Stability of anthocyanins extracted from grape skins

Anthocyanins concentration by adsorption onto chitosan and alginate beads: Isotherms, kinetics and thermodynamics parameters

The anthocyanins health benefits are diverse, but numerous factors affect the anthocyanins stability, thus, this work aimed to extract anthocyanins from Pinot Noir grape skins and, afterward, to concentrate them onto edible and safety adsorbents, chitosan and alginate beads, by adsorption operation. Chitosan was obtained from shrimp waste, and alginate was purchased. Batch adsorption experiments were carried out as pH function, and the highest adsorption capacities and removal percentages were, respectively, 216 mg g^-1 and 65% for chitosan beads at pH 8, and 126.4 mg g^-1 and 38% for alginate beads at pH 4. All equilibrium isotherms models were suitable for chitosan beads, while for alginate beads only Langmuir and Freundlich models showed fitting. The thermodynamic parameters demonstrated physical adsorption and endothermic behavior for the chitosan and alginate beads. The pseudo-first order model best described the kinetic behavior for both beads. It was demonstrated that is possible to concentrate the different molecular structures of anthocyanins onto chitosan and alginate beads with high yields.

Copigmentation of Malvidin-3-O-Monoglucoside by Oenological Tannins: Incidence on Wine Model Color in Function of Botanical Origin, pH and Ethanol Content

The effect of the botanical origin, pH level and ethanol content of different oenological tannins on the color of malvidin-3-O-monoglucoside solution, including their effectiveness as copigments, was studied. Briefly, a model wine solution (4 g/L of tartaric acid, pH 3.5 and 12% ethanol) containing 50 mg/L of malvidin-3-O-monoglucoside was prepared and supplemented with 0.1, 0.2 and 0.4 g/L of commercial tannins using (−)-epicatechin as reference control copigment. Six additional model wine solutions (12% ethanol at pH 3.1, 3.5 or 3.9, and 10%, 12% or 14% ethanol at pH 3.5) were prepared as previously described. Samples were stored under airtight conditions. After a week the full absorbance spectrum in the visible range (400–800 nm) was measured and CIELAB color space was determined. These measurements, including an increase in a* (redness), a decrease in b* (yellowness) and a decrease in L* (lightness), indicated that all oenological tannins had a clear positive effect on color copigmentation. Moreover, hydrolysable tannins appeared to be better copigments than condensed tannins as the copigmentation effectiveness (Cp) was found to be between two to four times higher. The effects of these tannins were dose-dependent because a higher addition resulted in a greater impact on copigmentation. In general, an increase in pH and ethanol content resulted in a decrease of the effect of tannins on color. Independent of intrinsic wine conditions, hydrolysable tannins, more specifically gallotannin, remain the most effective in increasing red wine color. These results prove that supplementation with oenological tannins, especially hydrolysable tannins, could be an interesting tool for the improvement of the red wine color.

Storage Temperature Impacts on Anthocyanins Degradation, Color Changes and Haze Development in Juice of "Merlot" and "Ruby" Grapes (Vitis vinifera)

This study evaluated the degradation kinetics of selected anthocyanins and the change in polymeric color, browning index, and haze development of grape juices from “Merlot” and “Ruby” grape cultivars stored at 5, 25, and 35°C for up to 360 days. Five major anthocyanins namely malvidin-3-O-glucoside (M3G), delphinidin-3-O-glucoside (D3G), petunidin-3-O-glucoside (Pt3G), peonidin-3-O-glucoside (Pn3G), and cyanidin-3-O-glucoside (C3G) were identified. Juice from “Merlot” had significantly higher (p < 0.05) content of all individual anthocyanins as compared to “Ruby.” During the long-term storage, total, and individual anthocyanins from both cultivars degraded following first-order reaction kinetics at the rate strongly dependent on temperature. At the end of the storage, noticeably higher loss of anthocyanins (95–99.9%) was observed at 25 and 35°C as compared to storage at 5°C [50–60% (“Merlot”); 74–81% (“Ruby”)]. Considerably lower rate of decay was observed at 5°C (k = 0.01–0.04) as compared to 25 (k = 0.04–0.14) and 35°C (k = 0.05–0.14) storage temperatures. The most temperature sensitive anthocyanin compounds were C3G (E_a = 66.5 kJ/mol) and D3G (E_a = 63.3 kJ/mol). At higher storage temperatures, significant (p < 0.05) and strong negative correlations were observed between anthocyanin concentrations and the levels of haze, polymeric and brown color development during storage. Storing grape juice, at lower temperature conditions could reduce the continuous loss of biologically active anthocyanins as well as the development of haze and brown color.

