Adsorption Of Pigments Research Articles

SYNTHESIS OF METAL-ORGANIC FRAMEWORK Ni-MOF USING 2-METHYLIMIDAZOLE AND APPLICATION FOR ADSORPTION OF ORGANIC PIGMENTS

Among the metal-organic framework materials, Ni-MOF is considered one of the promising materials due to its high porosity and structure containing active transition metal ions. In particular, by changing the organic ligands and synthesis conditions, organic framework nickel materials with different structures and properties have been synthesized and evaluated for applicability in many fields. In this study, the metal-organic framework Ni-MOF was synthesized by solvothermal approach using the organic ligand 2-methylimidazole. The obtained material was characterized using infrared (IR) spectroscopy, X-ray diffraction (XRD), EDX spectroscopy and SEM images. The results of analyzing the physico-chemical properties of materials showed that the obtained material has a porous structure with a relatively low crystallinity. The surface morphology, elemental composition and crystallinity depend on the nature of the nickel salt and the molar ratio of nickel/2-methylimidazole ligand. The synthesized material was used as an adsorbent for the removal of MB and RhB from aqueous solution. The results showed that the synthesized Ni-MOF material has good adsorption capacity of organic pigments. The influence of synthesis conditions, including the molar ratio of nickel salt and 2-methylimidazole, synthesis temperature and synthesis time, on the adsorption capacity of Ni-MOF materials was studied. It was shown that Ni-MOF material synthesized by solvothermal method using nickel nitrate and 2-methylimidazole ligand with a molar ratio of 1:8, calcined at 180 °C after 8 hours, has the best adsorption ability for the removal of pigment from aqueous solution. The adsorption capacity of Ni-MOF for MB and RhB removal reached 105.45 mg/g and 51.48 mg/g, respectively. For citation: Dinh Van Tac, Vu Thi Duyen Synthesis of metal-organic framework Ni-MOF using 2-methylimidazole and application for adsorption of organic pigments. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 12. P. 33-38. DOI: 10.6060/ivkkt.20246712.7062.

Enhanced composite Co-MOF-derived sodium carboxymethyl cellulose visual films for real-time and in situ monitoring fresh-cut apple freshness

Natural biopolymers have extensively applications in intelligent food packaging due to their renewable nature, easy availability, environmental-friendly, low-cost and excellent processibility. Recently, the integration or embedding of nanocomposites on polymer substrates to improve the multi-faceted performance of packaging materials has attracted widespread attention. Herein, the irregular spherical Co-based metal-organic framework (Co-MOF) loaded with phenol red (PR) and bromothymol blue (BTB) were fabricated, resulting in absorbed nanocomposites Co-MOF/PR and Co-MOF/BTB. Afterward, the nanocomposites were integrated into a sodium carboxymethyl cellulose (CMC-Na) substrate to prepare a CO2-responsive packaging material (CMC-Na/PR/Co-MOF and CMC-Na/BTB/Co-MOF) for real-time and in-situ monitoring apple freshness. The synthesis of Co-MOF and the hydrogen-bonding interactions between MOF and pigments adsorption were confirmed. The advantages exhibited by the film with adding Co-MOF, including excellent hydrophobicity and water resistance, improved time-temperature stability and mechanical properties, were explored. Notably, the Co-MOF-based composite film exhibited enhanced UV–visible barrier, anti-migration performance of pigment, and thermal stability. Finally, a significant linear response (R2 = 0.9923 and 0.9781) between the total color difference values (ΔE) of Co-MOF-based film and hardness and total soluble solids (TSS) of fresh-cut Fuji apples at 4 °C was demonstrated, respectively. These findings indicate the significant potential of CMC-Na-based composite film containing multifunctional MOF nano-filler as a visual monitoring system, which will pave the way for fresh-cut fruit intelligent packaging.

