Potassium Metabisulfite & Yeast

[Linetec]

Evening all! I come you guys and gals for some input. This morning i cracked up the lids to 4 6 gal buckets of juice. I went ahead and added the 1/4 tsp of potassium metabisulfite. Approx 8 hours later I pitched the yeast. My question is this, should I have waited 24 hrs after adding the potassium meta or will my fermentation be ok? If it’s not going to be ok, do I need to pitch another round of yeast and if so will the extra addition of yeast hurt the outcome of the wine.

Thanks In advance for any and all input all of you share with me.

 

[Jovimaple]

You might be okay. Try stirring the must. In a day or so, if you don't see fermentation activity and the specific gravity hasn't started dropping yet, pitch more yeast. You won't hurt the must by pitching more.

 

[Linetec]

You might be okay. Try stirring the must. In a day or so, if you don't see fermentation activity and the specific gravity hasn't started dropping yet, pitch more yeast. You won't hurt the must by pitching more.

Gotcha! If I have to pitch yeast again, should I use go-fern again along with the new yeast?

 

[winemaker81]

Commercial yeast is typically K-meta tolerant, so you're probably fine.

If you pitch another round, I'd make the starter the same as you did the last one. The Go Ferm is designed to help the yeast reproduce quickly, and you want that.

 

[Linetec]

Commercial yeast is typically K-meta tolerant, so you're probably fine.

If you pitch another round, I'd make the starter the same as you did the last one. The Go Ferm is designed to help the yeast reproduce quickly, and you want that.

Ok I did not know that about commercial yeast being k-meta tolerant. I assumed it killed the commercial yeast given that it kills the wild yeast. Thanks for the info!

 

[rsportsman]

1/4 teaspoon is about 1.4 g KMBS x 0.57 SO2/KMBS = .798 g SO2 in 6 gal x 3.8L/gal = .798g/22.8L = 35 mg/L SO2. Most commercial yeasts can handle this much, and after 8 hours it would be less anyway.

When we sulfite our musts we shoot for 50 mg/L SO2 just by the way.

 

[winemaker81]

Ok I did not know that about commercial yeast being k-meta tolerant.

Generally, K-meta tolerance is a requirement for commercial yeast, as K-meta will be used to kill or stunt wild yeast and bacteria.

When you decided to make wine, you had NO idea how much biology, chemistry, and physics you'd be learning, did you?

 

[Linetec]

Generally, K-meta tolerance is a requirement for commercial yeast, as K-meta will be used to kill or stunt wild yeast and bacteria.

When you decided to make wine, you had NO idea how much biology, chemistry, and physics you'd be learning, did you?

Man you ain’t kidding!! Lol. You gotta gave your degree in chemistry!! Haha

 

[Siwash]

Just reading this.. I did not know that wild yeasts had to be killed off with juice pails! I've done this ONLY with fresh grapes! The supplier I've been getting my juices from told me a while back that it was not necessary to kill off the wild yeast as vineyards added k-meta before packing (although I don't see this as an ingredient on the pails). So the yeast I added is in competition with the wild yeast at this point? I've got two pails fermenting right now..

 

[winemaker81]

I did not know that wild yeasts had to be killed off with juice pails!

Yeast grows on the skins of grapes, which is why they ferment without being inoculated. Unless the juice/must is pasteurized, there will be yeast in it.

K-meta is not a requirement. Commercial yeasts are selected for numerous characteristics, and a common one is fast reproduction so it crowds out competition. However, adding K-meta initially kills or stunts competition, so the commercial yeast has a bigger advantage.

Me? I add K-meta as I'm more concerned about mold, mildew, and bacteria than wild yeast. But it handles it all.

 

[Siwash]

Interesting... I have always understood that the creation of co2 kept the nasties at bay... anyhow, ya learn something new every day in this hobby.

Hopefully my selected yeasts did the job and outcompeted the native yeast.

 

[winemaker81]

@Siwash, the CO2 keeps the O2 at bay, not necessarily the micro-critters.

I'm of 2 minds with regard to "natural" fermentation. One school of thought is that the yeast that grows on the skins of a particular varietal is the best pair for it. This sort of makes sense, but I don't see the grapes or yeast caring what humans want or don't want.

In areas where the vineyards are decades or even hundreds of years old, it does make sense. Humans kept the vines that produced the best wines, and replaced the lesser contenders. Over time, this process may have resulted in vineyards where the grape/yeast combination was optimal for winemaking purposes. It wasn't natural selection, it was human selection based upon what worked best.

In areas like this, natural fermentation sounds like a good idea. The efforts of previous generations made it so.

OTOH, I have NO idea what the age or conditions are in the vineyard(s) I get grapes from. Some form of selection may -- or may not -- have occurred. I have far too much invested to chance the grape/yeast combination, so I inoculate with commercial yeast.

 

[Rice_Guy]

Just reading this.. I did not know that wild yeasts had to be killed off with juice pails! I've done this ONLY with fresh grapes! The supplier I've been getting my juices from told me a while back that it was not necessary to kill off the wild yeast as vineyards added k-meta before packing (although I don't see this as an ingredient on the pails). So the yeast I added is in competition with the wild yeast at this point? I've got two pails fermenting right now..

In testing buckets that the Vinters club orders red juice will typically have between 10 and 15 ppm free SO2, white typically a trace or zero ppm.
To the original post, one hours should oxidize the readily consumed SO2 , there may be some yeast that are viable since kill is a time related function. Folks in the Vinters club will frequently open and inoculate without additional treatment, the exception being if active fermentation is going on when delivered.

Interesting... I have always understood that the creation of co2 kept the nasties at bay... anyhow, ya learn something new every day in this hobby.
Hopefully my selected yeasts did the job and outcompeted the native yeast.

The CO2 is effective at preventing chemical oxidation of alcohol to make acetaldehyde, by itself it is not effective at preventing micro growth. The cut off for most bacterial growth is 5% alcohol therefore a recipe will do things to have enough yeast to reach that barrier. Another controll is pH, food poisoning organisms don’t grow below pH 4 so I/ country wine making recipes increase the acid to provide safety. Now to complicate things when CO2 is produced it will form carbonic acid which helps get the pH down where it is effective.

 

[Siwash]

My dad never or rarely added yeast back in the day when he used to press fresh grapes. The wines ranged from ok/decent to not very good some years.

 

[winemaker81]

My dad never or rarely added yeast back in the day when he used to press fresh grapes. The wines ranged from ok/decent to not very good some years.

Some of my early mentors did the "crush and see what happens", and their wine was hit-n-miss. I like to provide for success!

 

[wood1954]

I didn’t add any so2 to The juice buckets I got through rice-guy’s club this year. The wild yeast added a little funky smell but once my commercial yeast took off it must have dominated the wild yeast as the smell went away by day four. It’s currently undergoing MLF and tastes and smells good.