The phenolic composition of berries has important effects on winemaking operations and on the quality of the out coming wines. The concentrations of different phenolic compounds are affected by environmental and agronomical factors. Girdling of cluster-baring shoots affect phloem transport of sugars and is used to accelerate grape ripening. This technique affects sugar accumulation in the berry but its effects on the concentration of phenolic compounds are little known. The aim of this work was to study the influence of sugar content modifications in the berries, obtained by shoot girdling, on the phenolic composition of grape berries. The experiment was carried out during the years 1997 and 1998 in Piedmont, Italy. Treatments were: A: stem girdling above cluster; B: stem girdling below cluster; 2X: stem girdling in both positions leaving the leaf opposite the cluster; 2XL: stem girdling in both positions without the leaf opposite the cluster (only in 1998); C: control (no girdling, no leaf removal). For each treatment five shoots were girdled. By spectrophotometric methods totals anthocyanin, flavonoid and phenol contents of the berry skins were analyzed; by HPLC, anthocyanic profiles were made on the same samples. The year 1997 was exceptional on a climatic point of view in Piedmont; temperatures and summer rainfall were higher than average and this determined earlier ripening. Only treatment A increased berry sugar content in comparison with controls, but it did not show significative changes of polyphenol content. Some effects of girdling were detected for the anthocyanin profile, particularly on 2X clusters: the content of acylated anthocyanins was higher than in C clusters, and peonidin-3-glucoside and cyanidyn-3-glucoside contents were lower. The year 1998 was climatically normal. Clusters from B treatment accumulated more sugars if compared with other treatments; an increase of phenol content was also detected. Different ripening levels of clusters from the different treatments corresponded to variable anthocyanin profiles. The results do not substantiate a strict relationship between berry ripening and the amount of phenolics accumulated in berry skins, while they show that the girdling treatments affected the anthocyanin profiles.
Effect of girdling on phenolic composition in grape berry skins cv Nebbiolo.
GUIDONI, Silvia;SCHUBERT, Andrea
2000-01-01
Abstract
The phenolic composition of berries has important effects on winemaking operations and on the quality of the out coming wines. The concentrations of different phenolic compounds are affected by environmental and agronomical factors. Girdling of cluster-baring shoots affect phloem transport of sugars and is used to accelerate grape ripening. This technique affects sugar accumulation in the berry but its effects on the concentration of phenolic compounds are little known. The aim of this work was to study the influence of sugar content modifications in the berries, obtained by shoot girdling, on the phenolic composition of grape berries. The experiment was carried out during the years 1997 and 1998 in Piedmont, Italy. Treatments were: A: stem girdling above cluster; B: stem girdling below cluster; 2X: stem girdling in both positions leaving the leaf opposite the cluster; 2XL: stem girdling in both positions without the leaf opposite the cluster (only in 1998); C: control (no girdling, no leaf removal). For each treatment five shoots were girdled. By spectrophotometric methods totals anthocyanin, flavonoid and phenol contents of the berry skins were analyzed; by HPLC, anthocyanic profiles were made on the same samples. The year 1997 was exceptional on a climatic point of view in Piedmont; temperatures and summer rainfall were higher than average and this determined earlier ripening. Only treatment A increased berry sugar content in comparison with controls, but it did not show significative changes of polyphenol content. Some effects of girdling were detected for the anthocyanin profile, particularly on 2X clusters: the content of acylated anthocyanins was higher than in C clusters, and peonidin-3-glucoside and cyanidyn-3-glucoside contents were lower. The year 1998 was climatically normal. Clusters from B treatment accumulated more sugars if compared with other treatments; an increase of phenol content was also detected. Different ripening levels of clusters from the different treatments corresponded to variable anthocyanin profiles. The results do not substantiate a strict relationship between berry ripening and the amount of phenolics accumulated in berry skins, while they show that the girdling treatments affected the anthocyanin profiles.
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