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Correction: Enhanced pigment content estimation using the Gauss-peak spectra method with thin-layer chromatography for a novel source of natural colorants
[This corrects the article DOI: 10.1371/journal.pone.0251491.].
Journal Article
Composition, Color Stability and Antioxidant Properties of Betalain-Based Extracts from Bracts of IBougainvillea/I
Betalains in bracts of Bougainvillea are of great application potential as natural food colorants and antioxidants. This study explored the color, spectra, composition, storage stability, and antioxidant properties of betalain-based Bougainvillea bracts extracts (BBEs) to verify their application value. The results showed that Bougainvillea bract color variance is due to varied contents and proportions of betacyanins (Bc) and betaxanthins (Bx). Bc or Bx alone determined hues of purple or yellow, respectively; the co-existence of Bc and Bx would produce varied hues of red. BBEs showed bright color and good antioxidant properties under a wide pH range. The pH range of 5–6 was optimal for the highest color stability, and pHs 3–8 were optimal for stronger antioxidants. Bc mainly underwent color fading during storage, while Bx easily produced dark precipitates or melanism under strong acidic (pH < 4) or alkaline conditions (pH > 8). However, Bougainvillea Bx showed 3–4 times higher antioxidant ability than Bc. Different considerations for Bc and Bx are needed for varied application purposes. The purple bracts containing only Bc would be more suitable as colorant sources, while additional Bx can bring enhancement of antioxidant ability and richness of Bougainvillea extract color.
Journal Article
Inhibition of bleaching of stored red hot pepper through appropriate postharvest technologies and practices
The colour qualities of hot red pepper are the major issue in pepper value chain. Due to poorly coordinated scientific evidence, information on the factors causing colour loss and the inhibition mechanism is not well known. Therefore, this review paper aimed to summarize the inhibition mechanism of stored red hot pepper bleaching through appropriate postharvest technologies and practices. The information in this paper was gathered from a variety of sources, including journal articles, books, book chapters, workshop proceedings, FAO reports, and AOAC official methods of analysis. According to these studies, carotenoids, surface colour, and extractable colour (ASTA value) are the primary colourants that define hot red pepper. The findings demonstrate that low-temperature drying methods, such as open sun drying, are best for preserving the red hot pepper powder's colour quality, while higher temperatures cause the colour to darken. Blanching, the use of desiccants (Ca[Cl.sub.2]), and chemical dipping are pretreatments that preserve the best colour quality by hastening the drying time. Similarly, storage of red hot pepper powder at lower temperatures (5[degrees]C) resulted in less colour degradation. In other words, materials used for packaging that have a high barrier to light, moisture, and air, such as laminated aluminium, amber or black polyethylene, and high-density polyethylene, maintained a higher level of colour quality. Through their influence on drying and processing times, breeding technologies, varieties, and maturity level also impact colour quality. In conclusion, the colour quality of red hot pepper is highly influenced by environmental, biological, and processing methods. It is, therefore, critical to use appropriate drying and pretreatment techniques, storage time, well-managed storage temperature, appropriate processing methods and packing materials, and improved agronomic practices for the sustainable management of colour fading and adulteration that can occur throughout the value chain.
Journal Article
Spectroelectrochemical and Theoretical Study of Sisub.4: A Potential Polychromatic Electrochromic Dye
Complexes consisting of earth-abundant main group metals such as silicon with polypyridine ligands are of interest for a variety of optical and electronic applications including as electrochromic colorants. Previous spectroelectrochemical studies with tris(2,2′-bipyridyl)silicon(IV) hexafluorophosphate, [Si(bpy)[sub.3]](PF[sub.6])[sub.4,] demonstrated an ability to control the color saturation of the potential electrochromic dye, with the intensity of the dye’s green color increasing as the charge state sequentially reduces from 4+ to 1+. In this study, the synthesis of bis(4′-(4-tolyl)-2,2′:6′,2″-terpyridine)silicon(IV) hexafluorophosphate, [Si(ttpy)[sub.2]](PF[sub.6])[sub.4], is reported along with electrochemical and spectroelectrochemical analyses. Computational modeling (density functional theory) is used to further elucidate the electrochromic properties of previously reported Si(bpy)[sub.3] [sup.n+] species and the new Si(ttpy)[sub.2] [sup.n+] species. While the homoleptic tris(bidentate)silicon(IV) complexes are attractive as electrochromic dyes for tunable color saturation, the bis(tridentate)silicon(IV) complexes are attractive as polychromatic electrochromic dyes.
