LC/MS/MS characterization of phenolic constituents in dried plums

Dried plums are known as a healthy food in the West and used as medicine in India. They have been characterized by high concentrations of phenolic compounds, which are believed to play a crucial role in protection against various age-related diseases. Liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) with four different conditions was used to analyze the phytochemicals in commercial dried plums. The major components were neochlorogenic acid and cryptochlorogenic acid. Forty minor components were characterized by their MS/MS spectra and LC retention time. Six of them are novel ester isomers formed by two caffeic acids and one quinic acid. The diagnostic fragmentation patterns of different phenolics are presented on the basis of electrospray ionization (ESI) MS/MS data of components in dried plums and fourteen authentic standards.     

Structural characterization of new malvidin 3-glucoside-catechin aryl/alkyl-linked pigments

The condensation reaction between malvidin 3-glucoside and catechin mediated by isobutyraldehyde, benzaldehyde, and isovaleraldehyde was conducted in model solutions at two pH values (1.5 and 3.2). The formation of new alkyl/aryl-linked adducts corresponding to the structures malvidin 3-glucoside-isobutylcatechin, malvidin 3-glucoside-benzylcatechin, and malvidin 3-glucoside-3-methylbutylcatechin was respectively observed from each aldehyde. The structural characterization of these new structures has been elucidated by 1D and 2D NMR, mass spectrometry, and UV-vis techniques. These new adducts showed the same lambda(max) in the visible region at 540 nm, which is bathochromically shifted 15 nm when compared with the original anthocyanin (lambda(max) = 525 nm).     

Analytical characterization of madeira wine

For a correct characterization of Madeira wine commercially available in the market, 52 samples having different types and ages, representative of the delimited region of Madeira (liquor wine of quality produced in delimited region), were analyzed in relation to physicochemical and sensorial parameters. Standard methodology for spirits and alcoholic beverages as well as a council of tasters were adopted respectively to quantify such parameters, according to European Union regulations. The main physicochemical parameters analyzed demonstrated that Madeira wine represent a high quality beverage without toxicological risks, as all constituents have in general contents clearly below the maximum concentration admissible by the national and/or international rules. A reasonable differentiation of properties could be achieved between samples having different types and ages, when principal component, discriminant and cluster analyses were applied to the analytical data, especially for physicochemical parameters.     

Characterization of pigments from different high speed countercurrent chromatography wine fractions

A red wine, made from Cabernet Sauvignon (60%) and Tannat (40%) cultivars, was fractionated by high speed countercurrent chromatography (HSCCC). The biphasic solvent system consisting of tert-butyl methyl ether/n-butanol/acetonitrile/water (2/2/1/5, acidified with 0.1% trifluoroacetic acid) was chosen for its demonstrated efficiency in separating anthocyanins. The different native and derived anthocyanins were identified on the basis of their UV-visible spectra, their elution time on reversed-phase high-performance liquid chromatography (HPLC), and their mass spectra, before and after thiolysis. The HSCCC method allowed the separation of different families of anthocyanin-derived pigments that were eluted in different fractions according to their structures. The hydrosoluble fraction was almost devoid of native anthocyanins. Further characterization (glucose quantification, UV-visible absorbance measurements) indicated that it contained flavanol and anthocyanin copolymers in which parts of the anthocyanin units were in colorless forms. Pigments in the hydrosoluble fraction showed increased resistance to sulfite bleaching and to the nucleophilic attack of water.     

Evolution and stability of anthocyanin-derived pigments during Port wine aging.

For three years, the evolution of the three major anthocyanidin monoglucosides (malvidin 3-glucoside, malvidin 3-acetylglucoside, and malvidin 3-coumaroylglucoside) and their anthocyanin-pyruvic acid adducts was monitored in Port wines stored in oak barrels. The degradation reactions of all pigments followed first-order kinetics in all the wines studied. The degradation rate constants of the anthocyanin-pyruvic acid adducts were much lower than those of the anthocyanidin monoglucosides. The results of both anthocyanins and pyruvic acid adducts show that acylation on the sugar moiety of all the pigments decreased their stability in wine. The levels of malvidin 3-glucoside-pyruvic acid adduct and its acylated forms increased right after wine fortification with wine spirit before starting to decrease around 100 days. The initial formation of anthocyanin-pyruvic acid adducts was concurrent with the degradation of anthocyanidin monoglucosides.     

