Is my fermentation stuck?

[Jagoda]

He Everyone,
I am new to wine making, just started my first wine 12 days ago. I bought Zinfandel frozen must (starting brix 28.5 or SG of about 1.2, starting ph 3.3, starting TA 8.2 g/l). I allowed the must to thaw for three days and then added potassium metabisulfite and waited 24 hours. After 24 hours I added one packet of yeast. There is activity in the must when I punch the cap each day, bubbles are coming up. I measured sugar 3 days ago and it was still SG 1.12 and then measured it again today and SG was 1.10. Is it normal that it is taking so many days and I only see the sugar go down after 12 days or is it a sign that my fermentation is having problems? I also measured ph today and it is 2.9. The juice tastes sweet and acidic. What can I do to keep going with this wine? I read in wine making guides that pressing should be done when SG is 1.0 and it looks like my must still has a lot of work to do to get there but it is already 12 days. I appreciate any help you can give me.

 

[SBWs]

A few questions.

What was the temperature of the must when you pitched the yeast?

What is the temperature of the must now?

What yeast did you use?

Did you add any nutrients?

How are you checking pH and acid?

 

[Bergmann]

How are you measuring the Specific Gravity? Are you sure of a SG of 1.2 that would give a potential alcohol of over 30% and would surly stall the fermentation regardless of the yeast used. Actually I am surprised it started.

 

[Jagoda]

What was the temperature of the must when you pitched the yeast? - 70F

What is the temperature of the must now? - 74 F

What yeast did you use? - Lalvin RC 212

Did you add any nutrients? - No

How are you checking pH and acid? - I used an electronic PH meter to measure PH now; the original PH and TA numbers were given to me by the wine supplier where I purchased the must. Do I need to measure both components? I will buy TA measuring tools if I need to but I thought PH level would give an indication if there is something wrong.

How are you measuring the Specific Gravity? Are you sure of a SG of 1.2 that would give a potential alcohol of over 30% and would surly stall the fermentation regardless of the yeast used. Actually I am surprised it started. - I am sorry, I made a typo - it should say SG of 1.12 not 1.2. I measure it with hydrometer.

 

[Julie]

Evan at 1.12 that is pretty high for a juice bucket, normally they run 1.090. Do you have more than one hydrometer? I would check it with another hydrometer.

 

[grapeman]

If the supplier listed 28.5 brix then 1.120 is correct (this was a bucket of frozen must, not juice). You say you used a meter to measure the pH. Did you calibrate it with known good calibration standard solutions? How much sulfite di you initially add? If too much you could have stunned or killed the yeast. You can try and make a nice yeast starter and repitch that to see if you can get it going. Also use some type of yeast nurtient in the nust to help the fermentation stay healthy.

 

[JohnT]

If I could also weigh in here..

I have been using RC-212 for a solid 25+ years. That particular strain of yeast yields a flavor profile that is simply fantastic.

In dealing with it for so long, I know for certain is that it really does need nutrient. Without nutrient you run a particularly serious risk of H2S issues.

 

[blazerpb]

Oh Boy!!! 28.5 BRIX is high even for Zin grapes. Hi Brix grapes with too much sugar can cause problems with the primary and secondary fermentations. This is beyond the outer reaches of RC212 which works well 24 to 26 BRIX. I'm guessing you will end up somewhere around 18% alcohol.

Adding acidulated water can help lower the BRIX. Might be too late for that now. Never having to lower the BRIX, I'm more of a student on that topic. But Nutrients are a definite with a Brix that hi and RC212.

 

[Jagoda]

Update: I pressed the grapes and moved the juice to the carboy. I added more yeast to the juice and nutrients and the fermentation was going pretty well (bubbles coming out every 10 seconds or so), sugar went down to 1.05. But I noticed it started slowing down significantly again (bubbles are now coming out every 2 minutes). The taste is still sweet and tastes like grape juice (quite good though). Should I add another packet of yeast and nutrients to get it down to SG 1.0 or just wait some more for the fermentation to go on for a bit longer? I am afraid this would be the third packet of yeast being added to the juice. Thank you for your input.

 

[heatherd]

Jagoda,

Welcome to the hobby!

I would just give it more time.

Do you have a process for making the wine? If not, Morewine has a guide that you can download and print. There's one for reds and one for whites. It is important, when you are starting out, to know what steps to take.
http://morewinemaking.com/content/winemanuals

Heather