Effect of genuine non-anthocyanin phenolics and chlorogenic acid on color and stability of black carrot (Daucus carota ssp. sativus var. atrorubens Alef.) anthocyanins

Effect of co-pigments on anthocyanins of wild cranberry and investigation of interaction mechanisms

This study systematically evaluated the color-enhancing effects of different co-pigmented molecules (amino acids, peptides, flavonoids and phenolic acids) with cranberry anthocyanins under different environmental conditions (light, dark, high temperature and ascorbic acid) and their potential mechanisms by various means, such as degradation kinetics, color stability, H NMR spectroscopy, and structural simulation analyses. The results showed that the introduction of co-pigments induced a strong color-enhancing effect and bathochromic shift, inhibited the degradation of anthocyanins (9.34 % ∼ 45.00 %), and prolonged the half-life of anthocyanins (14.33 % ∼ 104.56 %). Among them, catechin, ferulic acid and tryptophan, by virtue of their large molecular planes, flexible side chains and abundant substituents, altered the core structure of anthocyanins and the electron cloud density of H atoms on the acylated molecules, which significantly enhanced their stability upon binding to anthocyanins. In addition, molecular docking simulations revealed an interaction mode between co-pigments and anthocyanins dominated by hydrogen bonding and π-π stacking interactions.

Factors affecting the stability of anthocyanins and strategies for improving their stability: A review

Anthocyanins, as the most common and widely distributed flavonoid compounds, are widely present in fruits and vegetables. Anthocyanins show various biological activities including antioxidant, anticancer, anti-inflammatory, antibacterial, and immunomodulatory activities. Hence, anthocyanins are widely used in the fields of food and pharmaceuticals. However, anthocyanins are susceptible to environmental and processing factors due to their structural characteristics, which leads to poor storage and processing stability. Numerous studies have indicated that structural modification, co-pigmentation, and delivery systems could improve the stability and bioavailability of anthocyanins in the external environment. This article reviews the main factors affecting the stability of anthocyanins. Moreover, this review comprehensively introduces methods to improve the stability of anthocyanins. Finally, the current problems and future research advances of anthocyanins are also introduced. The findings can provide important references for deeper research on the stability, biological activities, and bioavailability of anthocyanins.

Enzymatic acylation of cyanidin-3-O-glucoside with aromatic and aliphatic acid methyl ester: Structure-stability relationships of acylated derivatives

Anthocyanins are water-soluble pigments, but they tend to be unstable in aqueous solutions. Modification of their molecular structure offers a viable approach to alter their intrinsic properties and enhance stability. Aromatic and aliphatic acid methyl esters were used as acyl donors in the enzymatic acylation of cyanidin-3-O-glucoside (C3G), and their analysis was conducted using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). The highest conversion rate achieved was 96.41 % for cyanidin-3-O-(6″-feruloyl) glucoside. Comparative evaluations of stability revealed that aromatic acyl group-conjugated C3G exhibited superior stability enhancement compared with aliphatic acyl group derivatives. The stability of aliphatic C3G decreased with increasing carbon chain length. The molecular geometries of different anthocyanins were optimized, and energy level calculations using density functional theory (DFT) identified their sites with antioxidant activities. Computational calculations aligned with the in vitro antioxidant assay results. This study provided theoretical support for stabilizing anthocyanins and broadened the application of acylated anthocyanins as food colorants and nutrient supplements.

Stability of individual anthocyanins from black carrots stored in light and darkness - Impact of acylation

Black carrot anthocyanins have gained increasing attention as natural coloring agent, owing to their higher stability than anthocyanins from berries. The stability has been attributed to their higher degree of acylation. This study investigated the impact of acylation on the stability of individual anthocyanins during storage in light and darkness. We hypothesized that the acylated anthocyanins would be more stable than the non-acylated ones. The major five anthocyanins were fractioned by semi-preparative HPLC and stored at pH 4.5 in light and darkness to investigate how acylation affected the stability. The stability was evaluated by absorption spectroscopy and mass spectrometry (MS). Two of the anthocyanins were non-acylated; 3-xylosyl(glucosyl)galactoside and cyanidin 3-xylosylgalactoside, and three were acylated; cyanidin 3-xylosyl(sinapolyglucosyl)galacto-side, cyanidin 3-xylosyl(feruloylglu-cosyl)galactoside, and cyanidin 3-xylosyl(coumaroyl-glucosyl)galactoside. Both methods (spectroscopy and MS) showed a clear effect of acylation when stored in light, but surprisingly the two non-acylated anthocyanins, showed higher stability than the three acylated ones.

Seasonal and Morphology Effects on Bioactive Compounds, Antioxidant Capacity, and Sugars Profile of Black Carrot (Daucus carota ssp. sativus var. atrorubens Alef.)

Black carrot (Daucus carota ssp. sativus var. atrorubens Alef.) is widely recognized for its bioactive compounds and antioxidant properties. The black carrot of Cuevas Bajas (Málaga) is a local variety characterized by a black/purple core, which differs from other black carrot varieties. Therefore, this autochthonous variety was characterized according to the root size and the harvesting season by means of a study of its antioxidant capacity analyzed by three methods, its total carotenoids content, and its sugars and phenolic compounds profile by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-MS). A total of 20 polyphenolic compounds were quantified in 144 samples analyzed. The anthocyanidins group was observed to be the most abundant, followed by the hydroxycinnamic acids group. Moreover, pelargonidin 3-sambubioside was observed in black carrot for the first time. The medium-sized carrots presented the highest content of phenolic compounds, largely due to their significantly higher anthocyanidins content. Comparatively, the small carrots showed a higher content of simple sugars than the large ones. Regarding the influence of season, significantly higher quantities of glucose and fructose were observed in the late-season carrots, while sucrose was the main sugar in early-season samples. No significant differences were observed in the total carotenoid content of black carrot.