MALDI-TOF MS characterization of glycation products of whey proteins in a glucose/galactose model system and lactose-free milk

The major modifications induced by thermal treatment of whey proteins α-lactalbumin (α-La) and β-lactoglobulin (β-Lg) in a model system mimicking lactose-free milk (L(-) sugar mix) were investigated by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). The analysis of the intact α-La revealed species with up to 7 and 14 adducts from lactose and sugar mix, respectively, whereas for β-Lg 3 and up to 5 sugar moieties were observed in the case of lactose and sugar mix experiments, respectively. A partial enzymatic hydrolysis with endoproteinase AspN prior to mass spectrometric analysis allowed the detection of further modifications and their localization in the amino acid sequence. Using α-cyano-4-chlorocinnamic acid as MALDI matrix, it could be shown that heating α-La and β-Lg with glucose or galactose led to the modification of lysine residues that are not glycated by lactose. The higher glycation degree of whey proteins in a lactose-free milk system relative to normal milk with lactose reflects the higher reactivity of monosaccharides compared to the parent disaccharide. Finally, the analysis of the whey extract of a commercial lactose-free milk sample revealed that the two whey proteins were present as three main forms (native, single, and double hexose adducts).     

Isolation and structures of oligomeric wine pigments by bisulfite-mediated ion-exchange chromatography.

Methods have been developed that are based on cation exchange chromatography in the absence and presence of excess bisulfite for the isolation of wine pigments from Australian red wine and grape marc extract. The pigments were identified using HPLC and electrospray ionization mass spectrometry. The mass spectral data indicate that these pigments are C4-substituted anthocyanins with a tetracyclic structure. The pigments form a series of closely related oligomeric pigments which include those previously described in the literature, such as pigment A and vitisin A, as well as some newly identified pigments.     

天然花青素提取物与壳聚糖明胶复合膜的制备和表征

为了开发天然的抗氧化活性包装材料,以紫甘蓝、黑米、玫瑰、蓝莓为原料制备天然花青素提取物与壳聚糖明胶的复合膜,比较分析了不同天然花青素提取物对复合膜的物理、机械、抗氧化活性及形貌结构的影响。结果表明：天然花青素提取物的加入,增加了膜的厚度,显著（P<0.05）影响膜的含水率、水溶性及外观形貌。壳聚糖明胶复合膜的水蒸汽透过率（water vapor permeability,WVP）为10.69×10-11 g/(m·s·Pa)。玫瑰花青素提取物的加入使得WVP值降低,而其他花青素提取物的加入使得WVP值增大。玫瑰复合膜的拉伸强度最大,达到27.03 MPa,断裂伸长率最小,黑米花青素提取物可增加复合膜的延展性,断裂伸长率最大为57.67%。傅里叶红外光谱表明天然花青素提取物的羟基基团与壳聚糖的氨基基团产生相互作用。扫描电镜结果表明花青素提取物影响微观结构,而且生物相容性较好。加入天然花青素提取物后,复合膜抗氧化活性均显著（P<0.05）提高,且玫瑰复合膜有着较高的抗氧化活性,1,1-二苯基-2-苦基肼（DPPH）自由基清除能力达到95.47%。结果表明：玫瑰花青素提取物更有利于开发阻湿性能好,水溶性低,抗拉伸和抗氧化活性高的包装材料,具有良好的应用前景。     

Screening for potential pigments derived from anthocyanins in red wine using nanoelectrospray tandem mass spectrometry

Red wine extracts were screened for potential wine pigments derived from anthocyanins, using a combination of nanoelectrospray tandem mass spectrometry techniques. Fourteen aglycons were considered to be of anthocyanidin origin on the basis of their MS/MS spectra. The proposed structures of the aglycons were anthocyanidin C-4 substituted with vinyl linkage between C-4 and the hydroxy group at C-5. The anthocyanidin derivatives identified in the wine extracts were vinyl, vinylmethyl, vinylformic acid, 4-vinylphenol, 4-vinylguaiacol, and vinylcatechin adducts of malvidin as well as vinylformic acid and 4-vinylphenol adducts of peonidin and petunidin. The presence of vinyl alcohol, 4-vinylcatechol, and 4-vinylsyringol adducts of malvidin was also proposed.     

