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Journal of analytical atomic spectrometry 37(1), 114 - 129 (2022). doi:10.1039/D1JA00271F, Redox processes activated by environmental factors have been identified as the main cause of the chromatic alterations of a number of artists' pigments, including the yellow pigment orpiment (As$_2$S$_3$). Although a general comprehension of the mechanisms has been provided through characterization of degradation compounds of As$_2$S$_3$, experimental evidences to prove how other paint components and how different environmental agents influence the formation pathways of specific secondary compounds are still lacking. Thus, it becomes fundamental to develop a methodological strategy which enable achieving a discrimination among the causes affecting the chemical stability of more heterogenous As$_2$S$_3$-based paints and defining the mechanism through which the alteration establishes and evolves, with the ultimate goal of optimizing the preventive conservation measures of unique masterpieces. In this paper, we propose a comprehensive multi-material and multi-method approach based on the combination of synchrotron radiation X-ray micro-analytical techniques (i.e., X-ray diffraction, X-ray fluorescence and X-ray absorption near edge structure spectroscopy at S K-/Ag L$_3$-/As K-edges) and vibrational micro-spectroscopy methods to unveil the causes and mechanism of darkening of ���fake-gilded��� decorations in tempera paintings, originally consisting of an unusual mixture of A$_2$S$_3$ and metallic silver (Ag$^0$). Such degradation process is a not yet understood phenomenon threatening a series of Old Master paintings, including those by the Italian painters Cimabue and Pietro Lorenzetti. The high specificity, sensitivity and lateral resolution of the employed analytical methods allowed providing first-time evidence for the presence of black acanthite ($��$-Ag$_2$S), mimetite [Pb$_5$(AsO$_4$)$_3$Cl] and syngenite [K$_2$Ca(SO$_4$)$_2$��H$_2$O] as degradation products of the ���fake-gilded��� decorations in the Maest�� by Cimabue (Church of Santa Maria dei Servi, Bologna, Italy). Furthermore, the study of the painting combined with that of tempera paint mock-ups permitted to explore and define the environmental agents and internal factors causing the darkening, by proving that: (i) Ag$^0$ and moisture are key-factors for triggering the transformation of As$_2$S$_3$ to $��$-Ag$_2$S and As-oxides; (ii) S$^2$--ions arising from the degradation of A$_2$S$_3$ are the main responsible for the formation of $��$-Ag$_2$S; (iii) light exposure strengthens the tendency of the paint components towards alteration. Based on our findings, we finally propose a degradation mechanism of As$_2$S$_3$/Ag$^0$-based tempera paints., Published by ChemSoc, Cambridge

Non-diazotrophic cyanobacteria respond to nitrogen starvation by growth arrest and pigment degradation (chlorosis), resulting in dormant cells that are able to survive starvation periods for extended periods of time. Resuscitation from chlorosis by nutrient availability is a developmental process that is supported by a highly organized, genetically determined program.

Chemical deterioration can affect the quality and safety of food products. This chapter is aimed at providing a better understanding of chemical deterioration in food, including its cause, influence on food quality and available detection methods. Specifically, major types of chemical deterioration are presented, such as enzymatic deterioration, nonenzymatic browning, lipid oxidation, protein oxidation, vitamin and pigment degradation. Currently available methods for detection of chemical deterioration in food are also overviewed, including sensory evaluation, physic and chemical analysis, spectroscopic and chromatographic methods as well as electronic nose, electronic tongue, and electronic eye.

Numerous experimental techniques of analysis find applications in many branches of the archaeometry. Among them, Raman spectroscopy carved out a niche in the field of diagnostic and conservation of cultural heritage. The exceptional ability to predict and discover the structural properties of materials set for Raman spectroscopy, an exclusive role among the analytic techniques, is further boosted when it is coupled with mathematical or statistical models able to deepen the studied phenomena. In this work, we present a review of recent studies where pairing Raman spectroscopy and mathematical models allowed achieving important results in the case of potteries, porcelains, ancient and modern paper, ancient jewelry, and pigment degradation. The potentialities of this approach are evidenced and analyzed in detail.

A recently developed xenon arc-based accelerated weathering cycle, ASTM D7869-13, has been validated for automotive and aerospace coatings, but its ability to predict the gloss and color retention of premium architectural finishes has not yet been evaluated. We review new weathering data comparing the performance of poly(vinylidene fluoride) (PVDF) architectural finishes in south Florida exposure as well as several accelerated exposure methods including ASTM D7869-13. ASTM D7869 accurately reproduced Florida rank order gloss and color retention trends for coatings made with PVDF-acrylic blends and inorganic pigments, as well as the gloss and color changes seen in Florida for 70% PVDF masstone coatings made with a number of single organic pigments. However, the D7869 cycle has difficulty predicting the rank order of rutile TiO2 grades for the gloss retention of PVDF coatings in Florida, as well as the magnitude and direction of color fade from organic pigment degradation in organic pigment/inorganic pigment blends. One open question that remains is whether the ASTM D7869 cycle might have some utility for industry standard or specification purposes, if the test is limited to specific reference colors or more ideally to specific reference pigments.

The pea aphid, Acyrthosiphon pisum (Harris), shows body color shifting from red to pale under starvation in laboratory conditions. These body color changes reflect aphid’s adaptation to environmental stress. To understand the color-shifting patterns, the underlying mechanism and its biological or ecological functions, we measured the process of A. pisum’s body color shifting patterns using a digital imagery and analysis system; we conducted a series of biochemical experiments to determine the mechanism that causes color change and performed biochemical and molecular analyses of the energy reserves during the color shifting process. We found that the red morph of A. pisum could shift their body color to pale red, when starved; this change occurred rapidly at a certain stress threshold. Once A. pisum initiated the process, the shifting could not be stopped or reversed even after food was re-introduced. We also discovered that the orange-red pigments may be responsible for the color shift and that the shift might be caused by the degradation of these pigments. The carbohydrate and lipid content correlated to the fading of color in red A. pisum. A comparative analysis revealed that these reddish pigments might be used as backup energy. The fading of color reflects a reorganization of the energy reserves under nutritional stress in A. pisum; surprisingly, aphids with different body colors exhibit diverse strategies for storage and consumption of energy reserves.

