Live yeast in bottled wine(?)

WINE TALK
1

Many of the posts in the two threads regarding storage temperature mention the activity of yeast in bottled wine. I am not a winemaker, and certainly know much less about the process and chemistry than many here, but I am under the impression that most (properly-made) wine does not contain any (or any significant) live yeast when bottled.

I know that sometimes brett is present, and while apparently sometimes intentionally, this is to me another subject.

When sparkling wines are made by Champagne Method, yeast is added with sugar to produce the secondary fermentation, suggesting that live yeast is not already present in the still wine. Further, when the dosage is added afterwards, there seems to be no fear that yet a third fermentation will occur, so apparently no live yeast remains at this time either.

Any wine which is fortified somewhere north of 17% or so is presumably yeast-free. Wines which spend years under a cap of yeast such as Manzanilla and Vin Jaune have pretty much nothing left for yeast to metabolize, and also seem undeniably stable in the bottle.

I regularly drink German rieslings which are low in alcohol and significantly sweet. Oftentimes these wines have been in the bottle for a decade or two. Perhaps any remaining live yeast was killed with SO2 at bottling, but however accomplished, none remained, or certainly these wines would all be spritzy.

As a matter of fact, sometimes I open a bottle and it is indeed spritzy, it seems to me almost a sure sign of secondary fermentation, so produced by live yeaast. Yet I have observed this even very slightly perhaps 1% of the time, certainly this suggests that most wine does not contain live yeast in the bottle.

Finally, it seems to me that if it was normal for wine to be bottled with live yeast, the situation of bottle variation would be wildly magnified from what all of us have observed.

I certainly may be missing something, but is wine really knowing bottled with live yeast, typically?

Thanks!

2

Spritz in your German Riesling is probably not refermentation in bottle, but retained CO2 from primary fermentation. That said, I think many high quality wines will have some live yeast in the bottle. Those that have not undergone sterile filtration. A combination of low sugar, high acidity, high alcohol, SO2, ect. will minimize the chance of refermentation in the bottle. I have had some red wines to which this has occurred. Nasty, stinky stuff.

3

Steve - I’m not a winemaker either, but I think Eric has it right. In dry wines, you assume there’s no fermentable sugar left so even if there are some live yeasts at bottling, they won’t multiply because they have nothing to feed on.

With sweet wines, SO2 was the traditional solution. The sulfur was often quite apparent when the bottles were open. I believe micro-filters are more common now. Sweet German wines today show MUCH less sulfur on the nose than they did a couple of decades ago.

As Eric says, the spritziness of some wines – mainly whites – is almost always CO2. That’s less common in reds because they’re aged and racked more, so the CO2 tends to dissipate.

4

Well, on second thought, I think you are both right. This does however further support that live yeast may not be an issue in the whole bottled wine/storage temperature/aging discussion.

5

I agree with the posts above, however yeast may not need sugar to stay alive. They can turn dormant and stop multiplying, but that doesn’t mean they are dead and wont continue to produce toxins/off notes when they’re stressed. Who knows, maybe they can use some of the sugars from the alcohol to stay alive a little longer if they get heated up? Pasteurization is really the only way to ensure there are no microbs and that’s not going to happen with (most) wine.

Edit: Also, acids can be broken down into sugar/calories, which is obviously present in wine. There’s no way around it, those little bugs are alive.

6

If a wine is sterile filtered, it will be no live yeast cells what so ever.

If a wine is unfiltered, there is a greater chance of live yeast cells, both saccharomyces and perhaps Brett cells, depending upon numerous factors.

The chance of any of these live cells reproducing will be based on usable sugar left on the wine, a nitrogen source, and temperature of the wine.

Cheers.

7

Larry, well said. These discussions weren’t necessarily about unfiltered wine, so Steve’s OP still stands in my eyes.

8

What Larry said, plus O2. Yeast needs O2 to multiply. Without it and without sugar, its not going far.

9

Larry, my assumption is that still bottled wine which is not flawed has substantially no living yeast in it. Do you agree with that statement?

10

FWIW, some red wines get minimal racking and can have a mild spritz from dissolved CO2. Pinot Noir is a prime example.

-Al

11

Think of two thresholds in relation to toxicity. One is where microbes are inhibited, the higher where they are dead. Things like ethanol, SO2 and acidity are toxic to yeast and other microbes. Different strains of yeast have their own tolerances. Think of the old late harvest Zins. They fermented until the ethanol level became toxic to the yeast, stopping the fermentation despite the remaining sugar. Any dry wine will have living yeast at the end of fermentation. If you don’t have residual sugar or other lingering nutrients, filtering out the microbes or doing something like nuking them with Velcorin or not are choices. Some wines taste exactly the same before and after filtering, while others become stripped of character. You can see why some may sometimes opt for a low risk over devastating a wine. You can also see where personal philosophies could guide these choices.

The case with fortified wine is you are adding ethanol to a level that will kill the yeast. With a late harvest wine, the last yeast working had the highest tolerance of anything that was there. If any cells are still alive it shouldn’t matter.

12

So. Can we discount yeast from future discussions?

13

I’m not. I studied food micro in college and know better than to ever discount a living organism in food. Just because there is no sugar to ferment doesn’t mean they still can’t produce other chemicals/off notes or even convert acids into useable carbohydrates. Stress, like heat, can cause them to do some weird stuff.

14

As I stated above, if a wine is sterile filtered, which many are these days, there are no viable cells left. Period. Likewise, if a wine is hit with Velcorin at bottling, which is now widely used by wineries who do not want to filter but want to ‘be sure’ that there are no living yeast cells, there will be no living yeast cells.

The only way that yeast cells may still be present is if the wine is unfiltered - and for the reasons stated above, they may or may not be viable. This does not rule out the possibility of secondary fermentation via bacteria still occurring in bottle or other bacterial issues.

Hope that clears things up.

15

I’m not sure what you mean by ‘not flawed’. Still bottled wine certainly can still have living yeast cells in it if it is not filtered - and these can grow in the future given the right conditions.

Cheers.

16

And this?
https://twitter.com/TheFigen_/status/1790869266226393550

1 Like
17

Yes, I saw that video yesterday. Hilarious. Plainly these folks had not read this old thread.