Selective Removal of Chlorophyll and Isolation of Lutein from Plant Extracts Using Magnetic Solid Phase Extraction with Iron Oxide Nanoparticles.

In recent years, there has been a growing interest in plant pigments as readily available nutraceuticals. Photosynthetic pigments, specifically chlorophylls and carotenoids, renowned for their non-toxic antioxidant properties, are increasingly finding applications beyond their health-promoting attributes. Consequently, there is an ongoing need for cost-effective methods of isolation. This study employs a co-precipitation method to synthesize magnetic iron oxide nanoparticles. Scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) confirms that an aqueous environment and oxidizing conditions yield nanosized iron oxide with particle sizes ranging from 80 to 140 nm. X-ray photoelectron spectroscopy (XPS) spectra indicate the presence of hydrous iron oxide FeO(OH) on the surface of the nanosized iron oxide. The Brunauer-Emmett-Teller (BET) surface area of obtained nanomaterial was 151.4 m2 g-1, with total pore volumes of pores 0.25 cm3 g-1 STP. The material, designated as iron oxide nanoparticles (IONPs), serves as an adsorbent for magnetic solid phase extraction (MSPE) and isolation of photosynthetic pigments (chlorophyll a, lutein) from extracts of higher green plants (Mentha piperita L., Urtica dioica L.). Sorption of chlorophyll a onto the nanoparticles is confirmed using UV-vis spectroscopy, Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS), and high-performance liquid chromatography (HPLC). Selective sorption of chlorophyll a requires a minimum of 3 g of IONPs per 12 mg of chlorophyll a, with acetone as the solvent, and is dependent on a storage time of 48 h. Extended contact time of IONPs with the acetone extract, i.e., 72 h, ensures the elimination of remaining components except lutein, with a spectral purity of 98%, recovered with over 90% efficiency. The mechanism of chlorophyll removal using IONPs relies on the interaction of the pigment's carbonyl (C=O) groups with the adsorbent surface hydroxyl (-OH) groups. Based on molecular dynamics (MD) simulations, it has been proven that the selective adsorption of pigments is also influenced by more favorable dispersion interactions between acetone and chlorophyll in comparison with other solutes. An aqueous environment significantly promotes the removal of pigments; however, it results in a complete loss of selectivity.

Ultrasound bleaching and quality evaluation of rice bran oil

AbstractRice bran oil (RBO) contains rich nutrients that are beneficial to the human body, but RBO suffers from severe nutrient loss due to bleaching difficulties. This article investigates low‐power ultrasound‐assisted bleaching as a new method for RBO during the bleaching process, which could potentially reduce nutrient loss and lipid oxidation. First, florisil (FL), magnesium trisilicate (MAT), and activated blending earth (ABE) were selected to use a mixture design for formula optimization from six adsorbent types, and then, central composite design was employed to optimize the parameters of the bleaching process for the ultrasound‐assisted adsorbent formula. The results showed that the optimal formula was 66% FL, 10% MAT, and 24% ABE, the highest L* value and the lowest a* value is obtained at ultrasound power of 50 W for 9 min. The various parameters of RBO were subjected to comparison before and after ultrasound‐assisted bleaching. Following this bleaching procedure, the color and quality of RBO experienced notable enhancements, all the while maintaining micronutrient and fatty acid compositions within acceptable ranges. The characterization analysis of the adsorbent by FT‐IR spectroscopy and atomic force microscopy confirmed its adsorption of pigments and other substances. The results indicate that the low‐power ultrasound‐assisted bleaching is effective for RBO bleaching and may provide a promising alternative to the adsorption‐based bleaching method.Practical ApplicationsRBO is made from pressed rice bran and has high nutritional value, such as fatty acids, vitamin E, sterols, and oryzanol, with over 90% absorption by the body. The dark color of RBO makes it difficult to produce clear, transparent, and light‐colored rice bran oil, and even if bleaching is achieved, it results in significant nutrient losses. Conventional bleaching methods are commonly inefficient while emerging technologies cannot be applied industrially. Three adsorbents were selected for formulation optimization based on the fact that the bleaching effect of a single adsorbent is not obvious. Low‐power ultrasound‐assisted bleaching was performed to reduce nutrient loss and lipid oxidation. The aim is to find new bleaching methods that achieve bleaching results with acceptable nutrient losses.

