The production of yellow pigments from (+)-catechin and dihydroxyfumaric acid in a model wine system

The oxidation of tartaric acid by hydroxyl radicals, produced by gamma-irradiation of aqueous solutions of tartaric acid, was shown to generate dihydroxyfumaric acid. To confirm the importance of this oxidative degradation pathway in wine oxidation, dihydroxyfumaric acid was itself reacted with (+)-catechin in a wine-like solution and the yellow pigments formed were identified by liquid chromatography mass spectrometry (LC-MS) studies as xanthylium cations. The concentration of these pigments increased if the wine-like system also contained 0.6 mg/L copper(II). The results clearly demonstrate a link between the production of yellow xanthylium cation pigments from (+)-catechin and the degradation of tartaric acid by hydroxyl radicals.     

Influence of light exposure, ethanol and copper(II) on the formation of a precursor for xanthylium cations from tartaric acid

The production of xanthylium cation pigments was greatly increased when an aged, tartaric acid buffered, 12% (v/v) aqueous ethanol solution was used in a model white wine system. This suggested the formation of a precursor to the pigments during the ageing of the tartaric acid solution. On examining factors responsible for the generation of tartaric acid oxidation products in wine-like solutions it was observed that on exposure of samples to sunlight, glyoxylic acid, a known precursor to xanthylium cations, was produced. The production of glyoxylic acid was achieved in both the absence and presence of ethanol and copper(II). Hydrogen peroxide was also detected in these solutions. The results were consistent with the presence of glyoxylic acid in the aged tartaric acid buffered, 12% (v/v) aqueous ethanol solution that had frequent aeration and periodic exposure to sunlight throughout its storage. Studies on the role of hydrogen peroxide in the production of glyoxylic acid were also investigated. On the addition of hydrogen peroxide to tartaric acid solutions, with heating at 45°C in darkness, glyoxylic acid was only determined in solutions without ethanol.     

Xanthylium salts formation involved in wine colour changes

Summary The reaction of (+)-catechin in wine-like model solution was investigated. First appearance of colourless dimeric compounds consisting of two flavanol units linked by carboxy-methine bridge was observed. Their isolation and further incubation was found to yield two types of yellowish pigments showing visible absorption maxima at 440 and 460 nm, respectively. Mass spectroscopy (MS) spectral analysis showed that the first type were xanthylium salt pigments formed by dehydration of the colourless compounds followed by an oxidation process. The loss of a water molecule was shown to take place between two A ring hydroxyl groups of the colourless dimers. The second type were shown to be ester derivatives of the first ones. Thus ethylester of xanthylium salt was obtained and fully characterized by mass and nuclear magnetic resonance (NMR) spectroscopy. Esterification was found to involve the colourless compound before dehydration and thus a general scheme for xanthylium salt formation was postulated. The proposed scheme constitutes a new xanthylium formation pathway as up to now only anthocyanin-flavanol reactions were supposed to form xanthylium salt derivatives during wine ageing. This work also provides new support to the contribution of xanthylium salt in colour evolution observed during wine ageing which is generally expressed in an increase of absorption in the 400–500 nm, region of xanthylium salt absorption maxima.     

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.     

Light-induced changes in bottled white wine and underlying photochemical mechanisms

Bottled white wine may be exposed to UV-visible light for considerable periods of time before it is consumed. Light exposure may induce an off-flavor known as “sunlight” flavor, bleach the color of the wine, and/or increase browning and deplete sulfur dioxide. The changes that occur in bottled white wine exposed to light depend on the wine composition, the irradiation conditions, and the light exposure time. The light-induced changes in the aroma, volatile composition, color, and concentrations of oxygen and sulfur dioxide in bottled white wine are reviewed. In addition, the photochemical reactions thought to have a role in these changes are described. These include the riboflavin-sensitized oxidation of methionine, resulting in the formation of methanethiol and dimethyl disulfide, and the photodegradation of iron(III) tartrate, which gives rise to glyoxylic acid, an aldehyde known to react with flavan-3-ols to form yellow xanthylium cation pigments.     

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.     

