Nov
14
The last couple of weeks, the weather has warmed up, and the wines in barrels have warmed up too. This causes any microbes in the wines to get active as well. Malolactic bacteria are microbes found in unfinished wines . Often they are added, in dried form, by the winemaker, to ensure a large population, as their presence is desirable. We don’t do this; we reckon the bacteria are endemic in our winery and the wines will go through malo in their own time. Their role in winemaking is in the conversion of the less palatable Malic acid to the softer Lactic acid, and this they do very well. There is some discussion about whether the resulting wine is any better, or even if the difference can be detected, but the overall benefit is that the wine is rendered more stable. Known as “malolactic fermentation”, (although it is not really a fermentation process), or “malo”, the process produces large amounts of carbon dioxide, along with some of the most gruesome and foul smelling gases you will ever encounter! (These smells are transient - they disappear fairly readily with a good, aerative racking.) So obviously, if you can get this process to occur BEFORE it is in a bottle, it is much better! (Unless corks exploding out of bottles in the cupboard under the stairs suits you.).
Sulfur is the enemy of the malolactic bacteria, so until malo is finished, you cannot sulfur the wine, which leaves it in a relatively unprotected state with regard to other, more sinister bacteria. So it is obviously best if the wine goes through malo fairly early in its career, and usually, most of our wines go through just after the initial fermentation at vintage. However, at that time the weather starts to cool, the nights in particular, and the later picked wines, or wines with particularly high alcohol levels, tend to go through the malo process slower, meaning that sometimes, when the winter chills hit, the bacteria become inactive, leaving unfinished business.
The first vintage I made, in 2002, in the machinery shed, frightened the hell out of me. I hadn’t realised how violent malo could be, and it wasn’t until I unbunged a barrel, to proudly show my wine to a friend, that I discovered it. Thick, purple goo started to gurgle and ooze out of the bunghole, looking nothing like the wine I remembered from a few weeks ago, and certainly nothing you’d want to show off about, so I quickly stuffed the bung back in, and stood back, relieved to have stoppered the evil genie that had obviously taken up residence in my barrel. Like a geyser, the wine shot straight up into the air about 12 feet; the bung hit the roof of the machinery shed with a bang, and bounced off the tractor roof. All I could see was my beautiful, hard won merlot going everywhere, (all that tending! All that picking!) so I flung myself over the top of the barrel, to save what surely could only be the last few litres out of the 220 litre barrique. When the geyser had dried up, I retrieved the bung, and then gingerly checked the others. After I had the same reaction from a couple of other barrels, I knew it was time to call the doctor. I rang a couple of experienced winemaking mates, and shakily told my story. They laughed, and told me that my wines “…were behaving like perfectly normal babies”,and not to put the bungs in so tight for a while…
That vintage was a very steep learning curve for us!
These days, we are more relaxed about these things. However, a few of our wines hadn’t finished before the 2007 winter, and it was a somewhat anxious Andrew who called me while I was away one day, to let me know that the wines had woken up, and bungs were shooting out of barrels under the pressure of carbon dioxide building up. So we eased all the bungs, loosening them in the actively bubbling, crackling barrels and putting valves in the barrels that were not quite as active. The S-shaped valves have water in them, and allow carbon dioxide out of the barrel, bubbling through the water, but do not allow air back into the barrel. The barrels that were actively going through malo, we are able to leave the bungs sitting loosely in the bunghole, as the amount of carbon dioxide being produced stops any air getting in anyway.
This was a couple of weeks ago, and the only wine not through yet is the 2007 Petit Verdot. It is still grumbling away, and smelling pretty yukky. However, with the current run of warm weather, it should finish in a few days, and I’ll then be able to continue with the next winemaking thing - racking. (Where the clear wine is removed carefully from the barriques, leaving impurities and particles behind; the barrels cleaned, the wines sulfured and then returned to the cleaned barrels, for the next phase of maturation.) A time when foul language becomes the language of the day, as the pump refuses to prime, and I overflow the barrels while I’m off doing something else. Stay tuned!
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One Response to “The weathers warming up, and the wine is waking up…”
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Hi,
You mentioned how difficult it was to control MLF. One thing that can help is monitoring its progress, and adjusting temperature or some other factor. I do have a vested interest in suggesting monitoring. I’ve developed some quick test strips for testing Malic Acid in wine. They’re produced by Accuvin, LLC, and are available from Novasys Group in VIC, or Aim Scientific in SA. Knowing the end of MLF can also tell you the bes time to add your sulfite.
Regards,
The Reluctant Chemist