First characterisation of thiol precursors in Colombard and Gros Manseng: comparison of two cultivation practices

Background and Aims

The thiol aromatic potential of the grape cultivars, Colombard and Gros Manseng, from Côtes de Gascogne was characterised for the first time.

Methods and Results

We demonstrated that both cultivars contained a concentration of glutathionylated and cysteinylated precursors of 3-sulfanylhexan-1-ol up to 454 and 21 μg/kg, respectively, which makes them good cultivars for the production of wines rich in thiols. No precursors, however, of the 4-methyl-4-sulfanylpentan-2-one were detected. We then studied the impact of cultivation practices by comparing conventional and organic training systems on the biosynthesis of thiol precursors in grapes. We showed that the concentration of glutathionylated precursors of 3-sulfanylhexan-1-ol in Gros Manseng varied significantly according to the type of cultivation, whereas they remained unaffected in Colombard grapes. Organic Gros Manseng grapes (copper concentration of 466 ± 275 μg/kg) exhibited up to 30% loss of thiol precursors compared to that found in conventional grapes (copper concentration 199 ± 91 μg/kg).

Conclusions

The free copper concentration at harvest does not correlate with the decrease in thiol precursor concentration, leading to the conclusion that differences found between the management of the two vineyard practices are not simply related to copper but are a multifactorial phenomenon.

Significance of the Study

Colombard and Gros Manseng contain a high concentration of thiol-type aromatic compounds, the concentration of which can be modulated by agronomic practices.