The effect of ascorbic acid on oxidative browning of white wines and model wines

The effects of ascorbic acid addition to white wines and model wines were either anti-oxidative or pro-oxidative, and depended, inter alia , on the duration of storage. Soon after its addition, ascorbic acid decreased the redox potential and brown colour of model wines and white wines. However, with time, these effects were reversed, and redox potential, SO₂ consumption and browning were greater in samples with added ascorbic acid. The point at which the net effect of ascorbic acid addition was to increase browning occurred earlier at higher SO₂ levels. Under a variety of accelerated (45®), or prolonged (ranging from three months to five years) storage conditions, the browning of model wines and white wines was invariably enhanced by ascorbic acid addition, and this enhancement took place whether or not SO₂ was present. The addition of SO₂ alone, rather than ascorbic acid alone or SO₂ plus ascorbic acid, appears to be the most effective and least expensive way of protecting white wine from browning during bottle conservation.     

Ascorbic acid and white wine production: a review of beneficial versus detrimental impacts

We review the use of ascorbic acid in winemaking and the benefits as well as the detrimental outcomes associated with its use. Initial discussion focuses on the antioxidant activity of ascorbic acid. The impact of the wine matrix and wine production practices, especially storage in bottle and oxygen ingress, on its antioxidant efficiency is discussed. The complementary roles of the antioxidant pair, ascorbic acid and sulfur dioxide, are presented. Thereafter, the ability of ascorbic acid to contribute to spoilage processes is covered. This includes both pro‐oxidant and non‐oxidative mechanisms induced by ascorbic acid that may lead to a reduced shelf life of white wine. Based on this review of scientific literature, the conditions most conducive to the beneficial impacts of ascorbic acid in wine are highlighted. Areas where lack of chemical knowledge still exists are identified for future research.     

Impact of ascorbic acid on the oxidative colouration and associated reactions of a model wine solution containing (+)−catechin,caffeic acid and iron

Background and Aims: The aim of this study was to examine the oxidative reactions and associated colouration changes relevant to white wine in a synthetic wine system consisting of different combinations of 200 mg/L caffeic acid, 150 mg/L (+)?catechin and 1000 mg/L ascorbic acid, in the presence of 1.5 mg/L iron(II). Method and Results: Reactions were monitored by UV/VIS, CIELab, LC‐DAD and LC‐MS techniques. When ascorbic acid was less than 90% depleted in samples, it induced yellow/green colouration but prevented brown colouration that would otherwise result from catechin‐ and caffeic acid‐derived yellow and red pigments. However, during the loss of ascorbic acid, in the presence of either catechin and/or caffeic acid, reactions were still occurring to ‘prime’ the system for rapid colour formation. When the ascorbic acid was more than 90% depleted, the samples with catechin and/or caffeic acid had an increased rate of brown colouration compared with those to which ascorbic acid was not added. Conclusions: This study demonstrates that ascorbic acid is an effective anti‐browning agent provided it persists in the wine after bottling, but if depleted, serious brown colouration ensues. Significance of the Study: Findings detailed in this report will provide useful guidelines for the more effective use of ascorbic acid as an anti‐browning agent in bottled wine.     

The influence of ascorbic acid on the composition, colour and flavour properties of a Riesling and a wooded Chardonnay wine during five years' storage

This paper presents the results from an investigation to assess the development of a Riesling and a wooded Chardonnay wine over five years. The wines were bottled either with or without added ascorbic acid and stored under controlled temperature and humidity conditions. Ascorbic acid addition to wine at bottling had little effect on wine aroma and flavour when the wines in this study had been in bottle for 6 months or less. For both wines, at bottle storage times of 3 years or more, addition of ascorbic acid at bottling resulted in wines with no difference in aroma or less oxidised and/or more fresh fruity aromas, even if all the ascorbic acid had been depleted at the time of assessment, compared to wines without addition of ascorbic acid at bottling. In terms of colour, for the Chardonnay wines, the effect of ascorbic acid addition at bottling assessed between two weeks and two years after bottling suggested that wines without addition were browner and had more overall colour intensity. For the Riesling wines, ascorbic acid addition had no significant effect on brownness and overall colour intensity although the Riesling wines with ascorbic acid were generally higher in yellow colour. The A₄₂₀ measurements, which are widely used to estimate the brown colour of wines, did not always appear to correlate with the brown scores obtained by visual assessment or colour measures by CIELAB when wines with and without ascorbic acid addition were compared together. For both wines, after three and five years storage, the concentration of the antioxidant sulfur dioxide was either little different or else slightly(statistically significantly) higher in wines to which ascorbic acid was added at bottling than those without addition.     

