Pulsed electric field (PEF) treatment is an emerging technology that is arousing increasing interest in vinification processes for its ability to enhance polyphenol extraction performance. The aim of this study was to investigate the effects of PEF treatment on grape skin histocytological structures and on the organization of skin cell wall polysaccharides and tannins, which, until now, have been little investigated. This study relates to the effects of two PEF treatments on harvested Cabernet Sauvignon berries: PEF1 (medium strength (4 kV/cm); short duration (1 ms)) and PEF2 (low intensity (0.7 kV/cm); longer duration (200 ms)). Histocytological observations and the study of levels of polysaccharidic fractions and total amounts of tannins allowed differentiation between the two treatments. Whereas PEF1 had little effect on the polyphenol structure and pectic fraction, PEF2 profoundly modified the organization of skin cell walls. Depending on the PEF parameters, cell wall structure was differently affected, providing variable performance in terms of polyphenol extraction and wine quality.

Aims:The objective was to better understand the mechanisms involved in grape ripening that brings about important changes in the physiology and chemistry of the fruit. So we focused on the involvement of two growth regulators: abscisic acid (ABA) and indol-acetic acid (IAA) in controlling grape berry ripening process Methods and results:We described the evolution of the two plant growth regulators during the development of cv. Merlot grapes (Vitis vinifera L.). In order to better understand the role of ABA and IAA in the ripening control, these two growth regulators were applied on the grapes at the onset of veraison. The hormonal profile was established on treated berries and different physiological parameters were assayed to evaluate the effects of both applications. The partitioning of both plant growth regulators in nontreated berries showed that ABA and IAA accumulated at the onset of ripening. Moreover, it appeared that endogenous ABA decreased progressively in the flesh while accumulated in the skin from the beginning of the colour change to maturity. The hormonal treatments modified the hormonal profile and several physiological parameters: sugar, acidity, colour, and Botrytis sensibility. Conclusion:These findings suggest that both treatments have modified the ripening process. Exogenous ABA has induced advancement in grape ripening, while IAA application has delayed this process. These observations support the view that the grape ripening process may be influenced by the hormonal status.Significance and impact of study: This study gives new information about the ripening control of the non-climacteric fruits. In grape berries, it provides evidence of a possible co-involvement of ABA and IAA in controlling ripening process.Key words: abscisic acid, indol-acetic acid, hormonal balance, grape berry ripening, Vitis vinifera L.Objectif : L'objectif est de mieux appréhender les mécanismes impliqués dans la maturation de la baie de raisin, qui provoquent de profonds changements physiologiques et chimiques du fruit. Ainsi, nous nous sommes intéressés à l'implication de deux régulateurs de croissance : l'acide abscissique (ABA) et l'acide indole acétique (AIA) dans le contrôle du processus de maturation des baies.Méthodes and résultats : L'évolution de ces deux régulateurs de croissance a été suivi au cours du développement de baies de cépage Merlot (Vitis vinifera L.). Pour mieux comprendre le rôle de l'ABA et de l'AIA dans le processus de maturation, ces deux régulateurs de croissances ont été appliqués sur les baies au moment du déclenchement de la véraison. Le profil hormonal a été établi sur les baies traitées et différents paramètres physiologiques ont été testés afin d'évaluer les effets de ces deux applications. La répartition des deux régulateurs de croissance dans les baies non traitées montre que l'ABA et l'AIA s'accumulent au début de la véraison. De plus, il apparaît que les teneurs en ABA endogène diminuent progressivement dans la pulpe alors qu'elles s'accumulent dans la pellicule du début vérais...

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