Stuck (really!)

Jonathan, Does your stuck fermentation have a "hot" aftertaste? lum

I was told by my supplier that once the alcohol level reaches a point, it kills the yeast, so mabee this is your problem. He told me to use champagne yeast as it is most resillient to alcohol. Been using it with sucess in higher octane wines (14-16%). Good luck.

Your supplier is correct, however the yeast Mr. Albert mentions (Lavlin D47) is alcohol tolerant to about 14%. The starting Brix of 20º he mentioned would only yield about 11.4 % alcohol --- if fermented to dryness. But, since it stuck at 6º Brix, there is currently less than 8% alcohol in the wine! The stated must temperature is also within acceptable range for this yeast. Thus, there must be another reason for the stuck fermentation. It can't be lack of nutrients, since he added some. Unless he added to much nitrogen? Perhaps the pH or TA is outside of the acceptable range?

I'm very curious as to what Lum is alluding when he asked, "Does your stuck fermentation have a "hot" aftertaste?"

What are you thinking Lum?

Don

Good thought, since I don't test for either pH or TA. Since the only pH measurement I could do quickly today was to grab a MultiStix urinalysis dipstick from the hospital today...doesn't really help, since the lowest pH it will measure in urine is 5.0 (D'Oh!). Well, at least that's proof that my wine is not piss.

Interestingly, the test showed negative to trace glucose, but the SG correlates with my Brix measurement. Nitrites were negative. Blood positive (huh...it's a Saignée, but that's ridiculous!).

Will try to pick up an acid measurement kit tomorrow.

-- ACEY

Not entirely sure what, specifically, you're speaking of, but no. No hot aftertaste....just tastes like sweet wine. There is definitely alcohol, but not what I'd expect.

-- ACEY

As others have said, D47 should easily be tolerant to the 8% alcohol by vol. in the wine now. Even so, the Red Star Premier Cuvée is actually an excellent champagne yeast (better than Pasteur Champagne, to my knowledge), and very tolerant to sulfites to boot.

-- ACEY

Hey, stop that "Mr. Albert" stuff! I'm Dr. Albert...seriously, Acey is great (that Dr. stuff still scares me a bit).

Can too much nitrogen be a problem? How so?

-- ACEY

Most yeast nutrients and "energizers" contain a large amount of diammonium phosphate, which provides nitrogen to the yeast cells. I believe, like plants, they use it for fuel. It's my understanding that too much nitrogen can be counterproductive, and kill the yeast. Sort of like "too much" alcohol (a mythical quantity I've never encountered) being dangerous to your health. :)

Hi Acey,

Acetic acid is toxic to all strains of Saccharomyces (wine) yeast. Fermentation slows when the acetic acid content exceeds about 0.1 percent, and when the acetic acid exceeds 0.2 to 0.3 percent, few viable yeast cells can be found.

Low acid, high pH grapes are common in warm growing regions. Controlling native bacteria with sulfur dioxide is difficult when the pH of the juice is high, and a large population of Lactobacillus bacteria sometimes develops during the primary sugar fermentation. The bacteria convert grape sugars directly into acetic acid, and the acetic acid content of the fermentation becomes excessive. Under these conditions, little or no ethyl acetate is produced, and without ethyl acetate, the winemaker is often unaware of the problem. The lactic bacteria can quickly raise the acetic acid level of the juice into the range of 0.1 or more. The yeast is unable to tolerate such high concentrations of acetic acid and the fermentation sticks. This kind of stuck fermentation is very difficult to restart because of the excessive amounts of acetic acid, and the fermentation is often a total loss.

Acetic acid produces a distinctive, "hot" aftertaste. But, your wine tastes OK, so I don't know what to suggest to help you ferment out that residual sugar. Sorry. lum

I'm thinking more like if the starting sugar content gave you a potential alcohol content of 20%, & the remaining content is 6%, then you have achieved 14%. If the yeast mentioned is tolerant to 14%, then the story is told, unless my math is rusty. I use a hydrometer to see where I'm at before & after & I was always under the impression that that's how it all worked. I backup the end result with an alcohol content tester & it always agrees with the hydrometer. If I'm wrong, please fill me in.

You are confusing "Brix" with "potential alcohol". Brix is the percent of sugar in the juice. The potential alcohol is estimated to be 0.55 (or .57) times the Brix of the unfermented juice. Thus a starting Brix of 20º 11-11.4% potential alcohol, not 20%.

A winemaking "hydrometer" may measure specific gravity, Brix, potential alcohol, or all three.

What sort of "alcohol tester" do you use? I had a "vinometer" that showed every dry wine as being 30%. I threw it away.

Little glass device that looks like a thermometer with a straight funnel at one end & graduated on the stem. About 4" long. Pour your wine in the big end & let it drip thru the small end, flip it over & the liquid runs out but enough remains in the tube to indicate the %. Used mine on a merlot I made from a kit @11% & my apple anywhere from

Lum,

Thanks for the input. There's definitely no vinegary taste or aroma to the wine right now, but it is possible.

In talking to the vineyard owner, he reports generally apporopriate TA and pH in his cab. sauvingnon and cab. franc musts. However, this is the first time he and I have actually made saignées. His stayed on the skins for about

I'm taking a sample to the hospital lab tomorrow for pH measurement...will see if we can measure acetic acid (don't think so).

-- ACEY

OK,

You need to rack your wine off the existing lees ASAP.

Don't add anymore nutrients to this wine, at this stage the yeast cells are incapable of metabolising the nutrients anyway.

Start a new culture of yeast in fresh juice if you've got some, a champagne yeast is preferable as your glucose is probably almost all gone and you are left with fructose which most wine yeasts don't particularly like. Champagne yeasts (such as EC-1118 or PDM) don't mind fructose. Add some nutrients here.

This culture should be aerated for the first day, use an aquarium bubbler. Watch the sugar levels, as they drop add a bit more juice. After a while the ferment should be going well. SLOWLY start adding your stuck ferment to the culture. Say if you have 2-3 litres of culture add 2-3 litres of stuck juice. Watch the ferment, once it is strong do this again (ie double the volume) keep going until its all in and hopefully it will go through to dry.

This is how we handle stuck ferments as professional winemakers (you wouldn't believe how many we actually get with all the best equipment abd care even!)

The secret is to acclimatise your new yeast culture to the stuff you are trying to get going. Just adding a new culture directly will shock the yeast and it will die very quickly.