Stamatina Kallithraka

Metabolism of Anthocyanins by Human Gut Microflora and Their Influence on Gut Bacterial Growth

Consumption of anthocyanins has been related with beneficial health effects. However, bioavailability studies have shown low concentration of anthocyanins in plasma and urine. In this study, we have investigated the bacterial-dependent metabolism of malvidin-3-glucoside, gallic acid and a mixture of anthocyanins using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal human large intestine conditions. Most anthocyanins have disappeared after 5 h incubation while gallic acid remained constant through the first 5 h and was almost completely degraded following 24 h of fermentation. Incubation of malvidin-3-glucoside with fecal bacteria mainly resulted in the formation of syringic acid, while the mixture of anthocyanins resulted in formation of gallic, syringic and p-coumaric acids. All the anthocyanins tested enhanced significantly the growth of Bifidobacterium spp. and Lactobacillus-Enterococcus spp. These results suggest that anthocyanins and their metabolites may exert a positive modulation of the intestinal bacterial population.

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.

Sensory assessment and chemical measurement of astringency of Greek wines: Correlations with analytical polyphenolic composition

The purpose of this study was to measure the astringency of selected Greek red wines and to assess the relationship between sensory and chemical data. Nine red wines produced by three native Greek grape varieties (agiorgitiko, xinomavro and mavrodafni) were used and their astringency and bitterness was assessed by a trained panel. In addition, their astringency was estimated chemically employing the ovalbumin precipitation method. Their polyphenolic composition was also determined by High Performance Liquid Chromatography (HPLC). The sensory data showed that mandilaria was the most astringent variety whereas agiorgitiko was the least. Statistical analysis of the results indicated that the chemical data obtained for astringency significantly correlated with the sensory determinations. In addition, significant correlations were obtained between the sensory data and the wine polyphenolic composition.

Grape brandy production, composition and sensory evaluation

Grape brandy is a spirit drink produced by wine distillation and is matured in wooden casks. According to legislation, it can be characterised by the geographical area where the grapes were produced, the grape variety used and the selected distillation and ageing techniques. Distillation increases ethanol concentration and aromatic constituents which are already present in grapes or are developed during fermentation and distillation. During maturation in wooden casks, compounds that contribute to the aroma and taste are extracted from the wood. Hence the spirit acquires the desired softer mouth feel, aromatic complexity and overall quality. Different methods of analysis are used in order to pursuit this process by analysing volatile and non-volatile substances and correlate composition with quality. Analysis can also be useful in identification of brandy safety, potential adulterations, provenance and differentiation from other spirits drinks.

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.

Optimization of polyphenol extraction from red grape pomace using aqueous glycerol/tartaric acid mixtures and response surface methodology.

ABSTRACT Grape pomace is a food industry waste containing a high burden of antioxidant polyphenols and several methodologies have been developed for their efficient extraction. However, a sustainable and environmentally friendly process should involve recovery means composed of benign, non-toxic solvents, such as tartaric acid and glycerol, which are natural food constituents. In this line, this study examined the extraction of polyphenols using aqueous tartaric acid/glycerol solutions. The aim was to assess the role of acid and glycerol concentration in the extraction yield, employing a Box-Behnken experimental design and response surface methodology. The results showed that solutions containing only glycerol (20%, w/v) are more suitable for retrieving polyphenols, flavonoids, and pigments from grape pomace, while tartaric acid exerted a negative effect in this regard, when tested at concentrations up to 2% (w/v).

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.

Differentiation of Wines Treated with Wood Chips Based on Their Phenolic Content, Volatile Composition, and Sensory Parameters

The effects of both wood chips addition and contact time on phenolic content, volatile composition, color parameters, and organoleptic character of red wine made by a native Greek variety (Agiorgitiko) were evaluated. For this purpose, chips from American, French, Slavonia oak, and Acacia were added in the wine after fermentation. A mixture consisting of 50% French and 50% Americal oak chips was also evaluated. In an attempt to categorize wine samples, various chemical parameters of wines and sensory parameters were studied after 1, 2, and 3 mo of contact time with chips. The results showed that regardless of the type of wood chips added in the wines, it was possible to differentiate the samples according to the contact time based on their phenolic composition and color parameters. In addition, wood-extracted volatile compounds seem to be the critical parameter that could separate the samples according to the wood type. The wines that were in contact with Acacia and Slavonia chips could be separated from the rest mainly due to their distinct sensory characters.

Effect of the degree of toasting on the extraction pattern and profile of antioxidant polyphenols leached from oak chips in model wine systems

The effect of the degree of toasting of oak chips used in wine ageing on the extraction pattern of polyphenols was investigated using model wine systems. Pattern identification was carried out employing a Box–Behnken experimental design and response surface methodology, using resident time (t) and amount of chips (AChip) as the independent variables. The responses selected to assess the process were the total polyphenol concentration, the antiradical activity and the reducing power of the model wines. Further, a deeper insight into the effects exerted by chip toasting was provided by the examination of the analytical polyphenolic composition of model wines, using liquid chromatography–mass spectrometry. The results obtained demonstrated that even moderate toasting provoked drastic decrease in the native oak wood polyphenols (ellagitannins), as indicated by the Folin–Ciocalteu assay, with a concomitant reduction in both the antiradical activity and reducing power. The evolution pattern for all three independent variables during model wine treatment with chips having different degree of toasting was also substantially affected. Light toasting was shown to generate a series of small molecular weight phenolics, but some of them did not survive more intense (heavy) toasting.

Analytical phenolic composition and sensory assessment of selected rare Greek cultivars after extended bottle ageing.

BACKGROUND The Hellenic vineyard embraces a large number of native cultivars, which are mostly unexploited for their ageing potential. Therefore, it was thought that analyzing some quality parameters of 14 red wines produced by rare native varieties would be of great importance in obtaining a general picture of their potential for commercial use. Various analytical methods were applied to the selected wines, at bottling and after 8 years of ageing, in an attempt to provide reliable answers to this issue. In addition, it was of interest to investigate the alteration of the phenolic content and color parameters of the wines after extended bottle storage and to evaluate the overall changes with respect to their sensory properties. RESULTS Most of the oligomeric phenolic compounds identified in the wines studied diminished after 8 years of bottle storage, while significant correlations were obtained between wine chemical composition and sensory data. CONCLUSIONS After 8 years of bottle storage some of the unexploited varieties (Vitis vinifera) were found to be worthy of further study and use for the production of quality wines. Wines with the best sensory characteristics were those made by Limniona, Mavrotragano, Bakouri, Thrapsa and Mavrothiriko, in accordance (more or less) with the results of chemical analyses.