A dry powdered pigment extract was prepared from a Roselle liquid concentrate obtained from Trinidad. The pigment base was added to two dry pack foods, a beverage mix and a gelatin dessert, and evaluated under various temperature and humidity conditions. During a 16-week storage period, color, flavor, and pigment stability were evaluated versus those of Red No. 2. All samples were less stable than those with Red No. 2 but showed good stability up to 4 weeks of storage, after which, the rate of pigment degradation accelerated. Reconstituted products showed good light and refrigeration stability but the roselle powder imparted an unacceptable flavor to the products.

Heritage Science 7(1), 67 (2019). doi:10.1186/s40494-019-0309-3, The use of non-invasive macroscopic imaging techniques is becoming more prevalent in the field of cultural heritage, especially to avoid invasive procedures that damage valuable artworks. For this purpose, an X-ray powder diffraction scanner (MA-XRPD) capable of visualising crystalline compounds in a highly specific manner was recently developed. Many inorganic pigments present in paintings fall into this category of materials. In this study, the 17th century oil painting Girl with a Pearl Earring (c. 1665) by Johannes Vermeer was analysed with a combination of transmission and reflection mode MA-XRPD. By employing this scanner in reflection mode, the relative sensitivity for compounds that are present at the paint surface could be increased, establishing it as a highly relevant technique for investigating the degradation processes that are ongoing at paint surfaces. Many of the original pigments employed by Vermeer could be identified, along with four secondary alteration products: gypsum (CaSO4·2H2O), anglesite (PbSO4), palmierite (K2Pb(SO4)2) and weddellite (CaC2O4·2H2O). The formation of gypsum was linked to the presence of chalk in the upper glaze layer while the formation of palmierite and weddellite is driven by the presence of lake pigments (and their substrates). In this manner, MA-XRPD can also be used to pinpoint locations relevant for sampling and synchrotron µ-XRPD analysis, which provides information on the microscopic make-up of the paint. A paint cross-section taken from an area rich in palmierite was analysed with synchrotron µ-XRPD, which confirmed the presence of this secondary compound at the interface of the upper paint layer with the ground layer as well as the presence of anglesite in the ground layer. The capacity of MA-XRPD to identify and chart secondary alteration products in a non-invasive manner has only very recently been demonstrated and makes it a highly relevant technique for the assessment of the chemical condition of works of art., Published by Chemistry Central, London

Despite years of research, the application of natural pigments as food ingredients is still limited by their low stability. This research investigated the storability of carotenoid-containing chromoplasts, as novel natural food colorant from unsold tomatoes. The 30-day stability of chromoplasts (Chr), in comparison to free carotenoid-based extract (Free car), was investigated by the kinetic degradation model of carotenoids (UV–visible spectrophotometer assay), and by the color attributes as CIELab* parameters [i.e. total color difference (ΔE); red-yellow ratio (a*/b*) and chroma value (C*)], under dark and UV-light exposure at different temperatures (4, 25 and 40 °C). Regardless of the different storage conditions (temperature and UV-light exposure), the lowest pigment degradation rates were found for Chr [0.014 days−1 (25 °C in the dark) - 0.057 days−1 (40 °C under UV-light)] rather than Free car [0.018 days−1 (25 °C in the dark) - 0.071 days−1 (40 °C under UV-light)]. Furthermore, Chr better retained the colorimetric parameters, especially at 4 °C (ΔE ~ 4.0) and 25 °C (ΔE ~ 4.5) in the dark. These results proving that a tailored enzymatic-assisted extraction allowed the recovery of stable natural red-orange pigments better preserved by their chromoplast envelop.

Minerals, as raw structural materials or pigments, play a fundamental role in archaeometry, for the understanding of nature, structure and status of an artefact or object of interest for cultural heritage. A detailed knowledge of the mineral phases is crucial to solve archaeological problems: Raman spectroscopy is a powerful investigation technique and has been applied extensively in the last 30 years on mineral identification and on pigment degradation. Here we report an updated review, covering the last decade, of the applications of Raman techniques to issues in which raw minerals, including mineral pigments, are involved. Particular attention is devoted to cases where the Raman analysis of minerals is deeper than a simple identification of the phases present in an archaeological or artistic object. Copyright © 2016 John Wiley & Sons, Ltd.

Red drupelet reversion (RDR; also referred to as red drupelet disorder) in blackberries is a physiological disorder that causes the postharvest reddening of individual or groups of drupelets, resulting in economic loss due to a reduction in marketability. This paper reviews recent advances in the understanding of RDR including the physiochemistry, causes of expression and genotypic variation in its incidence. RDR is associated with a significant reduction in anthocyanin pigment concentration, which can vary in severity causing degrees of partial or full colour change. This is associated with observations of disrupted cellular structural integrity and loss of membrane integrity. Drupelets affected by RDR are characterised by anthocyanin species containing disaccharides or acylated sugar moieties that are not degraded as readily as those containing monosaccharides and non-acylated sugars. Susceptibility to RDR is genotypically influenced, with identified links between cultivar texture, postharvest weight loss and incidence of RDR. Current findings indicate that RDR is primarily caused by mechanical injury to the fruit that has induced cell decompartmentalization, for example in one study 85 % of handled fruit developed RDR relative to only 6% of non-handled fruit. We found that various methods have been employed for assessment of RDR and we propose a red drupelet index and/or image analysis approach that accurately reflects visual appearance and will enable comparison between studies. Gaps in knowledge are highlighted in relation to the mechanism for pigment degradation, and to investigate confounding genotypic and environmental effects (pre- and post-harvest) on incidence of RDR.