红曲色素的色调及发酵工艺条件对色调的影响

用扫描式分光光度计对 3种纯红曲色素及板层析分离的色素进行分析 ,得出了其特征性吸收峰及对应波长。安卡红曲黄素 (黄色 ) ,红曲玉红素 (橙色 )分别在 388nm ,464nm ,而红斑玉红胺 (紫色 )在 51 6nm和 41 8nm 2处有吸收峰。复合色素的主吸收峰在 490～ 50 0nm处。此外 ,板层析上还有深黄和米黄等色素。红曲米的色调取决于多种色素的相对比例。红曲米的发酵工艺条件对色素的相对比例具有重要的影响。锌离子对红曲霉产色素具有促进作用。培养过程中添加醋酸不利红曲霉产生橙色素 ,而有利黄色素的产生。     

ETHANOL FERMENTATION OF VARIOUS RED RICES WITHOUT COOKING

With various red rices as raw material, fermentation without cooking was allowed to proceed at pH 4.0 and 30°C for 4 d for production of novel alcoholic beverages. Ethanol fermentation was achieved with various rice grains. In particular, uncooked wild-rice (Zizania aquatica) is reported now for the first time as being used for ethanol fermentation. The final concentration of ethanol achieved during fermentation was 8.8–9.3% (v/v). Rice wine made from aromatic red rice (Oryza sativa var. Indica, Tapol) had a wine-like red color. It was rich in a fruity aroma and had a characteristic sour taste, as revealed by organoleptic testing. Volatile substances formed have been analysed by gas chromatography. Rice wine made from black rice (Oryza sativa var. Indica) also had a wine-like red color and a sour taste. By contrast, rice wines made from red rice (Oryza sativa var. Japonica) and wild-rice were faintly yellow in color and had a sake-like and a somewhat green tea-like flavor, respectively. Although the red pigments of the aromatic red rice and black rice were solubilized during uncooked ethanol fermentation, the pigments of red rice and wild-rice were insoluble and not available as material for brewing of red-colored alcoholic beverages. Aromatic red rice appears to be a suitable material for the production of a wine-like alcoholic beverage.     

Wine bottle colour and oxidative spoilage: Whole bottle light exposure experiments under controlled and uncontrolled temperature conditions

Exposure of a Chardonnay wine to light from a mercury vapour lamp under controlled temperature conditions showed that colour enhancement was dependent on bottle colour. The increase in colouration was Antique Green < French Green < Arctic Blue < Flint, in agreement with the transmission characteristics of each bottle type. Xanthylium pigments were identified as one component contributing to the observed enhancement of colour. The presence of oxygen was shown to be a critical factor to initiate the formation of these xanthylium pigments during light exposure. Without temperature control, wine colour development was highest in Antique Green and lowest in Flint. This alternate order reflects the ability of the darker bottles to retain heat longer than lighter coloured ones as confirmed by surface temperature decay rates. Specific pigments contributing to the wine colour enhancement in uncontrolled temperature/light exposure experiments could not be identified, although tentative evidence was obtained for the presence of flavan-3-ol based compounds. The different bottle glass surfaces did not influence the rate of loss of dissolved oxygen or oxidation of ascorbic acid. The potential to develop the results obtained in this study to identify markers for light and/or temperature exposure of white wines is discussed.     

Enhancement of red wine colour by pre-fermentation addition of copigments

The effects of pre-fermentation additions of catechin and caffeic acid to musts were investigated. The cultivar Listan negro, a major red grape grown in the Canary Islands, was used for these studies. The addition of catechin at 120 mg/l resulted in only 10% enhancement in wine colour (AU at 520 nm) after fermentation, while caffeic acid, at the same level, enhanced the wine colour by 60%. These results appear to be the first report of such a significant increase in wine colour achieved by pre-fermentation treatments with natural grape constituents, supporting the view that red wine colour is generally limited by the levels of cofactors for copigmentation rather than by the level of anthocyanins alone. This demonstrates the importance of non-pigment composition in establishing red wine colour and the influence of initial must composition.     

ANTIOXIDANT ACTIVITY OF WHITE WINE EXTRACTS AND SOME PHENOLIC ACIDS TOWARD CORN OIL OXIDATION

The ability of white wine extracts and some phenolic acids to inhibit corn oil oxidation was evaluated by monitoring the absorbance at 234 nm and the p-anisidine value. Wine extracts, each at 120 mg/L total phenolics, were tested in corn oil stripped of tocopherols kept at 50C. Two extracts rich in phenolic acids significantly inhibited oil oxidation, the most active being equivalent to butylated hydroxyanisol (BHA) at 200 mg/L. Moreover, four phenolic acids were tested in corn oil stripped of tocopherols kept at 50C and in edible corn oil kept at 110C. Gallic acid and caffeic acid, each at 80 mg/L, appeared to be stronger antioxidants than BHA at 200 mg/L. The present results indicate that some white wine phenolics, such as phenolic acids, may be strong antioxidants in corn oil. Moreover, the antioxidant activity of gallic acid and caffeic acid indicates their potential application in corn oil.

