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

Abstract

20In order to better understand the processes involved in the development of H 2 S and 21 methanethiol (MeSH) along anoxic storage of wines, 24 wines were stored in strict anoxia

The effects of copper fining on the wine content in sulfur off-odors and on their evolution during accelerated anoxic storage

“…Results presented in this work confirm previous observations on the strong increases in the levels of free forms of VSCs during the anoxic storage of wines (Franco-Luesma & Ferreira, 2016b). In fact, increases of these VSCs during wine aging have been repeatedly reported, even if the wine is stored in containers not completely anoxic (Lopes et al, 2009;Ugliano et al, 2012;Ugliano, Kwiatkowski, et al, 2011).…”

“…As shown in Figures 1 and 4, increases depend on the wine, on the level of copper and on the time of anoxic storage, in accordance with previous reports. The magnitudes of the increases (20-40 µg/L after two weeks of anoxic storage) are slightly above those previously reported in a similar experiment (Franco-Luesma & Ferreira, 2016b), and double or even quadruple those found to accumulate after 1 year of reductive aging at room temperature (Franco-Luesma & Ferreira, 2016a). These higher increases were expected since the wines studied in the present work had been selected because of their known tendency to develop sulfur offodors.…”

“…The increases of BR-H 2 S measured in the three wines of the experiment are much higher than those previously reported. In fact, in accelerated reductive storage experiments carried out with bottled commercial wines, average levels of BR-H 2 S in red wines did not significantly increase (Franco-Luesma & Ferreira, 2016b) and in the few samples in which that happened, increases were quite modest (the highest 6.7 µg/L). In most cases, levels of BR-H 2 S remained approximately constant since the beginning of the experiment, while free H S steadily increased tending, but never reaching, the to levels of BR-H 2 S. Taking into account that dilution in brine can cleave some H 2 S-metal complexes (maybe some other weak associations), but cannot reduce disulfides or polysulfides, and cannot of course can release H 2 S from cysteine, it was concluded that in bottled commercial wines the quantitatively most important process explaining the accumulation of free H 2 S was the release of metal-complexed forms.…”

“…On the other hand, several reports have suggested that added copper may be active in detrimental reactions in wine. In fact, the relationship between the presence of residual copper and H 2 S levels has been suggested by several researchers (Bekker, Mierczynska-Vasilev, et al, 2016;Franco-Luesma & Ferreira, 2016b;Ugliano, Kwiatkowski, et al, 2011;Viviers et al, 2013). Residual copper may be active in the catalytic desulfuration of cysteine and methionine, which would contribute to increased levels of H 2 S and MeSH (Bekker, Mierczynska-Vasilev, et al, 2016) through complex synergic effects with other wine metals (Viviers et al, 2013).…”

“…Reductive or sulfur-like off-odors are responsible for an important proportion of faulty wines with potentially large economic losses (Goode, 2014). Such a problem is mostly caused by the development of low molecular weight Volatile Sulfur Compounds (VSCs) of which H 2 S is the most frequently found above its odor threshold followed by MeSH (Franco-Luesma & Ferreira, 2016b;Siebert, Solomon, Pollnitz, & Jeffery, 2010;Ugliano, Kolouchova, & Henschke, 2011). Dimethyl sulfide (DMS) is also frequently included within the group of reductive problems, although it strongly differs from H 2 S and MeSH both in sensory effects (Escudero, Campo, Farina, Cacho, & Ferreira, 2007;Franco-Luesma et al, 2016;Lytra et al, 2014;Segurel, Razungles, Riou, Salles, & Baumes, 2004) and in chemical origin (Loscos et al, 2008).…”