Reusing yeast after suck back

So here is the problem. I planned to brew 2 Belgians using the same strain by reusing the yeast after washing. So I went on and brewed using WLP530. I wanted to clarify the first batch so I set my chest freezer temp. controller to 5C this morning. I came back to find my blow off tube liquid empty (guess where it went ). This liquid was originally iodophor, but during fermentation some yeast came out. This solution stayed there for 3 weeks until today, where I'm almost ready to bottle and brew my second batch.

Now the question is, would you reuse this yeast? I'm very scared it might be infected. I will be brewing this Saturday and I may change my recipe in fear of wasting 2 batches

The solution in the blow off tube is sanitized, so it shouldn't be a problem. All the liquid from the blow-off? Are you talking about a standard 3-piece air lock, or an actual blow-off? Because at least when I use a blow off there is about a pint of sanitized water, so that would be a lot to suck back.

The yeast going into the tube and back in shouldn't be a problem. If fermentation is done, then there is alcohol and healthy yeast, which means it is hard for the infectious bugs to do anything.

After you bottle or rack to a bottling bucket take a smell of the yeast cake. Does it smell like a standard Belgian yeast cake, or does it smell terrible? If it smells fine then your beer is fine.

Long story short; you should be fine, nothing to worry about, but if you are nervous then just pitch new yeast. $7 for piece of mind may be worth it, but that is coming from someone who is neurotic at times about his brews.

I used a blow off tube yes. I'd say the amount solution was a bit over a pint. Fermentation is done yes, its been going for 3 weeks, I also tested the FG and it is fine.

What I'm scared of is that even if the solution was originally sanitary, after 3 weeks in contact with air there is a good chance that it is not. I'm not really scared about the bugs hurting my current brew, but more about the next brew.

I need to go buy the ingredients in a couple of hours. I will have to make up my mind fast! Maybe I'll do an APA instead of the planned Leffe Radieuse clone...

I would not worry too much about infection, but I would worry a little bit about a pint of iodophor in your beer. 5 gallons I take it? Probably okay, but I would smell it and taste it very carefully for any trace of an iodine smell.

The reason I would not worry too much about infection: Your blowoff tube was still pointing down at the exit, right? If so, it is VERY difficult for any nasties to actually make it through to your beer. Louis Pasteur did these experiments when he was proving the existence of micro-organisms in the first place -- bacteria don't have legs, it turns out, so unless there is a way for them to fall into your beer, it is very difficult for them to get in there.

I suppose the reverse pressure might have sucked some air in, and that could bring the nasties in... but presumably the reverse pressure dissipated after the temperature had equalized, and I would go further and presume that wasn't too awful long after the last of the iodophor got sucked away... so the surfaces of the blowoff hose were still probably sanitary, and you probably had a pool of sanitizer sitting on top of your beer.

In order to get an infection, the nasties would have had to get sucked up into the blowoff hose during the brief period in between when the last of the iodophor was consumed and when the temperature equalized, they would have had to make the entire trip without ever touching the sides of the (I presume curved) blowoff hose, and then they would have had to have landed in a fully fermented and chilled beer -- not exactly ideal conditions for bacteria -- that had a frikkin' puddle of iodine sitting on top to welcome any nasties, and the bad guys would have to live through all that and still successfully set up shop, and out-compete any residual yeast that was still in suspension.. Seems like a long shot to me.

Edit: Oh wait, I see now you were concerned the iodophor itself wasn't sanitary anymore. Hmmm... tough to say. I'd still be inclined not to worry. And if this beer is fine, seems like the next ought to be as well, because if the nasties didn't infect the current beer, they are probably all dead. I suppose there could be dormant wild yeast spores, in theory, but... seems like a small risk.

Indeed, I am assuming that the iodine would be completely evaporated after 3 weeks. But you may still be right. The blow off tube is in a 2L erlenmayer flask that had 1.5L or so of iodophor in it. Maybe half of the solution evaporated, and the rest went it. I was also concerned about oxydation, but after reading that CO2 is heavier than air I am not as worried.

I'm pretty sure it is not the first time it happens. The problem is probably that I have a very small chest freezer and that the flask is sitting on the pump. When full, I think the solution level is higher than the beer, which may have caused the siphon.

Maybe I will reuse it to brew another batch.... for scientific reasons

Yalpe said:

I'm pretty sure it is not the first time it happens. The problem is probably that I have a very small chest freezer and that the flask is sitting on the pump. When full, I think the solution level is higher than the beer, which may have caused the siphon.

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Why don't you just switch to an airlock when you go to cold crash it? I only use a blowoff hose for the first couple days of fermentation, until the kraeusen stabilizes. Then I pop an airlock on there. Less messy (assuming the risk of blowoff has passed), more compact, and just plain cooler-looking.

It doesn't fit inside the freezer (prevents it from closing).

Yalpe said:

It doesn't fit inside the freezer (prevents it from closing).

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Hah! I almost guessed that after you said the chest freezer was so small you had to put the flask on the pump. Bummer...

If you're getting the suck-back problem on a regular basis, I almost wonder if it would be better to let the blowoff hose hang loose while it's in the freezer? For the reasons I said before, I would think the actual risk of infection -- especially when you are cold-crashing it -- would be minuscule... I dunno, just a random thought.

(I don't have a temp control system at all yet, so I'm not one to talk)

Ooo, I have an idea!

Instead of the airlock, stick in about 6-8 inches of 1/2" (or so) siphon hose, run it down the side of the fermenter and then squeeze it in an S-shape, and secure it with a rubber band... then fill it with water/sanitizer/vodka as you would a regular S-shaped airlock. Sort of a side-hanging airlock, if you will. Like so:



Eh? Think it might work?

I might just avoid crash cooling. Wouldn't have a longer hose give me the same behavior with the regular blow off setup?If I ever get a suck back it would take quite a lot of liquid to start a siphon with a long hose.

Yalpe,

I would suggest changing out the blow-off tube for a normal air lock once the majority of fermentation is complete. I do this with my Belgian ales that I stick in the fridge to condition for a long time. This way I don't have a huge reservoir of liquid, and you shouldn't actually need a blow-off at the time of cold crashing.

Tall_Yotie said:

Yalpe,

I would suggest changing out the blow-off tube for a normal air lock once the majority of fermentation is complete. I do this with my Belgian ales that I stick in the fridge to condition for a long time. This way I don't have a huge reservoir of liquid, and you shouldn't actually need a blow-off at the time of cold crashing.

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I already suggested that. The airlock won't fit in his freezer!

Ah whoops, guess I skimmed over that. If a glass carboy is being used then perhaps go to a brew bucket, as it is shorter. If that is not the case, then I got nothing. Maybe make a table for the blow off bucket so it is off the compressor.

Yeah I will definitely have to review my setup if I plan on cold crashing again in the future. I think I'm just going to buy another yeast vial and make a starter... I won't risk spoiling a batch, especially one with such a high OG (1.082) $$$!