PRACTICAL APPLICATIONS

The antioxidant activity of white wine phenolic extracts toward corn oil oxidation and the characterization of active phenolic compounds may be useful in developing nutrient antioxidants for corn oil. Moreover, the antioxidant activity of gallic acid and caffeic acid indicates their potential application in corn oil.     

Identification of Candidate Amino Acids Involved in the Formation of Blue Pigments in Crushed Garlic Cloves (Allium sativum L.)

ABSTRACT:  The color-forming ability of amino acids with thiosulfinate in crushed garlic was investigated. We developed reaction systems for generating pure blue pigments using extracted thiosulfinate from crushed garlic and onion and all 22 amino acids. Each amino acid was reacted with thiosulfinate solution and was then incubated at 60 °C for 3 h to generate pigments. Unknown blue pigments, responsible for discoloration in crushed garlic cloves ( Allium sativum L.), were separated and tentatively characterized using high-performance liquid chromatography (HPLC) and a diode array detector ranging between 200 and 700 nm. Blue pigment solutions exhibited 2 maximal absorbance peaks at 440 nm and 580 nm, corresponding to yellow and blue, respectively, with different retention times. Our findings indicated that green discoloration is created by the combination of yellow and blue pigments. Eight naturally occurring blue pigments were separated from discolored garlic extracts using HPLC at 580 nm. This suggests that garlic discoloration is not caused by only 1 blue pigment, as reported earlier, but by as many as 8 pigments. Overall, free amino acids that formed blue pigment when reacted with thiosulfinate were glycine, arginine, lysine, serine, alanine, aspartic acid, asparagine, glutamic acid, and tyrosine. Arginine, asparagine, and glutamine had spectra that were more similar to naturally greened garlic extract.     

Effect of copper on oxidation of (+)-catechin in a model solution system

Summary Autoxidation of ( +)‐catechin in a model solution system, containing cupric ions, was monitored by high‐performance liquid chromatography with diode array detection. The rate of (+)‐catechin oxidation and the extent of browning increased with the copper concentration, showing an effect of copper on browning of flavanols. The progression of the reaction showed that the appearance of new compounds, which were initially absent in the mixture, was concomitant with (+)‐catechin decrease. Numerous reaction products, including both colourless compounds and pigments absorbing at 440, 460 and 550 nm, were detected. Among the colourless derivatives, four dimeric compounds, consisting of two catechin units linked by a carboxymethine bridge, were detected. Their formation involved the condensation of flavanols, mediated by glyoxylic acid, following a mechanism similar to that previously observed with iron. The yellowish compounds that were detected were identified as xanthylium salts and their corresponding esters, showing absorption maxima at 440 and 460 nm, respectively. Comparison of the results obtained with those reported with iron showed that copper ions play similar roles in enhancing the oxidation rate of (+)‐catechin and flavanols.     

聚乙烯醇比浊法测定柠檬酸液中的硫酸根离子

基于聚乙烯醇(PVA)比浊法研究并建立了柠檬酸溶液中硫酸根离子的分析方法,探讨了检测波长、柠檬酸浓度和聚乙烯醇浓度对硫酸钡分散体系的影响。研究表明,聚乙烯醇可提高柠檬酸液中硫酸钡颗粒的形成速率以及分散体系的稳定时间。检测波长为440 nm,聚乙烯醇浓度为1.0 g/L时,低于3.0%的柠檬酸溶液中,硫酸根离子的线性范围为2-24 mg/L,线性方程为A=0.010 6C-0.018 3(A和C分别为吸光度和硫酸根离子质量浓度,R2=0.9976)。分析方法的重复性RSD为0.73%,加标回收率为97.5%-102.9%。此分析方法快速、简便,可准确分析柠檬酸液中的硫酸根离子。     

羽衣甘蓝叶片色素的基本特性及其稳定性研究

在提取纯化的基础上分析羽衣甘蓝叶片色素的基本特性及其稳定性。结果表明：羽衣甘蓝叶片色素为紫红色,极易溶于水等极性溶剂,在pH2.0 的水溶液中于540nm 波长下有最大吸收峰值。羽衣甘蓝叶片色素的颜色和吸光度受溶液pH 值变化的影响。在pH2.0 的水溶液中,羽衣甘蓝叶片色素的耐光性较好,但不耐受50℃以上的温度。酸味剂柠檬酸、苹果酸、乳酸,糖类物质蔗糖、葡萄糖、乳糖和表面活性剂SDS 对羽衣甘蓝叶片色素均有非常明显的增色与护色作用,使该色素的稳定性增强。但糖类物质会随着时间的延长(6d 以后),对色素的增色、护色作用逐渐减弱,并又逐渐出现减色作用。     