Journal Article
Semisynthesis of Betaxanthins from Purified Betacyanin of IOpuntia dillenii/I sp.: Color Stability and Antiradical Capacity
The availability of pure individual betalains in sufficient quantities which permit deeper understanding is still a challenge. This study investigates the high-yielding semisynthesis of betaxanthins using betalamic acid from a natural source (Opuntia dillenii), followed by condensation with ʟ−amino acids and further purification. Moreover, the color stability of the four synthesized individual betaxanthins, namely proline (ʟ−ProBX), alanine (ʟ−AlaBX), leucine (ʟ−LeuBX), and phenylalanine (ʟ−PheBX) betaxanthins, was investigated at different pHs. Their relative contribution to free radical scavenging was also scrutinized by TEAC and DPPH. ʟ−AlaBX and ʟ−LeuBx showed a significantly (p < 0.05) higher antioxidant activity, whereas ʟ−ProBX was the most resistant to the hydrolysis of betaxanthin and hence the least susceptible to color change. The color stability was strongly influenced by pH, with the color of ʟ−ProBX, ʟ−LeuBX, and ʟ−AlaBX at pH 6 being more stable, probably due to the easier hydrolysis under acid conditions. The semisynthesis and purification allowed us to have available remarkable quantities of pure individual betaxanthins of Opuntia dillenii for the first time, and to establish their color properties and antioxidant capacity. This study could be a step forward in the development of the best natural food colorant formulation, based on the betalain structure, which is of special interest in food technology.
Journal Article
Computational, Investigational Explorations on Structural, Electro-Optic Behavior of Pelargonidin Organic Colorant for TiOsub.2 Based DSSCs
In an expedition for green-energy generation and to lower the cost per watt of solar energy, environmentally friendly biotic colorants were separated from Tectona grandis seeds. The prime colorant in the extract is pelargonidin which sensitizes titanium dioxide (TiO[sub.2])-based photo anodes. The pelargonidin-sensitized TiO[sub.2] nanomaterials endured structural, photosensitive, spectral and current-voltage interpretations. Frontier molecular orbital analysis, physicochemical and electronic parameter computation, UV-visible and DOS spectral analysis, van der Waals prediction and molecular electrostatic potential map were performed theoretically with Gaussian tools, and IR symmetry response was computed using the crystal maker software package. The pelargonidin-sensitized TiO[sub.2]-created dye-sensitized solar cells which exhibited capable solar light energy to photon conversion proficiency. For comparative purposes, the commercial P25 Degussa TiO[sub.2]-based DSSC was also fabricated and its proficiency was analyzed. The commercial TiO[sub.2] exhibited 57 % higher proficiency in comparison to the sol-gel-derived TiO[sub.2]-based DSSC.
Journal Article
Extraction and Spray Drying-Based Encapsulation of Anthocyanin Pigments from Jabuticaba Sabará Peel
Jabuticaba (Myrciaria jaboticaba (Vell.) O. Berg) peel is a native Brazilian fruit by-product recognized for its high anthocyanin (ANC) content and strong antioxidant potential, making it a valuable natural source for food applications. This study aimed to optimize the extraction and spray drying-based encapsulation of ANCs from the peels of Sabará jabuticaba. Extraction was performed using ethanol acidified with HCl (6 M) under varying conditions of pH (1.0–3.0), temperature (14–50 °C), and solvent volume (100–250 mL). The highest anthocyanin yield (328.13 mg/100 g dry basis) was achieved at pH 1.0, 50 °C, and 250 mL solvent volume. For encapsulation, gum arabic and maltodextrin were used as wall materials at different mass ratios (1:1, 1:2, 1:3, 1:4, 2:1, 3:1, and 4:1 w/w). The 1:2 ratio (gum arabic/maltodextrin) resulted in the highest retention of anthocyanins (315.37 mg/100 g dry basis), with encapsulation efficiency of approximately 96%, low water activity (0.27), and reduced moisture content (3.6%). These characteristics are essential for ensuring product stability during storage. The optimized anthocyanin-rich microparticles present promising potential for application as natural colorants and functional ingredients in food formulations or as antioxidant carriers in pharmaceutical products.
Journal Article