Metabolomic and transcriptomic changes underlying cold and anaerobic stresses after storage of table grapes.

The currently accepted paradigm is that fruits and vegetables should be consumed fresh and that their quality deteriorates during storage; however, there are indications that some metabolic properties can, in fact, be improved. We examined the effects of low temperature and high-CO2 conditions on table grapes, Vitis vinifera L. cv. 'Superior Seedless'. Berries were sampled at harvest (T0) and after low-temperature storage for 6 weeks under either normal atmosphere conditions (TC) or under an O2 level of 5 kPa and elevated CO2 levels of 5, 10 or 15 kPa (T5, T10, T15). Accumulation of 10 stilbenes, including E-ε-viniferin, E-miyabenol C and piceatannol, significantly increased under TC treatment as compared to T0 or T15. Sensory analysis demonstrated that elevated CO2 elicited dose-dependent off-flavor accumulation. These changes were accompanied by an accumulation of 12 volatile metabolites, e.g., ethyl acetate and diacetyl, that imparted disagreeable flavors to fresh fruit. Transcriptome analysis revealed enrichment of genes involved in pyruvate metabolism and the phenylpropanoid pathway. One of the transcription factors induced at low temperature but not under high CO2 was VvMYB14, which regulates stilbene biosynthesis. Our findings reveal the potential to alter the levels of targeted metabolites in stored produce through understanding the effects of postharvest treatments.

LC-QTOF characterization of non-anthocyanic flavonoids in four Tunisian fig varieties.

Flavonoids are compounds characterized by antioxidant activity, and their intake in the human diet is considered useful for health and nutrition. Non-anthocyanic flavonoids in 4 different types of Tunisian figs belonging to the smyrna-type Ficus carica varieties known as Kholi, Tchich Asal, Himri, and Bidhi were studied by liquid chromatography/high-resolution mass spectrometry UHPLC-QqTOF. Twenty-two compounds belonging to the classes of flavanones (naringenin and eriodictyol), flavones (3 apigenin and 5 luteolin derivatives), and flavonols (2 kaempferol and 7 quercetin derivatives) were identified. Three O-methoxy flavonols (tamarixetin, syringetin, and isorhamnetin-3-O-glucoside) were found in figs for the first time. Total content of non-anthocyanic flavonoids found in dark varieties (between 410 and 830 mg/kg) show that these F. carica are fruits qualitatively and quantitatively rich of dietary polyphenols.

High-resolution mass spectrometry metabolomics of grape chemical markers to reveal use of not-allowed varieties in the production of Amarone and Recioto wines.

INTRODUCTION: Grape varieties allowed to produce Amarone della Valpolicella and Recioto DOCG wines are strictly regulated by their disciplinary of production. These are Corvina Veronese and Corvinone grapes, to a lesser extent also Rondinella can be used. The use of other varieties, is not allowed. OBJECTIVES: To identify chemical markers suitable to reveal addition of two not allowed grape varieties to the Corvina/Corvinone blend, such as Primitivo or Negro Amaro. METHODS: The identification of the secondary metabolites of the four grape varieties was conducted by high-resolution mass spectrometry (HRMS) metabolomics. By using the signals of these metabolites the indexes able to identify the presence of Primitivo or Negro Amaro grapes in the Corvina/Corvinone 1:1 blend were calculated. RESULTS: Indexes of laricitrin (Lr), delphinidin (Dp), and petunidin (Pt) signals were effective to identify the use of 10% Primitivo, while α-terpineol pentosyl-hexoside and linalool pentosyl-hexoside reveal the presence of Negro Amaro in the grape blend. CONCLUSIONS: Varietal markers useful to detect the presence of Primitivo and Negro Amaro in the grape blend were identified by HRMS metabolomics, a method suitable to check the identity of grapes on arrival at the winery, as well as the fermenting musts. The effectiveness of the identified markers in the final wines have to be confirmed. Potentially, a similar approach can be used to reveal analogous frauds performed on other high-quality wines.

