Food colorants: their past,present and future

Whether we are purchasing fresh vegetables from a market stall, ready meals from the supermarket, eating at home or in a five‐star restaurant, we use colour to tell us what to expect in terms of taste, nutrition and safety. This review considers the techniques that have, over the years, been employed to modify the colour of our food, and the interactions of these techniques with issues of safety and nutrition. The demand for brightly coloured food resulted in the incorporation of some questionable inorganic and organic chemistry being used in food products. A limited number of synthetic dyes are still used in food today, but health concerns and the consumer‐driven demand for natural colorants has brought about a change in the way food is coloured. The proliferation of products with labels that state they contain “No artificial colours” on supermarket shelves suggests that the future of azo dyes and their various derivatives is strictly limited. Nature produces an abundance of colours and many of these are extracted and used as natural food colorants; however, they are subject to application limitations and stability problems. Significant research by academia and industry into methods to stabilise and expand the application possibilities for the various approved natural food colorants is ongoing, but most developments that food colour manufacturers proclaim are enhanced vehicles for delivering established natural pigments into food products.     

Properties of ink‐jet printed,ultraviolet‐cured pigment prints in comparison with screen‐printed,thermo‐cured pigment prints

A collection of printed fabrics for men’s shirts was designed and prepared using computer‐aided design/computer‐aided manufacturing technology. The colours for designs were ink‐jet printed on cotton fabrics with pigments and ultraviolet‐cured. These prints represented the target colours for subsequent flat‐screen printing, which was performed using pigment printing pastes and thermal curing. For an exact transfer of colours of the ink‐jet‐printed standard into the screen‐printing process, a computer recipe prediction method was used. A comparison of colorimetric parameters of fabrics printed with both printing techniques shows minimal and acceptable differences in the CIELab colour values. A comparison of colour fastness properties proves that very good colour fastness is achieved on the pigment‐printed fabrics produced with both printing techniques. The flat‐screen‐printed fabrics show better colour fastness to washing, perspiration and rubbing, while ink‐jet‐printed fabrics show better colour fastness to dry‐cleaning and light. The fabrics printed with both printing techniques have high rigidity and non‐elastic properties. The mechanical and physical parameters are strongly dependent upon the amount of the dry substance of the printing media applied on the cotton fabric surface, which is higher on screen‐printed fabrics. The ink‐jet‐printed fabrics show better air permeability than flat‐screen‐printed fabrics.     

Production and characterisation of iron-chromium pigments and their interactions with transparent glazes

In this study, production and characterisation of pigments by using less expensive raw materials such as limonite and chromite was undertaken. The resulting pigments were characterised by using X-ray diffraction (XRD) and UV-Vis spectrophotometer. The colour of glazed tiles containing 3 wt.% pigment change from dark brown to light brown depending on the calcination temperature and limonite content. With pigments prepared with 50% limonite content calcined at 1250 °C, the chocolate brown colour was obtained corresponding to the commercial brown pigments. An iron-chromium black pigment was synthesised from a mixture of pure chromium (III) oxide (Cr₂O₃) and iron (III) oxide (Fe₂O₃) powders and was used to determine possible interactions between a pigment and a transparent glaze. The interactions were studied using a scanning electron microscope (SEM) attached with an energy dispersive X-ray spectrometer (EDX). The results showed that black pigment particles give brown colour to the glaze. EDX analysis on pigment crystals embedded in the glaze clearly showed that Zn and Mg diffused into pigment crystals and caused a change of colour from black to brown.     

Synthesis of fluorite ceria based solid solutions from mixed rare earth carbonates

The synthesis of new class of compound based on CeO₂ as pigments has been reported. The starting material used for preparation of the compound is mixed rare earth carbonate, which is an intermediate product obtained during beneficiation of monazite mineral to separate different rare earth metals. This paper presents direct use of the mixed rare earth carbonate without separation of individual rare earth oxides for pigment preparation, thereby reducing cost and improving eco-efficiency of the process. The effect of dopants, and different mineralizers on colour formation has been studied in detail by XRD, SEM and UV–vis spectrophotometer (CIELAB parameters), particle size analyzer. From this study, we optimized the conditions for the syntheses of mixed rare earth oxide by solid state reaction route to develop the brown colour pigments. Pigment properties such as moisture content, oil absorption, bleed resistance, opacity, gloss, etc., of the product has been evaluated and found to be in acceptable range. Nominal composition of the product was found to be Ce_0.75Pr_0.05Ln_0.20O_1.9, where Ln includes, La, Nd, Sm, Gd.     