This review is to be considered part of the development of the MEMORI dosimeter, to evaluate the impact of climate (relative humidity, temperature, illumination, etc., including volatile organic compounds) on moveable objects. In the framework of the MEMORI project, Ghent University was given the task to assess pigment degradation upon acetic acid exposure, and to collect information on pigments’ stability. Moreover, to obtain a wider knowledge on the stability of common pigments, the effect of a variety of parameters was reviewed from literature. Discolouration and degradation of pigments significantly alter the legibility of polychrome works of art, so that the development of monitoring methods to ensure the preservation of cultural heritage objects is of primary importance.

Sea-ice samples intended for biological analyses, e.g., chlorophyll-a, cell enumeration of algae and protozoa and primary production, are affected by the sampling and sample processing methods. In this study, we compared different sample processing methods by melting Baltic Sea ice samples in different ways (direct melting, buffered melting in filtered seawater (FSW) and buffered melting in artificial seawater at two different salinities with added nutrients) at two temperatures [+4 °C and room temperature (RT)]. We show that sea-ice samples intended for most commonly used biological analyses can be melted without the addition of FSW. In particular, adding artificial seawater should be avoided. To minimize biological processes, such as growth, death, predation and pigment degradation, the melting should be done rapidly at RT preferably by gently shaking the sample to keep the melt cool.

Chemical transformations in paintings often induce discolorations, disturbing the appearance of the image. For an appropriate conservation of such valuable and irreplaceable heritage objects, it is important to have a good know-how on the degradation processes of the (historical) materials: which pigments have been discolored, what are the responsible processes, and which (environmental) conditions have the highest impact on the pigment degradation and should be mitigated. Pigment degradation is already widely studied, either by analyzing historical samples or by accelerated weathering experiments on dummies. However, in historic samples several processes may have taken place, increasing the complexity of the current state, while aging experiments are time-consuming due to the often extended aging period. An alternative method is proposed for a fast monitoring of degradation processes of semiconductor pigments, using an electrochemical setup mimicking the real environment and allowing the identification of harmful environmental parameters for each pigment. Examples are given for the pigments cadmium yellow (CdS) and vermilion (α-HgS).

Mural paintings of exceptional quality, which can be discerned in spite of their extensive mechanical damage and colour fading, have been uncovered in the church of St. Gallus in Kuivody, Northern Bohemia, dated to the second half of the 13th century. Materials research with particular use of portable X-ray fluorescence, Raman micro-spectroscopy and powder X-ray micro-diffraction revealed the presence of rare pigments. In Kuivody, it is only a second identification of intentionally used yellow mineral crocoite (PbCrO4) in European art. Its identification is facilitated by providing a very good Raman scattering, even when present in small amounts in fragmentarily preserved colour layers. Light yellow mimetite (Pb-5(AsO4)(3)Cl) was never before mentioned as intentionally used pigment in Europe. Its finding in Kuivody, however, corresponds more likely with undesirable physical-chemical conditions causing its formation by alteration of orpiment (As2S3) and minium (Pb3O4). Obtained results highlight the importance of Raman spectroscopy for direct identification of mineral pigments in low concentrations, which may be crucial for interpreting cultural heritage objects in historical context. By materials, the almost forgotten paintings in Kuivody can be seen as outstanding and rare example of ancient artistic tradition that has spread to Europe from Mediterranean in early Middle Ages. After all, mineral crocoite was already used by ancient Egyptians to paint sarcophagi and degraded orpiment decorates the walls of the Nefertari's tomb in Thebes.

Vivianite (Fe3(PO4)2·8H2O) is a rare blue historical pigment, which can be profitably used in authorship ascription or copy identification. However, its tendency to degrade complicates its proper identification in paint layers. Reference vivianite mineralogical samples were analysed in order to compare and to test the limits of structural analyses on possibly degraded vivianite samples (X-ray diffraction and vibrational spectroscopies). The same methods, in their μ-configuration, were tested on micro-samples of the paintings and their limits evaluated. A sedimentary origin of the pigment has been suggested. Vivianite was detected in various works by Jean George de Hamilton (1672–1737) and in a Late Gothic Transylvanian altarpiece.

Extracts from centipedegrass ( Eremochloa ophiuroides Munro) have been previously identified as having beneficial effects medically and cosmetically. In this study, the effects of gamma irradiation on pigment removal and biological activities of centipedegrass extracts to promote industrial application were investigated. The methanolic extracts were exposed to gamma irradiation at dose ranging from 2 to 20 kGy. The major pigments of centipedegrass extracts, cyanidin-3- O -glucoside and cyanidin-3- O -(6″-malonyl-)glucoside, were found to be effectively removed by gamma irradiation above 10 kGy. Although the reddish-orange color of the cyanidins was markedly decreased by gamma irradiation, the biological activities were relatively unaffected. The biological activities such as 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, inhibition of tyrosinase activity, and inhibition of elastase activity in methanolic extracts were modulated from 50.5% to 70.2%, from 50.9% to 65.8% and from 65.6% to 94.0%, respectively. Surprisingly, the biological activities have the highest activities after 6–8 kGy of gamma irradiation. These results indicate that despite pigment degradation, biological activities were maintained or increased by gamma irradiation. Based on these results, gamma irradiation may be a useful tool to remove the undesirable reddish-orange color present in centipedegrass without any loss of biological activities, thereby promoting its utility in industrial applications such as manufacturing of cosmetic products.

