Identification of degradation pathways and products of cyanidin-3-sophoroside exposed to pulsed electric field

Efficient and safe removal of free and casein-bound oxytetracycline from milk via pulsed electric field

Oxytetracycline (OTC) residues in milk spontaneously bind to casein, forming casein-OTC complexes that complicate their removal. This study assessed the degradation effect of pulsed electric field (PEF) treatment on OTC, with a particular focus on its protein-bound form. Casein-bound OTC was successfully prepared, and the effectiveness of PEF in removing casein-bound antibiotics was confirmed using DESI-MSI technology. Under optimal treatment conditions, the degradation rates of OTC in casein-free whey (86.30 % - 93.43 %) and milk (82.47 % - 90.31 %) showed no significant difference, further confirming that the removal efficacy of PEF on OTC was unaffected by casein binding. The degradation of OTC in both matrices followed the Hülsheger model. Four major degradation products were identified, involving three distinct pathways: epimerization, demethylation, and deamidation. Furthermore, cytotoxicity assays demonstrated that PEF treatment significantly reduced the overall toxicity of OTC in milk. This study provides an effective and safe strategy for removing OTC residues from milk.

Thermal degradation of red cabbage (Brassica oleracea L. var. Capitata f. rubra) anthocyanins in a water model extract under accelerated shelf-life testing

Red cabbage (RC) represents a source of anthocyanins acylated with hydroxycinnamic acids (HCA) that are described to enhance their stability. Nevertheless, data about their thermal degradation are still controversial. Our aim was to comprehensively analyse the degradation kinetics of individual RC anthocyanins in a model aqueous extract treated at 40 °C × 30 days to simulate severe but realistic storage conditions. Free anthocyanins and radical-scavenging capacity showed different kinetics. The results confirm the high stability of RC anthocyanins (t1/2: 16.4-18.4 days), although HPLC analyses of each molecule displayed distinct kinetics with t1/2 from 12.6 to 35.1 days. In particular, the sinapoyl acylation negatively affected the stability of the anthocyanins, while the forms monoacylated with glycosyl p-coumaric and ferulic acids exhibited higher stability. In conclusion, our results indicate that acylation is not a prerogative of stability, as this is instead more dependent on specific acylation patterns and the glycosylation of HCA.

The promising stability of carboxylpyranocyanidin-3-O-glucoside during food processing and simulated digestion and its bioavailability research

BACKGROUND

Pyranoanthocyanins are stable anthocyanin derivatives. Carboxylpyranoanthocyanin is one of the simplest pyranoanthocyanin, among which the production of carboxylpyranocyanidin-3-O-glucoside (crboxyl-pycy-3-gluc) is most feasible as a result of the abundance of its reactant, cyanidin-3-O-glucoside (Cy-3-gluc).

RESULTS

In the present study, carboxyl-pycy-3-gluc was synthesized and its stability during processing and after ingestion as well as its bioavailability in vivo were comprehensively evaluated. Our results indicated that the color of carboxyl-pycy-3-gluc remained more stable compared to Cy-3-gluc when facing the large-span pH variation. The high retention of anthocyanin symbolized the superb stability under thermal processing, sulfur dioxide bleaching and ultrasonic treatment of carboxyl-pycy-3-gluc. Because of the stability under the alkaline condition, carboxyl-pycy-3-gluc is more stable after oral-gastrointestinal digestion. After in vitro gut microbiota fermentation, the retention of carboxyl-pycy-3-gluc was significantly higher than that of Cy-3-gluc. The larger molecular size made absorption of carboxyl-pycy-3-gluc into blood more difficult than its precursor.

CONCLUSION

The present study demonstrated the promising stability of carboxyl-pycy-3-gluc during food processing and after digestion, confirming the potential of carboxyl-pycy-3-gluc as a colorant. © 2023 Society of Chemical Industry.