Optimization of extraction and microencapsulation of bioactive compounds from red grape (Vitis vinifera L.) pomace

Grape (Vitis vinifera L.) pomace constitutes a promising source of phenolic compounds, gallic acid, flavan-3-ols, flavonoids, stilbene and anthocyanins that are beneficial for human health. The objectives of this study were to optimize the extraction and microencapsulation of red grape pomace. Central composite designs with two factors were conducted for optimization using response surface methodology. The temperature (45-85 °C), and the time (2-8 h) were designed for the extraction. The results indicated that the extraction temperature and time introduced the increasing the extraction yield, total phenolic content, anthocyanin and resveratrol, but the long extraction time reduced the tannin content. The results showed that the optimize condition was the extraction at 80 ± 1 °C for 2 h 53 min. This provided the highest content of polyphenolic compounds. The next experiment was microencapsulation of the extract which studied the amounts of maltodextrin (7-28 % w/v) and carboxymethylcellulose (CMC) (0-1.4 % w/v). The results showed that the optimized microencapsulation used 10.21 % w/v maltodextrin and 0.21 % w/v CMC to maximize all polyphenolic compounds, and also to minimize bitterness and astringency. This study illustrated that the optimal conditions for extraction and microencapsulation of the red grape extract have a high potential to produce functional ingredients.

Changes of polyphenols, sugars, and organic acid in 5 Vitis genotypes during berry ripening

The concentrations of sugars, organic acids, and polyphenols during berry ripening in 5 grape genotypes were analyzed using HPLC and HPLC-MS to determine which were correlated. Veraison is critical stage during grape berry development, and marks the beginning of ripening. Glucose and fructose accumulated sharply in a 1: 1ratio, though the concentration of fructose was slightly higher than that of glucose at maturation. Malic acid and tartaric acid were the dominant organic acids, and they decreased rapidly during berry ripening. The 5 cultivars contained 28 anthocyanins and 8 other polyphenols. All anthocyanins accumulated and were positively correlated with the sugars and negatively correlated with the organic acids. Hydroxycinnamic acids declined and were positively correlated with anthocyanin contents. Changes in flavanols and flavonols different among the 5 genotypes, with flavonols positively correlated with anthocyanin content, but the flavanols procyanidin B1and epicatechin negatively correlated with anthocyanins content. There were obvious differences in patterns of change of polyphenols among 5 grape genotypes.

PRACTICAL APPLICATION

The results could be used for improving grape berry quality during ripening and developing a comprehensive database of primary and secondary metabolites in the Vitis for grape breeding.

Effect of temperature and some added compounds on the stability of blood orange marmalade

Jams and marmalades are often wrongly believed to be stable products, as the degradation of pigments such as anthocyanins, browning reactions, and the formation of sugar degradation products may occur during storage. The paper aims at studying some of the degradation reactions occurring in blood orange marmalade stored at 20 °C and 35 °C. The addition of natural (tea extract) and naturally occurring (ascorbic acid, cysteine, gallic acid) compounds to marmalade was addressed at investigating the possible effect on retarding such phenomena. Results highlight the dependence of anthocyans and 5-hydroxymethyl-2-furaldehyde (HMF) levels on the storage temperature. Marmalades added with cysteine, unlike the samples added with phenol compounds, showed higher anthocyans and lower HMF levels just after processing, together with a reduced anthocyan loss kinetics and a slowdown of HMF formation during storage at both temperatures.