Copper(II)-mediated oxidation of (+)-catechin in a model white wine system

This study was undertaken to establish the role played by copper(II) in enhancing the rate of oxidation of flavanols. A model white wine system consisting of 12% (v/v) aqueous ethanol saturated with potassium hydrogen tartrate and adjusted to pH 3.2 was used to allow experimentation under well-defined conditions. (+)-Catechin was the oxidisable substrate and copper(II) concentrations up to 0.6 mg/L were employed. The model white wines were maintained at 45C to induce the browning process. Under these conditions an increase in absorbance at 440 nm occurred provided the copper(II) concentration was 0.3 mg/L or greater. The coloured species responsible for the increase in absorbance were identified as xanthylium cations, formed by linkage of two (+)-catechin molecules. Glyoxylic acid acted as the bridge between the phloroglucinol-type moiety of the (+)-catechin molecules. The production of the xanthylium cations was inhibited by ethanol and also by mannitol and the implications of these observations for a free-radical induced mechanism are discussed.     

Chemistry of copper in white wine: a review

Copper is one element in wine that has considerable notoriety. While current winemaking practice tends to minimise the amount of copper that results from vineyard and winery sources, the addition of copper(II), either as its sulfate or citrate, to remove sulfidic off‐odours may result in an elevated concentration in the finished (bottled) wine. Residual copper in white wine has been linked to oxidative and reductive spoilage processes, although the mechanisms are at times speculative. The presence of copper has been implicated in haze formation (copper casse) and linked to protein instability. More recent concerns include the coexistence of residual copper and hydrogen sulfide in wine stored under low oxygen conditions. The chemistry of copper is important in both white and red wine. While there are some overlapping issues, especially with respect to sulfidic off‐odours, both white and red wine display their own unique chemistry. Thus, this review describes the state of knowledge of copper in white wine, differentiating between evidence‐based claims and speculation. It also identifies areas of research that will provide a much clearer understanding of the role of copper in wine spoilage.     

UPC~2快速测定葡萄酒中抗坏血酸和异抗坏血酸含量研究

建立了超高效合相色谱法(Ultra Performance Convergence Chromatography,UPC2)分离和测定葡萄酒中抗坏血酸和异抗坏血酸的方法。超高效合相色谱(UPC2)技术集合超临界流体色谱(Supercritical Fluid Chromatography,SFC)和超高效液相色谱(Ultra Performance Liquid Chromatography,UPLCTM)的技术优点,流动相CO2为主体,0.1%磷酸甲醇为助溶剂。选用Waters BEH色谱柱,流速1.5 m L/min,检测波长为245 nm,方法检出限为2.0 mg/kg,定量限为6.0 mg/kg,线性范围为2.5~80.0 mg/L;加标回收率范围为93.2%~105.9%;相对标准偏差RSD为4.5%~9.8%,该方法操作便捷、检测速度快、准确性高、重复性好、节约成本,能够满足葡萄酒中抗坏血酸和异抗坏血酸的检测。      

Factors influencing the production and stability of xanthylium cation pigments in a model white wine system

The influence of various wine parameters on the production and stability of xanthylium cation pigments in a wine-like medium is reported. The xanthylium pigments have an absorbance maximum in the visible region at 440 nm that is close to the measured absorbance used by the wine industry to indicate the browning of wine (i.e. 420 nm). The results of this study show that iron is more efficient than copper in both the colouration and production of xanthylium cation pigments in wine-like solutions of tartaric acid and (+)-catechin. The non-flavonoid caffeic acid can inhibit the accumulation of the xanthylium cation pigments, despite the presence of metal ions, and also influence the stability of the pigment. Sunlight leads to a decrease in the concentration of xanthylium cation pigments while a temperature difference of 20 ^oC in the absence of light was observed to have little influence on concentration. The results suggest that the xanthylium cations are more likely to be a transitory species during white wine oxidation rather than accumulating pigments based on their instability with caffeic acid.     

Effect of ellagitannins,ellagic acid and volatile compounds from oak wood on the (+)‐catechin,procyanidin B1 and malvidin‐3‐glucoside content of model wines

