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Natural Colorants
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Natural Colorants

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Colorants".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 25173

Special Issue Editors

Dr. Eulogio J. Llorent-Martínez

E-Mail Website
Guest Editor
Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
Interests: spectroscopy; luminescence; automation; chlorophylls; phenolics; natural compounds; natural colorants; food analysis; HPLC-MS; nanomaterials; antioxidant; in vitro digestion; analytical methods for the determination of colorants
Special Issues, Collections and Topics in MDPI journals
Dr. Ruperto Bermejo-Román

E-Mail Website1 Website2
Guest Editor
Department of Physical and Analytical Chemistry, Linares High Polytechnic School (EPSL), University of Jaén, Campus Científico Tecnológico, 23700 Linares, Spain
Interests: functional foods based on olive oils enriched with bioactive compounds; purification and characterization of high added value biotechnological compounds; scale-up processes; food additives purification and characterization; molecular spectroscopy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Colorants are not used only in food industry, but also in other products. This issue will thus cover a wide range of research areas concerning natural colorants. Research or review articles are welcomed, including (but not limited to) identification of novel natural colorants, advances in sample treatment, improvements in analytical methods for quantitation and quality control purposes, new trends in colorants purification, stability studies, theoretical and experimental studies on the (bio)chemical properties of natural colorants, and potential industrial applications of new natural colorants.

Dr. Eulogio J. Llorent-Martínez
Dr. Ruperto Bermejo-Román
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • natural products
  • natural colorants
  • biotransformation
  • quality control,
  • structure elucidation,
  • sample treatment
  • industrial applications, stability

Published Papers (7 papers)