The use of a novel smartphone testing platform for the development of colorimetric sensor receptors for food spoilage

This work presents a novel smartphone testing platform for the validation of colorimetric sensor receptors (CSRs) in the form of layers that enables reliable and straightforward determination of their color change in a closed system using a commercially available color sensor. The food-compatible model CSR used for the method development was made of black carrot extract and ethyl cellulose. The colorimetric responses were studied in detail for NH₃, dimethylamine (DMA), and trimethylamine (TMA) by analyzing changes in the value of the total color difference (ΔE) with the increasing logarithm of the mass concentration (log γ) of the analytes. The method was partially validated for the detection limit (LOD), the limit of quantification, sensitivity, and linear γ range. The fastest reaction times were obtained for the NH₃ analyte, while the calculated LOD values were quite similar (1.48 mg L^-1 for NH₃, 1.55 mg L^-1 for DMA, and 1.58 mg L^-1 for TMA). The applicability of CSRs was shown for different types of muscle food. Frozen (boneless and skinless) hake fillets were used for additional experimental work in which the color changes of the CSRs were correlated with the values of the total volatile basic nitrogen (TVB-N) and the total counts of aerobic and anaerobic microorganisms. The developed testing platform shows great promise for the development of CSRs that define the quality of a broad variety of muscle food.

Comprehensive evaluation of the effect of five sterilization methods on the quality of black carrot juice based on PCA, TOPSIS and GRA models

The effect of thermal pasteurization (TP), high temperature long time (HTLT), ultra-high temperature instantaneous (UHT), high hydrostatic pressure (HHP) and thermosonication (TS) sterilization on the physicochemical, sensory and functional properties of black carrot juice (BCJ) were studied. And for the first time, the comprehensive quality of sterilized BCJ was quantified by mathematical modeling. UHT was the least suitable sterilization method for BCJ resulting from the most severe deterioration in functional properties. TS had adverse effects on sensory and physicochemical properties, but significantly increased the total flavonoids and anthocyanins contents (p < 0.05) and showed the strongest antioxidant activity, making it a nutritional high-value processing method. TP and HHP balanced the improvement of sensory properties and the retention of functional properties, which were the most suitable sterilization methods for BCJ. This study determined the optimal sterilization methods of BCJ, and provided a scientific solution for the screening of high quality processing methods.

Analysis of Floral Color Differences between Different Ecological Conditions of Clematis tangutica (Maxim.) Korsh

The Clematis tangutica (Maxim.) Korsh. is a wild flowering plant that is most widely distributed on the Qinghai-Tibet Plateau, with beautiful, brightly colored flowers and good ornamental properties and adaptability. In diverse natural environments, the blossom color of C. tangutica (Maxim.) Korsh. varies greatly, although it is unclear what causes this diversity. It was examined using UPLC-MS/MS and transcriptome sequencing for the investigation of various compounds, differentially expressed genes (DEGs), and flavonoid biosynthesis-related pathways in two flowers in two ecological settings. The results showed that a total of 992 metabolites were detected, of which 425 were differential metabolites, mainly flavonoid metabolites associated with its floral color. The most abundant flavonoids, flavonols and anthocyanin metabolites in the G type were cynaroside, isoquercitrin and peonidin-3-O-glucoside, respectively. Flavonoids that differed in multiplicity in G type and N type were rhoifolin, naringin, delphinidin-3-O-rutinoside, chrysoeriol and catechin. Rhoifolin and chrysoeriol, produced in flavone and flavonol biosynthesis, two flavonoid compounds of C. tangutica (Maxim.) Korsh. with the largest difference in floral composition in two ecological environments. In two ecological environments of flower color components, combined transcriptome and metabolome analyses revealed that BZ1-1 and FG3-1 are key genes for delphinidin-3-O-rutinoside in anthocyanin biosynthesis, and HCT-5 and FG3-3 are key genes for rhoifolin and naringin in flavonoid biosynthesis and flavone and flavonol. Key genes for chlorogenic acid in flavonoid biosynthesis include HCT-6, CHS-1 and IF7MAT-1. In summary, differences in flavonoids and their content are the main factors responsible for the differences in the floral color composition of C. tangutica (Maxim.) Korsh. in the two ecological environments, and are associated with differential expression of genes related to flavonoid synthesis.

