How Do I Know Whether Reused Yeast is Infected?

I am going to attempt my first brew with reused yeast: Wyeast 1056. I used it in a pale ale and want to brew an IPA with it. The yeast has been in the fridge in a sealed container for about 2-3 weeks now.

My brewing plan is to pitch that yeast into starter at least 24 hours before brewing and then brew up my new IPA.

Maybe I'm just being a worrywort but how will I know whether this yeast is infected? I'd hate to pitch infected yeast and not know about it until a few months later after eventually drinking my new brew. Are there any telltale signs (i.e., smell, lack of activity in the starter, etc.) I should look out for before pitching it into the new beer?

Thanks all.

Your best bet would be to taste the spent starter. If it tastes infected, then your yeast sample is the likeliest source. If it tastes normal, it's unlikely that you'll have any infection in your beer.

Actually, the spent starter will prolly taste bad regardless due to O2. I'd pour the yeast into the starter and then take a small taste of the actual yeast from the container you poured FROM. The yeast should smell and taste good.

ThePearsonFam said:

Actually, the spent starter will prolly taste bad regardless due to O2. I'd pour the yeast into the starter and then take a small taste of the actual yeast from the container you poured FROM. The yeast should smell and taste good.

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There's a world of difference between oxidized beer and infected beer, and that difference should be readily apparent.

Tasting the contents of the storage container will detect contaminants if they had already wrecked havoc on the sample, but there's no way a taste-test will pick up on a small infectious colony living in a larger population of dormant yeast. As soon as that small infection gets pitched, however, it may quickly out compete the yeast.

if it formed a pellicle or firm-filmy bubbles, it's infected

ReverseApacheMaster said:

if it formed a pellicle or firm-filmy bubbles, it's infected

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Yeah, that would be a hint

...of course, just because there isn't a pellicle doesn't mean that it's not infected.

I reuse yeast all the time, lots longer time frames than that. I make a starter, pitch the yeast, then taste the oxidized (yuck) fermented starter. If it is infected you can smell it! If it is infected you can definately taste it.

I agree that there's a world of difference between oxidized and infected. I would definitely taste the starter if it were from a vial or pack, but it's reused. If the cake is infected, then you'll most likely smell and taste it by sampling the yeast too. Either way works for reused yeast.

ive read on here that your starter will have a sour like taste to it and it doesnt taste good either. I have never tasted my starter before but just a heads up.

Starters don't taste good because of oxidation. The goal is to grow yeast cell counts, not make beer, so we intentionally allow O2 into the process. The result is more yeast and a bad taste...

Honestly, if the yeast is strong, wouldn't that be enough to fight an infection? And also, does infection really mean a bad beer? Beers like Lambic and other open "spontaneous" brews use infections to brew, right? So is it really a huge concern for reusing yeast?

I ask because most of the procedures I see for brewing and yeast re-culturing really aren't all that sanitary to begin with, as well. It seems like this isn't a huge concern but I'd like clarification in case I decide to reuse my own yeast.

Thanks!

Skullfingr said:

Honestly, if the yeast is strong, wouldn't that be enough to fight an infection? And also, does infection really mean a bad beer? Beers like Lambic and other open "spontaneous" brews use infections to brew, right? So is it really a huge concern for reusing yeast?

I ask because most of the procedures I see for brewing and yeast re-culturing really aren't all that sanitary to begin with, as well. It seems like this isn't a huge concern but I'd like clarification in case I decide to reuse my own yeast.

Thanks!

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Not really, the unwelcome guest will still be there. Usually wild yeast or unwelcome bacteria are more aggressive than domesticated brewing yeast strains and will show up sooner or later in the beer. You might be able to get a starter of mostly brewing yeast and make an ok beer if you drink it fast or keg and keep the keg cold. At first the infection might be slight and unnoticeable but if you rewash it over and over it's most likely going to become noticeable.

For every good tasting infection, there are probably 10,000 nasty infections. Getting an unwelcome guest is different from a spontaneously fermented beer.

You should be as sanitary as possible with your yeast procedures. The less sanitary you are, the sooner you will start to develop infections.

Well, to me, the only way to be completely sanitary is to brew in a lab, to whiteout all potential hazards using heat and/or UV. It's hard to be completely sanitary in a kitchen! Haha.

I'm considering just tossing my reused yeast in the trash now. Haha.

You could always acid wash it. It's not foolproof but it's something that can help with bacteria. It won't help with wild yeast though.

Something else you could do is keep 500ml of the pitched wort in a beaker on your stir plate with an airlock and do a forced fermentation in the upper 80's. It will finish must sooner than your beer and you'll know the end result...and the FG to expect

The simple answer to this question is that if it is infected, you will know. If your sanitation is typically up to snuff and the stored yeast looks and smells fine, you are probably good to go. Do a starter to ensure it is still viable. and if that looks good, pitch it. Worrying is healthy, it keeps us on top of sanitation.