Portable X-ray Fluorescence Spectrometry (pXRF) was used to survey 33 works in Washington and Lee University’s collection of Louise Herreshoff’s paintings. This work was done both to support a condition assessment of the paintings and their pigments and to determine which paintings might be appropriate for further study in the context of ongoing key synchrotron research into the degradation mechanisms of cadmium sulfide yellow pigment (CdS).

Istraživanjima u okviru ove doktorske disertacije ispitan je uticaj polutunelskog sistema gajenja na najznačajnije fenološke osobine (vreme cvetanja i zrenja), parametre vegetativnog (broj izdanaka po žbunu, visina i prečnik izdanka) i generativnog (broj rodnih grančica, cvasti i plodova po izdanku, prinos) potencijala, pomološke osobine (morfometrija ploda, hemijski sastav i organoleptička ocena ploda), kao i na pojavu sive truleži ploda sorte kupine ‘Čačanska bestrna’. Analizirana je i korelacija između količine šećera u plodu i stepena depigmentacije tokom čuvanja zamrznutih plodova, uporednim proučavanjima sa sortama kupine ‘Loch Ness’ i ‘Chester Thornless’. Istraživanja su obavljena u proizvodnom zasadu kupine od 2011. do 2013. godine u ekološkim uslovima Čačka po standardnoj metodologiji. Rezultati istraživanja su pokazali da je najveći broj analiziranih parametara bio uslovljen sistemom gajenja i ekološkim uslovima u periodu ispitivanja, kao i njihovom interakcijom. Ispitivani sistem gajenja nije uticao na odstupanja u početku fenofaza cvetanja i zrenja dvogodišnjih izdanaka u odnosu na standardni sistem. U pogledu parametara vegetativnog potencijala, veći broj i dužina izdanaka utvrđeni su kod kupine gajene u polutunelskom, a veći prečnik izdanka u standardnom sistemu gajenja. Poređenjem dobijenih rezultata svih ispitivanih parametara generativnog potencijala kupine, veće vrednosti su dobijene kod polutunelskog sistema gajenja. Morfometrijske osobine ploda kupine, izuzev mase ploda, bile su uslovljene značajnim uticajem sistema gajenja i veće vrednosti svih pomenutih osobina utvrđene su u uslovima polutunelskog sistema gajenja kupine. U uslovima polutunelskog sistema gajenja kupine dobijene su veće vrednosti za sve parametre biohemijskog sastava ploda, izuzev za sadržaj ukupnih kiselina i sadržaj vanilinske kiseline. Dobijeni rezultati su potvrdili prisustvo flavonola kvercetina i dominantno prisustvo antocijana cijanidin-3-glukozida u plodu kupine. Među detektovanim fenolnim jedinjenjima, u plodu ispitivane sorte, utvrđena je visoka koncentracija galne i elaginske kiseline... This doctoral dissertation research examined the effect of rain-shield cultivation system on major phenological traits (flowering and ripening time), vegetative potential parameters (number of canes per bush, cane height, cane diameter), generative potential parameters (number of fruiting laterals, inflorescences and berries per cane, yield), pomological properties (fruit morphometry, chemical composition and organoleptic scores of the fruit) and the incidence of gray mold in blackberry cv. ‘Čačanska Bestrna’. Moreover, the correlation between the sugar content of the fruit and the rate of pigment degradation during frozen storage was analyzed and compared with the blackberry cvs. ‘Loch Ness’ and ‘Chester Thornless’. The research was conducted in a commercial blackberry planting during 2011-2013 under the environmental conditions of Čačak using the standard methodology. The results showed that most of the tested parameters were affected by production system and environmental conditions during the research, as well as by their interaction. The rain-shield system did not cause any deviation in the onset of flowering and ripening in floricanes compared to open-field cultivation. In terms of the vegetative potential parameters, number of canes and cane length were greater in blackberries under rain shields, whereas cane diameter was higher under open-field cultivation. When comparing the results obtained for the generative potential parameters, higher values were found under rain-shield cultivation. Pomological properties of blackberry, except fruit weight, were significantly affected by production system, with higher values for all pomological traits obtained under rain shields. The rain-shield system resulted in higher values for all parameters of the biochemical composition of the blackberry fruit, except the contents of total acids and vanillic acid. The results confirmed the presence of the flavonol quercetin and the dominant presence of the anthocyanin cyanidin-3-glucoside. Among the phenolic compounds detected in the fruit of the tested cultivar, gallic acid and ellagic acid were found in high concentrations...

For the first time the degradation of lead white pigment in mature oil paint has been used as an internal marker for the degree of saponification and hence chemical degradation of oil paint. Computational image analysis of the backscattered electron images quantified the degree of the intact lead white pigment versus the nonpigmented and lead-rich areas (degraded lead white) in the paint layers. This new methodology was applied to a series of paint samples taken from four painted wall hangings (dated 1778), which makes it possible to study the influence of indoor climate on chemical degradation of aged oil paintings. The visual interpretation and computational image analysis of the backscattered electron images revealed clear trends. The highest degree of lead white degradation in the room was found in samples from the north wall close to the windows, whereas degradation diminished further away from the window. Lead white from the south wall was less degraded, but showed a similar trend as in the paintings on the north wall. These results imply a strong relationship between chemical degradation of paint and location of the paint in the room.