Combined Pulsed Electric Field and Microwave-Assisted Extraction as a Green Method for the Recovery of Antioxidant Compounds with Electroactive Potential from Coffee Agro-Waste

Coffee agro-waste is a potential source of polyphenols with antioxidant activity and application in the food and cosmetic trades. The usage of these byproducts persists as a challenge in the industrial landscape due to their high content of purported toxic substances hindering management. This study presents a green extractive process using pulsed electric field (PEF) and microwave assisted extraction (MAE) to recover polyphenols from coffee parchment and two varieties of pulp, posing quick processing times and the use of water as the only solvent. The performance of this process with regard to the bioactivity was assessed through the Folin-Ciocalteu assay, total flavonoid content, DPPH, ABTS and FRAP antioxidant tests. The phenolic composition of the extracts was also determined through HPLC-MS and quantified through HPLC-DAD. When compared to treatment controls, PEF + MAE treated samples presented enhanced yields of total phenolic content and radical scavenging activity in all analyzed residues (Tukey test significance: 95%). The chromatographic studies reveal the presence of caffeic acid on the three analyzed by-products. The HPLC-DAD caffeic acid quantification validated that a combination of MAE + PEF treatment in yellow coffee pulp had the highest caffeic acid concentration of all studied extraction methods.

Co-pigmentation of strawberry anthocyanins with phenolic compounds from rooibos

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Strawberry anthocyanins may be co-pigmented with rooibos phenolics.

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Adding rooibos extract enhanced color and heat stability of strawberry anthocyanins.

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Green and fermented rooibos phenolics acted as potential co-pigments (CP).

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A flavonoid-rich fraction of green rooibos extract provided the most potent CPs.

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Flavonoids luteolin and orientin were effective CPs for pelargonidin 3-glucoside.

Anthocyanin-rich strawberry model solutions were co-pigmented with rooibos phenolics to enhance color and heat stability. The addition of green and fermented rooibos extracts at pigment-to-co-pigment molar ratios of 1:10, 1:50, and 1:100 pelargonidin-3-glucoside equivalents: orientin equivalents induced hyper- and bathochromic shifts at room temperature and during thermal processing at 80 °C for an hour. Co-pigmentation effects on hyperchromic shift were up to 96%, and bathochromic shift reached 19 nm when adding flavonoid-rich fractions of green rooibos phenolics. Following the co-pigmentation tests with rooibos extracts, selected pure phenolic co-pigments were tested for their monomeric contribution to the observed co-pigmentation effects. Orientin was identified as a potent co-pigment for pelargonidin-3-glucoside, showing stronger co-pigmentation effects than that of its aglycon luteolin. Additionally, orientin had the most pronounced bathochromic shift in heat-treated solutions. Rooibos extracts, particularly flavonoid-rich fractions composed of luteolin, apigenin, and quercetin glycosides, are suggested as color enhancers and stabilizers for strawberry products.

Updated insights into anthocyanin stability behavior from bases to cases: Why and why not anthocyanins lose during food processing

Anthocyanins have received considerable attention for the development of food products with attractive colors and potential health benefits. However, anthocyanin applications have been hindered by stability issues, especially in the context of complex food matrices and diverse processing methods. From the natural microenvironment of plants to complex processed food matrices and formulations, there may happen comprehensive changes to anthocyanins, leading to unpredictable stability behavior under various processing conditions. In particular, anthocyanin hydration, degradation, and oxidation during thermal operations in the presence of oxygen represent major challenges. First, this review aims to summarize our current understanding of key anthocyanin stability issues focusing on the chemical properties and their consequences in complex food systems. The subsequent efforts to examine plenty of cases attempt to unravel a universal pattern and provide thorough guidance for future food practice regarding anthocyanins. Additionally, we put forward a model with highlights on the role of the balance between anthocyanin release and degradation in stability evaluations. Our goal is to engender updated insights into anthocyanin stability behavior under food processing conditions and provide a robust foundation for the development of anthocyanin stabilization strategies, expecting to promote more and deeper progress in this field.

Ultrahigh Pressure Facilitates the Acylation of Malvidin and Chlorogenic Acid to Increase the Stability and Protective Effect of Malvidin Derivatives on H2O2-Induced ARPE-19 Cells

We explored the effects of ultrahigh-pressure technology and chlorogenic acid on the color stability and structure-activity relationship of malvidin (MV). Experimental conditions were optimized through single-factor experiments and response surface analysis at a pressure of 300 MPa, mass ratio of MV to chlorogenic acid of 1:3.64 (w/w), and time of 5 min. Compared with MV, MV derivatives showed higher stability and in vitro antioxidant activity. X-ray diffraction analysis, UV-vis spectroscopy, Fourier transform infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry were conducted to determine the structures of MV derivatives for the first time. Ultrahigh pressure facilitated acylation of chlorogenic acid and MV and produced four new MV derivatives. Analysis of the effect of malvidin-3-O-6-(acrylic acid-(2-hydroxy, 4-carboxy-cyclohexanol) ester)-guaiacol (Mv3ACEC) on ARPE-19 cells exposed to H₂O₂ by RNA transcriptome sequencing showed that Mv3ACEC simultaneously inhibited various inflammatory and apoptotic signal transduction pathways, exerted a synergistic effect, and partly inhibited cell apoptosis through the MAPK signaling pathway. Therefore, the results show that ultrahigh pressure will cause acylation of chlorogenic acid and MV to produce four new MV derivatives, and MV derivatives protect ARPE-19 cells from H₂O₂-induced oxidative stress.