Role of Oak Ellagitannins in the Synthesis of Vitisin A and in the Degradation of Malvidin 3-O-Glucoside: An Approach in Wine-Like Model Systems

Recent studies highlight the influence that oak ellagitannins can have on wine astringency and color. Direct reactions between flavanols or anthocyanins with vescalagin have been reported to occur, but participation of these compounds in the formation of other types of derivatives has only been suggested but not demonstrated. This study aims at evaluating, in wine-like model systems, the possible different roles of the main oak ellagitannins, castalagin and vescalagin, alone or combined, in the synthesis of vitisin A and in the degradation of malvidin 3-O-glucoside. In the presence of pyruvic acid, the anthocyanin disappeared mainly as a result of the synthesis of vitisin A, whereas in its absence, degradation reactions prevailed. In general, ellagitannins increased the synthesis of vitisin A, decreased the total content of degradation products, and changed the degradation profile, with differences observed between castalagin and vescalagin. The results of the study revealed that the fate of malvidin 3-O-glucoside is conditioned by the presence of ellagitannins.

Comparing the thermal stability of 10-carboxy-, 10-methyl-, and 10-catechyl-pyranocyanidin-3-glucosides and their precursor, cyanidin-3-glucoside

Pyranoanthocyanins are vibrant, naturally derived pigments formed by the reaction of an anthocyanin with a cofactor containing a partially negatively charged carbon. This study compared the thermal stability and degradation products of 10-carboxy-pyranocyanidin-3-glucoside (pyruvic acid cofactor), 10-methyl-pyranocyanidin-3-glucoside (acetone cofactor), and 10-catechyl-pyranocyanidin-3-glucoside (caffeic acid cofactor) with their anthocyanin precursor to evaluate the role of the pyranoanthocyanin C10 substitution on stability. Pyranoanthocyanins exhibited absorbance half-lives ~2.1-8.6 times greater than cyanidin-3-glucoside, with ~15-52% of their original pigment remaining after 12 h of 90 °C heating at pH 3.0. 10-Methyl-pyranocyanidin-3-glucoside was the most stable (p < 0.01) based on UHPLC-PDA analysis, while 10-catechyl-pyranocyanidin-3-glucoside had the most stable color in part due to contribution from a colored degradation compound. Protocatechuic acid formed in all heated samples, which suggested a similar degradation mechanism among pigments. In conclusion, the C10 substitution impacted the extent of pyranoanthocyanin stability and the degradation compounds formed.

Bio Discarded from Waste to Resource

The modern linear agricultural production system allows the production of large quantities of food for an ever-growing population. However, it leads to large quantities of agricultural waste either being disposed of or treated for the purpose of reintroduction into the production chain with a new use. Various approaches in food waste management were explored to achieve social benefits and applications. The extraction of natural bioactive molecules (such as fibers and antioxidants) through innovative technologies represents a means of obtaining value-added products and an excellent measure to reduce the environmental impact. Cosmetic, pharmaceutical, and nutraceutical industries can use natural bioactive molecules as supplements and the food industry as feed and food additives. The bioactivities of phytochemicals contained in biowaste, their potential economic impact, and analytical procedures that allow their recovery are summarized in this study. Our results showed that although the recovery of bioactive molecules represents a sustainable means of achieving both waste reduction and resource utilization, further research is needed to optimize the valuable process for industrial-scale recovery.

A Review of the Current Knowledge of Thermal Stability of Anthocyanins and Approaches to Their Stabilization to Heat

Anthocyanins are colored valuable biocompounds, of which extraction increases globally, although functional applications are restrained by their limited environmental stability. Temperature is a critical parameter of food industrial processing that impacts on the food matrix, particularly affecting heat-sensitive compounds such as anthocyanins. Due to the notable scientific progress in the field of thermal stability of anthocyanins, an analytical and synthetic integration of published data is required. This review focuses on the molecular mechanisms and the kinetic parameters of anthocyanin degradation during heating, both in extracts and real food matrices. Several kinetic models (Arrhenius, Eyring, Ball) of anthocyanin degradation were studied. Crude extracts deliver more thermally stable anthocyanins than purified ones. A different anthocyanin behavior pattern within real food products subjected to thermal processing has been observed due to interactions with some nutrients (proteins, polysaccharides). The most recent studies on the stabilization of anthocyanins by linkages to other molecules using classical and innovative methods are summarized. Ensuring appropriate thermal conditions for processing anthocyanin-rich food will allow a rational design for the future development of stable functional products, which retain these bioactive molecules and their functionalities to a great extent.