A unique composite bilayer tablet composed of porous organic frameworks and two kinds of green solvents for adsorption of fluoroquinolone antibiotics and anionic pigments from water

Due to convenient use, adjustable composition and easy preparation, sorbent tablets are considered to have obvious characteristics in the field of separation, especially for water environmental pollutants. In this study, the green, facile and catalyst-free way was employed to synthesize deep eutectic solvent and ionic liquid@porous organic frameworks (DES@POF and IL@POF), which showed specific surface area and stability; and their adsorption capacities were 187.74 (ciprofloxacin) and 111.28 mg/g (carmine), respectively. Then the two complexes were mixed with diluent and pressed to become monolayer and bilayer composite tablets; especially, the latter had two sides like a coin, which were based on DES@POF and IL@POF, respectively. During the following studies, the tablets exhibited satisfied continuous working ability and adsorption efficiency (99.57% as the highest) for the selected antibiotics and pigments. The key influential factors for their preparation and performance were investigated systematically, and separation mechanisms as well as selectivity were also discovered. The whole process was well fitted by the Langmuir isotherm model and quasi second-order kinetic model. Such a kind of sorbent tablets can be reused and renewed, which can provide useful reference on the development for new forms of separation mediums.

Activated carbons from open air and microwave-assisted impregnation of cotton and neem husks efficiently decolorize neutral cotton oil

The decolorization of cottonseed oil with activated carbons (ACs) from neem and cotton husks has a dual interest: elimination of undesirable pigments in oil and valorization of the husks; by-products of neem and cottonseed processing, which would otherwise be dumped along riverbanks and farms causing environmental pollution. ACs were produced from neem and cottonseed husks after acid impregnation assisted by microwave heating and in ambient air for the decolorization of neutral cottonseed oil. The experimental data were analyzed by the intraparticle diffusion and the pseudo-second-order kinetic models as well as the Langmuir and Freundlich isotherm models. The method of impregnation and carbonization time had dramatic effects on the specific surface area (800–1500 g/m2), the quantity of burn-off (50–70 %), and methylene blue index (300–5000 mg/g) values which indicated the potential of the prepared activated carbons in the bleaching of vegetable oil and in other applications such as environmental clean-up and in agriculture. Pigment adsorption increased with temperature for all ACs indicating that the decolorization process was endothermic. The quantity of adsorbent equally had a significant effect on the pigment adsorption process for all ACs. All the activated carbons prepared in this work were 30–80 % more efficient in pigment adsorption than bleaching earth that is normally used in decolorizing neutral cotton seed oil in industries. All tested models are adequate to describe pigment adsorption by the ACs. Both methods of preparation of ACs were effective for oil decolorization, but microwave impregnation is more appealing because it requires only 1 h compared to 6 h for ambient air. Optimum decolorization conditions were 90 °C for 40min and adsorbent concentration of 2 %.

Zinc oxide‐doped carbon aerogel derived from bagasse cellulose/sodium alginate/zinc nitrate composite for dye adsorption, storage energy and electrochemical sensing

