Effect of post-harvest ozone treatments on the skin phenolic composition and extractability of red winegrapes cv Nebbiolo and Berbera

Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - UL

In many industrial sectors, ozone has been tested as an alternative to sanitizing products and chemical disinfectants, it has been tested also in oenological sector. Its use on raw material has been studied in few researches and we have studied its impact on wine grapes. In this work, we have considered different tannins concentrations present in berry skin extracts of two Italians vines, Barbera and Nebbiolo. They are post-harvest differently treated with ozone, to evaluate variations of phenolic compounds extraction post treatment. It has been possible identify qualitative and quantitative differences on samples after chemical analysis We have noticed that ozone treatments cause anthocyanic extraction slowdowns on Barbera samples. In Nebbiolo we have noticed a different behaviour, small increases of extraction percentage. To analyse, in specific, flavans extraction variations that ozone treatments can cause, we have conducted analysis on high molecular weight flavanic compounds. We have used proanthocyanidins spectrophotometric index and, according to previous analysis, ozone treatments have caused slowdowns of extraction kinetics in Barbera vine, that is not found in Nebbiolo, in which there was higher extraction percentage in treated samples. The analysis of proanthocyanidins spectrophotometric index compounds has been done on berry skins after macerations periods. In case of anthocyanins not extracted in macerations, in Barbera samples (Ozone 24 hours, Ozone 72 hours), there is a higher anthocyanins content in samples treated for 72 hours, that is not noticed for Nebbiolo samples. In Nebbiolo, in control grapes and ozone treated grapes, significant proanthocyanins concentrations variations and flavans reactive to vanilline not extracted during maceration are not noticed. In Barbera, we have noticed a small increase of high molecular weight not extracted flavanic compounds, relative to treatment time This work lead to interesting matter for reflection that deserves another studies, in order to analyse ozone effects. In fact, it has been necessary qualitative analysis with flavans compounds determination with H.P.L.C.