Anthocyanins Recovered from Agri-Food By-Products Using Innovative Processes: Trends, Challenges, and Perspectives for Their Application in Food Systems

Anthocyanins are naturally occurring phytochemicals that have attracted growing interest from consumers and the food industry due to their multiple biological properties and technological applications. Nevertheless, conventional extraction techniques based on thermal technologies can compromise both the recovery and stability of anthocyanins, reducing their global yield and/or limiting their application in food systems. The current review provides an overview of the main innovative processes (e.g., pulsed electric field, microwave, and ultrasound) used to recover anthocyanins from agri-food waste/by-products and the mechanisms involved in anthocyanin extraction and their impacts on the stability of these compounds. Moreover, trends and perspectives of anthocyanins' applications in food systems, such as antioxidants, natural colorants, preservatives, and active and smart packaging components, are addressed. Challenges behind anthocyanin implementation in food systems are displayed and potential solutions to overcome these drawbacks are proposed.

STABILITY OF CHITOSAN-TRIPOLYPHOSPHATE COMPLEX-ENCAPSULATED ANTHOCYANIN AT HIGH WATER ACTIVITY

Previous study successfully conducted encapsulation of the purple-fleshed sweet potato’s anthocyanin but the study has yet to reveal the stability of encapsulated anthocyanin. Therefore, this research aims to observe the stability of encapsulated anthocyanin regarding the characteristic of low anthocyanin stability, which depends on environmental factors, such as temperature, pH, humidity, and water activity. The kinetic parameters of stability, including kinetic constant (k), reaction order, and half-life (t1/2), were also studied. Stability testing was conducted in high water activity of 0.75 and various in-cubation temperatures at 16, 25, 35, and 45°C. Un-encapsulated anthocyanin extract was also tested for its stability in the same condition in order to be compared with encapsulated anthocyanin. This study re-vealed that the encapsulated anthocyanin had lower stability than un-encapsulated anthocyanin extract. It was proven by higher kinetic constant and lower half-life of encapsulated anthocyanin for every incubation temperature which was induced by higher pH of encapsulated anthocyanin compared with anthocyanin extract. Besides, high water activity reduced glass transition temperature (Tg), in which encapsulated anthocyanin was in rubbery state. Both encapsulated anthocyanin and anthocyanin extract were degraded following the first order kinetic. Using the Arrhenius equation, it was obtained that the degradation kinetic constant of encapsulated anthocyanin was stated as k= 420.44 exp (-23.33/RT). Meanwhile, k= 1.12x106 exp (-46.70/RT) described degradation of kinetic constant of anthocyanin extract. The stability test re-vealed that the application of encapsulated anthocyanin was not suitable for wet-type food product.

Comparative Study on the Stability and Antioxidant Activity of Six Pyranoanthocyanins Based on Malvidin-3-glucoside

Pyranoanthocyanins are the important color and functional compounds in red wine. Six common kinds of pyranoanthocyanins were synthesized through the reaction of malvidin-3-O-glucoside (Mv-3-gluc) with acetone, pyruvic acid, p-cumaric acid, caffeic acid, ferulic acid, and sinapid acid, respectively, and their pH (1.0-11.0), SO₂ (0-250 ppm), and thermo (50-98 °C) stabilities and antioxidant activities were comparatively studied. Results showed that the six pyranoanthocyanins all exhibited higher pH and SO₂ color stability than Mv-3-gluc, especially vitisin-A with a carboxy group on the D ring. The six pyranoanthocyanins also showed much more thermostability than Mv-3-gluc, especially methylpyranomv-3-gluc. The degradation kinetics of Mv-3-gluc and its derivatives all fitted to a first-order reaction. Moreover, pinotin-A with the o-dihydroxyl group on the E ring presented the strongest antioxidant capability, as evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric ion reducing power (FRAP) assays. Additionally, the increase in the number of rings is beneficial to the improvement of the DPPH radical scavenging ability of anthocyanins.