Raman microscopy has been used to identify the pigments decorating three valuable items owned by the Worshipful Company of Barbers (established in 1308 in London), one being a large leather screen dating to before 1712, the other two being illuminated title pages of books of ordinances of the Company dating to 1605 and 1658. Pigments which could not be fully characterised by this technique (particularly the green paints) have also been subject to XRF or SEM–EDX analysis. The combined analytical approach has shown that the pigments identified on all three items are typical of those in use as artists’ pigments in the 17th C and include azurite, indigo, vermilion, red lead, pink and yellow lakes, verdigris, lead white, calcite (and chalk), gypsum, carbon-based black, and gold and silver leaf. However in the case of the screen alone, restoration in the 1980s has been carried out with different pigments – haematite, phthalocyanine green, rutile, and a mixture of azurite, malachite and barium sulfate. This work constitutes the first in-depth study of painted leatherwork and demonstrates that the palette used for this purpose is similar to that used on other works of art of the same date. It has also allowed the original colour schemes of the decorations to be determined where pigment degradation has occurred. The combined analysis has also provided a more complete understanding of the materials used for, or on, objects to which access is limited.

Historical painted works of art have a very complex inner structure. The period painting technique led to the execution of a ground layer followed by several layers of underpainting and a top paint layer, over which a layer of glaze has been applied to increase the resistance to external wear. Each of these colour layers is composed of a dye or a pigment (or their mixture) bound by organic binder. Throughout the history, pigments were commonly prepared from minerals, either extracted from natural deposits or created artificially. In these heterogeneous layers containing both inorganic and organic components, undesirable degradation changes either driven by processes taking place directly in the colour layer or influenced by external agents may occur. Mineralogical approach, which focuses primarily on the structure of studied pigments, helps in the clarification of the occurring processes, in the determination of conditions leading to degradation as well as in the identification of original/degradation phases. Furthermore, it can be profitably applied in the micro- analysis of mineral pigments present in tiny micro-samples obtained from works of art, contributes to the artwork's provenance/authorship studies and the determination of regional provenance of the employed mineral pigments. This Ph.D....

Anthocyanin pigments are responsible for the attractive red to purple to blue colors of many fruits, vegetables, flowers, and cereal grains. In plants they serve as attractants for pollination and seed dispersal, give protection against the harmful effects of UV irradiation, and provide antiviral and antimicrobial activities. Anthocyanin-based colorants are commercially manufactured for food use from horticultural crops and from processing wastes. There is a large body of knowledge on anthocyanin chemistry in the literature that includes established, systematic methods for identifying anthocyanins and measuring their concentration and color properties. Structural variation (B-ring substitution, glycosidic substitution, and acylation) produces a multiplicity (over 400) of anthocyanins. Color intensity and hue, as well as stability, are markedly affected by pH, which can be a major limitation for many food applications. Increased glycosidic substitution and acylation with cinnamic acids will improve pigment stability. However, the matrix in which the pigments exist can have a much greater impact on pigment degradation. Anthocyanin pigments are very effective scavengers of free radicals. Currently, there is much research activity on their possible health benefits. While anthocyanin-based colorants are universally approved for food use, there are considerable regulatory differences among countries.

Purple pitaya (Hylocereus polyrhizus) fruits have been recently proposed as a promising source of betalains. In the present study, purple pitaya juice processing at pilot-plant scale is reported for the first time. Each processing step was examined in terms of juice colour and betacyanin retention. Lightness (L *) and hue angle (h°) values were strongly influenced by juice filtration, while chroma (C *) and betacyanin retention were most strongly altered by pasteurisation. Three systems of juice pasteurisation were evaluated. Betacyanin loss and colour alteration were minimal upon pasteurisation in an HTST system and a standard tubular heat exchanger, respectively. Additionally, storage experiments using mucilage-free purple pitaya juice were conducted. Whereas light exposure of unsupplemented samples resulted in significant pigment degradation, detrimental effects of light exposition were completely prevented by the addition of 1% ascorbic acid prior to storage. After 6 months, about 70% of the initial betacyanin content was retained in the presence of ascorbic acid, irrespective of illumination.

Weathering can cause colour changes in pigmented PVC plastisol coatings. The rate of colour change is dependent on a number of factors, such as PVC resin, pigment type and concentration, and local climate. In this paper, an investigation into the mechanisms that cause these colour changes is reported. The investigation involves a set of 350 paints, based on a typical plastisol formulation, that has been exposed to natural weathering at sites in Lancashire and Sussex in the UK, and to accelerated weathering using QUV testers with UVA-340 lamps and condensation cycles. Colour changes were measured using a Gretag SPM50 reflectance spectrophotometer. It was found that the reflectance spectra measured in this way provided a more potent tool for investigating the chemical reactions that cause discolouration in coatings during weathering than the CIE L*a*b* parameters that are normally used to describe colour changes. Reflectance spectroscopy has been shown to facilitate the correlation between natural weathering and accelerated weathering, by giving a better understanding of the prevalent chemical processes that take place in the coatings during different accelerated weathering programmes (with and without condensation) and with natural weathering at different locations (high UV climates and higher rainfall climates). Phenomena such as PVC dehydrochlorination and organic pigment degradation could be analysed conveniently using reflectance spectrophotometry.

Effects of pH, sugar, ascorbic acid, organic acids and light sources on the stability of anthocyanin pigment extracted from Korean purple-fleshed potatoes (PL-6, PL-28, PL-31 and Jasim) were studied. The pH had remarkable influence on the color stability of anthocyanin pigment. With increasing pH, the color gradually fades as colorless pseudobases are formed. In acidic pH, anthocyanin was stable, but with increasing pH the color gradually changed to colorless. The addition of sugar decrease in color stability of the pigment during storage period. The most of organic acids, such as a tartaric, citric and succinic acids, were found to improve the stability of the pigment, while malic and malonic acid reduced the stability of the pigment. The addition of ascorbic acid considerable decreased in anthocyanin pigment stability, but the effect was not decreased by adding thiourea. The effect of light sources such as a darkroom, a fluorescent light, and sunlight, reduced gradually the stability of anthocyanin pigment. Therefore the pigment degradation could be minimized by shielding the light from the pigment.

