in a detrimental effect on the color of the beef patties for all treatments. Lightness and yellowness increased (P&lt;0.001) and redness decreased (P&lt;0.001) after high-pressure processing. The effect remained the same throughout the course of the study. However, there were less color changes in samples treated with reducing compounds. Both synthetic and natural sources of nitrite and ascorbic acid/erythorbate performed similarly in terms of their ability to maintain redness. Treatments leading to formation of nitrosylmetmyoglobin (Fe3+) had less severe color change compared to the treatments leading to the generation of nitrosylmyoglobin (Fe2+).

Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores

Sulfur and fluorine substituted Sn2Nb2O7 pyrochlore compounds were synthesized to produce brilliant orange/red colors as an environmentally friendly alternative to other toxic inorganic pigments. Neutron structure refinements indicate that the studied compositions crystallize in the pyrochlore structure with a large number of cation and/or anion vacancies and significant local structural disorder. The cubic unit cell decreases with increasing sulfur and fluorine content. The Sn2+ cation is off-center by 0.39–0.48 Å from the ideal site, and the oxygen O′ is strongly displaced to the 32e position by an extraordinarily large distance that has never been reported for a pyrochlore type phase. The unprecedented displacive disorder and unusual lattice evolution upon sulfur substitution are presumably driven by the strong lone pair stereoactivity associated with Sn2+. Chemical analysis confirmed the existence of sulfur and fluorine, and 119Sn Mössbauer spectroscopy quantified the presence of both Sn2+ and Sn4+ in all compositions. The general formula representative of sulfur-containing pigments is nonstoichiometric Sn2−z2+(Nb2-ySny4+)O7-z-y/2-xSx with the color varying according to x. The fluorine compound is refined to be Sn22+(Nb0·958Ti0.984Sn0.0584+)O6·376F0.206 with exclusively anion vacancies. Optical characterization was performed through diffuse reflectance and color meter measurements. The band gap is determined to be in the range of 2.35 to 2.05 eV as sample color changes from yellow to orange/red. All powder samples show 60–95% reflectance in the near-infrared (NIR) region, adding new functionality to the application of these compounds as “cool” pigments.

Effect of freezing rate and storage on the texture and quality parameters of strawberry and green bean frozen in home type freezer

The focus of interest of this research was freezing preservation of green bean and strawberry in a home type freezer. Freezing time and freezing rates were determined from the cooling curves obtained experimentally. Home type freezing provided slow freezing rate. NMR Relaxometry measurements showed that freezing did not keep the cellular integrity in strawberries and green beans due to structural damage and extracellular ice formation. Packaged samples were stored at −27 °C for approximately 3 months. Although total phenolic content, antioxidant activity and color changes of samples were not significant, significant L-ascorbic acid losses were determined for 13 weeks’ frozen storage of strawberries and green beans. Home freezing should be done at appropriate freezing rate to preserve the texture and the nutritional content of fruits and vegetables.

Effect of Osmotic Pre-treatment and Temperature Storage Conditions on Water Activity and Colour of Dried Apple

Abstract The cylinders of apples cv. Braeburn were subjected to osmotic dehydration in a sucrose solution with the addition of chokeberry juice concentrate. After osmotic pre-treatment the pieces of apples were dried by two methods: freeze-drying and air-drying. The storage results of dried apples at temperature 25–45 °C for 7 and 12 months were satisfactory. Mass changes were very minor. During storage dried apples obtained by both methods exhibited microbiological stability even after 7 and 12 months of storage, due to the fact that the water activity did not exceed the value of 0.4. Under the influence of the technological processes application, as well as storage conditions, appearance changes in the samples occurred. Higher temperature of storage had an increase impact in colour changes of control samples (without osmotic pre-treatment) and also osmotically dehydrated into sucrose solution, mainly in the case of samples which had dried using freeze-drying. Previously immersed in chokeberry juice concentrate, dried apples had colour changes comes from colour of solution.

Effects of thermal treatments on the colloidal properties, antioxidant capacity and in-vitro proteolytic degradation of cricket flour

Insects are gaining increased interest as rich, viable and sustainable sources of edible proteins. However, low consumer acceptance of insects as human food stimulates a need to mask the insects' appearance through various processing operations, such as grinding, cooking and baking. This research studied the implications of thermal processing of cricket (Acheta domesticus) flour on its physiochemical properties, antioxidant capacity and bioaccessibility in the gastrointestinal tract. Thermal processing led to marginal changes in colloid sizes and zeta-potentials at 3.0 < pH < 7.0. Concomitantly, sample color changes upon processing (delta E) were found to at least double when processed in the presence of fructose compared to processing without fructose (evaluated by L*a*b*color values). Overall, processed cricket flour changes were all ascribed to thermally-induced phenomena, such as protein denaturation, cross-linking, Maillard glycation and/or aggregation. Next, antioxidant activity examined by FRAP and ORAC assays revealed thermally-treated cricket flour had a significantly (p < 0.05) diminished electron transfer ability with a simultaneous rise in its proton abstraction capability exceeding 400 μM Trolox equivalents. This improved antioxidant activity may be attributed to conformational changes in cricket proteins exposing proton-donating residues, namely cysteine. Finally, dynamic in vitro digestion of untreated and treated cricket flours showed that baking increased the gastric proteolysis of cricket proteins and their subsequent bioaccessibility. Thus, justifying further investigation of industrial processes that could be harnessed to fabricate palatable and nourishing insect-based products.