AbstractBACKGROUNDFollowing the trend of green and sustainable development, multi‐application materials utilizing biomass waste have been developed, leading that trend is carbon aerogel (CA). In this study, zinc oxide‐doped CA was synthesized from bagasse cellulose (Zn‐BCA) through simple processes: Cross‐linking to form a sol–gel system, freeze‐drying, and pyrolysis. To synthesize suitable materials, precursor and crosslinking ratios, the content of Zn2+, and pyrolysis temperature in N2 were investigated. The characteristics of ZnO were investigated through modern methods: Scanning electron microscopy, Raman spectroscopy, X‐ray diffraction, Fourier‐transform infrared spectroscopy, and energy‐dispersive X‐ray spectroscopy. The dye adsorption capacity of Zn‐BCA was evaluated through the UV–Vis method. Furthermore, the electrochemical properties are shown through cyclic voltammetry, galvanostatic charge‐discharge, electrochemical impedance spectroscopy results, and glucose sensing results were obtained through linear sweep voltammetry.RESULTSZn‐BCA shows potential for multiple applications with crystal violet pigment adsorption capacity up to 39 mg/g, specific capacitance reaching 164 F/g, and glucose sensing capabilities.CONCLUSIONThus, Zn‐BCA shows wide applicability in adsorbents and electrode materials, in addition to using bagasse biomass as green precursor to synthesize materials. © 2023 Society of Chemical Industry (SCI).

Designing integrated Janus membrane based on a double-cross-linked polyphenol hydrophilic layer for complex emulsion separation

Efficient separation materials with multifunctional and switchable properties are urgently needed to treat submicron-scale oily droplets. Herein, tannic acid (TA) and polyethylenimine (PEI) were blended with poly(vinylidene fluoride) (PVDF) and used to coat a polydimethylsiloxane (PDMS)-modified non-woven fabric immersed in a CuSO4/H2O2 coagulation bath. TA and PEI form a phenolamine hydrophilic network that migrates to the surface and firmly binds to the PVDF substrate. CuSO4 catalyses the H2O2 oxidation, promoting the self-polymerisation of phenol hydroxyl group for forming a carboxyl group. Furthermore, the remaining Cu2+ ions complex with TA to form a metal–phenol cross-linked network. A double-cross-linked hydrophilic layer with polyphenols as connection points was formed on the PVDF surface. The hydrophilic contact angle of the membrane reached 0°. A rough structure with PDMS micro-/nanoparticles was constructed on the PVDF underside via surface nanocasting and the hydrophobic contact angle of the membranes reached 165°. In experiments, each side of the obtained Janus membranes demonstrated surface superhydrophilic and superlipophilic properties and a high flux and excellent separation efficiency for various oil–water emulsions. The integrated Janus membranes are suitable for unidirectional liquid collection, oil–water emulsion separation, cationic pigment adsorption and dealing with complex dye–emulsion pollutants. The integrated structure formed by the hydrophilic layer and the membrane enhances the fouling resistance of the membrane and the removal rate of pollutants reached >99 %. This research presents a simple approach to prepare Janus membranes with asymmetric wettability.

Grape skin anthocyanin extraction from red varieties during simulated maceration: Influence of grape seeds and pigments adsorption on their surface.

The impact of seeds on anthocyanin extraction from skins was assessed on four Italian red winegrape varieties presenting different anthocyanin profile. Grape skins were macerated alone or in presence of seeds for ten days in model solutions. Aglianico, Nebbiolo, Primitivo, and Sangiovese cultivars showed differences in the anthocyanin extraction rate, content, and profile. The presence of seeds did not significantly affect the anthocyanin content and forms extracted from skins and kept into solution, but it generally led to an increase in the polymerization rate. For the first time, anthocyanins adsorbed on seed surface have been quantified after maceration. The amount of anthocyanins retained by seeds was less than 4mg/kg berries and it seems variety-dependent, with a possible role of seeds number and weight. Individual anthocyanin forms were adsorbed mainly according to their abundance in the solution, but cinnamoyl-glucoside anthocyanin forms showed a higher affinity with seed surface.

