Reductive off-odors in wines: Formation and release of H2S and methanethiol during the accelerated anoxic storage of wines

In order to better understand the processes involved in the development of H2S and methanethiol (MeSH) along anoxic storage of wines, 24 wines were stored in strict anoxia at 50 °C for 3 weeks. Free and total forms of H2S and MeSH were measured at different times. Results showed that: (1) all wines contain relevant proportions of bonded forms of H2S and MeSH (93% and 47% on average); (2) such % decreases with age; (3) levels of total forms are related to wine metal composition; (4) anoxic storage brings about an increase of free forms, a strong decrease in the percentage of bonded forms, and except for H2S in red wines, an increase in total forms. Both de novo formation and release contribute to reductive off-odors. Release is predominant for reds and H2S, while at 50 °C, de novo formation dominates for whites and rosés and MeSH.