Sliced cooked ham was vacuum packaged and held in the dark at −15C. 10C, and 30C, and at 10C in the light, for up to 96 h. At 24 h intervals, samples were analyzed for pigment concentration by spectrophotometry. A decrease in pigment concentration was observed over time under all conditions. Pigment degradation increased at higher temperatures and with light exposure. Kinetic parameters were determined, indicating that pigment degradation follows first order kinetics and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energy was 3.3 kcal/mol. The visible spectra for the extracted pigments in cooked ham showed the typical pattern of nitrosylmyoglobin. Pigments extracted from ham displayed in the light had spectra with similar absorption maxima to those from those stored in the dark.

Dunaliella salina is a microalga rich pigment carotenoids that can be used asnatural dyes. The problemfaced for temporative β-carotene stability which is unstable and easily degraded is unstable and easilydegraded. The purpose ofthis researchwas to determine content and stability of β-carotene pigment inD.salina with fixings addition of MgCO3 and NaHCO3 with temperature treatment as factor that influenceβ-carotene pigment degradation during storage condition. The research method used β-carotene pigmentwhich was obtainedbymaceration and adding fixing agent (NaHCO3 0,5% and without fixings addition),and was heated at temperature of (50°, 70° and 90°C), be measured the content of β-carotene pigmentduring storage (observation hour 0, 24, 48, 72, 96, 120 and 144). Data analyzed by ANOVA and HonestlySignificant Different (HSD). The result showed that content of β-carotene pigment at 50°C temperatureshowed that stability and pH value performed slowest degradation after144 hours. While stability and pHvalue at 90°C temperature performed fastest degradation after 96 hours. Based on this study the addition ofNaHCO3 gave more effective in retaining β-carotene degradation compared to that of MgCO3 which showedby high stability in sample NaHCO3 0,5%, temperature 50°C in 144 hours storage length.

Microcapsules containing water and lipid dispersible natural colorants were formed using as wall materials mesquite gum and gum arabic. The theoretical total pigment concentration of the microcapsules was 4.6 g/kg. Spectrophotometric measurements indicated that the microencapsulated pigments underwent zero order degradation kinetics, and that mesquite gum provided the pigments a better protection than gum arabic. Mesquite gum microcapsules complied with the requisite of exhibiting a pigment degradation of less than 10% during 6 months, while the gum arabic microcapsules did not. Likewise the chromatic parameters a, b and L experienced zero order kinetics decrease, which was more pronounced for the gum arabic microcapsules. The superior protection provided by mesquite gum is attributed to the thicker adsorbed polymer layers of the microcapsules due to its higher molecular mass as compared to that of gum arabic. Trouts fed diets containing the microcapsules for three weeks acquired muscle pigmentat...

This study investigated zooxanthellae densities, chlorophyll a and c2 concentrations, and zooxanthellae morphologies in replicate samples of Stylophora pistillata colonies before and during the 1998 coral-bleaching event in Okinawa, Japan. During the bleaching event sea surface temperatures reached 31 °C and Stylophora pistillata colonies supported significantly reduced mean chlorophyll a and c2 concentrations per cm2, and significantly more pale zooxanthellae cells in hospite than before the bleaching. Although the number of healthy zooxanthellae decreased during the coral-bleaching event, the total density of zooxanthellae in S. pistillata colonies (i. e., including the pale zooxanthellae) did not change significantly. Thus, the presence of pale zooxanthellae within colonies numerically compensated for the loss of healthy zooxanthellae. We suggest that pigment degradation in zooxanthellae and subsequent cell shrinkage, rather than zooxanthellae expulsion, was the mechanism involved in S. pistillata bleaching.

Isolated chloroplasts of Euglena gracilis Klebs were kept for 10 d in complete darkness at 4 C in a maintenance buffer (pH 7.5) without shaking. During incubation, the qualitative and quantitative changes in the pattern of photosynthetic pigments were evaluated by the combined use of spectrophotom etry in the visible range of whole chloroplasts and their acetone extracts, of in vivo spectrofluorimetry and of reversed-phas e HPLC. Microscopic and submicroscopic modifications were also followed by UV and transmission electron microscopy.

In previous work by our group, a general mechanistic model was developed to describe chlorophyll degradation to pheophytin, chlorophyllide, and pheophorbide. This model was expanded in this work to include pheophorbide degradation to colorless degradation products and to account for incomplete pigment degradation. The model can now be utilized to help understand, and eventually help control, chlorophyll degradation in green tissue. Keywords: Chlorophyll; degradation; kinetics; model

Commercial interest in the use of natural pigments isolated from microorganisms has increased in recent years; hence, molecules belonging to the polyisoprenoid group (i.e., β-carotene, astaxanthin, and canthaxanthin) have been the focus of much attention. The bacterium Gordonia jacobaea readily synthesizes and accumulates large amounts of canthaxanthin (β- β′-carotene-4,4′-dione), which is widely used in the food and cosmetics industries. In the present work, the integral process of canthaxanthin production by G. jacobaea is analyzed together with its application as natural sources for the industry. A great influence of culture media is observed on canthaxanthin levels. Also, the ability is found of extract the pigments with ethanol from bacteria. The concentration of the samples is a crucial point of the process, being mandatory to discard any process of heating the samples, because this provoked the pigment degradation. Despite this, the described method allows to consider G. jacobaea as a potential canthaxanthin producer for the industry. © 2012 Springer Science+Business Media, LLC.

