Changes in methionol concentration in a rose wine packaged in pet bottles with oxygen scavengers

Abstract

As alternatives to glass bottles, Polyethylene Terephtalate (PET) bottles are now used for wine packaging. Tis increase the problematic of wine oxidation due to the high O₂ permeability of these materials. To face this problem, oxygen scavengers (OS) were included in PET matrix. The aim of this study was to predict the impact of OS on the oxidation of methionol, an oxygen sensitive aroma compound. For this, methionol oxidation was monitored in model wine solutions with different initial oxygen concentrations and in the presence of 1% and 3% OS incorporated in PET. In parallel, changes in methionol concentration of a rosé wine packed in PET bottles containing 1 or 3% of OS (named 1OSPET and 3OSPET) were followed during 12 months of storage. In model solution, with an oxygen concentration found in wine (3.8 mg/L), methionol was less degraded in the presence of 3 % of OS. For a lowest concentration of oxygen, the presence of scavengers slowed down the methionol degradation both with 1% and 3%: the oxidation reached about 52% and 32% of initial concentration respectively against 63% in the absence of scavengers. A mechanistic model based on second order reactions for methionol degradation and oxygen consumption by scavengers was proposed to predict methionol degradation in relation to OS amount. Even if these results are obviously difficult to transpose to a real wine, where numerous compounds can be also oxidised and where transfer through packaging may occurred, it has been found that methionol was preserved in 3OSPET bottles during the 12 months of storage. In contrast in 1OSPET bottles, methionol concentration was decreasing. It was clearly demonstrated that the losses of methionol were mainly due to oxidation since sorption and permeation of this compound were negligible. To conclude, in PET packaging, oxygen sensitive compound is only preserved if the OS amount is sufficient.