Anthocyanins: New techniques and challenges in microencapsulation

Anthocyanins are a bioactive compound belonging to the flavonoid classthatis present in human nutrition through plant-based foods. Due to their antioxidant properties, several health benefits related to their consumption are reported in the literature. The stability of the color and the properties of anthocyanins is strongly affected by pH, solvent, temperature, and other environmental conditions. In addition, the insufficient residence time of anthocyanins in the upper digestive tract causes apartialabsorption, which needs to be improved. These factshave led researchers to investigate new forms of processing that provide minimal degradation. Microencapsulation is a promising possibility to stabilize anthocyanin extracts and allow their addition to food products in a more stable form. The microcapsules can still provide a prolonged gastrointestinal retention time caused by the improvement of the bioadhesive properties in the mucus covering the intestinal epithelium. Although there are efficient and emerging techniques, anthocyanins microencapsulation is still a challenge for the food industry. The purpose of this work is to provide an overview of anthocyanins structure, absorptionand protection, and to show the main conventional and emerging microencapsulation methods and their pros and cons.

The Difference in Colour Shifting of Clitoria ternatea L. Flower Extract at pH 1, 4, and 7 During Storage

Objective:

A research to evaluate the colour shift of Clitoria ternatea L. flower (CT) extract at pH 1, 4, and 7 during storage at 30oC in the dark has been conducted.

Methods:

The evaluation comprised of the measurement of colour intensity (CI), violet index (VI), and browning index (BI).

Results:

The extract was very stable at pH 1, although its colour slightly shifted to redder. Conversely, at pH 4 the extract slightly decreased, but the colour hue remained stable. At pH 7, the extract exhibited much less colour stability by demonstrating considerable decrease of CI and VI.

Conclusion:

The absence and presence of the colour shift at pH 4 and 7, respectively, indicated that there were two different ways of the colour fading. It was proposed that the colour degradation at pH 4 occurred through the unfolding of hydrophobic interaction, while at pH 7 through the deacylation. The deacylation was proven by the high-performance liquid chromatography analysis equipped by diode array detector at 530 nm.

The kinetics of thermal degradation of polyphenolic compounds from elderberry ( Sambucus nigra L.) extract

This main focus of this study was to evaluate the thermal degradation kinetics and the phytochemical characterization of the elderberries extract. Pelargonidin-3-sophoroside and delphinidin-3-glucoside were identified as the major anthocyanin compounds and catechin hydrate as the major flavonoid compound. In order to further understand the action of the heat treatment on the bioactive compounds from elderberry extract, fluorescence studies were also carried out. In general, heating at temperatures ranging from 100 to 150 ℃ for up to 90 min caused a decrease in fluorescence intensity, simultaneously with significant redshifts in λ_max suggesting important molecular changes inside the anthocyanins structure, affecting the antioxidant activity. Increasing the heating time up to 120 min, the elderberry extract peaked at about 88 nm shifted toward higher wavelengths with respect to that of untreated solutions (peak at 442 nm). The kinetics studies of anthocyanins, fluorescence intensity, and antioxidant activity evidenced a decrease of the degradation rate constants with increased temperature while the activation energies for heat-induced fluorescence intensity, monomeric anthocyanins, and antioxidant activity were 39.62 ± 9.60, 49.97 ± 5.61, and 31.04 ± 19.92 kJ/mol, respectively. Our results can be valuable in terms of establishing the appropriate processing and formulation protocols that could lead to a more efficient utilization of these pigments in actual food products and/or nutraceuticals.