PRACTICAL APPLICATION

Transformation of blood oranges into marmalade represents an alternative to fresh market in periods when the high availability of the citrus causes the collapse of prices. Blood orange marmalade is characterized by a high nutritional value, however, it is not widely distributed yet. Its storability is limited by color and organoleptic changes that influence consumers' acceptance. The optimization of blood orange marmalade preparation could help producers improve storability and widen distribution.

Anthocyanins and their variation in red wines I. Monomeric anthocyanins and their color expression

Originating in the grapes, monomeric anthocyanins in young red wines contribute the majority of color and the supposed beneficial health effects related to their consumption, and as such they are recognized as one of the most important groups of phenolic metabolites in red wines. In recent years, our increasing knowledge of the chemical complexity of the monomeric anthocyanins, their stability, together with the phenomena such as self-association and copigmentation that can stabilize and enhance their color has helped to explain their color representation in red wine making and aging. A series of new enological practices were developed to improve the anthocyanin extraction, as well as their color expression and maintenance. This paper summarizes the most recent advances in the studies of the monomeric anthocyanins in red wines, emphasizing their origin, occurrence, color enhancing effects, their degradation and the effect of various enological practices on them.

CIELAB coordinates in response to berry skin anthocyanins and their composition in Vitis

Berry skin color OIV index, anthocyanin composition, and content of 78 grape cultivars were surveyed using a CIELAB system and high-performance liquid chromatography (HPLC)-mass spectrometry (MS) coupled with photodiode array detection. There were high correlations between L*, b*, and color, while a* was not a representative parameter. L* and b* values declined as berry skin color OIV became darker, and a* increased as berry skin color OIV became darker in pink and red grape cultivars only. The composition and content of anthocyanins varied widely among the cultivars. Total anthocyanins and types of anthocyanins were significantly correlated with color OIV parameters. Through multiple linear regression analysis, cyanidin derivatives had a positive effect on values of L* and b*. Delphinidin derivatives had positive effects on the value of a*. The CIELAB system gave good results for differentiation of grape berry skin color OIV.

Loss of anthocyanins in red-wine grape under high temperature

To determine the mechanism of inhibition of anthocyanin accumulation in the skin of grape berries due to high temperature, the effects of high temperature on anthocyanin composition and the responses in terms of gene transcript levels were examined using Vitis vinifera L. cv. Cabernet Sauvignon. High temperature (maximum 35 degrees C) reduced the total anthocyanin content to less than half of that in the control berries (maximum 25 degrees C). HPLC analysis showed that the concentrations of anthocyanins, with the exception of malvidin derivatives (3-glucoside, 3-acetylglucoside, and 3-p-coumaroylglucoside), decreased considerably in the berries grown under high temperature as compared with the control. However, Affymetrix Vitis GeneChip microarray analysis indicated that the anthocyanin biosynthetic genes were not strongly down-regulated at high temperature. A quantitative real time PCR analysis confirmed this finding. To demonstrate the possibility that high temperature increases anthocyanin degradation in grape skin, stable isotope-labelled tracer experiments were carried out. Softened green berries of Cabernet Sauvignon were cut and aseptically incubated on filter paper with 1 mM aqueous L-[1-(13)C]phenylalanine solution for 1 week. Thereafter, the changes in (13)C-labelled anthocyanins were examined under different temperatures (15, 25, and 35 degrees C). In the berries cultured at 35 degrees C, the content of total (13)C-labelled anthocyanins that were produced before exposure to high temperature was markedly reduced as compared with those cultured at 15 degrees C and 25 degrees C. These data suggest that the decrease in anthocyanin accumulation under high temperature results from factors such as anthocyanin degradation as well as the inhibition of mRNA transcription of the anthocyanin biosynthetic genes.