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The aim of this paper is to study the real influence of seeds and stems on wine composition, astringency, and bitterness. A decolored grape juice and a grape juice macerated for 4 days from the same Cabernet Sauvignon grapes were fermented with or without supplementation with 100% seeds, 300% seeds, or 100% stems. Once alcoholic fermentation had finished, the wines were analyzed and tasted. The presence of seeds and stems increased the concentration of flavan-3-ol monomers with respect to the controls. However, the seeds mainly released (+)-catechin and (-)-epicatechin, whereas the stems mainly released (+)-catechin and (+)-gallocatechin. The seeds and stems also released proanthocyanidins; those from seeds have a lower mDP and a high percentage of galloylation, whereas those from stems have a higher mDP and a relatively high percentage of prodelphinidins. The presence of seeds and stems brought about a slight but significant increase in pH and lowered titratable acidity and ethanol content. The presence of seeds boosted color intensity, whereas stems had the opposite effect. Finally, both seeds and stems increased wine astringency and bitterness.

Background and Aims According to one of the classical postulates of viticulture, cultivars with smaller berries produce the best red wines. During grape development, some differences at berry level lead to a wide range of fruit heterogeneity at harvest. One source of heterogeneity at harvest is berry size. The aim of this work is to determine if berry size affects the colour and chemical composition of wine. Methods and Results Cabernet Sauvignon grapes were harvested at optimal ripeness, and screened by two sieves, to select three groups of grapes of large, medium and small size. Wines were made from each size class in triplicate, with the control being wine made from unselected grapes. The colour properties and composition of the phenolic substances of the wines were determined. Conclusions Wine colour showed the clearest trend in this experiment: the smaller the berries, the deeper the wine colour, as measured by the CIELab coordinates as well as by (wine) colour intensity. Moreover, stilbene concentration increased when berry size decreased, while pH did the opposite. Finally, wines made from small berries had a titratable acidity, total phenolic index and monomeric flavan‐3‐ol concentration higher than that of wines made from the large‐ and medium‐sized berry sizes. Significance of the Study These data suggest that berry size classification in wineries would be an interesting tool for management of wine composition.

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Aims: The aim of this research was to determine and quantify the ability of enological tannins to reduce laccase activity and, consequently, to protect wine color against enzymatic browning and/or oxidasic haze.Methods and results: Botrytized grape juice with laccase activity was obtained by inoculating Botrytis cinerea in healthy mature grapes. Laccase activity was determined in grape juice before and after supplementation with enological tannins using the syringaldazine method. White micro-fermentations were performed in the presence or not of laccase activity and supplemented or not with enological tannins in order to determine how the color was affected. Similarly, red micro-fermentations were performed using white grape juice supplemented with malvidin-3-O-glucoside. All enological tannins inhibited laccase activity and protected the wine color.Conclusion: Supplementation with enological tannins is an interesting tool to inhibit laccase activity and protect the color of white wines from browning and the color of red wines from oxidasic haze.Significance and impact of the study: This is the first scientific study evidencing the inhibitory effect of enological tannins on laccase activity in winemaking conditions.

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