The effects of Daucus carota extract against PC3, PNT1a prostate cells, acetylcholinesterase, glutathione S-transferase, and α-glycosidase; an in vitro-in silico study

Daucus carota L. ssp. major (DCM) plant is widely used in traditional medicine to treat some types of cancer and various diseases. Therefore, we evaluated the biological activities of this plant to define its effects against prostate cancer (PCa), Alzheimer's disease (AD), oxidation, and diabetes mellitus (DM) as well as identified its phenolic composition. To determine the anti-cancer properties of the plant extract, we treated PCa cells with the extract at a concentration range of 0.25, 0.5, 1, 2, and 4 mg/ml. Significant results were obtained against the PC3 cells compared to normal PNT1a prostate epithelial cells. As a result of precise measurements at the millimolar level, it was observed that the plant extract showed an effective inhibition (IC₅₀ ) against glutathione S-transferase (GST; 12.84 mM), acetyl cholinesterase (AChE; 15.07 mM), and α-Gly (11.75 mM) enzymes when compared with standard inhibitors. Antioxidant activities of DCM methanol extract were determined via two well-known in vitro techniques. The extracts showed antioxidant activities against the DPPH and ABTS⁺ . The LC-ESI-MS/MS was used to determine the phenolic compounds of methanol extract from DCM. Chlorogenic acid (2,089.096 µg/g), shikimic acid (193.14 µg/g), and coumarin (113.604 µg/g) were characterized as major phenolic compounds. In addition, the interactions of chlorogenic acid, chrysin, coumarin, and shikimic acid with the used three enzymes have been calculated using molecular docking simulation. PRACTICAL APPLICATIONS: Plant natural phenolic compounds have protective effects such as anti-inflammatory, antioxidant, anticarcinogen, and enzyme inhibitory. Therefore, it has an important place in the food and pharmaceutical industry. The present study aims to reveal the enzyme inhibitory, antioxidant, and anticarcinogenic properties of the Daucus carota ssp. Major (DCM) plant extract. Significant results were obtained against the PC3 cells compared to normal PNT1a prostate epithelial cells. DCM extract demonstrated considerable antioxidant activity and inhibitory potential on used metabolic enzymes. These biological effects are thought to have a relationship with rich chemical composition.

Stabilization of Lycium ruthenicum Murr. anthocyanins by natural polyphenol extracts

Anthocyanins are a group of flavonoids widely used as natural pigments and in functional foods. However, the sensitivity of anthocyanins to environment factors limits their utilization. The present study examined the stabilizing effects of polyphenol extracts from raspberry, sea-buckthorn, Lonicera edulis, and blackcurrant on Lycium ruthenicum Murr (LRM)-derived anthocyanins. After light and heat exposure, contents of total anthocyanins and the monomers were detected with the pH differential method and the HPLC. Remarkably, polyphenol extracts from raspberry, Lonicera edulis and blackcurrant extended the half-lives of anthocyanins, while the effect of the sea-buckthorn extracts was negligible. Noticeably, petunidin-3-O-[6-O-(4-O-trans-p-coumaroyl-alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside]-5-O-[beta-D-glucopyranoside], the major component of LRM-derived anthocyanins, exhibited a dramatic increase in half-life with the presence of polyphenol extracts from raspberry, Lonicera edulis, and blackcurrant. In summary, our findings suggest the polyphenol extracts could be developed into copigments for stabilization of anthocyanins.

Application of Crude Pomace Powder of Chokeberry, Bilberry, and Elderberry as a Coloring Foodstuff

Berry pomace, rich in polyphenols, especially anthocyanins, accumulates during the production of red juices. Pomace from chokeberry (Aronia melanocarpa Michx.), bilberry (Vaccinium myrtillus L.), and elderberry (Sambucus nigra L.) represent good sources of coloring foodstuffs. Pomace powders (PP) were prepared by milling the seedless fractions of the three dried berry pomaces (50 °C, 8 h). Techno-functional properties of the powders such as particle size distribution, bulk density, sedimentation velocity, and swelling capacity were determined to evaluate the powders for possible food applications. Total anthocyanin content was quantified by UHPLC-DAD before and during a storage experiment to monitor the degradation of anthocyanins in the PP and in a yogurt model application. The high content of phenolic compounds and the still intact cell structure ensured high stability of anthocyanins over 28 days of storage. In the model application, color saturation was stable over the whole storage time of 14 days. Regarding the techno-functional properties, only a few differences between the three PP were observed. The particle size of elderberry PP was larger, resulting in lowest bulk density (0.45 g/mL), high cold-water solubility (16.42%), and a swelling capacity of 10.16 mL/g dw. Sedimentation velocity of the three PP was fast (0.02 mL/min) due to cluster formation of the particles caused by electrostatic and hydrophobic properties. Compared to other high-intensity coloring foodstuffs, the use of PP, showing acceptable color stability with potential health-promoting effects, represents a wide applicability in different food applications and especially in products with a longer shelf-life.

Multiple co-pigments of quercetin and chlorogenic acid blends intensify the color of mulberry anthocyanins: insights from hyperchromicity, kinetics, and molecular modeling investigations

BACKGROUND

The effect of multiple co-pigments on the color intensification of mulberry anthocyanins (ACs) using spectroscopic techniques in combination with a molecular docking study was studied. The hyperchromicity of ACs co-pigmented with chlorogenic acid (CH) and quercetin (Q) blends was measured and their color stability in liquid and encapsulated particle models was evaluated.