Effect of particle size on pigments colour

The historical pigments, contrary to modern ones, are not constituted by particles having all the same size and this influences the colour of the paint layers. The hiding power and colouring power of a pigment depends, in fact, on its particle size. The aim of this study was to evaluate the influence of particle size on optical characterization of paintings in terms of reflection of light and related colour specification. Starting from the qualitative observation, we have attempted to quantify the pigments colour variations induced by grinding and then attributable to granularity. Powdered pigments of principal colours have been selected in specific particle size range by mechanical sieving. The measurements were performed both on pigment pellets and on paintings realized with binder casein. All samples were characterized by an optical and colorimetric point of view through spectrophotometric analysis and for the surface morphological observation through scanning electron microscopy. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 236–243, 2017     

虹彩型云母钛珠光颜料的制备与表征

本文研究了虹彩型云母钛珠我颜料的制备方法。通过电子能谱，光谱反射率，色度值，涂覆率及比表面积等的测试，表征了颜料的组成及颜色，归纳出涂层的光学厚度与虹彩效应，光学性能的关系及周期性递变规律的机理。     

Light-harvesting and light-protecting pigments in simple life forms

Photosynthesis is the basis of life on the earth and the development of the vast range of simple organisms existing today can often be traced back to the earliest geological times. Most life forms depend directly or indirectly on the synthetic processes which harvest the sun's energy, utilising a range of pigments such as the chlorophylls and carotenoids, which not only determine the colour of each organism, but often also serve a protective role against the adverse effects of ultraviolet radiation. Recent research has elucidated the detailed photochemical mechanisms and the complex nature of the light-harvesting pigment–protein complexes. This review covers algae and fungi and their symbiotic forms in lichens and corals, particularly with respect to the pigments they synthesise and the commercial uses to which these and other metabolites have been (and may in the future be) put.     

Colour and appearance in nature part III. Color and appearance of homo sapiens

The principles of human colouration are very similar to those applying to other organisms, as outlined in the first and second articles of this series. The races of man are coloured differently for the very good reasons of adaptation to our environment, and any deviation from what is considered our normal colour is a good guide to the state of our wellbeing. Human beings have evolved and adapted to a reproductive sexual environment as well as to a climatological environment. Neanderthal man, at the start of the homo sapiens line, included ceremony and colour in his life pattern, and anthropologists have identified a basic colour triad used in body painting. There are various types of decoration and many motives to use colour, but it seems that body colour and decoration in general have remained vitally important to man's culture, enjoyment, and fear of life through the succeeding ages.     

Corrosion inhibition of copper and brass pigments in aqueous alkaline media by copolymers

Copper and brass pigments corrode in aqueous alkaline media with absorption of oxygen which can be measured gasvolumetrically. These corrosion reactions can be inhibited by certain copolymers, the metallic sparkle and the colour of the pigments being preserved. The brass pigment (rich gold) is inhibited more effectively by copolymers than the copper pigment. The corrosion inhibiting effect of styrene–maleic acid–acrylic ester copolymers on copper pigment decreases with increasing the chain length of the ester alcohol of the acrylate monomer. The most effective copolymer examined in this study is the styrene–maleic acid–ethyl acrylate copolymer which inhibited the corrosion reactions of copper and brass pigment both at pH 8.5 and 10.     