Adsorption features of pigments onto iron oxides: Co-effect of the molecular structure of adsorbates and the varied surface properties of minerals

The knowledge about the adsorption properties of pigments onto different iron oxide minerals is still limited. The adsorption behaviors of three typical pigments, including amaranth (AR), tartrazine (TA), and brilliant blue (BB), onto three iron oxides (ferrihydrite, goethite, and hematite) were investigated. The primary mechanism of their interactions was the electrostatic attraction. The affinities of iron oxides toward any pigment were generally in the sequence of ferrihydrite > goethite > hematite (e.g., the maximum adsorption amounts (qmax) of AR onto the three iron oxides were 35.5 mg/g, 11.6 mg/g, and 4.2 mg/g, respectively), which was related to the differences in physicochemical properties of minerals (e.g., specific surface area, surface hydroxyl density, and crystal structure). Interestingly, for a given iron oxide, the pigment-binding capacity of the mineral was in the order of AR > TA > BB. This effect was attributed to variations in pigment molecular sizes and electrostatic interactions between pigments and minerals. The pigment-binding capabilities of iron oxides changed as the solution pH varied. Hydrogen-bonding and electrostatic interactions were the main mechanisms below and above pH > pHPZC (pH value at zero point charge), respectively. Furthermore, adding Cu2+ facilitated pigment adsorption, mainly stemming from the surface-bridging effect. Pigments also enhanced Cu2+ adsorption onto iron oxides due to the decreasing electrostatic repulsion between Cu2+ and particles as well as the complexion between Cu2+ with pigment molecules adsorbed on mineral surfaces. The insightful information demonstrates that ubiquitous iron oxide minerals can affect the fate of pigments in natural environments.

INFLUENCES OF DIFFERENT SOLUTIONS ON THE COLOUR STABILITY AND MICROHARDNESS OF CONTEMPORARY LIGHT CURED COMPOSITES: AN IN VITRO STUDY Received 2022-12-09; Accepted 2023-03-18; Published 202

Despite the accumulation of dental plaque, adsorption of colourant pigment from foods and beverages was found to influence the quality of aesthetic restorations. The study aimed to evaluate the influence of different solutions on colour stability and microhardness of microhybrid and nanofilled composite resins. This project was a laboratory based experimental study. Three types of composite resins were used; microhybrid (FiltekTM Z250), nanohybrid (FiltekTM Z250 XT) and universal nanocomposite (FiltekTM 350 XT). A total of 135 disc-shaped specimens were prepared and were randomly divided into five subgroups (n = 9): artificial saliva, mouthwash, carbonated drink, energy drink and coffee. Samples were immersed in the solutions at time intervals of 24 hours, 7 days, 14 days, 21 days and 28 days. All specimens were assessed for the staining effect using a spectrometer (QE65000) and microhardness evaluation using the Vickers indenter (LECO LM 248AT, St. Joseph, Michigan, USA). Data on spectrometer colour spectrum and surface hardness were subjected to a one-way ANOVA and Tukey HSD test at a significance level of P < 0.05. There was a significant difference in discolouration between all three types of composite resins when immersed in all solutions regardless of the pH values (P < 0.05). Vickers hardness test showed statistically significant microhardness among all composite resins on Day 28. The staining medium caused significant discolouration and decreased the hardness of all the materials tested. Microhybrid composite resin reported the lowest colour variations and resistance to hardness test.

Nipa palm shell-derived magnetic carbon aerogel for absorbents and storage energy

At this time, multi-application materials are developing to match the trend of green sustainable energy development. And with characteristics acting as high porosity, light weight, bulk form with diverse pores, and high chemical compatibility, metal-doped carbon aerogel becomes a potential material. In this study, Fe-doped carbon aerogel with crosslinking sodium alginate (Fe-SA-CA) was synthesized through a simple process of freeze-drying, aerogel pyrolysis, and pyrolysis temperatures (600–800 °C) were investigated to find suitable materials for adsorption and electrochemical applications. The characteristics of the material are analyzed by modern methods, proving that the surface of the material has a variety of pores with a size approximately 2 nm, and has the main components including C, O, and Fe. Fe-SA-CA shows potential for adsorption of oils, organic solvents, and crystal violet pigments. In particular, electrochemical properties of Fe-SA-CA are determined through cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedence spectroscopy, to obtain high specific capacitance (203 F/g at 50 mV/s), constant discharge capacity over 500 cycles. Futhermore, thanks to the presence of the element Fe, the magnetic material is easily recovered with a magnet after used. In addition, the precursor used in the study is cellulose from nipa coconut shells - a large amount of biomass waste in Vietnam, thereby reducing production costs, limiting chemicals, and expanding the potential application of the Fe-doped carbon aerogel.

