Yorgos Kotseridis

Irrigation and rootstock effects on the phenolic concentration and aroma potential of vitis vinifera L. cv. Cabernet Sauvignon grapes

Compositional changes of skin and seed phenolic compounds and berry glycosylated aroma precursors were measured in Vitis vinifera L. cv. Cabernet Sauvignon onto 1103P and SO4 rootstocks, in three irrigation regimes (FI, 100% of evapotranspiration; DI, 50% of evapotranspiration; and NI, non-irrigated). The study was conducted in a commercial vineyard of central Greece, in a factorial experiment during two growing seasons (2005-2006). Grape samples were obtained at commercial harvest. The deficit water supply decreased berry size but did not affect the skin/pulp weight ratio. Water limitation, especially pre-veraison, caused a substantial increase of skin anthocyanin concentration, and this effect was independent of water deficit-induced reductions in berry size and vine vigor. Among individual anthocyanins, malvidin-3-O-glucoside was mostly affected by water supply. The rootstock genotype did not affect berry growth parameters and skin polyphenol concentrations. The irrigation regime (mainly post-veraison) and rootstock genotype affected total flavan-3-ol monomers in seed tissue, mainly as a result of variations in the catechin amount. The lower seed phenolic concentration was found in non-irrigated and SO4-grafted vines, probably as a result of the restriction of scion vigor caused by these treatments, thereby altering cluster exposure. Skin and seed tannins were not affected by either rootstock or irrigation. The limited water supply was associated with increased aroma potential at harvest.

Quantitative analysis of 3-alkyl-2-methoxypyrazines in juice and wine using stable isotope labelled internal standard assay

A solid phase microextraction (HS-SPME)-GC-MS methodology was established for the analysis of 3-alkyl-2-methoxypyrazines (MPs) in wine using a stable isotope dilution assay. The compounds analysed were 3-isobutyl-2-methoxypyrazine (IBMP), 3-sec-butyl-2-methoxypyrazine (SBMP), and 3-isopropyl-2-methoxypyrazine (IPMP) using their respective deuterated analogues ([2H3]-IBMP, [2H3]-SBMP, [2H3]-IPMP) as internal standards, synthesised during this work. A divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) fibre was selected for isolation of MPs and the effects of matrix parameters such as pH and ethanol concentration were examined in the development of the method. Best results were obtained at a pH of approximately 6 and with a wine dilution factor of 1:2.5, resulting in an ethanol concentration of approximately 5% (v/v). Relative standard deviations (RSDs) of replicate samples were 5.6-7% for all MPs at 5 ng L(-1) and <5% for 15 and 30 ng L(-1) samples. The limit of detection was <0.5 ng L(-1) in juice and 1-2 ng L(-1) in wine. The recovery efficiencies for spiked wine samples were between 99 and 102% for all three MPs. Using this method, we investigated the impact of the Multicoloured Asian Lady Beetle (MALB) on MPs in wine. In red wine fermented with live MALB, IPMP is the most prevalent MP detected, although SBMP concentrations are also increased and IBMP is unchanged from background levels. MALB that have been dead for 1 day before addition to juice can still contribute to elevated SBMP concentrations in wine, but not if they have been dead for 3 days or longer. Clarifying juice prior to fermentation leads to substantially lower IPMP concentration in the subsequent wine when compared with unclarified juice.

Effects of severity of post-flowering leaf removal on berry growth and composition of three red Vitis vinifera L. cultivars grown under semiarid conditions.

The effects of the severity of post-flowering leaf removal on the growth and phenolic composition of berry skin and seeds were studied in three Vitis vinifera L. genotypes over two consecutive seasons, 2007 and 2008. The study was conducted in a commercial vertical shoot positioned (VSP)-trained nonirrigated vineyard of northern Greece, planted with cultivars Merlot, Cabernet Sauvignon, and Sangiovese. Three different severities of leaf removal in the fruit zone were applied manually at berry set: nondefoliated (ND), removal of the lateral shoots of the first six basal nodes (LR), and full removal of the total leaf area (main leaves and lateral shoots) of the first six basal nodes (FR). Grape samples were obtained at commercial harvest. Leaf removal decreased yield per vine and cluster weight in Merlot and Sangiovese. Cluster compactness was reduced with the severity of defoliation only in Merlot, due to a decrease in berry number per cluster; berry fresh weight was unaffected in both cultivars. On the contrary, in Cabernet Sauvignon, yield was unaffected but berry size was restrained by leaf removal. Skin and seed mass followed variations in berry mass (except for seed mass in Sangiovese). Fruit zone leaf removal did not affect must soluble solids and increased titratable acidity only in Merlot. Defoliation increased skin anthocyanins in Merlot and Cabernet Sauvignon in the order FR > LR > ND but significantly reduced seed flavan-3-ols mainly as a result of the reduction in catechin and epicatechin amount. For these varieties, FR had lower seed flavan-3-ols than ND in both varieties, whereas LR had intermediate values. However, in Sangiovese, the highest seed phenolic content was recorded in LR. The results showed that post-flowering leaf removal improved the overall berry composition in Merlot and Cabernet Sauvignon but had limited effect in Sangiovese.