含铅颜料代用品的开发进展

含铅颜料是主要的铅污染源。介绍了国外含铅颜料代用品的开发情况,它们是新型无毒防锈颜料、正确调整的有机颜料、金红石型混相颜料、钒酸铋黄、稀土颜料和安全黄。     

Method of extraction and resolubilisation of pigments from Chlorociboria aeruginosa and Scytalidium cuboideum,two prolific spalting fungi

Twelve solvents were tested for their ability to extract the pigments of Chlorociboria aeruginosa and Scytalidium cuboideum, two fungi used primarily for the spalting of decorative wood. Solvents were assessed on the basis of the saturation of pigment produced, their ability to diffuse through filter paper, and whether they reacted with the extracted pigments. Solvents that performed well in extraction testing were then tested to determine whether they could also dissolve the extracted pigment once dried. Of the solvents tested, only dichloromethane was capable of quick, non‐reactive extraction with filter paper diffusion, as well as being able fully to redissolve dried pigment extracted from C. aeruginosa. The results of this study show dichloromethane to be an ideal solvent for extracting and applying fungal pigments that offers new possibilities for spalting in which fungi do not need to be grown directly on a substrate in order to produce pigmented wood.     

我国天然色素的现状及发展方针

天然色素的制备及使用在我国具有悠久的历史,目前我国的天然色素产业已初具规模,年产量约1.8万～2万t。其中有些品种还远销国外。随着食品工业的不断蓬勃壮大,食用天然色素的发展具有广阔前景。我们应立足于国内市场,开拓国际市场,大力发展“天然、营养、多功能”的食用色素。     

The role of colorants in the generation,storage, and output of digital still images

The purpose of this review is to highlight the important role that dye and pigment colorants play in the areas of image generation, image storage, and image output with respect to digital still images. Colorants in the form of dyes and pigments play an integral part in the digital still imaging process, from the initial conversion of the original greyscale image into a full‐colour RGB additive image, followed by electronic image storage, and finally to hard‐copy output via non‐impact printing technologies such as inkjet and thermal dye transfer. In addition, both dyes and pigments are also utilised for image generation in the fast‐developing world of electronic paper display technologies. Dyes and pigments were the mainstay of many of the early analogue photographic processes in the areas of image capture and image reproduction, and this review sets out to show that, in the new age of digital imaging, this situation is still prevalent.     

Self-stratifying coatings containing barrier and active anticorrosive pigments

The influence of decorative and anticorrosive pigments on the distribution of pigments and protective properties of self-stratifying epoxy/acrylic coating systems was investigated. The separation of pigments was determined basing on their properties and the type of additives used and was expressed as a factor determining the separation of the pigments between the upper and bottom layer. The pigment distribution coefficient was calculated basing on the colour difference between the upper and bottom layer as well as by means of the XRF method.     

Weathering performance of rigid PVC pigmented with iron-containing pigments: The relationship between weathering and the chemical nature of the iron contained

Weathering performance of rigid PVC pigmented with iron oxide or some complex inorganic pigments (CIP) containing iron can be poor. Consideration of iron-containing CIP's for use in exterior PVC leads to the common question: “How much ‘free iron’ is present in the pigment?” It has been unclear what “free iron” means and therefore difficult to know which iron-containing pigments will weather well and which will not. Some formulators may avoid iron-containing pigments altogether by electing not to formulate in a color space only achievable with those pigments. We compare the weathering performance of a series of iron-containing CIP's to the amount of iron contained, the crystal phases, and the amount of acid-extractable iron. We see a strong correlation between the weathering performance and the extractable iron content. Many iron-containing pigments have good weathering performance in PVC, so one shouldn't exclude iron-containing pigments from consideration based solely on the iron content. The acid-extractable iron is an indicator of the expected weathering performance. Careful evaluation and selection of pigments may allow consideration of previously avoided pigment combinations.     