Occurrence of pyranoanthocyanins in sparkling wines manufactured with red grape varieties

The anthocyanin pigments in rosé (Vitis vinifera cv. Garnacha) and blanc de noir (V. vinifera cv. Monastrell) base and sparkling wines were studied by LC-DAD/ESI-MS. Anthocyanins of grape origin and pyranoanthocyanins resulting from C-4/C-5 cycloaddition of the former ones with pyruvic acid, acetaldehyde, 4-vinylphenol, 4-vinylguaiacol, and 4-vinylcatechol were identified in the different wines. Rosé wines presented a higher total pigment content than blanc de noir wines. Pyranoanthocyanins represented 68.9-76.0% of total pigment content in rosé wines and 49.4-60.7% in blanc de noir wines. Malvidin 3-glucoside-pyruvate was the most abundant pigment in both rosé and blanc de noir base wines. Important qualitative and quantitative changes were observed in terms of the anthocyanin and pyranoanthocyanin pigments after the second (bottle) fermentation and 9 months of aging on yeast lees, but not after a further time (3-9 additional months) of aging on lees. Evaluation of the wine color characteristics was consistent with a greater color stability for the rosé sparkling wines that could be associated with the high content, structural diversity, and spectroscopic features of the pyranoanthocyanins present in these wines.     

Effect of wine inhibitors on free pineapple stem bromelain activity in a model wine system

The influence of potential inhibitors, naturally present in wine, on the activity of stem bromelain was investigated in order to evaluate the applicability of this enzyme for protein stabilization in white wine. Bromelain proteolytic activity was tested against a synthetic substrate (Bz-Phe-Val-Arg-pNA) in a model wine system after adding ethanol, sulfur dioxide (SO(2)), skin, seed, and gallic and ellagic tannins at the average range of their concentration in wine. All the inhibitors of stem bromelain activity tested turned out to be reversible. Ethanol was a competitive inhibitor with a rather limited effect. Gallic and ellagic tannins have no inhibitory effect on stem bromelain activity, while both seed and skin tannins were uncompetitive inhibitors. The strongest inhibition effect was revealed for sulfur dioxide, which was a mixed-type inhibitor for the enzyme activity. This study provides useful information relative to a future biotechnological application of stem bromelain in winemaking.     

Antioxidant action of glutathione and the ascorbic acid/glutathione pair in a model white wine

Glutathione was assessed individually, and in combination with ascorbic acid, for its ability to act as an antioxidant with respect to color development in an oxidizing model white wine system. Glutathione was utilized at concentrations normally found in wine (30 mg/L), as well as at concentrations 20-fold higher (860 mg/L), the latter to afford ascorbic acid (500 mg/L) to glutathione ratios of 1:1. The model wine systems were stored at 45 °C without sulfur dioxide and at saturated oxygen levels, thereby in conditions highly conducive to oxidation. Under these conditions the results demonstrated the higher concentration of glutathione could initially provide protection against oxidative coloration, but eventually induced color formation. In the period during which glutathione offered a protective effect, the production of xanthylium cation pigment precursors and o-quinone-derived phenolic compounds was limited. When glutathione induced coloration, polymeric pigments were formed, but these were different from those found in model wine solutions without glutathione. In the presence of ascorbic acid, high concentrations of glutathione were able to delay the decay in ascorbic acid and inhibit the reaction of ascorbic acid degradation products with the wine flavanol compound (+)-catechin. However, on depletion, the glutathione again induced the production of a range of different polymeric pigments. These results highlight new mechanisms through which glutathione can offer both protection and spoilage during the oxidative coloration of a model wine.     