Measurements of light absorption by chromophoric dissolved organic matter (CDOM) from sub-surface waters of the tropical Atlantic and Pacific showed a distinct absorption shoulder at 410–415 nm, indicating an underlying absorption of a pigment. A similar absorption maximum at ~410 nm was also found in the particulate fraction and is usually attributed to absorption by respiratory pigments of heterotrophic unicellular organisms. The CDOM absorption shoulder was described earlier in the Indian Ocean at 600 m depth and was related to a "deep red fluorescence" found in the same depth, i.e. in the oxygen minimum zone (Breves et al., 2003; Broenkow et al., 1983). In our study, fluorescence measurements of pre-concentrated DOM samples confirmed that the absorption at ~410 nm was related to a specific fluorescence at 650 nm. The absorption characteristic of this specific fluorophor was examined by fluorescence emission/excitation analysis and this showed a clear excitation maximum at 415 nm (in methanol) that can explain the absorption shoulder in the CDOM spectra. The spectral characteristics of the substance found in the dissolved and particulate fraction did not match with those of chlorophyll a degradation products (as found in a sample from the sea surface) but can be explained by the occurrence of respiratory pigments from heterotrophs. Combining the observations of the "deep red fluorescence" and the 410 nm-absorption shoulder suggests that there are high concentrations of a pigment degradation product (cytochrome c) in DOM of all major oceans. Most pronouncedly we found this signal in the deep chlorophyll maximum and the oxygen minimum zone of tropical regions. The origin, chemical nature, turn-over rate, and fate of this molecule is so far unknown.

International audience; IPANEMA, a research platform devoted to ancient and historical materials (archaeology, cultural heritage, palaeontology and past environments), is currently being set up at the synchrotron facility SOLEIL (Saint-Aubin, France; SOLEIL opened to users in January 2008). The new platform is open to French, European and international users. The activities of the platform are centred on two main fields: increased support to synchrotron projects on ancient materials and methodological research. The IPANEMA team currently occupies temporary premises at SOLEIL, but the platform comprises construction of a new building that will comply with conservation and environmental standards and of a hard X-ray imaging beamline today in its conceptual design phase, named PUMA. Since 2008, the team has supported synchrotron works at SOLEIL and at European synchrotron facilities on a range of topics including pigment degradation in paintings, composition of musical instrument varnishes, and provenancing of medieval archaeological ferrous artefacts. Once the platform is fully operational, user support will primarily take place within medium-term research projects for 'hosted' scientists, PhDs and post-docs. IPANEMA methodological research is focused on advanced two-dimensional/three-dimensional imaging and spectroscopy and statistical image analysis, both optimized for ancient materials.

Polyphenol oxidase activity, anthocyanin concentration, endogenous ethylene production and anatomical features of mature lychee (Litchi chinensis Sonn.) pericarp were studied to understand better post-harvest tissue browning. Polyphenol oxidase (PPO) activity decreased significantly once fruit were harvested. Although anthocyanin degradation occurred, it was far slower than tissue browning. It is considered unlikely that pericarp browning is due to direct pigment degradation by polyphenol oxidase. Pericarp browning may in fact be caused by non-PPO mediated anthocyanin decolorization, coupled with localized PPO activity affecting secondary metabolites other than anthocyanin. Pericarp browning was correlated with moisture loss. The development of pericarp micro-cracking after harvest was observed, and may be involved in facilitating rapid pericarp moisture loss.

A new approach to shelf life modeling of photosensitive foods was developed taking into consideration the example of a saffron-containing yellow beverage highly prone to oxidative photobleaching. The beverage was exposed to different light levels at increasing temperatures. During exposure, samples were analyzed for bleaching rate, pigment content, and pigment degradation products. The results obtained clearly showed that shelf life testing of light-sensitive foods must take into proper account the effect of light. In addition, for these foods, shelf life models based on the sole accelerating effect of temperature may be misleading. By contrast, the concomitant exploitation of the accelerating effects of both light and temperature was used to develop and validate a simple model correctly predicting the shelf life of the beverage under actual storage conditions. The methodology proposed may allow solving of the difficult task of predicting shelf life of photosensitive foods usually marketed in the presence of light.

Pesto is a widely diffused Italian pasta sauce, whose main ingredient is basil. Since its appearance is a key factor for marketing, the determination of its pigment content is of fundamental interest. To this aim, a method for the determination of pesto pigments by C18-HPLC is proposed. Only β-carotene was determined directly by Vis-spectrophotometry, as a consequence of sample purification over a silica cartridge. The proposed method is reliable allowing, for the first time, an easy determination of chlorophylls, pheophytins, lutein and β-carotene in a complex matrix such as pesto. The results show great differences in pigment composition among the samples, with pheophytins as the main components. Only non-thermally processed product show appreciable chlorophyll content as a consequence of the different production technique. Principal Component Analysis performed on the pigment contents showed great variability among the different samples.

Publisher Summary This chapter discusses the molecular structures, the general physicochemical properties of plant pigments, and the mechanisms involved in pigment degradation. The invasive and noninvasive methods used for pigment analysis, including the mechanisms involved in pigment degradation, are reviewed. The chapter presents different analytical methods that can be used to identify pigments. All the methods are invasive techniques that are time consuming and often expensive. To reduce sampling and analytical costs, and to speed up the analyses, noninvasive analytical procedures have been developed with the aim to characterize the pigment content of samples, and in the case of food products, to estimate the impact of a color change on the visual perception of the product. The complete extraction of pigments requires several steps and may use a mixture of several solvents. This is true when the sample contains pigments of different polarities or pigments that are present in a complex matrix. Research on plant pigments is fascinating because it involves many methods and a deep knowledge in several fields. Plant pigment studies should be continued because they may procure several immediate interesting impressions, and commercial and health advantages.