Changes in grape polyphenols (V. vinifera L.) as a consequence of post-harvest withering by high-resolution mass spectrometry: Raboso Piave versus Corvina.

Grape dehydration is an oenological process used for the production of high-quality reinforced and sweet wines. Corvina and Raboso Piave are two red grape varieties used for production of high-quality Italian wines, such as Recioto, Amarone di Valpolicella and Raboso Passito. Changes of polyphenolic composition of the grapes as a consequence of the withering were studied by ultra-high performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC/QTOF); for identification of compounds a homemade HR-MS database of grape and wine metabolites, was used. Concomitant with trans-resveratrol and viniferins, relevant increases of other stilbenes (piceatannol, resveratrol trimers and tetramers) and antioxidant compounds (quercetin, syringetin and tamarixetin) were observed. These compounds are part of the induced metabolism occurring during the withering process and in general improve the nutraceutical properties of grapes and wines. On the other hand, longer processes showed to decrease flavan-3-ols and glycoside flavonols. Constant increase of E/Z ε-viniferin ratio was observed in all samples, and this parameter can be used to monitor the process. Copyright © 2016 John Wiley & Sons, Ltd.

Characterization of Non-Anthocyanic Flavonoids in Some Hybrid Red Grape Extracts Potentially Interesting for Industrial Uses.

Previous studies showed that hybrid grapes often have qualitatively and quantitatively higher polyphenolic contents than the common V. vinifera grape varieties. In general, these compounds are studied for grape chemotaxonomy and for nutraceutical purposes due to their relevant antioxidant activity. Non-anthocyanic flavonoid composition of five red hybrid grape varieties produced by crossing of V. vinifera, V. aestivalis, V. cinerea, V. berlandieri, V. labrusca, V. lincecumii, and V. rupestris were studied by liquid chromatography/high-resolution mass spectrometry. Thirty-one compounds were identified, including methylnaringenin, a tetrahydroxy-dimethoxyflavanone-hexoside, two flavonols (quercetin and a pentahydroxyflavone isomer), 20 glycoside flavonols (four quercetin, two myricetin, two kaempferol, three isorhamnetin, one laricitrin, two syringetin, one kaempferide and two dihydroflavonol derivatives; myricetin-glucoside-glucuronide; myricetin-diglucoside; syringetin-dihexoside), three flavan-3-ols (-)-epicatechin, (+)-catechin, (-)-epicatechin gallate) and four proantocyanidins (procyanidin B1, procyanidin B2, procyanidin B3 or B4/B5, procyanidin T2 or T3/T4/C1). Seibel 19881, Seyve Villard 12-347 and Seyve Villard 29-399 were particularly rich in polyphenols. These findings emphasize that these grapes are especially interesting for the production of antioxidant extracts for nutraceutical and pharmaceutical uses.

Fast analysis of isobaric grape anthocyanins by Chip-liquid chromatography/mass spectrometry.

In a previous work, direct-infusion electrospray ionization ion trap tandem mass spectrometry (ESI-IT-MS/MS) was applied to the study of anthocyanins in extracts from the skins of Clinton grapes, a non-Vitis vinifera red grape variety qualitatively and quantitatively rich in anthocyanins. A good characterization of anthocyaninins was obtained, but it was impossible to differentiate some compounds with the same nominal mass but with different elemental composition. In this work, the capabilities of quadrupole time-of-flight mass spectrometry (QTOF-MS) coupled with Chip-liquid chromatography (LC-Chip) were applied to the study of Clinton anthocyanins and this method provided the complete sample anthocyanin fingerprint in less than 5 min. Multi-stage mass spectrometry (MS(n); n >2) was not necessary to identify isobaric compounds, nor were deuterium-exchange experiments necessary to distinguish between compounds containing the same aglycone. The fast separation bypasses the problem of petunidin-3-O-(6-O-acetyl)monoglucoside and delphinidin-3,5-O-diglucoside quantification, present in the direct-infusion ESI-ITMS approach, due to overlapping with matrix interferences.

Collisionally induced fragmentation of [M-H](-) species of resveratrol and piceatannol investigated by deuterium labelling and accurate mass measurements.