Cyanidin-3-O-glucoside inhibits the UVB-induced ROS/COX-2 pathway in HaCaT cells

Ultraviolet (UV) radiation from sunlight, especially UVB (290-320nm), is one of the most important environmental factors that destroys the integrity of the skin and causes epidermal cell apoptosis, potentially even leading to skin cancer. UVB irradiation can cause skin damage by stimulating inflammatory and apoptotic pathways. Anthocyanins are flavonoids that are common in many vegetable foods, and have also demonstrated chemopreventive effects. Cyanidin-3-O-glucoside, as a typical anthocyanin, exhibits anti-inflammatory and anti-oxidant effects. This study aimed to investigate the effects, as well as the underlying mechanisms, of treating UVB-exposed HaCaT cells with Cyanidin-3-O-glucoside. We demonstrated that Cyanidin-3-O-glucoside could effectively prevent the UVB-induced apoptosis of HaCaT cells. This protective effect can be explained by the scavenging of ROS and the suppression of COX-2 expression by interaction with the MAPK and Akt signaling pathways. Furthermore, we used Celecoxib as a positive control, and results showed that Cyanidin-3-O-glucoside was more effective at decreasing EGFR phosphorylation than Celecoxib, which translated into a stronger inhibitory effect against the downstream elements p38, ERK, and JNK. Taken together, these results indicate that Cyanidin-3-O-glucoside can protect HaCaT cells against UVB radiation, which could provide a basis for the development of a potent nutritional therapy for UVB-induced skin disorders.

Influence of fruit juice processing on anthocyanin stability

Anthocyanins are quality determining compounds in red fruits and their corresponding juices. The fate of anthocyanins during production of juices is determined by countless factors and all of these need to be taken into consideration to optimize juice processes. Storage and pre-press procedures like freezing and thawing may influence the fruit's integrity and accordingly affects the extraction of valuable components during the subsequent mashing and pressing. Conventional thermal or novel non-thermal treatments to ensure microbial safety have both positive and negative effects on the anthocyanins. By inactivation of oxidizing enzymes, profiles and quantities of anthocyanins may be maintained, but more severe conditions may have adverse effects. To improve juice extraction and to increase yield, enzyme-assisted degradation of the cell walls is conducted. The applied enzyme preparations contain numerous side activities which also may degrade anthocyanins. Clarification and concentration will further reduce the final anthocyanin concentrations. Many studies have been published regarding evaluating individual fruits or single processing steps but, obviously, these results are not necessarily transferable. Accordingly, this review aims to summarize all relating studies comprehensively to the fate of anthocyanins during juice processing giving an overview of underlying mechanisms as well as the chemical and analytical background.

Sonodegradation of cyanidin-3-glucosylrutinoside: degradation kinetic analysis and its impact on antioxidant capacity in vitro

BACKGROUND

As an alternative preservation method for thermal treatment, ultrasound comprises a novel non-thermal processing technology that can significantly avoid undesirable nutritional changes. However, the recent literature indicates that anthocyanin degradation occurs when ultrasound is applied in juice at high amplitude parameters. Such work has mainly focussed on the effect of ultrasound on stability, the antioxidant capacity of cyanidin-3-glucosylrutinoside (Cy-3-glc-rut) and the correlation between anthocyanin degradation and ·OH generation in a simulated system.

RESULTS

The spectral intensities of Cy-3-glc-rut at 518 and 282 nm decreased with increasing ultrasound power and treatment time. The degradation of Cy-3-glc-rut was consistent with first-order reaction kinetics (r²  > 0.9000) and there was a good linear correlation between anthocyanin degradation and hydroxyl radical formation induced by ultrasound (r²  = 0.9258). Moreover, a decrease in the antioxidant activity of Cy-3-glc-rut after ultrasound evaluated by the 1,1-diphenyl-2-picrylhydrazyl and ferric reducing antioxidant power methods was observed.

CONCLUSION

Overall, the results of the present study show that ultrasound will accelerate the degradation of Cy-3-glc-rut with the growth of power over time. © 2016 Society of Chemical Industry.