1,10-Phenanthroline based colorimetric and fluorescent sensor for Hg2+ in water: Experimental and DFT study

A novel colorimetric probe (L) was prepared and its metal ion sensing properties were investigated. Probe L exhibited obvious colorimetric response toward Hg2+ in water. The association constant for probe L-Hg2+ in water containing 0.5% DMSO (v/v) was determined as 1.77×105M−1. The detection limit of probe L for the analysis of Hg2+ was determined as 21.72ppb. Moreover, probe L can be used for selective sensing of Hg2+ based on the obvious color changes in real samples. Further, the interaction between the probe L and Hg2+ was investigated by 1H NMR titration and the probable structure of probe L-Hg2+ complex was predicted by B3LYP method.

A colorimetric probe for dual sensing of Hg2+ and Cu2+ ions in water

A colorimetric probe (L) was prepared and its metal ion sensing properties were investigated. Probe L exhibited obvious colorimetric response toward Hg2+ and Cu2+ with different color changes in water. The association constant for probe L-Hg2+ and probe L-Cu2+ in water containing 0.5% DMSO (v/v) was determined as 5.62×107M−1 and 1.26×107M−1, respectively. The detection limit of probe L for the analysis of Hg2+ and Cu2+ was determined as 0.19ppm and 0.39ppm, respectively. Moreover, probe L can be used for selective sensing of Hg2+ and Cu2+ based on the distinct color changes in real samples.

A cleaner route for nanocolouration of wool fabric via green assembling of cupric oxide nanoparticles along with antibacterial and UV protection properties

There is a need for substitution or reduction of toxic chemicals and processing steps in all aspects of chemical manufacturing such as textile dyeing and finishing due to the environmental and economic considerations. In this contribution, green-assembled cupric oxide nanoparticles have been utilized to nanocolor wool fibers considering surface plasmon resonance effect as well as antibacterial and ultra violet protection properties through one single step processing as a cleaner and economic approach. This was carried out by green reduction of copper acetate solution in presence of wool fabric under alkaline condition provided by the commercial ashes of burnt leaves and stems of Seidlitzia Rosmarinus plant. The formation of cupric oxide nanoparticles on the wool fabric confirmed with X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, mapping, Field-emission scanning electron microscope images, Fourier transform infrared spectra and UV–vis spectrum. The brown color of the treated fabrics obtained from light to dark with very good fastness against washing, rubbing, light and alkali spotting. The cupric oxide colored fabrics indicated moderate fastness towards acid spotting due to leaching of metallic and metal oxide nanoparticles in contact with acids. The color change of samples can be potentially used for colorimetric detection of highly concentrated sulfuric and formic as strong inorganic and organic acids during the entire leaching of cupric oxide nanoparticles from the fabric. Further, the treated fabrics exhibited excellent antibacterial actions against both pathogenic bacteria consisting Staphylococcus aureus as a Gram-positive and Escherichia coli as a Gram-negative bacteria with an improvement in tensile strength as well as UV protection properties. Finally, this simple and eco-friendly route can be applied for multifunctional textiles via green assembled cupric oxide nanoparticles in large scale.

Carrier-assisted dyeing of poly(l-lactic acid) fibers with dispersed photochromic spiropyran dyes

The effects of dyeing carriers on the color strength (K/S values) of poly(l-lactic acid) (PLLA) fibers were investigated, using the photochromic dye 1′,3′,3′-trimethyl-6-nitro-spiro(2H-1-benzopyran-2,2′-indole) (6-nitro BIPS). Both an organic solution (based on tetrachloroethylene) and an aqueous dispersion of the dye were applied to the PLLA fibers, and the resulting change in color of the PLLA samples irradiated by ultraviolet (UV) light was evaluated by spectrocolorimetry. In the case of aqueous dispersion processing, the uptake of 6-nitro BIPS on the PLLA fibers was expected to be increased when using o-phenylphenol as a carrier. The value was four times higher than that obtained using the organic solution. The energy diagrams associated with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the 6-niro BIPS for the two dyeing processes were determined using photoelectron yield spectroscopy.