Effect of closure and packaging type on 3-alkyl-2-methoxypyrazines and other impact odorants of Riesling and Cabernet Franc wines.

3-Alkyl-2-methoxypyrazines (MPs) represent an important and potent class of grape- and insect-derived odor-active compounds associated with wine quality. Thirty nanograms per liter each of 3-isobutyl-2-methoxypyrazine (IBMP), 3-isopropyl-2-methoxypyrazine (IPMP), and 3-sec-butyl-2-methoxypyrazine (SBMP) was added to Riesling and Cabernet Franc wines and monitored with headspace solid-phase microextraction and gas chromatography-mass spectrometry over 18 months to investigate the effects of various closure and packaging options on MPs. Changes in MP concentrations during bottle aging varied with closure/packaging option, with the greatest decrease evident in Tetrapak cartons. After 18 months, IBMP, IPMP, and SBMP in both Tetrapak-stored wines decreased by approximately 45, 32, and 26%, respectively. Similar changes were observed in other impact odorants to previous studies, including a greater decrease in odorant concentrations in wines closed with synthetic corks compared to natural corks and screw caps. These differences are thought to be due to the differential sorptive capacities of the various closure types. Overall, the data suggest that differences in gas permeability/contribution from the different closure and packaging options strongly associate with changes in wine composition during aging.

Enhanced ethanol production, volatile compound biosynthesis and fungicide removal during growth of a newly isolated Saccharomyces cerevisiae strain on enriched pasteurized grape musts

The kinetic behavior of a newly isolated Saccharomyces cerevisiae strain, grown on pasteurized grape musts enriched with industrial sugars, was studied after the addition of various concentrations [0.0 (reference), 0.4 and 2.4 mg/L] of the fungicide quinoxyfen to the medium. Batch‐flask cultures were carried out. Significant quantities of biomass (10.0±0.8 g/L) were produced regardless of quinoxyfen addition to the medium; therefore, the addition of the fungicide did not seriously inhibit biomass production. Ethanol was synthesized in very high quantities in all trials (highest concentrations 106.4–119.2 g/L). A slight decrease of ethanol production in terms of both absolute value and conversion yield of ethanol produced per sugar consumed was, however, observed when the quinoxyfen concentration was increased. The addition of quinoxyfen led to significantly lower ethylic ester levels, which also pertains to the acetates analyzed in this study. Fusel alcohol synthesis seemed to be activated when 0.4 mg/L quinoxyfen was added, but at 2.4 mg/L of added fungicide, no statistically significant differences were observed compared with the control trial. Volatile acid levels did not present a uniform trend in relation with the added fungicide. Finally, the fermentation was accompanied by a significant reduction of the fungicide concentration (79–82 wt% fungicide removal).

Methoxypyrazine Analysis and Influence of Viticultural and Enological Procedures on their Levels in Grapes, Musts, and Wines

This review discusses the factors that affect the concentrations of methoxypyrazines (MPs) and the techniques used to analyze MPs in grapes, musts, and wines. MPs are commonly studied pyrazines in food science due to their contribution of aroma and flavor to numerous vegetables such as peas and asparagus. They are described as highly odorous compounds with a very low olfactory threshold. The grape varietals that exhibit green or herbaceous aromas that are characteristic of MPs are predominantly Vitis vinifera cv. Cabernet Sauvignon and Sauvignon Blanc, but include others. The most extensively studied MPs include 3-isobutyl-2-methoxypyrazine, 3-isopropyl-2-methoxypyrazine, and 3-sec-butyl-2-methoxypyrazine. It outlines the significance of methoxypyrazines in grapes, musts, and wines in terms of the concentrations that are capable of contributing their sensory characteristics to wines. This review discusses methods for analyzing MPs including gas chromatography-mass spectroscopy (one or two dimension) and high-performance liquid chromatography, the appropriate extraction techniques, and the efficacy of these methods. Additionally, this review explores factors that affect pyrazine content of grapes, must, and wines, such as the effects of different viticultural practices, effects of light exposure and grape maturation, climate, soil, the multi-colored Asian lady beetle and the effects of different vinification processes.

Development of a rapid method for the quantitative analysis of four methoxypyrazines in white and red wine using multi-dimensional Gas Chromatography-Mass Spectrometry.