Fate of Anthocyanins through Cocoa Fermentation. Emergence of New Polyphenolic Dimers

Fresh, ripe cocoa beans from Cameroon (German cocoa/Amelonado group and ICS 40/Trinitario group) were subjected to fermentation-like incubations in acetic acid, lactic acid, or both and to natural fermentation. Two naturally fermented samples from Cuba (UF 654/Trinitario group and C 411/Criollo group) were also investigated. Both cyanidin-3-galactoside and cyanidin-3-arabinoside (found as major anthocyanins in colored beans only) were drastically degraded through fermentation, especially in small beans and in the presence of acetic acid. On the other hand, emergence of a cyanidin-rhamnose isomer was evidenced, even in Criollo beans. In addition to the recently described structures F1 and F2 [m/z = 575 in ESI(-)], three additional polyphenolic structures [F3, F4, and F5; m/z = 557 in ESI(+)] were found after fermentation, the two former ones resulting from epicatechin oxidation. Synthesis of F5 requires an interclass reaction between cyani(di)n and epicatechin, which explains its absence in fermented Criollo beans.

Cyanidin-3-O-Glucoside Protects against 1,3-Dichloro-2-Propanol-Induced Reduction of Progesterone by Up-regulation of Steroidogenic Enzymes and cAMP Level in Leydig Cells

1,3-Dichloro-2-propanol (1,3-DCP) is a food processing contaminant and has been shown to perturb male reproductive function. Cyanidin-3-O-glucoside (C3G), an anthocyanin antioxidant, is reported to have protective effects on many organs. However, it remains unclear whether C3G protects against chemical-induced reproductive toxicity. The present study was therefore to investigate the intervention of C3G on 1,3-DCP-induced reproductive toxicity in R2C Leydig cells. Results demonstrated that C3G inhibited the 1,3-DCP-induced cytotoxicity and cell shape damage with the effective doses being ranging from 10 to 40 μmol/L. In addition, 1,3-DCP (2 mmol/L) exposure significantly increased the ROS level and mitochondrial membrane potential damage ratio, leading to a decrease in progesterone production, while C3G intervention reduced the ROS level, and increased the progesterone production after 24 h treatment. Most importantly, C3G intervention could up-regulate the cyclic adenosine monophosphate (cAMP) level and protein expression of steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase. It was concluded that C3G is effective in reducing 1,3-DCP-induced reproductive toxicity via activating steroidogenic enzymes and cAMP level.

Protective Effect of Cyanidin-3-O-Glucoside against Ultraviolet B Radiation-Induced Cell Damage in Human HaCaT Keratinocytes

Ultraviolet radiation is the major environmental harmful factor that has emotional impact on human skin. The aim of the present study was to determine the mechanism of protection of cyanidin-3-O-glucoside against ultraviolet B (UVB)-induced damage to human HaCaT keratinocytes. Our results show that cyanidin-3-O-glucoside decreased the levels of intracellular reactive oxygen species generated by UVB treatment. Cyanidin-3-O-glucoside also decreased the UVB-augmented levels of the DNA damage indicators phospho-p53 and phospho-ATM/ATR. In addition, cyanidin-3-O-glucoside protected keratinocytes from UVB-induced injury by overturning the disruption of mitochondrial membrane potential and reversing apoptosis. The expression of anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) was attenuated in UVB-exposed cells but restored in UVB/cyanidin-3-O-glucoside-treated cells. Furthermore, expression of the proapoptotic proteins Bcl-2-associated X (Bax) and the key apoptosis executer cleaved caspase-3 were increased in UVB-irradiated cells and decreased in UVB/cyanidin-3-O-glucoside-treated cells. For these reasons, the results demonstrate that cyanidin-3-O-glucoside protects human keratinocytes against UVB-induced oxidative stress and apoptosis. Our study provides a theoretical basis for the use of cyanidin-3-O-glucoside in the fight against light damage.