RESULTS

Multiple co-pigments exhibited higher hyperchromicity, pK_H -values, and heat-stability than their individual counterparts. Surflex-docking findings confirmed that stronger binding occurred between multiple ligands and AC than single ones due to their extra -OH, -COOH groups, and delocalization systems. The binding was allowed by increased H-bonding, van der Waals forces, and π-π sites by the extra groups of the multiple co-pigments with AC in aqueous juice and whey particle-based models.

CONCLUSION

This is the first report of the ternary mixture of phenolic acid-flavonol-anthocyanin which could be used as promising food red-colorants. © 2020 Society of Chemical Industry.

Synthesis of magnetic covalent organic framework molecularly imprinted polymers at room temperature: A novel imprinted strategy for thermo-sensitive substance

Molecularly imprinted polymers (MIPs) with specific selective recognition have shown excellent performance in the rapid and efficient separation and enrichment of targets in complex systems. Unfortunately, it is not suitable for thermosensitive substances with biological functions. To this end, an imine-linked MIPs with covalent organic frameworks and magnetic nanoparticles was developed by using a room temperature synthesis strategy for the purification of Cyaninin-3-O-glucoside (C3G) from black chokeberry. The prepared material recognized C3G through π-π interaction, assisted by hydrogen bond, and will not be disturbed by water environment. The adsorption capacity and equilibrium binding constant were 86.92 mg g^-1 and 1.46 L mg^-1, respectively. Based on this special structure, it can also act as a "protective umbrella" and improve the stability of C3G. Furthermore, it exhibited high selectivity compared with dummy template imprinting technique. After purification, the purity of C3G was obviously improved (from 11.96% to 84.72%). This work provided a new strategy for the selective separation of anthocyanin and a method to develop MIPs for thermosensitive substances.

Anthocyanins, Vibrant Color Pigments, and Their Role in Skin Cancer Prevention

Until today, numerous studies evaluated the topic of anthocyanins and various types of cancer, regarding the anthocyanins' preventative and inhibitory effects, underlying molecular mechanisms, and such. However, there is no targeted review available regarding the anticarcinogenic effects of dietary anthocyanins on skin cancers. If diagnosed at the early stages, the survival rate of skin cancer is quite high. Nevertheless, the metastatic form has a short prognosis. In fact, the incidence of melanoma skin cancer, the type with high mortality, has increased exponentially over the last 30 years, causing the majority of skin cancer deaths. Malignant melanoma is considered a highly destructive type of skin cancer due to its particular capacity to grow and spread faster than any other type of cancers. Plants, in general, have been used in disease treatment for a long time, and medicinal plants are commonly a part of anticancer drugs on the market. Accordingly, this work primarily aims to emphasize the most recent improvements on the anticarcinogenic effects of anthocyanins from different plant sources, with an in-depth emphasis on melanoma skin cancer. We also briefly summarized the anthocyanin chemistry, their rich dietary sources in flowers, fruits, and vegetables, as well as their associated potential health benefits. Additionally, the importance of anthocyanins in topical applications such as their use in cosmetics is also given.

Nanoencapsulation of anthocyanins-loaded β-lactoglobulin nanoparticles: Characterization, stability, and bioavailability in vitro

This work aims to investigate the effect of desolvation on the stability and bioavailability of nanoparticles of β-lactoglobulin (β-Lg) and anthocyanins (AC) extracted from red raspberry pomace. Interactions between the substrates were also studied using multispectral approaches. β-Lg-nanoparticles were fabricated via heat treatment at 85 °C for 30 min before initiating the desolvation method at pH 7. This method generated monodisperse particles, nano-scale size of β-Lg, and AC-β-Lg ranged from 129.13 to 351.85 nm with square morphology obtained by SEM. The AC extract was encapsulated successfully during desolvation process into β-Lg-nanoparticles with encapsulation efficiency (EE %) of ~77%. Results also showed that AC (from 1 to 13 × 10^-4 M) quenched the fluorescence intensity of de-solvated β-Lg estimated to be 98%, and a binding among them occurred with a K_a-value of 7.59 × 10⁸ M^-1 at 25 °C. Addition of AC also gradually increased the antioxidant activity of β-Lg-nanoparticles with values of 82.51% at the highest AC-concentration (13 × 10^-4 M) loaded on β-Lg-nanoparticles. AC-loaded β-Lg nanoparticles was more stable in mouth (pH 6.8), simulated gastric (SG, pH 2), and simulated intestinal (SI, pH 6.9) by showing high retention rate (%) than that of AC unencapsulated. Overall, de-solvated-β-Lg increased the heat-stability and bioavailability of AC, which could be further utilized in various food and pharmaceutical matrices. These findings recommend that β-Lg nanoparticles could be appropriated as delivery systems for anthocyanins.