Alkyl-methoxypyrazines (MPs) are important odour-active constituents of many grape cultivars and their wines. Recently, a new MP - 2,5-dimethyl-3-methoxypyrazine (DMMP) - has been reported as a possible constituent of wine. This study sought to develop a rapid and reliable method for quantifying DMMP, isopropyl methoxypyrazine (IPMP), secbutyl methoxypyrazine (SBMP) and isobutyl methoxypyrazine (IBMP) in wine. The proposed method is able to rapidly and accurately resolve all 4 MPs in a range of wine styles, with limits of detection between 1 and 2 ng L(-1) for IPMP, SBMP and IBMP and 5 ng L(-1) for DMMP. Analysis of a set of 11 commercial wines agrees with previously published values for IPMP, SBMP and IBMP, and shows for the first time that DMMP may be an important and somewhat common odorant in red wines. To our knowledge, this is the first analytical method developed for the quantification of DMMP in wine.

Effect of irrigation regime on anthocyanin content and antioxidant activity of Vitis vinifera L. cv. Syrah grapes under semiarid conditions

BACKGROUND Irrigation management is a powerful technique to control grape and wine colour. However, water deficit effects on anthocyanins are often contrasting, depending on the severity of water restriction. In addition, the effect of irrigation on the antiradical capacity of grapes has not been extensively studied. In this work the effect of water availability on anthocyanin profile and content as well as the antioxidant activity of Syrah grapes was investigated in an irrigation trial under semiarid climate conditions. RESULTS Three irrigation treatments were applied in a 15-year-old Vitis vinifera cv. Syrah vineyard, starting at berry set through harvest of 2011 and 2012: full irrigation (FI) at 100% of crop evapotranspiration (ETc), deficit irrigation (DI) at 50% of ETc and non-irrigated (NI). NI grapes were characterized by increased individual anthocyanin content. However, differences among irrigation treatments were significant only around 18-24 days after veraison, when anthocyanin accumulation was maximum. The antioxidant activity of the skin extracts was not affected by irrigation. CONCLUSION Irrigation proved to be an effective technique to control anthocyanin content in Syrah grapes under semiarid conditions. However, anthocyanin accumulation pattern should be considered by winemakers to appropriately select harvest time for improved wine colour.

Effect of irrigation regime on perceived astringency and proanthocyanidin composition of skins and seeds of Vitis vinifera L. cv. Syrah grapes under semiarid conditions

In this work, the effect of water availability on astringency of seed and skin extracts of Vitis vinifera cv. Syrah berries under the typical semiarid conditions of Greece was investigated. Moreover, astringency was assessed in relation to proanthocyanidin composition. For this purpose, three irrigation treatments were applied starting at berry set through harvest of 2011 and 2012: full irrigation (FI) at 100% of crop evapotranspiration, deficit irrigation (DI) at 50% and non-irrigated (NI). FI skin and seed extracts were perceived significantly more astringent than NI. Total phenol, total tannin, (+)-catechin, (-)-epicatechin and procyanidin C1 concentrations were positively correlated with astringency. Positive correlations were also obtained among astringency and average degree of polymerization and proportion of the extension units of shorter tannins while astringency of larger tannins was correlated with the proportion of terminal units. On the contrary, total anthocyanin and epigallocatechin contents were negatively correlated with astringency.

Influence of prefermentative treatments to the major volatile compounds of Assyrtiko wines.

A study of the volatile fraction of Assyrtiko wines, using gas chromatography coupled with olfactometry, was realized. Twenty-seven volatile compounds were identified as potent odorants, most of them originating from the fermentation process. Quantification of the major volatile compounds was realized developing a rapid analytical method based on fractionation of a 50 mL wine aliquot using C 18-reversed phase adsorbent. After elution of the volatile compounds with pentane-diethyl ether and concentration under nitrogen, the final wine extract was injected in a gas chromatography-flame ionization detection system. The method allows satisfactory determination of more than 15 volatile compounds of wine. The linearity of the method gave a typical r (2) between 0.990 and 0.999, while reproducibility ranged from 5.1 to 12.2% (as relative standard deviation) with 9.5% as the average. The method was applied to wines produced by Assyrtiko grapes (AOC Santorini), for two consecutive years, to compare the effect of skin contact prior to fermentation and the must clarification process. Direct press and skin contact wines were differentiated analytically; however, highly significant differences were not. Inversely, the differences found between direct press/clarified and nonclarified wines were significant. Wines produced by direct press and clarified must presented significantly higher levels of ethylic esters and fusel alcohol acetates but lower fusel alcohol levels, leading probably to more fruity wines. This difference, between clarified and nonclarified grape musts, was not significant in the case of the wines produced by skin contact of Assyrtiko berries. These findings were validated by preference sensory analysis tests.