Stability, Antioxidant Capacity and Degradation Kinetics of Pelargonidin-3-glucoside Exposed to Ultrasound Power at Low Temperature

As an alternative preservation method to thermal treatment, ultrasound is a novel non-thermal processing technology that can significantly avoid undesirable nutritional changes. However, recently literature indicated that anthocyanin degradation occurred when high amplitude ultrasound was applied to juice. This work mainly studied the effect of ultrasound on the stability and antioxidant capacity of pelargonidin-3-glucoside (Pg-3-glu) and the correlation between anthocyanin degradation and •OH generation in a simulated system. Results indicated that the spectral intensities of Pg-3-glu decreased with increasing ultrasound power (200–500 W) and treatment time (0–60 min). The degradation trend was consistent with first-order reaction kinetics (R² > 0.9100). Further study showed that there was a good linear correlation between Pg-3-glu degradation and •OH production (R² = 0.8790), which indicated the important role of •OH in the degradation of anthocyanin during ultrasound exposure. Moreover, a decrease in the antioxidant activity of solution(s) containing Pg-3-glu as evaluated by the DPPH and FRAP methods was observed after ultrasound treatment.

Anthocyanins degradation during storage of Hibiscus sabdariffa extract and evolution of its degradation products

Degradation parameters of two main anthocyanins from roselle extract (Hibiscus sabdariffa L.) stored at different temperatures (4-37°C) over 60days were determined. Anthocyanins and some of their degradation products were monitored and quantified using HPLC-MS and DAD. Degradation of anthocyanins followed first-order kinetics and reaction rate constants (k values), which were obtained by non-linear regression, showed that the degradation rate of delphinidin 3-O-sambubioside was higher than that of cyanidin 3-O-sambubioside with k values of 9.2·10(-7)s(-1) and 8.4·10(-7)s(-1) at 37°C respectively. The temperature dependence of the rate of anthocyanin degradation was modeled by the Arrhenius equation. Degradation of delphinidin 3-O-sambubioside (Ea=90kJmol(-1)) tended to be significantly more sensitive to an increase in temperature than cyanidin 3-O-sambubioside (Ea=80kJmol(-1)). Degradation of these anthocyanins formed scission products (gallic and protocatechuic acids respectively) and was accompanied by an increase in polymeric color index.

Effect of Temperature on Acidity and Hydration Equilibrium Constants of Delphinidin-3-O- and Cyanidin-3-O-sambubioside Calculated from Uni- and Multiwavelength Spectroscopic Data

Delphinidin-3-O-sambubioside and cyanidin-3-O-sambubioside are the main anthocyanins of Hibiscus sabdariffa calyces, traditionally used to make a bright red beverage by decoction in water. At natural pH, these anthocyanins are mainly in their flavylium form (red) in equilibrium with the quinonoid base (purple) and the hemiketal (colorless). For the first time, their acidity and hydration equilibrium constants were obtained from a pH-jump method followed by UV-vis spectroscopy as a function of temperature from 4 to 37 °C. Equilibrium constant determination was also performed by multivariate curve resolution (MCR). Acidity and hydration constants of cyanidin-3-O-sambubioside at 25 °C were 4.12 × 10(-5) and 7.74 × 10(-4), respectively, and were significantly higher for delphinidin-3-O-sambubioside (4.95 × 10(-5) and 1.21 × 10(-3), respectively). MCR enabled the obtaining of concentration and spectrum of each form but led to overestimated values for the equilibrium constants. However, both methods showed that formations of the quinonoid base and hemiketal were endothermic reactions. Equilibrium constants of anthocyanins in the hibiscus extract showed comparable values as for the isolated anthocyanins.