Resveratrol (3,5,4'-trihydroxystilbene) and piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene) are phytoalexins present in red grapes and wines. In vitro studies have revealed that piceatannol blocks LMP2A, a viral protein-tyrosine kinase implicated in leukemia, non-Hodgkin's lymphoma and other diseases associated with the Epstein-Barr virus, and has an antimelanoma effect on human melanoma cells. Resveratrol has several beneficial effects on human health, such as anticancer, cardioprotection, antioxidant, inhibition of platelet aggregation and anti-inflammatory activity. In this investigation, the collisional behaviour of deprotonated resveratrol and piceatannol obtained under electrospray conditions is described. The mechanisms involved in the fragmentation pattern of [M-H](-) species of the two compounds were investigated by performing MS(n) experiments, deuterium labelling and accurate mass measurements.

Differentiation of Vitis vinifera varieties by MALDI-MS analysis of the grape seed proteins.

Until now the study of pathogenic related proteins in grape juice and wine, performed by ESI-MS, LC/ESI-MS, and MALDI/MS, has been proposed for differentiation of varieties. In fact, chitinases and thaumatin-like proteins persist through the vinification process and cause hazes and sediments in bottled wines. An additional instrument, potentially suitable for the grape varieties differentiation, has been developed by MALDI/MS for the grape seed protein analysis. The hydrosoluble protein profiles of seeds extract from three different Vitis vinifera grape (red and white) varieties were analyzed and compared. In order to evaluate the environmental conditions and harvest effects, the seed protein profiles of one grape variety from different locations and harvests were studied.

A new sensitive and selective method for analysis of ochratoxin A in grape and wine by direct liquid chromatography/surface-activated chemical ionization tandem mass spectrometry.

A new sensitive and selective analytical method for the analysis of ochratoxin A (OTA) in grape and wine was developed by coupling liquid chromatography and surface activated chemical ionization and mass spectrometry with multistage fragmentation (LC/SACI-MS(3)). A high flow gradient was used to strongly reduce the matrix effect phenomenon, and the wine sample was directly injected onto the chromatographic column without sample pre-concentration or purification steps. The amount of OTA was determined for two grape extracts and the amount of OTA, percent accuracy error and percent precision error were analyzed for 15 wine samples. An excellent limit of detection of 0.02 ng/mL was achieved, and the limit of quantification was at least 20-fold lower than the maximum legal limit for OTA (2 ppb). Due to the low limit of quantification, this novel method is a potential tool for official OTA screening purposes.

Monitoring of the principal carbonyl compounds involved in malolactic fermentation of wine by solid-phase microextraction and positive ion chemical ionization GC/MS analysis.

A new method has been developed to determine acetaldehyde, 2,3-butanedione (diacetyl) and 3-hydroxy-2-butanone (acetoin) in wine by solid-phase microextraction (SPME) and positive ion chemical ionization GC/MS analysis of O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBOA) derivatives. For SPME, a 65-microm PEG/DVB fibre was used; chemical ionization was performed with methane as reagent gas. The best analysis-time/sensitivity compromise was to perform the PFBOA reaction at 50 degrees C for 20 min, followed by 5-min SPME at the same temperature. Quantitative analysis was performed in SCAN mode using o-chlorobenzaldehyde as internal standard (IS), on the signal of the [M + H](+) ion at m/z 240 for acetaldehyde, 266 for acetoin (corresponding to the [M + H - 18](+) ion), 282 for diacetyl (protonated mono-derivatized compound), and 336 for IS. The accuracy and repeatability of the method were suitable for the study aims, and linearity was good in the range of concentration studied, with correlation coefficients of calibration curves 0.997, 0.998 and 0.988 for acetaldehyde, diacetyl and acetoin respectively. Due to the higher polarity of acetoin with respect to other two compounds, lower sensitivity in the detection of this compound was observed. By following the variation of the three carbonyl compounds, malolactic fermentations (MLF) were monitored in Merlot wines and this was carried out in the laboratory by two different bacteria strains.