I've tasted all my starters and to be honest all of them have tasted bad. (They however do their jobs nicely and ferment my wort to wonderful tastey beer.) When they (the starters) ferment they smell great, however once I cold crash them prior to pitching them, they don't smell as pleasant. What does infected starter taste and/or smell like?

I'm just not keen on the idea of wasting so much cash on a five gallon brew to see it infected and dumped. The idea itself makes me sad.

MalFet said:

Yeah, that would be a hint

...of course, just because there isn't a pellicle doesn't mean that it's not infected.

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Skullfingr said:

I'm just not keen on the idea of wasting so much cash on a five gallon brew to see it infected and dumped. The idea itself makes me sad.

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I understand! I have 10 gallons right now of "band aid beer" that came from an infected starter from washed yeast. It seemed fine, but the beer is infected. That sucks. I tried to go another generation and I must have been a bit lax in the sanitation I guess. I haven't thrown the beer out yet, but I can't drink it either.

That's unfortunate and alarming, Yooper. It is for that reason that I'm giving serious consideration to never reusing. Or not, at least, until I have a lab or something to work in. Kitchens are never sanitary.

Skullfingr said:

That's unfortunate and alarming, Yooper. It is for that reason that I'm giving serious consideration to never reusing. Or not, at least, until I have a lab or something to work in. Kitchens are never sanitary.

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I've done far more sensitive work than yeast washing in my kitchen without trouble. With a bit of attention to environment, a kitchen can be plenty sanitary.

So the best way to tell if a yeast is contaminated is to brew a small batch of beer and see what happens?

Or just by looking?

Smells: vinegar, sulphur, Satan's anus, fruity when it isn't supposed to be.

Visuals: pellicle, stringyness instead of cloudy, persistent krausen ring on glassware that doesn't want to clean up like normal

Other: hydrometer reading way low of normal FG for yeast type

Tip; don't tell your wife to "come smell this!" for Satan's anus. She will not be amused.

Good call, lou. I'll try a starter with some DME and see what happens!

What are the chances that between the starter or the test beer and the actual beer (if the lag time is, say, a few days) of the yeast becoming contaminated by then?

Skullfingr said:

Good call, lou. I'll try a starter with some DME and see what happens!

What are the chances that between the starter or the test beer and the actual beer (if the lag time is, say, a few days) of the yeast becoming contaminated by then?

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Depending on how many a few is, you could go a couple ways. Definitely keep in fridge to retard any off growths. Another option is to do another step up of your starter to keep everything up and active. I have heard somewhere on here of guys adding some vodka to the top of their starter / trub to make an alcohol barrier to keep anything bad at bay. Any time you are going to have delays, sanitary technique becomes even more paramount in your process. Every kink in the system decreases your odds of a contaminant free brew.

So the last brew I did with a whitelabs California ale yeast, I took the yeast and washed it according to posts I read here. I stored it in the fridge for a couple weeks and brewed again. I bottled and it's been a couple weeks. There is some kind of filmy substance on the top of the beer in some of the bottles. Not all of them. I drank a couple with no film and they seemed fine, though I could taste some sour off flavors..(it's an ipa). So today I thought I'd be brave and try one with the film at the top. It is not terrible (mostly because the hops come through well)...but that sour off flavor is quite a bit stronger and there are some small particles that keep rising to the top instead of going to the bottom like typical homebrew yeast. I guess my questions are as follows....is this an infection or just bottle conditioning krausen? If it is an infection could it have come from reusing the yeast? And lastly and most importantly, am I going to die if I drink all 40 bottles of this, because I'm probably gonna try it just to compare flavors.

I use corn sugar to carbonate, but I have heard that if you use malt, you may get a ring up top. It is also reported to be a sign of infection. Even if infected, it is safe to drink. Personally, if it was drinkable, I would just go ahead and drink up, I hate to waste brew.

smata67 said:

I use corn sugar to carbonate, but I have heard that if you use malt, you may get a ring up top. It is also reported to be a sign of infection. Even if infected, it is safe to drink. Personally, if it was drinkable, I would just go ahead and drink up, I hate to waste brew.

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Ok thanks..now that I have permission I feel better. Though I don't know if I can take that taste much longer. I did use sugar to carbonate. However I did forget to add it I till it was all bottled. Then after realizing it I reopened all the bottles and portioned it out for each bottle and recapped. I'm guessing this could have been another point of infection. All around bad brewing practices. I was trying to hurry.

I tried making a starter of one of my batches (ringwood ale). I used white sugar and DME (wheat). I kept it warm to speed fermentation. The head when shaken is pure white, and things seem to look good but smelling it, smells like bandaids or plastic. Is it contaimation or just the sugars and warmth used?