Maria Assunta Previtali

Effects of defoliation on quality attributes of Nero di Troia (Vitis vinifera L.) grape and wine

Field studies were conducted in Puglia (Italy) to evaluate the influence of defoliation around cluster zones on grape and wine quality. Nero di Troia grapes were subjected to four different treatments: N: no leaf removal; E: leaf removal in the area of the clusters along the east side (at complete veraison); E/W: leaf removal in the area of the clusters along the east and west side (at complete veraison); and F: almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side. Grapes of defoliated vines generally showed higher sugar content, lower titratable acidity, total flavonoids, flavonoids different from anthocyanins, and total phenolic content than grapes from non-defoliated vines while their total anthocyanin concentration was not affected by defoliation at a significant level. Concerning wines, alcohol content, residual soluble solids, different forms of anthocyanins but also volatile acidity were generally higher in samples from defoliated vines. Differences were also highlighted among the defoliation treatments: the best results in terms of dry matter, sugar and alcohol content were observed in the samples submitted to the more severe defoliation as a consequence of the higher light availability and berry temperature. Concerning the concentration of the individual phenolics, significant differences were highlighted for: caffeic and caftaric acids, peonidin- and malvidin-3-p-coumaroylglucoside, which were higher in the E wines; quercetin-3-glucoside, galactoside, and rhamnoside, and procyanidins, which were higher in F wines.

Effect of infusion of spices into the oil vs. combined malaxation of olive paste and spices on quality of naturally flavoured virgin olive oils

Olive oil flavouring with aromatic plants and spices is a traditional practice in Mediterranean gastronomy. The aim of this work was to compare the influence of two different flavouring techniques (infusion of spices into the oil vs. combined malaxation of olives paste and spices) on chemical and sensory quality of flavoured olive oil. In particular, oxidative and hydrolytic degradation (by routine and non-conventional analyses), phenolic profiles (by HPLC), volatile compounds (by SPME-GC/MS), antioxidant activity, and sensory properties (by a trained panel and by consumers) of the oils were evaluated. The obtained results evidenced that the malaxation method was more effective in extracting the phenolic compounds, with a significantly lower level of hydrolysis of secoiridoids. As a consequence, antioxidant activity was significantly lower in the oils obtained by infusion, which were characterized by a higher extent of the oxidative degradation. The volatile compounds were not significantly influenced by changing the flavouring method, apart for sulfur compounds that were more abundant in the oils obtained by the combined malaxation method. From a sensory point of view, more intense bitter and pungent tastes were perceived when the infusion method was adopted.

Volatile composition and sensory profile of wines obtained from partially defoliated vines: the case of Nero di Troia wine

The effects of defoliation treatments performed in the bunch-zone on volatile composition and sensory attributes of the corresponding wines were evaluated. Nero di Troia grapes were subjected to four different treatments: no leaf removal (N); leaf removal in the fruit-zone along the east side (at complete veraison) (E); leaf removal in the fruit-zone along the east and west side (at complete veraison) (E/W); almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side (F). For each defoliation thesis, half of the wine was treated with oak chips in order to verify whether the treatments with oak chips can mask the effects of defoliation. Defoliation partially affected the volatile profiles. Data concerning the volatile profiles show that the highest concentrations of total acids were detected in N and E wines, while those of the total ethyl esters were detected in F wines, and the lowest terpenes concentrations were found in E wines. The oak-treated wines show the highest contents of 1-heptanol, 1-octanol, many ethyl esters, and total hydrocarbons. They were the only in which the whisky lactone was detected. From a sensory point of view, the wines from almost completely defoliated grapes exhibited the lowest scores of gustatory-olfactory intensity, persistence, and quality. The wines that were not treated with chips exhibited sensory profiles characterized by floral and fruity notes, while those treated with oak chips showed sensory profiles characterized by spicy and fruity notes.