Contamination risk of pitching onto (used) yeast cake?

Hi,

I am brewing more frequently in order to ramp up for some beer competitions this summer. I have 10 gallons of IPA in 2 fermenters that I'm going to keg / bottle (5 gals per) this weekend. I am also planning on brewing some Black Rye IPA this weekend. I am considering racking onto the yeast cakes in the two fermenters, but have 2 concerns:

1) Am I upping my risk of contamination by using an established yeast cake? I have some packets of US05 hanging around I could use. It is 10 gals, so I don't want to be risky with it, and I want it for competition so I want it to be good. However, even with a starter, I feel like I might be under-pitching.

2) I didn't secondary ferment the IPA; the fermenters I'd rack onto would be primary. There is a ton of hops in these beer, and I'm afraid that racking onto it for another month (I wasn't planning on secondarying the Black Rye IPA either) would result in an oxidized taste (due to old hops)?

Other details, if it matters:

The fermenters are plastic, 5 gallon.
The IPA has been in fermentation for 3 weeks.
I have not dry hopped the IPA.
The yeast for both beers is US05.

Thanks!

Everything would be fine long as you have good sanitation practices. Racking your IPA off would give you the opportunity to dry hop in the secondary and that yeast in your primary is ready to go. You could check out the sticky on yeast washing if you're really worried about it but I wouldn't stress. Just don't go more than a couple generations on old trub.

Yeah, assuming the first batch isn't contaminated, there shouldn't be any worries for the next one unless it occurs during transfer (which could happen anyways). You will probably be over pitching though, so washing the yeast and using less than the total could be a good option. That would also get rid of the hop trub you're worried about, although I don't think the trub will likely damage your beer at all.

On the other hand, if it were me (a little paranoid), I'd just use fresh yeast. Since you're using dry yeast anyways its what, a couple of bucks more to make sure that this batch is at its peak? Considering its a 10-gal Black IPA, you're probably in the range of >$50 for the batch, if not more. I'd probably rack the old beer away, clean out the fermenter, resanitize, and pitch new yeast. But like I said, I'm kinda paranoid! I don't see any trouble reusing the yeast if that's what you decide.

Double_D said:

Everything would be fine long as you have good sanitation practices. Racking your IPA off would give you the opportunity to dry hop in the secondary and that yeast in your primary is ready to go. You could check out the sticky on yeast washing if you're really worried about it but I wouldn't stress. Just don't go more than a couple generations on old trub.

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+1. I pitch onto yeast from a previous batch all the time. It's the best way to ferment a batch. It takes off faster than a starter and tastes a little better than using fresh yeast. Imho. As long as the beer coming out of the fermenter tastes good the yeast is ok to reuse.

The biggest risk is probably overpitching

you will definitely be over pitching by a very large margin. the beer will be lacking in esters and other flavors from yeast growth. Its fine if you like your beer like that but for competitions its probably not a great strategy. Dry yeast is so cheap people tend to just buy however much they need and not worry about starters or cakes.

So your beer would taste cleaner this way? I don't like esters anyway.

You're over pitching for sure. But I'd rather over pitch than under pitch. The beer lacks some esters but us-05 doesn't produce a lot of esters anyway. It may not work perfect depending upon the style or what you're trying to do. I've used this technique with English ale yeast and still got plenty of fruity notes. I personally think that the beer that I've made by pitching onto a yeast cake tastes more like beer from a micro brewery.

I've tried doing starters and washing yeast and I've found this is the best way to re-use yeast.

Grantman1 said:

So your beer would taste cleaner this way? I don't like esters anyway.

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If you don't like esters just use a super clean strain. 1007 for liquid, or k97 for dry will give you really really clean results. Don't purposely overpitch.