Methoxypyrazines as a potential "green" off-odour in wine distillates

Aroma is one of the main quality parameters of wine distillates. Avoiding generation of off-odours is therefore an issue of great concern in the industry and consequently numerous studies have investigated to identify off-odours using a variety of different approaches. Different wine distillates were studied for the expression of “green-earthy” notes by means of TD-MDGC-MS/O and two odoriferous zones were identified. The compounds identified were 3-isopropyl-2-methoxypyrazine (IPMP) for the first odoriferous zone with intense earthy note and 3-isobutyl-2-methoxypyrazine (IBMP) for the second odoriferous zone with intense green note. The quantification experiments showed high concentrations of IPMP and IBMP for an average of 46.2 and 51 ng/L respectively, with some extreme levels of 178 ng/L for IPMP and 126 ng/L for IBMP. Further experiments showed different kinetics for the extraction of methoxypyrazines during distillation process. Thus, extraction of IPMP is more pronounced in the first fractions, contrary of IBMP which is more present in the last fractions of distillation process. Moreover, the sensory impact of the methoxypyrazines was confirmed