| With numerous wildfire outbreaks all over the | | | | 2. There is a variation in smoke taint between |
| world in the last few years, vineyards adjacent to | | | | different grape varieties, Cabernet Sauvignon, |
| these horrific blazes are having to cope with a | | | | Pinot Noir and Sangiovese have a high |
| very new problem. As if there are'nt enough | | | | susceptibility, whereas Shiraz and Merlot are found |
| difficulties already within the wine industry, here is | | | | to be less susceptible. |
| yet another one. But this is not like any of the | | | | 3. Grapevines are most sensitive to smoke |
| others, it is smoke taint in wine, and causes | | | | exposure from 7 days after veraison (when the |
| concern to winemakers. | | | | skins become translucent) through to harvest |
| Most of the fires will have been started during an | | | | time. Prior to this advanced ripening stage, the |
| exceptionally hot spell of weather, or possibly a | | | | sensitivity is somewhat reduced. As the grapes |
| lightning strike on parched ground that has not | | | | ripen, the skins become lighter and thinner and |
| seen rain for some time. If this is a sign of what | | | | therefore are more easily penetrable by smoke, |
| is to come with changing weather patterns, then | | | | so any 'damage' would be immediately prior to |
| there are some extraordinary issues that will need | | | | picking. |
| to be addressed in the future - and one of them | | | | 4. Harvesting mechanically or by hand has a big |
| is how to rid the smoke taint from the wine. | | | | influence on the concentration of 'total guaiacol' in |
| How the smoke gets in the wine | | | | the volumes of juice collected. Machine harvesting |
| One only has to stand next to a fire or barbeque | | | | accounts for around 98% of the 'total guaiacol' |
| to come away with your clothes smelling of | | | | coming through in the pressings and lees, while |
| smoke. The garments will then have to be hung | | | | hand picking is in the region of 40%. |
| out in the open and aired to rid them of the smell. | | | | 5. The concentration of guaiacol in the juice |
| Smoke clings fast and is not easy to dispel. | | | | increases with the maceration time, and more so |
| Getting it out of wine, which has had the smokey | | | | if leaves are being macerated as well. |
| aroma in it since the grapes were pressed, is not | | | | 6. 30 minutes of a single heavy exposure of |
| straight forward. Being similar to the smoking of | | | | smoke to grapevines is sufficient to produce |
| fish where the fillets have been hung up in a | | | | smoke taint in wine, providing that the exposure |
| smoke filled building; the grapes in the vineyards | | | | has occurred during a period of high sensitivity. |
| have absorbed the smoke for some time. | | | | 7. The smokey character does not seem to |
| Smoke tainted aromas have often been described | | | | carry over from one year to the next. |
| as burnt, burn toast, burnt bacon and phenolic, not | | | | Grapevines that have absorbed smoke in one |
| too appealing. To an extent the disagreeable | | | | season do not then present the same affect in |
| qualities of the taint depend on the type of fuel | | | | the fruit the next season. |
| being consumed by the fire. Bush fires and conifer | | | | How to remove the smokiness from the wine |
| forests have differing chemical structures to say | | | | Fining agents have been used, mostly without |
| those of open grassland fires. | | | | success apart from activated charcoal. The use |
| If smoke is readily absorbed by the vines and | | | | of charcoal pre-fermentation to reduce guaiacol |
| grapes, then the flora of a certain wine region | | | | concentration is effective at rates of 1.0 g/l to 1.6 |
| must also leave its imprint not only on the grapes | | | | g/l. |
| but also on the finished wine. | | | | A process called 'Reverse Osmosis' can be used |
| Another area worthy of note is that of the | | | | to remove compounds from wine. Some |
| toasting level of a wine barrel, and the flavour | | | | compounds can be cleaned from the filtrate, and |
| intensity which is selectively sought by | | | | the remaining wine then returned back into the |
| winemakers. These same toasting levels impart | | | | system. As guaiacol is a fairly small compound |
| some similar compounds into a finished wine as | | | | with small molecules it can be removed, but other |
| fire smoke does - but this is desired and | | | | larger compounds which have not been removed |
| controlled. | | | | can easily dominate the aroma. |
| Some established scientific parameters about | | | | If the smoke taint in the wine is low, this removal |
| smoke taint in wine | | | | method is ideal as only one or two passes are |
| | | | necessary. However, heavily tainted wines |
| 1. Grape vines, leaves and skins absorb mainly | | | | requiring several passes run the risk of having |
| guaiacol and 4 methyl guaiacol from the smoke | | | | some of the fruit characters removed as well as |
| (as well as other compounds). It has been shown | | | | the taint. |
| that smoke taint is not just the consequence of | | | | Results from reverse osmosis treatment of red |
| small fire particulates falling onto the grapes, but is | | | | wines have shown a noticeable reduction in the |
| more systemic. Washing the grapes vigorously or | | | | concentration of guaiacol by roughly one third, and |
| removing the waxy surface of the grape, has no | | | | tests are on-going. While the fires no doubt will |
| effect on smoke taint present. What actually | | | | continue to burn, research is helping the wine |
| happens is that the fiery compounds penetrate | | | | industry to cope with the problem of smoke taint |
| right into the vines, leaves and skins. | | | | in wine. |