A ampla variabilidade genética nos pomares de aceroleiras brasileiros tem gerado frutos de coloração amarela a vermelha púrpura dificultando a obtenção de produtos de coloração avermelhada, cor esperada pelos consumidores. As antocianinas são pigmentos instáveis, responsáveis pela cor vermelha deste fruto maduro. Com o objetivo de determinar o teor destes pigmentos em polpa de acerola submetida ao congelamento foi instalado um experimento inteiramente casualisado. As polpas obtidas de frutos de 12 acessos (plantas) do Banco Ativo de Germoplasma da Universidade Federal Rural de Pernambuco (UFRPE) foram armazenadas a -18ºC, por um período de 06 meses. Unidades amostrais de 30g foram coletadas ao acaso, no período inicial e final do experimento, e submetidas a determinação quantitativa de antocianinas totais utilizando um método espectrofotométrico. Grande variação nos teores de antocianinas totais foi observada nos acessos estudados. No tempo zero de armazenamento o valor mínimo e máximo deste fitoquímico foi de 59,74mg e 3,79mg.100g -1 de polpa, respectivamente. Após seis meses de congelamento foi constatada uma redução de 3,4% a 23,6% no teor desse pigmento nas amostras avaliadas. Evidenciou-se, portanto, que o armazenamento a -18ºC por seis meses reduziu o teor de antocianinas e que os pigmentos antociânicos dos acessos 08 e 13 apresentaram-se mais estáveis ao congelamento. The great variability of the Brazilian acerola orchards results in fruits with yellow to red color, producing a light colored acerola pulp which is not as appealing as full red pulp. Anthocyanins are unstable pigments, responsible for red color in mature acerola. In order to examine some pigment degradation in frozen pulp acerola, it was installed a randomized experiment. Pulps obtained from 12 accesses (plants) of Germoplasm Active Bank from Federal Rural University of Pernambuco (UFRPE) were stored (-18°C) for 6 months. Total anthocyanins were determined in randomized samples (30g) collected at the beginning and end of the experiment, using spectrophotometer method. Great variation on the total anthocyanin content was observed in the studied accesses. At time zero of storage the lowest and highest level of this phytochemical were 3.79 mg and 59.74 mg 100 g-1 of pulp, respectively. After 6 months of storage, a reduction of 3.4 % to 23.6 % on content of these pigments were shown. The storage at -18ºC for six months reduced the anthocyanin content. The anthocyanin pigments of accesses 08 and 13 were the most stable during frozen storage.

The dynamics of the anthocyanin content reduction in the course of aging of the Ipomoea purpureа petals, which characterizes the rate of the degradation processes in a cell, has been studied. The analysis included the impact of various UV-B radiation doses on the rate of anthocyanin age-related decomposition. The experiment proved that but one dose – 12.6 kJ/m 2 contributed to the deceleration of the anthocyanin decomposition rate, within the range studied. The probable mechanisms that connect ageing and pigment degradation are being discussed.

The color of pigmented polyolefin melts was measured in-line during processing by using a fiber optic equipped visible-near-infrared spectrophotometer. Pigment loadings varied from 3.6 to 56 wt.% with some formulations containing up to 33.1 wt% calcium carbonate filler. Results showed that within specification color could be distinguished from off specification color. Also, pigment degradation and temperature tolerance could be assessed. Predicting needed off-line measured color from these in-line results will be the subject of Part II of this series.

Cranberry juice cocktail was chosen as a typical red fruit juice. Samples were heated at 65°C to simulate pigment degradation on storage. The heated samples were ranked for color visually and objectively using a Hunter Color Meter, a Gardner Color Meter and a G.E. recording spec-trophotometer. Most functions of color obtained from the instrument correlated highly with visual color except dominant wavelength, hue, and Hunter and Gardner b. Most instrumental values also correlated well with anthocyanin concentration except the three above. The expanded L, a*, b* scales, which were developed in previous work to eliminate the inversion of tristimulus scales with pigment concentration with dark beverages, also gave very high correlations with visual evaluations and with anthocyanin concentrations.

Problems relating to the measurement and description of color of wines are discussed, with wines providing an example of problems of volume color specification in general. The limitations of conventional directional spectrophotometric transmittance measurements are considered for colloidal, minimally light-scattering systems, where errors due to light lost through scatter can have profound consequences, particularly at shorter wavelengths. An alternative approach, referred to as transreflectometry, avoids the errors attributable to the directional geometry of conventional spectrophotometers. A review of its application to the colorimetry of wines considers three cases with different requirements to be met and different questions to be answered, from meeting strigent Federal Regulations in the case of very light white wines, to blending red and rose wines to predetermined color requirements, to studying the kinetics of pigment degradation and colored polymer formation in red wines under controlled storage conditions. These studies demonstrate the versatility of a simple methodological approach which provides information relating to visually perceived color and at the same time to chemical and physical properties of the systems.

In a previous study, we suggested that patterns in the vertical distribution of phaeopigments originate from a relatively simple pathway of pigment degradation. In the pathway, phaeopigments of chlorophyll a are produced by microzooplankton grazing and subsequently compartmentalized in small fecal particles that have negligible sinking velocities. Phaeopigments within such small particles are then lost by photooxidation. Thus, the concentration of phaeopigment at a given depth results from a balance between local rates of grazing and rates of photooxidation. To examine such a mechanism, rates of photooxidation of phaeopigments contained in marine particles were measured. Rates of photooxidation are adequately described by first-order kinetics and are strongly dependent on temperature. The mechanism was examined further by constructing a model of grazing and photooxidation in the upper waters of the temperate ocean.