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Research

12 pages, 20497 KiB  
Article
Spectral Characteristic, Storage Stability and Antioxidant Properties of Anthocyanin Extracts from Flowers of Butterfly Pea (Clitoria ternatea L.)
by Xueying Fu, Qiang Wu, Jian Wang, Yanli Chen, Guopeng Zhu and Zhixin Zhu
Molecules 2021, 26(22), 7000; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26227000 - 19 Nov 2021
Cited by 17 | Viewed by 5671
Abstract
Anthocyanins from flowers of the butterfly pea (Clitoria ternatea L.) are promising edible blue food colorants. Food processing often faces extreme pHs and temperatures, which greatly affects the color and nutritional values of anthocyanins. This study explored the color, spectra, storage stability, [...] Read more.
Anthocyanins from flowers of the butterfly pea (Clitoria ternatea L.) are promising edible blue food colorants. Food processing often faces extreme pHs and temperatures, which greatly affects the color and nutritional values of anthocyanins. This study explored the color, spectra, storage stability, and antioxidant properties of C. ternatea anthocyanin extract (CTAE) at different pHs. The color and absorption spectra of CTAEs at a pH of 0.5–13 were shown, with their underlying structures analyzed. Then, the storage stability of CTAEs were explored under a combination of pHs and temperatures. The stability of CTAE declines with the increase in temperature, and it can be stored stably for months at 4 °C. CTAEs also bear much resistance to acidic and alkaline conditions but exhibit higher thermal stability at pH 7 (blue) than at pH 0.5 (magenta) or pH 10 (blue-green), which is a great advantage in food making. Antioxidant abilities for flower extracts from the butterfly pea were high at pH 4–7, as assessed by DPPH free radical scavenging assays, and decreased sharply when the pH value exceeded 7. The above results provide a theoretical basis for the application of butterfly pea flowers and imply their great prospect in the food industry. Full article
(This article belongs to the Special Issue Natural Colorants)
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20 pages, 4680 KiB  
Article
Sustainable Hues: Exploring the Molecular Palette of Biowaste Dyes through LC-MS Metabolomics
by Ralph John Emerson J. Molino, Klidel Fae B. Rellin, Ricky B. Nellas and Hiyas A. Junio
Molecules 2021, 26(21), 6645; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26216645 - 02 Nov 2021
Cited by 2 | Viewed by 3600
Abstract
Underutilized biowaste materials are investigated for their potential as sustainable textile colorants through an approach based on mass spectrometry, bioinformatics, and chemometrics. In this study, colorful decoctions were prepared from the outer bark of Eucalyptus deglupta and fruit peels of Syzygium samarangense, Syzygium [...] Read more.
Underutilized biowaste materials are investigated for their potential as sustainable textile colorants through an approach based on mass spectrometry, bioinformatics, and chemometrics. In this study, colorful decoctions were prepared from the outer bark of Eucalyptus deglupta and fruit peels of Syzygium samarangense, Syzygium malaccense, Diospyros discolor, and Dillenia philippinensis. Textile dyeing was performed along with liquid chromatography–mass spectrometry (LC–MS)-based untargeted metabolomics to determine the small molecules responsible for the observed colors. Global Natural Products Social Molecular Networking (GNPS) guided the annotation of black-producing proanthocyanidins in D. philippinensis and E. deglupta through complexation with FeSO4 mordant. Flavonoids from the yellow-colored D. philippinensis extracts were found to be similar to those in Terminalia catappa, a known traditional dye source. A higher intensity of epicatechin in E. deglupta produced a red-brown color in the presence of Cu2+. Furthermore, Syzygium fruit peels have poor wash-fastness in cotton fibers, but bioactive chalcone unique to S. samarangense samples may be a potential nutritional food colorant. Unsupervised PCA and supervised OPLS-DA chemometrics distinguished chemical features that affect dyeing properties beyond the observed color. These findings, along with growing data on natural dyes, could guide future research on sustainable colorants. Full article
(This article belongs to the Special Issue Natural Colorants)
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13 pages, 2532 KiB  
Article
Characterization of a Natural, Stable, Reversible and Colourful Anthocyanidin Network from Sphagnum Moss Based Mainly on the Yellow Trans-Chalcone and Red Flavylium Cation Forms
by Helge Berland and Øyvind M. Andersen
Molecules 2021, 26(3), 709; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26030709 - 29 Jan 2021
Cited by 7 | Viewed by 2836
Abstract
Anthocyanins with various functions in nature are one of the most important sources of colours in plants. They are based on anthocyanidins or 3-deoxyanthocyanidins having in common a C15-skeleton and are unique in terms of how each anthocyanidin is involved in a network [...] Read more.
Anthocyanins with various functions in nature are one of the most important sources of colours in plants. They are based on anthocyanidins or 3-deoxyanthocyanidins having in common a C15-skeleton and are unique in terms of how each anthocyanidin is involved in a network of equilibria between different forms exhibiting their own properties including colour. Sphagnorubin C (1) isolated from the cell wall of peat moss (Sphagnum sp.) was in fairly acidic and neutral dimethyl sulfoxide characterized by nuclear magnetic resonance (NMR) and ultraviolet–visible (UV–vis) absorption techniques. At equilibrium, the network of 1 behaved as a two–component colour system involving the reddish flavylium cationic and the yellow trans–chalcone forms. The additional D- and E-rings connected to the common C15-skeleton extend the π-conjugation within the molecule and provide both bathochromic shifts in the absorption spectra of the various forms as well as a low isomerization barrier between the cis- and trans-chalcone forms. The hemiketal and cis-chalcone forms were thus not observed experimentally by NMR due to their short lives. The stable, reversible network of 1 with good colour contrast between its two components has previously not been reported for other natural anthocyanins and might thus have potential in future photochromic systems. This is the first full structural characterization of any naturally occurring anthocyanin chalcone form. Full article
(This article belongs to the Special Issue Natural Colorants)
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13 pages, 2247 KiB  
Article
Using a B-Phycoerythrin Extract as a Natural Colorant: Application in Milk-Based Products
by Ana Belén García, Eleonora Longo, Mª Carmen Murillo and Ruperto Bermejo
Molecules 2021, 26(2), 297; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020297 - 08 Jan 2021
Cited by 31 | Viewed by 3663
Abstract
Nowadays, there is a growing interest in finding new coloring molecules of natural origin that can increase and diversify the offer of natural food dyes already present in the market. In the present work, a B-phycoerythrin extract from the microalgae Porphyridium cruentum was [...] Read more.