Background and Aims: During ageing in oak barrels, wine undergoes changes because of the release of polyphenols and other molecules from wood. The aim of this study was to evaluate the influence of some oak wood‐derived volatile compounds, ellagic acid and oak wood extracts on the levels of (+)‐catechin, procyanidin B1 and malvidin‐3‐glucoside. Methods and Results: Phenolics and the oak wood derived volatile compounds studied were quantified by HPLC and by GC, respectively. Additionally, the new compounds formed in the solutions were characterised by their spectral properties. Ellagic acid and/or oak wood extracts slowed the decline in the levels of (+)‐catechin and procyanidin B1. In contrast, the decrease in malvidin‐3‐glucoside was more pronounced in the presence of ellagic acid and oak wood chip extracts. Furfural slowed (+)‐catechin degradation, while breakdown of malvidin‐3‐glucoside was slightly more pronounced in the presence of guaiacol, furfural, vanillin and eugenol. (+)‐Catechin, procyanidin B1 and malvidin‐3‐glucoside did not significantly affect the rate of the degradation of ellagitannins during the storage time studied. Finally, new HPLC peaks were detected in the solutions containing (+)‐catechin and ellagic acid, as well as with malvidin‐3‐glucoside with ellagic acid and oak wood extract. Conclusions: Malvidin 3‐glucoside and (+)‐catechin and procyanidin B1 presented distinct behaviours during time in the presence of volatile and non‐volatile compounds from oak wood. Significance of the Study: This work points out the importance of oak wood components in the degradation of anthocyanins and tannins, as well as the reactions that occur during the ageing of red wine.     

迷迭香酸在沙棘果酒中的应用研究

以沙棘果浆为原料,以不添加抗氧化剂、添加抗氧化剂迷迭香酸或二氧化硫进行果酒发酵。在发酵过程中和发酵结束后,通过DPPH法、水杨酸法和普鲁士蓝法测定果酒的抗氧化性。结果表明,添加迷迭香酸作为抗氧化剂替代二氧化硫,果酒的理化指标均在国标允许范围内,不会影响果酒发酵。3种方式发酵果酒清除DPPH·的能力大小顺序为迷迭香酸果酒（IC50=8.02 mg/mL）＞二氧化硫果酒（IC50=10.31 mg/mL）＞无添加抗氧化剂果酒（IC50=11.47 mg/mL）;清除·OH的能力大小顺序为迷迭香酸果酒（清除率99.31%）＞无添加抗氧化剂果酒（清除率98.83%）＞二氧化硫果酒（清除率98.67%）;还原力大小顺序为二氧化硫果酒＞迷迭香酸果酒＞无添加抗氧化剂果酒。     

Effect of pyruvic acid and ascorbic acid on stability of 3‐deoxyanthocyanidins

BACKGROUND: 3‐Deoxyanthocyanins are a rare class of plant pigments primarily found in sorghum and known to possess distinct chemical and bioactive properties. They have potential as natural food colourants. This work investigates how 3‐deoxyanthocyanin pigments react with pyruvic acid and their stability in the presence of ascorbic acid. RESULTS: Substitution at C‐5 was the major determinant of the mechanism of 3‐deoxyanthocyanidin complexation with pyruvic acid: hydroxyl substitution favoured cyclic condensation, whereas methoxyl substitution favoured oxidative ring contraction. Pure 3‐deoxyanthocyanidins generally showed poor stability in the presence of 500 mg L^?1 ascorbic acid at pH 2.0 and 3.2 but were stable at pH 5.0; pyruvic acid improved their stability at pH 2.0 and 3.2 and enhanced their colour intensity at pH 5.0. Crude sorghum pigment extract was very stable in the presence of ascorbic acid: 31% colour loss at pH 2.0; 1.9‐ and 1.3‐fold increases in colour intensity at pH 3.2 and 5.0 respectively. In contrast, red cabbage pigment lost 30–85% of its colour in the presence of ascorbic acid under the conditions used in the study. CONCLUSION: Crude sorghum pigments are very stable in the presence of ascorbic acid and may be useful as natural food colourants. Copyright © 2008 Society of Chemical Industry     

In situ measurement of white wine absorbance in clear and in coloured bottles using a modified laboratory spectrophotometer

In situ absorbance of visible light by white wine in bottles was determined with a modified spectrophotometer. A linear correlation was obtained between absorbance at 420 nm (A₄₂₀) measured in a cuvette (10 mm pathlength) and absorbance of that same wine measured in a 750 mL Flint bottle (colourless transparent glass). In addition, 5 types of coloured bottles, Emerald Green, Classic Green, French Green, Georgia Green and Cobalt Blue , also yielded strong correlations. A₄₂₀ of white wine in bottles of Antique Green or Amber glass could not be measured directly due to a strong absorbance of that wavelength by the glass. However, a strong correlation was established between measurement of A₄₂₀ (cuvette) and A₅₄₀ for white wine in Antique Green bottles and between A₄₂₀ (cuvette) and either A₅₄₀ or A₆₀₀ for white wine in Amber bottles. The method employed a standard UV-Visible spectrophotometer with an inexpensive modified sample port, and proved applicable to bottles with diameters ranging from 62 mm (375 mL capacity half bottles) up to 81 mm (750 mL capacity Burgundy bottles). In situ absorbance measurements plus subsequent chemical analysis and sensory assessment of a Chardonnay wine in Antique Green bottles showed that the method provided an estimate of oxidation in this white wine. Wine absorbance spectra over the full visible range were obtained in the Flint bottle. Measurements of the absorbance of visible light by the glass of empty bottles could also be obtained and used as a form of quality control for glass bottle manufacture.     