Chromic textiles: Colour fastness properties and irreversible colour change behaviour of textiles screen printed with thermochromic,photochromic and hydrochromic colourants

The objective of this work was to study how ultraviolet (UV) light exposure, washing and rubbing can influence colour and dynamic qualities of chromic textiles, and to explore how the results attained can be applied by designers for the development of colour changing palettes. The experimental work was conducted with 74% polyamide and 26% elastane elastics screen printed with thermochromic, photochromic and hydrochromic pigments in diverse colours. Initially, colourfastness properties of each pigment type versus colour were assessed. Although washing and rubbing can interfere in samples' colours by becoming lighter at different degrees, the results attained highlight the poor stability to lighting of thermochromic and photochromic pigments, which also present changes between hues along exposure time. For conventional textile applications, poor colour fastness commonly represents a limitation. This work proposes that the way textile colours and behaviour are permanently affected by the studied conditions can be interpreted as a creative variable in the design process. Research samples with a combination of pigments were developed and tested with a combination of cycles of different fastness tests, namely one washing cycle for every 4 h of UV light exposure, totalling 48 h and 12 washing cycles. Results demonstrate the possibility of creating interactive surfaces capable of displaying a wide range of colours that evolve to static within different hues, over stimuli conditions.     

Characteristics of pigments,modification, and their functionalities

Novel treatments of pigments with inorganic materials have tremendous industrial and commercial prospects. Specific treatment of pigment has a marked effect on its behavior during application. The treatment allows a broad modification of the surface characteristics of pigment particles which leads to improved functionalities. Surface modification of pigments is achieved via coating, polymerization with modifying reagent, treatment with derivatives or polymers, which alter either the optical, conductivity or dispersibility during processing and application. These and many other distinguishing factors that affect the characteristics of pigments such as the class, crystal structure, particle morphology, particle size, hiding power, pigment volume concentration, surface character, and surface treatment have been reviewed. Various organic pigments such as those from fungus and bacteria, and the various families of pigment types such as metallic pigment, light interference, and diffractive pigments which presents decorative quality such as leafing, nonleafing, pearlscent, and Fabry‐Perot effects on substrates have also been reviewed in addition to those from inorganic sources with emphasis on the structure and physiochemical modifications using metal and nonmetal Ions.     

ATO半导体颜料在伪装涂料中的应用研究

以SnCl4、SbC13、NaOH等为原料,采用共沉淀法制备ATO半导体颜料,采用XRD、SEM、EDS对颜料结构、成分、形貌进行表征,比较了ATO半导体颜料与常见的单组分颜料涂层红外发射率大小。通过颜色混合规律将ATO半导体颜料与着色颜料混合制备了绿色伪装涂料,制备的涂层具有较低的红外发射率,并且其光谱反射曲线满足美军标的光谱通道要求,具有较好的应用前景。     

Outlook for high‐oleic peanuts and peanut products in 21st century markets

The global oilseed market is dominated by and steadily is becoming more dependent on palm and soybean as major commodity sources to meet growing demand for edible vegetable oil and protein. However, the loss of GRAS status for hydrogenated oils in the U.S., concern for sustainable production practices, debate on dietary saturated fats, and other constraints signal the need for economic alternatives in the oilseed commodity market. Recent technological advances elevate the position of oilseed peanut in such consideration [1]. For example, analysis of the peanut genome sequence has: 1) revealed the chromosomal location of genes that can protect the crop against major diseases (thus reducing need for multiple applications of fungicides), and genes that mediate high‐oleic acid concentration (thus enhancing health benefits, longer product shelf‐life, and improved flavor); 2) generated DNA markers that help breeders track and stack desired genes in hybrid lines; and 3) enabled modern DNA‐sequence driven breeding methods that cut years off the timeline for developing varieties. These capabilities will help reduce cost of production, lead industry transition to high‐oleic products, and ensure an adequate supply of safe, nutritious and healthy peanuts and peanut products.     

色酚AS偶氮颜料（一）

色酚AS类颜料是由2-羟基-3-萘酰胺化合物作为偶合组分与取代基芳胺重氮盐偶合制得的偶氮颜料,主要给出红色谱,颜料分子中因含有甲酰氮基（-CONH-）具有良好的耐溶剂性能.文中介绍色酚AS偶氮颜料的发展历史、化学性质及生产、性能、应用,并介绍了目前市场上的二组商用色酚AS偶氮颜料,色酚AS偶氮颜料中红112、146以及170在传统工业领域的红色谱中具有相当的市场份额.