Tuning Pre-Solution of an Amphiphilic Polymeric Dispersant with Low Acid-Value toward Colored-Ink Preparation

Recently, a variety of amphiphilic block copolymers for water-based color inks as pigment dispersants have been developed. Although such dispersants require both high adsorption of pigments and dispersion-stability in water, the most crucial issue is the difficulty in controlling the affinity balance of the polymeric dispersants between the pigments and aqueous media. Therefore, it is important to increase the solubility of the hydrophobic polymers with low acid-value for ink design. Amphiphilic block copolymers containing styrene-based blocks as hydrophobic segments and methacrylic acid blocks as hydrophilic segments were prepared. The polymers with low acid-value could not dissolve in the alkaline solution directly. They could dissolve in methyl-ethyl-ketone (MEK) at room temperature and diethylene glycol (DEG), with heating. Polymer aqueous solutions were successfully prepared using polymer solutions in DEG as the pre-solutions. Because they were also unable to dissolve directly even in an alkaline solution containing DEG, the existence of DEG is not important, but the process employing the pre-solution is important. The influence of pre-solution viscosity on solubility in water was evaluated. The result suggests that the high viscosity of the DEG solution would work to slowly disperse the polymers in the alkaline solution, efficiently converting polymers into an aqueous soluble state, owing to there being enough time for the neutralization of the carboxylic acids of the polymers. Note that in the pre-solution of a lower concentration, the aqueous solution did not become clear, and the larger particle sizes were detected. These results showed that the viscosity of the pre-solution is an essential factor in solubilization in water. Using this method, the polymeric dispersants with low hydrophilicity were well dissolved in water, up to a high concentration.

Water purification by adsorption of pigments or pollutants via metaloxide

The growth in industrialization ultimately enhances the toxic discharges of wastewater containing hazardous dyes from various industrial units as a consequence severe ecological and public health issue exhibit a major challenge to conventional system to decontaminate water. Depending upon experimental constrains various physicochemical and biological treatment process have been made possible to remove pollutant of interest according to their functional abilities. In spite of all the treatment techniques, Adsorption process is considered one of the most excellent option due to the cost-effectiveness, ease of operation, high removal efficiency and regeneration of adsorbents. Over the decades, metal oxides and their composites-based absorbents showed tremendous efficiency in wastewater decontamination by dyes. The ample surface-active sites, tunable surface chemistry, ease to synthesize and functionalization, high accessible surface area, economic viability, and good recyclability make the metal oxide-based nanomaterials potential adsorbents for fast and effective removal of a wide range of heavy metal and metalloid ions. The presence of toxic dye molecules in water system poses a serious threat to aquatic ecosystem. This paper comprehensively reviews the source of contamination, possible health hazards, and adsorption technique by metal oxides to eliminate dyes from wastewater. Also, an environmentally friendly and self-sustainable treatment method should be explored to address this problem for emerging contaminants.

