Measuring the aromatic potential of Vitis vinifera L. Cv. Sauvignon blanc grapes by assaying S-cysteine conjugates, precursors of the volatile thiolsresponsible for their varietal aroma

The method presented for measuring the aromatic potential of Sauvignon blan c must is based on an assay of the S-cysteine conjugate precursors of three volatile thiols involved in the characteristic aroma of wines made from th is grape variety: 4-mercapto-4-methylpentan-2-one, 4-mercapto-4-methylpenta n-2-ol, and 3-mercaptohexan-1-ol. These compounds were released enzymatical ly from their precursors by percolating the must through an immobilized try ptophanase column (EC 4.1.99.1), catalyzing an alpha,beta-elimination react ion on the S-cysteine conjugate. The volatile thiols were analyzed by GC-MS , as were the deuterated analogues that had been released from synthesized deuterated precursors and were added as internal standards. The quantities of volatile thiols released under these conditions were proportional to the S-cysteine conjugate content of the must.