Sorption behavior of volatile phenols at the oak wood/wine interface in a model system

The sorption in a model system of aroma compounds of enological interest (mixture of the eight derivatives from guaiacol, 4-ethylphenol, and whiskylactone) onto wood was investigated to assess the influence of wood on the concentration of these volatiles during the aging of wine. To evaluate the influence of the solubility of aroma compounds in sorption phenomena, this parameter was determined for each volatile compound in model wine at 10 and 25 degrees C. The solubility is significantly higher in the model wine than in water and remains constant in the range of temperatures studied, except for guaiacol and vanillin. Kinetic and equilibrium sorptions were investigated. Sorption kinetics showed that the sorption equilibrium for all aroma compounds was reached after 6-7 days. From the study of the individual sorption isotherms, two distinct kinds of sorption behavior were observed depending on the presence or not of an ethylenic para substituent conjugated to the phenyl ring. K(ww) partition coefficients between the wood and the model wine were determined, which exhibited an unusual positive variation with temperature.     

Isolation and structural characterization of new anthocyanin-derived yellow pigments in aged red wines

Two newly formed yellow pigments that revealed unique spectral features were detected and isolated from an aged Port red wine by TSK Toyopearl HW-40(s) gel chromatography and characterized by UV-visible spectrophotometry, 1H NMR and 13C NMR, and mass spectrometry (LC-ESI/MS). The UV-vis spectra of these pigments showed maximum absorption at 478 nm that is significantly hypsochromically shifted from those of original grape anthocyanins and other pyranoanthocyanins, exhibiting a more yellow hue in acidic solution. The structures of these pigments correspond to methyl-linked pyranomalvidin 3-glucoside and its respective coumaroyl glucoside derivative. They were shown to arise from the reaction between acetoacetic acid and genuine grape anthocyanins. Isolation and NMR identification using 1D and 2D NMR techniques are reported for the first time for this new family of anthocyanin-derived yellow pigments occurring in red wines.     

Isolation and characterization of novel stilbene derivatives from Riesling wine

Besides the already known stilbenes trans-resveratrol as well as isomeric piceids seven novel stilbene derivatives have been isolated from a commercial Riesling wine. The newly identified compounds included the monostilbene 2,4,6-trihydroxyphenanthrene-2-O-glucoside, as well as two isomeric resveratrol-2-C-glucosides. In addition, four dimeric stilbenes, i.e., cis- and trans-epsilon-viniferin diglucoside as well as pallidol glucoside and pallidol diglucoside, have also been obtained for the first time from Riesling wine.     

Isolation and structural characterization of new acylated anthocyanin-vinyl-flavanol pigments occurring in aging red wines

Three newly formed pigments were detected and isolated from a 2-year-old Port wine through TSK Toyopearl HW-40(S) gel column chromatography and characterized by UV-visible spectrophotometry, NMR, and mass spectrometry (ESI/MS). (1)H NMR and (13)C NMR data for these pigments obtained using 1D and 2D NMR techniques (COSY, NOESY, gHSQC, and gHMBC) are reported for the first time. The structure of the pigments was found to correspond to the vinyl cycloadducts of malvidin 3-coumaroylglucoside bearing either a procyanidin dimer or a flavanol monomer ((+)-catechin or (-)-epicatechin). Additionally, conformational analysis was performed for one of these newly formed pigment using computer-assisted model building and molecular mechanics. A chemical nomenclature is proposed to unambiguously name this new family of anthocyanin-derived pigments.     

Colorimetric characterization for comparative analysis of fungal pigments and natural food colorants

Exogenous pigments produced by ascomycetous filamentous fungi belonging to the genera Penicillium, Epicoccum, and Monascus, preselected based on chemotaxonomic knowledge, have been extracted and characterized by quantitative colorimetry. The color characteristics of the fungal extracts were compared to water soluble natural colorants derived from sources currently in use. The tested fungal extracts also included some commercially available Monascus colorants. The a values for the fungal extracts were found to be both positive and negative, the b values were found to be positive, while the hue angles of the fungal color extracts ranged from 40 to 110 indicating the color distribution of fungal extracts over the red-orange-yellow region of the CIELAB color space. The fungal extracts exhibited additional color hues in the red spectrum and similar hues in the yellow spectrum as compared to the reference natural colorants. They were also found to be similar or brighter in terms of chroma to some of the reference natural colorants. Principal component analysis was performed to group and distinguish different colors based on the a and b values. The fungal color extracts could be grouped in accordance with the similarity or difference in the color to those of the existing natural colorants. The diversity of colors was not only found among different fungal genera and/or species but also within the same species on changing the media. There was a marked change in the color composition of the extracts resulting in relatively different hues. Our results, thus, indicate that there exists pigment-producing genera of ascomycetous fungi other than Monascus that produce color shades in the red and the yellow spectra in addition or similar to reference colorants. These color shades could add to the color palette of the natural colorants currently in use. In addition, the multivariate approach in distinguishing and classifying the colorants was shown to be a very useful tool in colorimetric comparison of colorants.     