Carrot Anthocyanins Genetics and Genomics: Status and Perspectives to Improve Its Application for the Food Colorant Industry

Purple or black carrots (Daucus carota ssp. sativus var. atrorubens Alef) are characterized by their dark purple- to black-colored roots, owing their appearance to high anthocyanin concentrations. In recent years, there has been increasing interest in the use of black carrot anthocyanins as natural food dyes. Black carrot roots contain large quantities of mono-acylated anthocyanins, which impart a measure of heat-, light- and pH-stability, enhancing the color-stability of food products over their shelf-life. The genetic pathway controlling anthocyanin biosynthesis appears well conserved among land plants; however, different variants of anthocyanin-related genes between cultivars results in tissue-specific accumulations of purple pigments. Thus, broad genetic variations of anthocyanin profile, and tissue-specific distributions in carrot tissues and organs, can be observed, and the ratio of acylated to non-acylated anthocyanins varies significantly in the purple carrot germplasm. Additionally, anthocyanins synthesis can also be influenced by a wide range of external factors, such as abiotic stressors and/or chemical elicitors, directly affecting the anthocyanin yield and stability potential in food and beverage applications. In this study, we critically review and discuss the current knowledge on anthocyanin diversity, genetics and the molecular mechanisms controlling anthocyanin accumulation in carrots. We also provide a view of the current knowledge gaps and advancement needs as regards developing and applying innovative molecular tools to improve the yield, product performance and stability of carrot anthocyanin for use as a natural food colorant.

Copigmentation and UPLC-ESI-MS/MS of anthocyanin in Ipomoea nil as potential source of food colorant

Anthocyanins are good alternative to synthetic dyes for food, pharmaceutical and nutraceutical industries. Owing to their wide occurrence in plant kingdom, an UPLC-ESI-MS/MS method was used to identify and quantify the constituents in flowers of Ipomoea nil. The qualitative evaluation of I. nil results in the characterisation of acylated and non-acylated anthocyanins. Besides characterisation, the total phenolic contents in different fractions of I. nil were found to be 49.69 ± 1.74 and 331.54 ± 1.14 mg GAE/g, respectively. The total anthocyanins content was also determined by spectrophotometer and found to be 5.89 mg/100g of cyanidin-3-O-glucoside equivalent. The antioxidant activity of different fraction of I. nil was evaluated by different assays (DPPH^●, ABTS^●+ and FRAP). In the direction of natural colour stability, we had studied different stabilising agents/copigments and were found to provide stability up to 140 °C. The extracted anthocyanins were evaluated for acute oral toxicity studies and observed to be non-toxic and may direct the use of I. nil for human consumption.

Pecan (Carya illinoinensis (Wagenh.) K. Koch) Nut Shell as an Accessible Polyphenol Source for Active Packaging and Food Colorant Stabilization

Herein, the antioxidant and food stabilizing properties of a pecan nut shell (PNS) hydroalcoholic extract (PNSE) are reported. Chemical degradation of PNSE demonstrated the presence of condensed tannins as the main phenolic components. PNSE showed remarkable antioxidant properties in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay (EC₅₀ = 0.004 mg/mL). PNSE was initially tested as an inhibitor of mushroom tyrosinase, exhibiting a quite low IC₅₀ value (0.055 mg/mL) against the enzyme diphenolase activity, suggesting its use in enzymatic browning inhibition. The anthocyanin stabilization properties were evaluated under accelerated aging conditions of both pure pigments and commercial fruit juices, and PNSE was found to be effective at concentrations (0.05 mg/mL) at which well-known stabilizers such as chlorogenic and ferulic acids proved to fail. PNSE also performed well in the stabilization of spray-dried anthocyanins for use as a food colorant, increasing the half-life of blackberry anthocyanins up to 20%. In order to explore the possibility of using PNSE as a functional additive for active packaging, polylactic acid (PLA) films containing PNSE were prepared by solvent casting, and no substantial alteration of the mechanical properties was found on addition of the extract up to 10% w/w. The films showed remarkable antioxidant properties (DDPH reduction >60% with a 3% w/w loading, at a dose of 1 mg/mL in the DPPH solution) and delayed the onset of browning of apple smoothies (ca. 30% inhibition with a 10% w/w loading). These results highlight the exploitation of PNS as a low-cost polyphenol source for food industry applications.

Impact of cultivar, growth temperature and developmental stage on phenolic compounds and ascorbic acid in purple and yellow potato tubers

Phenolic compounds and ascorbic acid were analyzed in one yellow and four purple-flesh potato cultivars grown at 13 °C and 18 °C and harvested at different stages of tuber development, using HPLC-DAD and UHPLC-MS. The expression of genes in the phenylpropanoid pathway was studied at transcription level using qPCR. Petunidin-3-p-coumaroylrutinoside-5-glucoside was the most abundant anthocyanin in 'Blue Congo', 'Blaue Schweden', and 'Synkeä Sakari', whereas malvidin-3-p-coumaroylrutinoside-5-glucoside dominated in 'Blaue Veltlin'. In mature tubers, the purple cultivar 'Synkeä Sakari' showed the highest content of anthocyanins (2.4 mg/g freeze-dried sample), and 'Blaue Veltlin' had the highest content of phenolic acids (5.5 mg/g). Cultivar was the main variable affecting the biosynthesis of the studied metabolites, whereas the temperatures studied did not show different impact. The content of the main phenolic acids and anthocyanins in the potato cultivars correlated positively with the expression levels of the genes involved in the phenylpropanoid pathway.