Nowadays, there is a growing interest in finding new coloring molecules of natural origin that can increase and diversify the offer of natural food dyes already present in the market. In the present work, a B-phycoerythrin extract from the microalgae Porphyridium cruentum was tested as a food colorant in milk-based products. Using spectroscopy and colorimetry, the extract was characterized and gave evidence of good properties and good stability in the pH range between 4.0 and 9.0. Coloring studies were conducted to demonstrate that samples carrying the pink extract could be used for simulating the pink color of marketed milk-based products. The staining factors, representing the amount of pink protein to be added to reproduce the color of strawberry commercial products, ranged between 1.6 mg/L and 49.5 mg/L, being sufficiently low in all samples. Additionally, color stability during a short period of cold storage was studied: it demonstrated that the three tested types of dairy products remained stable throughout the 11-day analysis period with no significant changes. These results prove the potential of the B-phycoerythrin extract as a natural colorant and alternative ingredient to synthetic coloring molecules. Full article
(This article belongs to the Special Issue Natural Colorants)
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11 pages, 2252 KiB  
Article
Improvement of Naturally Derived Food Colorant Performance with Efficient Pyranoanthocyanin Formation from Sambucus nigra Anthocyanins Using Caffeic Acid and Heat
by Nicole Straathof and M. Monica Giusti
Molecules 2020, 25(24), 5998; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25245998 - 18 Dec 2020
Cited by 12 | Viewed by 1595
Abstract
Consumers and regulations encourage the use of naturally derived food colorants. Anthocyanins (ACN), plant pigments, are unstable in foods. In aged red wines, ACN with a free hydroxyl group at C-5 condenses to form pyranoanthocyanins (PACN), which are more stable but form inefficiently. [...] Read more.
Consumers and regulations encourage the use of naturally derived food colorants. Anthocyanins (ACN), plant pigments, are unstable in foods. In aged red wines, ACN with a free hydroxyl group at C-5 condenses to form pyranoanthocyanins (PACN), which are more stable but form inefficiently. This study attempted to produce PACN efficiently using high cofactor concentration and heat. Elderberry anthocyanins were semi-purified and caffeic acid (CA) was dissolved in 15% ethanol and diluted with a buffer to achieve ACN:CA molar ratios of 1:50, 1:100, 1:150, and 1:200, then incubated at 65 °C for 5 days. The effect of temperature was tested using ACN samples incubated with or without CA at 25 °C, 50 °C, and 75 °C for 7 days. Compositional changes were monitored using uHPLC-PDA-MS/MS. Higher CA levels seemed to protect pigment integrity, with ACN:CA 1:150 ratio showing the highest tinctorial strength after 48 h. PACN content growth was fastest between 24 and 48 h for all ACN:CA ratios and after 120 h, all ACN had degraded or converted to PACN. PACN formed faster at higher temperatures, reaching ~90% PACN in 24 h and ~100% PACN in 48 h at 75 °C. These results suggest that PACN can form efficiently from elderberry ACN and CA if heated to produce more stable pigments. Full article
(This article belongs to the Special Issue Natural Colorants)
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15 pages, 1489 KiB  
Article
Characterization of Beet Root Extract (Beta vulgaris) Encapsulated with Maltodextrin and Inulin
by Martha A. Flores-Mancha, Martha G. Ruíz-Gutiérrez, Rogelio Sánchez-Vega, Eduardo Santellano-Estrada and América Chávez-Martínez
Molecules 2020, 25(23), 5498; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25235498 - 24 Nov 2020
Cited by 18 | Viewed by 4464
Abstract
Betalains are powerful antioxidants contained in beets. These are divided into betacyanins (red-violet) and betaxanthins (yellow-orange), and they can be used as natural colorants in the food industry. The effects of freeze-drying pure beet juice (B) and the encapsulation of beet juice with [...] Read more.
Betalains are powerful antioxidants contained in beets. These are divided into betacyanins (red-violet) and betaxanthins (yellow-orange), and they can be used as natural colorants in the food industry. The effects of freeze-drying pure beet juice (B) and the encapsulation of beet juice with a dextrose equivalent (DE) 10 maltodextrin (M) and agave inulin (I) as carrier agents were evaluated. The powders showed significant differences (p < 0.05) in all the variables analyzed: water absorption index (WAI), water solubility index (WSI), glass transition temperature (Tg), total betalains (TB), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA, via 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) and total protein concentration (TPC). The highest values of antioxidant activity were found in the non-encapsulated beet powder, followed by the powder encapsulated with maltodextrin and, to a lesser extent, the powder encapsulated with inulin. The glass transition temperature was 61.63 °C for M and 27.59 °C for I. However, for B it was less than 18.34 °C, which makes handling difficult. Encapsulation of beet extract with maltodextrin and inulin by lyophilization turned out to be an efficient method to increase solubility and diminish hygroscopicity. Full article
(This article belongs to the Special Issue Natural Colorants)
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13 pages, 3508 KiB  
Article
Study of the Relationship between Leaf Color Formation and Anthocyanin Metabolism among Different Purple Pakchoi Lines
by Bo Song, Hai Xu, Longzheng Chen, Xiaoxue Fan, Zange Jing, Song Chen and Zhigang Xu
Molecules 2020, 25(20), 4809; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25204809 - 19 Oct 2020
Cited by 13 | Viewed by 2401
Abstract
Purple pakchoi (Brassica rapa ssp. Chinensis) is particularly appreciated due to its high edible quality and ornamental value, but there are few studies on the underlying mechanisms of leaf color formation. To comprehensively assess the differences in purple formation in pakchoi, [...] Read more.
Purple pakchoi (Brassica rapa ssp. Chinensis) is particularly appreciated due to its high edible quality and ornamental value, but there are few studies on the underlying mechanisms of leaf color formation. To comprehensively assess the differences in purple formation in pakchoi, four lines of pakchoi with different purple leaves were used in this experiment to determine the pigment content and to investigate the distribution and components of anthocyanin using LCMS (Liquid Chromatography Mass Spectrometry) and leaf cross-sections. Moreover, the expression levels of anthocyanin synthesis-related genes in four lines were calculated by qRT-PCR. The results showed that three new purple lines rich in anthocyanin and of high-quality were bred, and the anthocyanin were mainly distributed in both the upper epidermis and lower epidermis of leaves. Thirteen anthocyanin components were separated and identified, all the anthocyanins were acylated and glycosylated cyanidins; the main anthocyanins in purple pakchoi were a diacylated form of cyanidin 3-trans-(feruloyl)diglucoside-5-(malonyl)glucoside. Both the ratio of non-aromatic acylated cyanidin to aromatic acylated cyanidin and the ratio of anthocyanin content to chlorophyll content were responsible for the color formation in different purple pakchoi lines. When the ratio was high, the leaf appeared reddish purple, and when the ratio was low, the leaf appeared deep purple, even blackish purple. The expression level of BrF3H was significantly correlated with the content of anthocyanin through the correlation coefficient, which was speculated to be the main anthocyanin synthesis-related gene resulting in color differences among the four purple pakchoi lines. These results will enhance our understanding for the cultivation of new purple pakchoi varieties. Full article
(This article belongs to the Special Issue Natural Colorants)
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