Confirmation of the allergenic peanut protein, Ara h 1, in a model food matrix using liquid chromatography/tandem mass spectrometry (LC/MS/MS)

Enzymatic digestion of total protein along with liquid chromatography/tandem mass spectrometry (LC/MS/MS) was used to confirm the presence of a major peanut allergen in food. Several peptides obtained from the enzymatic digestion of the most abundant peanut allergen, Ara h 1, were identified as specific peptide biomarkers for peanut protein. Using ice cream as a model food matrix, a method was developed for the detection of the allergen peptide biomarkers. A key component of the method was the use of molecular mass cutoff filters to enrich the Ara h 1 in the protein extracts. By applying the method to ice cream samples containing various levels of peanut protein, levels as low as 10 mg/kg of Ara h 1 could routinely be detected. This method provides an unambiguous means of confirming the presence of the peanut allergen, Ara h 1, in foods and can easily be modified to detect other food allergens.     

Reactivity of anthocyanins and pyranoanthocyanins. Studies on aromatic hydrogen-deuterium exchange reactions in methanol

Reactivity studies involving anthocyanin structures and their equilibrium forms will lead to better understanding of the properties of these antioxidants. Hydrogen-deuterium (H --> D) exchange reactions at various sites of the 3-glucosides of delphinidin (1), petunidin (2), malvidin (3), and the corresponding 3-glucosides of carboxypyranodelphinidin (4), carboxypyranopetunidin (5), carboxypyranomalvidin (6), and the flavonol quercetin 3-O-(6-alpha-rhamnopyranosyl-beta-glucopyranoside)(7) have been examined at room temperature in pure CD 3OD and in CD 3OD acidified with CF 3CO 2D. The H --> D exchange rate constants of H-6 and H-8 of 2 determined from (1)H NMR integration data were found to be independent upon pigment concentration (up to 4 x 10 (-2) M) and trifluoroactic acid concentration (0-15%, v/v), respectively. This suggest that these reactions follow first-order kinetics and unexpectedly to be independent of the acid concentration. H-6 and H-8 of the flavylium cation A-rings of 1- 3, and in the corresponding hydrogens of the hemiketal forms, exchanged with half-lives of approximately 100 h ( 1) and approximately 50 h ( 2 and 3), respectively. The pyranoanthocyanins (4-6) experienced no H --> D exchange for the analogous hydrogens, but H --> D exchange of H-beta (H-4)(t 1/2 approximately 25 h) for these compounds was observed. Only H-8 underwent significant H --> D exchange in 7. It is concluded that a stabilization of the sigma-complexes, assumed to be the intermediates in the reactions, takes place for the common anthocyanins (1-3) contrary to the pyranoanthocyanins (4-6).     

Aroma compound sorption by oak wood in a model wine

Oak wood used for wine barrels was immersed into a model wine containing eight aroma compounds (e.g., aromatic and terpene alcohols, ethyl esters, and aldehyde), for which activity coefficients in water and model wine were determined using the mutual solubility measurement. A mass balance of these volatiles considering their reactivity in model wine was established. For most of the studied aroma compounds, and mainly for linalool and ethyl octanoate, a sorption behavior into wood was reported for the first time. This phenomenon was selective and could not be related to the solubilities in model wine and hydrophobicities of the studied aroma compounds, suggesting that acid-base and polar characteristics of wood were more involved in this sorption mechanism. This study has also shown that the level of sorption is a function of the ratio of wood surface area/solution volume.