Efficiency of alternative chemical and physical treatments in reducing Brettanomyces Bruxellensis from oak wood

Tyrosol (TYR) and hydroxytyrosol (HYT) are bioactive phenols present in olive oil and wine, basic elements of the Mediterranean diet. TYR is reported in the literature for its interesting antioxidant, cardioprotective and anti-inflammatory properties. In wine, its concentration can reach values as high as about 40 mg/L
[Pour Nikfardjam et al. 2007] but, more frequently, this phenol – derived from yeast metabolism of tyrosine during fermentation – is present at lower levels, generally higher in red wines compared to whites. HYT was measured for the first time by Di Tommaso et al. [1998] in Italian wines – with maximum values of 4.20 mg/L and 1.92 mg/L for red and white wines, respectively – while definitely lower concentrations have been found later in Greek samples.

Céline Sparrow a, Christophe Morge a, a SOFRALAB SAS, 79, av. A.A. Thévenet – CS 11031 – 51530 Magenta, France Consumers’ health and security force authorities to limit, in wine as in others food industry products, the concentration in « dangerous » molecules. Therefore the legal limit in heavy metals keeps on decreasing. As per proof EU regulation just decrease the stain concentration in wine from 0,2 to 0,15 mg/l. Certain changes , such as sodium arsenite treatment in vines, disappearance of brass in wineries to the benefit of stainless steel, limit even more the concentration of heavy metals in wines. But the use of copper derivates in vines treatments is difficult to replace. In the case of wine and its elaboration, the problem is even more complex. Indeed, regulation forces the wine producers to control the concentration of certain heavy metals in final wines.

Ellagitannins (ETs) have been reported to be the main phenolic compounds found in oak wood. These compounds, belonging to the hydrolysable tannin class of polyphenols, are esters of hexahydroxydiphenic acid (HHDP) and a polyol, usually glucose or quinic acid. They own their name to their capacity to be hydrolysed and liberate ellagic acid and they have an impact on astringency and bitterness sensation, which is strongly dependant on their structure. The toasting phase is particularly crucial in barrels fabrication and influences wood composition.

(-)-Rotundone, an oxygenated sesquiterpene, is a potent odorant molecule with a characteristic spicy aroma existing in various plants including grapes1. It is considered as a significant compound notably in wines and grapes because of its low sensory threshold (16 ng L-1 in red wine, 8 ng L-1 in water) and aroma properties. (-)-Rotundone was first identified in red wine made from the grape cultivar Syrah (regionally called Shiraz) in Australia1, and then it was found in several grape varieties such as Duras, Grüner Veltliner, Schioppettino and Vespolina from Europe2, 3. Several environmental factors affecting the accumulation of (-)-Rotundone during the grape maturation, were reported such as ambient temperature4, soil properties and topography5, soil moisture from irrigation and light exposure in the bunch zone by leaf removal2.

During the tasting of a fine, old wine, the aromas generated in the glass are intertwined in an intimate, complex manner, expressing the fragrance of the aging bouquet. This aging bouquet, which develops during bottle storage through a complex transformation process, may result in a broad palette of nuances. Among these, undergrowth, truffle, toasted, spicy, licorice, fresh red- and black-berry fruit and mint descriptors were recently identified as features of its olfactory representation for red Bordeaux wines. Although a targeted chemical approach focusing on volatile sulfur compounds revealed the role played by dimethyl sulfide, 2-furanmethanethiol, and 3-sulfanylhexanol as molecular markers of the typicality of the wine aging bouquet of red Bordeaux wines, its chemical transcription has only partially been elucidated.