Magnetic metal–organic frameworks as adsorbents for the detection of azo pigments in food matrices

Azo pigments with azo functional groups (–NN–) are commonly used in foods. Through rational design, here we report synthesis of a novel magnetic metal–organic framework (MOF-545) and the use of Fe3O4@MOF-545 for the selective separation of azo pigments from beverages. We find that Fe3O4@MOF-545 exhibits excellent adsorption/removal capacities for new coccine (NC, 459 mg g−1) and lemon yellow (LY, 476 mg g−1) individually. The results indicated that the adsorption capacities of Fe3O4@MOF-545 were 5 times higher than reported previously. The large surface area (120.4 m2/g) and the suitable pore size (1.6 nm) of Fe3O4@MOF-545 provided multiple accessible channels for azo pigment adsorption. The adsorption kinetics, stability, recovery, and reusability of Fe3O4@MOF-545 were all reported. The recoveries ranged from 92.9 to 104.5%, reflecting the capacity of MOF-545 to efficiently separate NC and LY. Fe3O4@MOF-545 is suitable for azo pigment determination and separation in food matrices.

Engineering a unique Multi-tasking polymer that specifically prevents rhodamine B and fluoride ion toxicity with Anti-bacterial responses against MRSA

There is always a necessity for the invention of materials that can show improved efficiency to adsorption of organic dye and pigments and fluoride removal incubating the additional properties like antimicrobial responses when the finding is related to water remediation. We elaborated cross-linked ionic models where the crosslinker was tuned from 1,3-dibromopropane to 1,9-dibromononane, to invent multifunctional metal-free, water-immiscible, and easy-to-handle material. The synthesized cross-linked and ionic polymeric materials were well characterized using the standard spectroscopic and analytical techniques - NMR, ATR-FTIR, APC, and FE-SEM. The cross-linked polymers invoked for water remediation showed good potency in removing water-miscible wastes like rhodamine B (RhB) and fluoride. The analysis revealed 50 mg PVPC3 with 1,3-dibromopropane as crosslinker when treated with 10 ppm per 50 mL fluoride solution showed effective removal of 9.6 ppm fluoride, and 60 mg PVPC9 with 1,9-dibromononane as crosslinker removed around 78% RhB. Therefore with backbone PVP constant, the efficiency in removing different classes of waste can be tuned accordingly. Moreover, the ionic cross-linked polymers showed good responses against Methicillin-resistant Staphylococcus aureus (MRSA).

Discovering the Influence of Microorganisms on Wine Color.

Flavor, composition and quality of wine are influenced by microorganisms present on the grapevine surface which are transferred to the must during vinification. The microbiota is highly variable with a prevalence of non-Saccharomyces yeasts, whereas Saccharomyces cerevisiae is present at low number. For wine production an essential step is the fermentation carried out by different starter cultures of S. cerevisiae alone or in mixed fermentation with non-Saccharomyces species that produce wines with significant differences in chemical composition. During vinification wine color can be influenced by yeasts interacting with anthocyanin. Yeasts can influence wine phenolic composition in different manners: direct interactions—cell wall adsorption or enzyme activities—and/or indirectly—production of primary and secondary metabolites and fermentation products. Some of these characteristics are heritable trait in yeast and/or can be strain dependent. For this reason, the stability, aroma, and color of wines depend on strain/strains used during must fermentation. Saccharomyces cerevisiae or non-Saccharomyces can produce metabolites reacting with anthocyanins and favor the formation of vitisin A and B type pyranoanthocyanins, contributing to color stability. In addition, yeasts affect the intensity and tonality of wine color by the action of β-glycosidase on anthocyanins or anthocyanidase enzymes or by the pigments adsorption on the yeast cell wall. These activities are strain dependent and are characterized by a great inter-species variability. Therefore, they should be considered a target for yeast strain selection and considered during the development of tailored mixed fermentations to improve wine production. In addition, some lactic acid bacteria seem to influence the color of red wines affecting anthocyanins’ profile. In fact, the increase of the pH or the ability to degrade pyruvic acid and acetaldehyde, as well as anthocyanin adsorption by bacterial cells are responsible for color loss during malolactic fermentation. Lactic acid bacteria show different adsorption capacity probably because of the variable composition of the cell walls. The aim of this review is to offer a critical overview of the roles played by wine microorganisms in the definition of intensity and tonality of wines’ color.