Synergism between lipoxygenase‐active soybean flour and ascorbic acid on rheological and sensory properties of wheat bread

BACKGROUND: The interaction between lipoxygenase‐active soybean flour (LOX) and ascorbic acid (AA), on colour, rheological and sensory properties of wheat bread was studied with the aim of reducing the applied quantity of additives in bread formulations. RESULTS: The ascorbic acid (0–500 ppm) and active soybean flour (0–1%) mixture improved bread‐crumb colour by lowering the yellow hue in a higher proportion than those expressed by the components alone, characterising a synergistic mechanism (?_b = 15.1? (1.7 × LOX) ? (0.5 × AA) ? (5.8 × LOX × AA), where ?_b represent the estimated value for the yellow hue parameter). No differences in flavour and porosity were seen between the samples. As supported by the instrumental methods, breads made with active soybean flour and ascorbic acid (LOX + AA) had whiter crumbs and were softer and springier than controls as assessed by a trained sensory panel. In summary, the combination of both active soybean flour and ascorbic acid showed synergism, promoting a greater bleaching effect than when used alone. CONCLUSION: These results suggest the potential use of active soybean flour as a synergistic ingredient in the substitution of artificial additives in bread making. Since the interaction on the bleaching response was not linear and active soybean flour showed a higher iron concentration (66.40 ± 4.23 µg g^?1) than non‐active soybean flour (52.30 ± 0.40 µg g^?1), more studies are warranted to establish the biochemical mechanisms involved in this interaction. Copyright © 2007 Society of Chemical Industry     

The role of corks in oxidative spoilage of white wines

The permeability of corks to oxygen was examined by comparing the level of browning and the concentration of the antioxidants, free and total sulfur dioxide and ascorbic and erythorbic acids in wines bottled and sealed with two cork types and stored in an atmosphere of either nitrogen, oxygen or air. Three different batches of corks that had been treated with peroxide during processing, representing one cork type, and a batch of corks that had been treated with chlorine during processing representing the second cork type, were taken for the study. In bottled wines stoppered with one of the peroxide-treated corks (Cork A), there was a higher level of browning and a greater loss of the antioxidants in those wines in bottles stored under oxygen and air than that in the wines in bottles stored under nitrogen, indicating that corks of this batch were permeable to oxygen. There was no significant difference in the loss of ascorbic and erythorbic acid or the level of browning from bottled wines stored under the three gases and sealed with the chlorine-treated corks (Cork C). For the other two peroxide-treated corks (Corks B and D), there was no significant difference in the level of browning or loss of the antioxidants from bottled wines stored under the three gases and sealed with Cork B, nor was there a significant difference in the level of browning or loss of free or total sulfur dioxide from bottled wines stored under the three gases and sealed with Cork D. From comparative data, it was evident that oxidation of the wines sealed with Corks B and D was due to compounds in the corks rather than oxygen permeation through the corks, or oxygen ingress at bottling. Because the bottles of wine selected for this study were from batches that had already exhibited sporadic oxidation, the results found are indicative, but not necessarily representative, of the properties of all peroxide- and chlorine-treated cork types used in the wine industry.     

Effects of reaction parameters on generation of volatile compounds from the Maillard reaction between L‐ascorbic acid and glycine

The formation of volatiles from the reaction between L‐ascorbic acid (ASA) and glycine (Gly) at different reaction parameters, such as temperature, time and pH, were reported and 20 different volatile compounds were identified using solid‐phase microextraction–gas chromatography–mass spectrometry (SPME‐GC‐MS). The results showed that the reaction parameters had the different effects on formation of volatiles, while the effect of pH was the most remarkable. When the initial solution pH was 4.5, the major volatiles were found to be furfural or derivatives of furan; while when pH ranged from 6.8 to 9.5, the major volatiles were found to be derivatives of pyrazines, including 2,5‐dimethyl‐pyrazine, 2‐ethyl‐5‐methyl‐pyrazine, trimethyl‐pyrazine, 3‐ethyl‐2,5‐dimethyl‐pyrazine and 2,3‐diethyl‐5‐methyl‐pyrazine. The quantity of 2,5‐dimethyl‐pyrazine and 2‐ethyl‐5‐methyl‐pyrazine reached the maximum when pH was 8.0. Finally, a possible reaction mechanism of ASA and Gly and the pathway for the formation of the various kinds of volatile products were proposed.