Effects of area,year and climatic factors on Barbera wine characteristics studied by the combination of 1H-NMR metabolomics and chemometrics

Barbera is one of the most common red grape in Italy, found in almost every region of the country. The widespread market of the corresponding wine deserves studies on its traceability and authenticity. To this end, the ¹H-NMR database of several wine metabolites was built using spectra recorded in a wine-like matrix containing ethanol and tartaric acid with pH precisely adjusted. The combination of ¹H-NMR metabolomics study and chemometrics (multivariate data analysis) is able to discriminate between samples of such a wine produced in three different areas of Piedmont. The influence of climatic factors on the wine characteristics has also been studied.     

Influence of wine phenolic compounds on viability and exopolysaccharide production by Pediococcus pentosaceus

Low molecular weight phenolic fractions of Cabernet Sauvignon (LMF-C) and Malbec (LMF-M) wines from Colalao del Valle, Tucuman, Argentina, were isolated and chemically characterized. The effect of these phenolic fractions on viability and exopolysaccharide production of Pediococcus pentosaceus E2p, a wine spoilage bacterium, was examined in synthetic wine-like medium. The concentration of phenolic acids detected in LMF-C was 47.28% higher than that determined in LMF-M. The presence of LMF-C and LMF-M at concentration four times higher than detected in wine, produce a decrease in viable cells from the inoculum of 3.01 and 3.65 Log cfu mL^?1, respectively, and sometimes a significantly decrease in exopolysaccharide release was detected for both fractions. Considering the current trend in the search of potential and effective antimicrobial agents for total or partial replacement of sulfites in the winemaking process, these results could be of great interest, even though that phenolic compounds can also add extra value to the final product, considering their recognized beneficial properties on human health.     

Protection of volatile esters and terpenes during storage of a white wine and a model wine medium by a mixture of N-acetyl-cysteine and caffeic acid

A mixture of N-acetyl-cysteine + caffeic acid, at 10 + 30 mg/L respectively, was tested as inhibitor of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by the mixture, at 1.25 + 3.75 to 10 + 30 mg/L, was tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. The mixture of N-acetyl-cysteine + caffeic acid restricted the decrease of these volatiles to a large extent. In the model medium, the mixture inhibited the decrease of the three volatiles in a dose dependent manner. It was active at any concentration tested. The present results indicate that mixture of N-acetyl-cysteine + caffeic acid, containing each compound at low concentration, may be taken into account as an effective inhibitor of the disappearance of volatile aroma in wines.     

Caffeic acid copigmentation of anthocyanins from Cabernet Sauvignon grape extracts in model systems

Caffeic copigmentation of anthocyanins from Cabernet Sauvignon grape extracts in model system and yoghurt model system was investigated, as well as the influence of copigmentation on the stability of these pigments. In the model system, the dependence of anthocyanin stability on added caffeic acid was evaluated at temperatures (4 ± 1 °C and 29 ± 3 °C) and in the presence or absence of light, at two pH values: 3.0 and 4.0; in the yoghurt model system, the stability of the anthocyanins was evaluated at 4 ± 1 °C in the dark. The half-life and percentage of color retention of the anthocyanins in all treatments was calculated. The spectrophotometric results (Δλ, ΔA) revealed that interaction occurred between the crude extract of anthocyanins and caffeic acid suggesting copigmentation. The addition of caffeic acid (1:1 w/v) significantly increased (p < 0.05) the stability of anthocyanins in both model and yoghurt systems. In the model system the temperature and presence of light significantly influenced the stability of anthocyanins (p < 0.05), where the highest values for half-life were obtained for anthocyanins with caffeic acid at pH 3.0, stored in the dark at a temperature of 4 ± 1 °C (6.930 h). In the yoghurt system the caffeic acid increased the half-life time of anthocyanins to 6673 h.     

白酒过滤助剂离子析出能力的研究

实验通过活性炭和硅藻土对自来水、反渗透水、乙醇（99.7%）、38%vol乙醇、原度酒样、成品酒样处理,分析不同溶液中离子的变化情况,并在大生产上进行验证。结果表明：活性炭处理时,析出钙、硫酸根离子比较明显,镁离子次之,对酒样香味物质影响较小;硅藻土处理析出离子相对较小。此研究对白酒过滤助剂的质量要求及其白酒后处理上具有一定的指导意义。