Transcriptome Analysis Reveals Candidate Genes Related to Anthocyanin Biosynthesis in Different Carrot Genotypes and Tissues

Black carrots are characterized by a significant amount of anthocyanins, which are not only a good source of natural food colorant, but can also provide many health benefits to humans. In the present work, taproots of different carrot genotypes were used to identify the candidate genes related to anthocyanin synthesis, with particular a focus on R2R3MYB, bHLH transcription factors, and glutathione S-transferase gene (GST). The RNA-sequencing analysis (RNA-Seq) showed that DcMYB6 and DcMYB7 had a genotypic dependent expression and they are likely involved in the regulation of anthocyanin biosynthesis. They were specifically upregulated in solid black taproots, including both black phloem and xylem. DcbHLH3 (LOC108204485) was upregulated in all black samples compared with the orange ones. We also found that GST1 (LOC108205254) might be an important anthocyanin transporter, and its upregulated expression resulted in the increasing of vacuolar anthocyanin accumulation in black samples. Moreover, high performance liquid chromatographic (HPLC) analysis and liquid chromatography coupled to mass spectrometry (LC-MS) were used to identify the individual anthocyanin in the purple tissues of two carrot cultivars. The results showed that five main anthocyanin compounds and the most abundant anthocyanin were the same in different tissues, while the second-highest anthocyanin between three tissues was different, even in the same cultivar. In conclusion, this study combined anthocyanin profiles and comparative transcriptomic analysis to identify candidate genes involved in anthocyanin biosynthesis in carrots, thus providing a better foundation for improving anthocyanin accumulation in carrots as a source of colorants.

Gallic acid as a copigment enhance anthocyanin stabilities and color characteristics in blueberry juice

The aim of this study was to evaluate the influence of adding copigment gallic acid (GA) on the stability of anthocyanin and color in blueberry juice, and assays were carried out with different anthocyanin:GA molar ratios (1:0, 1:1, 1:3, 1:5) in accelerated experiments (40 °C for 10 days). Results showed that the addition of GA made blueberry juice to appear more crimson color tonality, color saturation and anthocyanins stability. The most obvious hyperchromic effect appeared in juice with 1:5 of anthocyanin:GA molar ratios, and in this ratio, total anthocyanin content (137.67 mg/L) and main anthocyanin peonidin-3-glucoside content (51.68 mg/L) of the blueberry juice were higher than juice without copigment (total anthocyanin of 116.96 mg/L and peonidin-3-glucoside of 34.2 mg/L). Furthermore, anthocyanins in blueberry juice copigmented with molar ratios 1:5 of anthocyanin:GA were more stable at 4 °C than that at 25 °C and 40 °C. Thus, the addition of gallic acid at appropriate levels might be a promising juice process technology to obtain juices with high color quality and anthocyanin stability.

Thermal and Photochemical Stability of Anthocyanins from Black Carrot, Grape Juice, and Purple Sweet Potato in Model Beverages in the Presence of Ascorbic Acid

Anthocyanins are natural dyes widely used in the food industry, but their chemical stability in beverages can be affected by the presence of additives. In the present paper, the interaction between anthocyanins and ascorbic acid (AA) is more particularly investigated. Ascorbic acid is an ubiquitous component in food products. In this study, the thermal stability at 43 °C and the photolysis stability in air and in an inert atmosphere (N₂) of anthocyanins extracted from black carrot (BC), grape juice (GJ), and purple sweet potato (SP) were studied in the presence and absence of ascorbic acid (in citrate buffer at pH 3). Discriminating the main environmental factors (i.e., heat and light) affecting anthocyanin stability is a key point for better understanding the degradation pathways. The stability of the anthocyanins was followed by UV-vis spectrometry. Moreover, to understand the degradation mechanisms in both the presence and absence of ascorbic acid, various techniques such as fluorescence quenching, cyclic voltammetry, and electron-spin-resonance (ESR) spectroscopy were also used to furnish a full coherent picture of the chemical mechanisms associated with the anthocyanin degradation. In addition, molecular orbitals and bond-dissociation energies (BDE) were calculated to extend the investigation. Moreover, the effects of some supplementary stabilizers (chlorogenic acid, sinapic acid, tannic acid, fumaric acid, β-carotene, isoquercitrin, myricitrin, green coffee bean extract, and rosemary extract) and sugars (sucrose, fructose, and glucose) on anthocyanins stability in the presence of ascorbic acid were examined.

Understanding the shielding effects of whey protein on mulberry anthocyanins: Insights from multispectral and molecular modelling investigations

Assembling between polyphenols and proteins has been recently spotlighted and this binding is of specific importance in food chemistry since these complexes are typically used in different foodstuffs. A study on the copigmentation among three encapsulation wall-materials, including maltodextrin, gum Arabic, and whey proteins, with mulberry anthocyanins (AC) proved that whey protein (WP) is an outstanding wall-material due to its wrapping and hyperchromicity effects. Additionally, high binding ability of WP with AC was shown to be responsible for its superior copigmentation effects. Accordingly, the underlying shielding mechanism of WP on AC based on their non-covalent assembling was deeply studied using multispectral and computational assays. The fluorometric results demonstrated that a static and heat-stable binding between WP and AC occurred, leading to modification in size, hydrophobicity, and secondary structures of WP. The docking results explained that WP-AC complex was mainly molded via hydrophobic effects of WP surface and subsequently be stabilized by H-bonding and van der Waals forces. These results may contribute to a better understanding on the enhanced colouring proprieties of anthocyanins by using whey proteins.

