Reuse Trub?

Hello all,
I am relatively new to this and am about to brew my 6th batch and had a question. I ordered an ale kit from AHB about 4 months ago and just never got around to brewing it. I did brew another one this past Sunday and am planning to brew the older kit this coming weekend. Since the White Labs yeast is a little out of date, I want to rack last weeks brew to secondary and then pour my newly brewed wert right on top of the left over trub from the old batch. In addition to this I was going to toss in the out of date yeast for good measure.

Are there any potential problems with doing this?

Thanks for your advice.

I wouldnt toss in the other one. There is no point in that. You will be fine pitching on top of the trub...in fact, it will probably take off in a couple of hours.

No problems at all, but you shouldn't even bother pitching another yeast in it. You'll have so much yeast in the yeast cake that it'll take off like gangbusters. You'd be wasting your vial by adding it too.

No problems at all pitching a fresh brew on a yeast cake, I do it quite frequently. You will want to make sure you have a blow-off tube setup though. It will be a pretty vigorous fermentation for the first few days.

Regarding the old kit, if it has any pre-crushed grains in it you may want to consider purchasing fresh replacements. Pre-crushed grains don't have much of a shelf life and you don't want your beer to taste stale.

If the yeast is out of date it isn't necessarily bad, you could make a starter out of it to see if it is still good. If it smells like beer after it ferments and it tastes ok the yeast are fine to use.

I would just add acouple things. Put the old vial in the fridge and make a starter with it the next time you brew. A starter will tell you if the yeast is good or not.
Also, are you sure that you know what to do with a blow off? Just making sure. If I can save you from a huge mess by asking again, why not ask? Good luck. Blow offs and starters have been discussed to death if you need to search for either of those in a previous thread.

I agree about the blow off for sure. I have done it before and definitely plan to do one for this one! My main concern was the possibility of imparting off flavors to the next batch, because there are alot of other things in the trub other than yeast.

Thanks for all of the advice and I will let you know how it goes / tastes!

First off, pitch on top of the old yeast cake, add a blow off and watch the show. Save the old yeast for another batch. If you dont want to make a seperate starter wort, I would save 2 qt's from your new batch for starter wort. Then with that wort make a starter with it and when the starter is finished brew another batch.

I repitched on top of my old yeast cake and major fermentation began within 2 hours! Holy Cow! I have never seen anything like it. It has been 4 days and this thing is still going like gang busters!!!! I had my fridge set at 65 degrees and the beer still got up to 75 deg before I found out. It is fermenting so rapidly that I am going to brew another batch and reuse the yeast cake again tonight!

Thanks for the advice. If I hadn't used a blow off tube, I know it would have ended up everywhere.

One question though. Why not use a blow off every time? I seem to like it much better than the 3 piece air locks.

CivEngPE said:

One question though. Why not use a blow off every time? I seem to like it much better than the 3 piece air locks.

Click to expand...

I always use a blow-off tube for the first 3 or 4 days of fermentation. Since I went to all-grain brewing almost every batch has needed it and I don't want to take the chance of it not being there. When pitching on a yeast cake it's a requirement not an option as you found out.

You could definitely stick with just the blow-off tube if you want, all that really matters is that you keep the nasties out of the fermenter. Personally I swap out the blow-off for an airlock as soon as the fermentation subsides, though I couldn't tell you why I do, I just do.

so what would everyone guestimate the shelf life of crushed grains to be? I have had some crushed grains in the fridge for about 3-4 weeks, has perhaps a slight amount of oxidation occurred? On the yeast note, old or past date liquid yeast is not usually a problem if it has been stored properly. Or at least that has been my limited experience. Before my LHBS got their latest shipment, I had been (unknowingly) using some older yeast. One vial had been past its "use within" dates for at least 3 or 4 months. Of course as everyone has thus far said, a starter was used.

Your grains may be ok, the best thing to do is pop a couple in your mouth and taste them. If they taste even a little stale I would replace them with fresh - you don't want your beer to be stale for the sake of a couple bucks.

Depending on the yeast, I never use the entire yeast cake. I swirl the primary up and pour half into a gallon jug and wash it for later use.

The remaining cake works just as well and as fast.

I agree with Bill. Using the whole yeast cake is overpitching by at least 3 fold. Jamil Z says "I know a number of people dump a new batch on top of the yeast cake, but you're not going to get the best beer that way. Yeast do need some growth to result in the right kind of ester profile, etc".

I have a couple of questions in light of the new comments.

1. What are the negative effects of utilizing too much yeast?
2. What is meant by washing the yeast and how does one do this?

CivEngPE said:

I have a couple of questions in light of the new comments.

1. What are the negative effects of utilizing too much yeast?
2. What is meant by washing the yeast and how does one do this?

Click to expand...

1. Increased chance of off flavours from the dead yeast in the trub. Fewer esters being produced during the yeast reproductive stage (these flavours often are distinguishing characteristics of certain yeasts).

2. Search the wiki. It is very well explained there.

Well this has turned out to be the strangest brew I have done yet.

I pulled the fermenting bucket out last night to rack the beer to secondary. Strangely, it looked a lot like chocolate milk. Well I racked to secondary, inserted the three piece airlock and placed it in my closet. For some reason or another, I decided to check on it about an hour later. Boy am I glad I did! The air lock was clogged and I could see tons of bubbles forming. I moved the carboy to the bathtub and inserted the blow off once again.

The reason I find this strange is that all of my other brews have started off kind of slowly, peaked in a couple of days and were nearly completed by day 5 of fermentation. Since I pitched the wort right on top of the previous batches trub, fermentation has been going like gang busters since 3 hours post pitch.

I just can't fathom that this beer still has this much aggressive fermentation left in it after five days of already unprecedented activity.

I wouldn't be surprised if this batch bottoms out at around 1.005 with all of this activity! The worst part may be that it could turn out to be the best batch I have ever made and I will never be able to duplicate it!