Determination of new carmine in beverages by one step rapid solid phase extraction based on metal organic framework extractant

胭脂红是一种广泛应用的偶氮类色素,我国对其在食品中的添加量有严格规定。由于食品基质的复杂性,针对这类痕量色素很难建立一种灵敏度高、富集性强且高效便捷的检测方法。研究利用卟啉环中的羧基与金属锆离子的配位作用制备了一种高比表面积的金属有机骨架材料(PCN-222),并将纳米材料填入注射式固相萃取装置中,以简化前处理过程,用于快速萃取饮料中胭脂红色素。采用多种表征手段研究了PCN-222纳米材料的形貌、结构及性能。较高的比表面积和静电作用共同决定了新型萃取剂对胭脂红色素具有极强的富集性能。通过优化萃取剂用量、样品溶液pH值、洗脱条件和洗脱剂体积等萃取条件,使目标物实现瞬时吸附,样品前处理时间缩短至5 min。在最佳条件下,该方法可使样品在高、中、低3个水平的加标回收试验中的回收率达到99.5%~109.4%,相对标准偏差小于3%,方法的检出限为0.1 μg/L(S/N=3),定量限为0.3 μg/L(S/N=10)。此外,针对所合成的材料进行萃取-解吸后发现,PCN-222在重复使用4次后仍保持90%以上的萃取能力,表明材料具备可循环性。该方法通过制备的新型金属骨架材料建立了一种高效、便捷、绿色环保的前处理技术,极低的检出限、较高的准确度和较好的重复性表明方法适用于饮料中痕量色素胭脂红的富集和检测。新型固相萃取技术的开发为食品安全检测提供了新思路。

Optimization of Methylene Blue Pigment Adsorption with Biomass Waste Adsorbent in a Continuous Operating Column

Optimization of Methylene Blue Pigment Adsorption with Biomass Waste Adsorbent in a Continuous Operating Column

Co-sensitization of natural and low-cost dyes for efficient panchromatic light-harvesting using dye-sensitized solar cells

Co-sensitization is an effective strategy to achieve panchromatic light-harvesting and to enhance dye-sensitized solar cell performance. In this work, the potential of the extracted natural dyes from Malva verticillata and Syzygium cumini was evaluated as mono and co-sensitizers in DSSCs. The UV–vis absorption spectra revealed that the combination of studied dyes had a high molar extinction coefficient and cumulative absorption properties in a way that its absorption spectra overlapped the spectral domain where the original sensitizers lacked light-harvesting. Moreover, all investigated dyes were characterized using circular dichroism, dynamic light scattering, zeta potential, cyclic voltammetry, and Fourier-transform infrared spectroscopy. The results of zeta potential analysis showed that the pigment aggregation and their colloidal stability, which has implications for the pigment adsorption process on TiO2 nanoparticles, were effectively controlled by varying the pH of the dye extract. Based on the CV results, the studied dyes indicated excellent redox stability and sufficient thermodynamic driving force for efficient electron injection. Based on the photovoltaic results, the acidified cocktail-DSSC had the highest Isc and η of 3.15 mA and 1.84 %, respectively. This superiority could be ascribed to the panchromatic light-harvesting, the excellent optical activity, and the appropriate energy levels of the acidified cocktail. Moreover, the loading of acidified cocktail dyes on the TiO2 surface was enhanced due to their homogeneous dispersion, less steric hindrances, and multi-anchor groups attached to the semiconductor surface. Based on the stability results, the treated cocktail-DSSC retained about 52.51 % of its as-fabricated efficiency after seven days while NDSSCs sensitized with acidified Syzygium cumini, Malva verticillata, Syzygium cumini, and cocktail retained about 26.24 %, 14.80 %, 16.35 %, and 15.25 %, respectively.