Anthocyanin pigment stability of Cornus mas-Macrocarpa under treatment with pH and some organic acids

The use of colors in food industry is essential for the creation of new products or their improvement. As an important pigment group, anthocyanin could be used as a natural coloring pigment in foods. This study aims at exploring strategies that result in color stability of anthocyanin in pear‐shaped variety of blueberry (Cornus mas–Macrocarpa). In this study, the effects of different pH values (1, 2, 3, 4) as well as various concentrations (0, 120, 240, 480, 960 mg/L) of five copigments, including tannic, caffeic, benzoic, and coumaric acids, on anthocyanin copigment complexes (ratio 1:1) were investigated. The studied copigments were tannic, caffeic, benzoic, and coumaric acids. Anthocyanin was influenced by the highest concentration of 960 mg/L copigment in the presence of different pHs. Five groups were considered, one of which contained anthocyanin without copigment and the rest consisted of copigments. To evaluate the response of copigmentation through spectrophotometer, absorbance from samples was measured after 30 min of adding copigment to anthocyanin in the range of 450–600 nm wavelengths. The results showed that caffeic acid possessed the greatest anthocyanin stability compared to other copigments and it was the best copigment. An increase in the concentrations of copigments led to a higher level of anthocyanin stability and changes in hyperchromic and bathochromic. Moreover, the results revealed that the strongest hyperchromic effect for all organic acids was observed in pH 2, and the strongest bathochromic changes were observed in pH 4.

Stable Benzacridine Pigments by Oxidative Coupling of Chlorogenic Acid with Amino Acids and Proteins: Toward Natural Product-Based Green Food Coloring

The occasional greening of sweet potatoes and other plant tissues observed during cooking or other food processing has been shown to arise from the autoxidative coupling of chlorogenic acid (CGA, 5-caffeoylquinic acid) with amino acid components, leading to trihydroxybenzacridine pigments. To explore the potential of this reaction for food coloring, we report herein the optimized biomimetic preparation of trihydroxybenzacridine pigments from CGA and amino acids such as glycine and lysine, their straightforward purification by gel filtration chromatography, the UHPLC-MS/MS analysis of the purified pigment fraction, and a detailed characterization of the pH-dependent trihydroxybenzacridine chromophore. Similar green pigments were also obtained by analogous reaction of CGA with a low-cost protein, bovine serum albumin, and by simply adding CGA to chicken egg white (CEW) under stirring. Neither the purified pigments from amino acids nor the pigmented CEW exerted significant toxicity against two human cell lines, Caco-2 and HepG2, at doses compatible with common use in food coloring. Additions of the pure pigments or pigmented CEW to different food matrices imparted intense green hues, and the thermal stability of these preparations proved satisfactory up to 90 °C. The potential application of the greening reaction for the sensing of fish deterioration is also disclosed.

Anthocyanins from purple sweet potato (Ipomoea batatas (L.) Lam.) and their color modulation by the addition of phenolic acids and food-grade phenolic plant extracts

Anthocyanin profiles and contents of three purple sweet potato provenances were investigated by HPLC-DAD-MSⁿ. In contrast to widely uniform profiles, the contents of total (558-2477mg/100gDM) and individual anthocyanins varied widely. Furthermore, quantitative and qualitative effects of intermolecular co-pigmentation were studied by adding chlorogenic and rosmarinic acids, and food-grade phenolic apple and rosemary extracts at various dosages to a diluted purple sweet potato concentrate at pH 0.9, 2.6, 3.6, and 4.6. Addition of co-pigments generally increased pK_{H estimate}-values of anthocyanins from 3.28 (without co-pigments) to up to 4.71, thus substantially broadening the pH range wherein colored forms prevail. The most pronounced hyperchromic shift by up to +50.5% at the absorption maximum was observed at pH 4.6. Simply by blending the co-pigments with purple sweet potato anthocyanins at pH-values ranging from 2.6 to 4.6, purplish-blue, light pink, magenta, brick-red, and intense red hues were accessible as expressed by CIE-L^∗a^∗b^∗ color values.

Fractionation of Plant Bioactives from Black Carrots (Daucus carota subspecies sativus varietas atrorubens Alef.) by Adsorptive Membrane Chromatography and Analysis of Their Potential Anti-Diabetic Activity

Black and purple carrots have attracted interest as colored extracts for coloring food due to their high content of anthocyanins. This study aimed to investigate the polyphenol composition of black carrots. Particularly, the identification and quantification of phenolic compounds of the variety Deep Purple carrot (DPC), which presents a very dark color, was performed by HPLC-PDA and HPLC-ESI-MS(n) analyses. The separation of polyphenols from a DPC XAD-7 extract into an anthocyanin fraction (AF) and co-pigment fraction (CF; primarily phenolic acids) was carried out by membrane chromatography. Furthermore, possible anti-diabetic effects of the DPC XAD-7 extract and its AF and CF were determined. DPC samples (XAD-7, CF, and AF) inhibited α-amylase and α-glucosidase in a dose-dependent manner. Moreover, DPC XAD-7 and chlorogenic acid, but not DPC CF and DPC AF, caused a moderate inhibition of intestinal glucose uptake in Caco-2 cells. However, DPC samples did not affect glucagon-like peptide-1 (GLP-1) secretion and dipeptidyl peptidase IV (DPP-4) activity. Overall, DPC exhibits an inhibitory effect on α-amylase and α-glucosidase activity and on cellular glucose uptake indicating potential anti-diabetic properties.