Gallic acid as a protective antioxidant against anthocyanin degradation and color loss in vitamin-C fortified cranberry juice

The objective of this study was to evaluate different antioxidants for anthocyanin (ACY) retention in vitamin C fortified cranberry juice and assess its quality. Cranberry juice was fortified with 40-80mg/100mL vitamin C and added hesperidin, catechin, and gallic acid at different concentrations. Juice was pasteurized at 85°C for 1min and stored at 23°C for 16days. ACYs, vitamin C, color intensity, and browning index (BI) were evaluated at 2-day intervals. Gallic acid was found to be the most effective antioxidant against ACYs degradation and significantly (p<0.05) increased red color intensity by 37% and ACY concentration by 41%, compared to the control. After 16-day storage, the BI of gallic acid-added juice was significantly lower (0.80 vs 1.00) than the control juice. The outcome of this research provided a potential solution of using gallic acid to preserve a health-beneficial component (ACYs), and endogenous red color in cranberry juice.

Influence of rutin and ascorbic acid in colour, plum anthocyanins and antioxidant capacity stability in model juices

Model juices at pH 3.7 were prepared with different combinations of ascorbic acid, rutin (quercetin 3-rutinoside) and concentrated anthocyanin extract of plums (cv. Black Gold). The anthocyanins in the concentrated extract were cyanidin 3-glucoside and cyanidin 3-rutinoside, in a proportion of 76% and 24% respectively. The model juices were stored during 17 weeks in darkness at 20 °C. The colour stability was improved by the presence of rutin and strongly damaged by the ascorbic acid. The fortification of anthocyanin model juices with ascorbic acid originated the degradation of most of anthocyanins. However, anthocyanins improved ascorbic acid stability during storage. The copigmentation of anthocyanin and rutin showed a beneficial effect on colour stability from the 5 weeks of storage. In model juices prepared exclusively with purified plum extract a high correlation (R(2)=0.881) between anthocyanins and antioxidant capacity was found.

The identification of degradation products and degradation pathway of malvidin-3-glucoside and malvidin-3,5-diglucoside under microwave treatment

Understanding the degradation of anthocyanins (Acys) during microwave treatment is required for the application of this novel technology to fruit and vegetable processing. The pH 3.5 buffer solutions containing 50mg/l malvidin-3-glucoside (Mv-3-glu) and malvidin-3,5-diglucoside (Mv-3,5-diglu), respectively, were treated with microwaves at 700 W. In comparison, the samples were heated at 98±2 °C in a water bath. In total, nine degradation products were detected (using LC-UV/Vis-MS/MS) for each Acys after microwave treatment. Anthocyanone A, hydroxycoumarins and dihydroxy phenylacetaldehyde were characterised as the main degradation products of both Acys under microwave conditions, which were not detected in the thermal treatment. In addition, syringic acid, 2,4,6-trihydroxybenzaldehyde, coumarin glucosides and 2,6-dimethoxyphenol were found simultaneously under the microwave and thermal treatments. During the microwave treatment, hydrogen peroxide was formed and resulted in the Baeyer-Villiger-type oxidation of the Acys, which was the main degradation pathway. At the same time, the conventional thermal degradation pathway of Acys also occurred.

Degradation kinetics of malvidin-3-glucoside and malvidin-3,5-diglucoside exposed to microwave treatment

Understanding the factors that contribute to the degradation of bioactive compounds during microwave treatment is meaningful for the practical application of this novel technology. The influence of microwave power, energy density, temperature, pH value, and initial concentration of anthocyanins (Acys) on the degradation behavior of malvidin-3-glucoside (Mv-3-glu) and malvidin-3,5-diglucoside (Mv-3,5-diglu) was investigated in this study. Results showed that the degradation of both Acys was accelerated with the increase of microwave power, energy density, temperature, pH value, and initial concentration of Acys. The degradation process of both Acys followed the first-order kinetics model (R² > 0.94), whereas the relationship between Acys degradation and energy density fitted to the logistic model well (R² > 0.98). In addition, Mv-3-glu was more susceptible to the microwave treatment than Mv-3,5-diglu. Compared with heating in a 98 ± 2 °C water bath, both Acys degraded more rapidly under microwave treatment at 100 °C, indicating the occurrence of microwave effect. The results provide a guide for the scientific application of microwave treatment.