Sunday, July 18, 2010

Fermenting In A Bag

I like to salvage and re-use yeast especially the Whitelabs liquid yeast that I prefer. Some of this yeast may cost me six or seven dollars a tube from my local homebrew store. Salvaging the yeast or brewing a new batch of beer and racking directly on to the yeast cake from a previous batch are two options for making the most out of the money I spend on an ingredient in homebrewing that tends to be the most expensive when it comes right down to it.

In this post I thought that I would elaborate on one technique that I've been using successfully over the years and which I also teach to the new students in my brewing classes. I wrote about it here in one of my 'brewing tricks' segments and I refer to it as 'fermenting in a bag'.

The following photos demostrate how it's done.

To begin with, I line the inside of my open fermenter with a food grade plastic bag, taping the top edges to keep the bag from collapsing into the fermenter. I then transfer the freshly aerated wort into the fermenter and allow the fermentation process to complete as normal.

In the image below you can see an active ferment inside the open fermenter that is lined with the food grade bag. Also note that I cover the fermenter with another bag to keep your run-of-the-mill vectors out during this stage.

When fermentation is complete I racked the beer into my kegs. At this point, I cover the fermenter until I'm ready for the next step which is to gather together the open end of the bag and lift it out of the fermenting vessel bringing with it the trapped yeast cake at the bottom.

I then lower the bag into a bucket of sanitizer (in this case, Iodophor) which will sanitize the exterior lower portion of the bag and at the same time I sanitized a knife which I will use to perforate the bag allowing the yeast to flow into a sanitized container. I used a funnel to catch the flowing yeast in this case but in the past have used Mason jars and just let the yeast drop in but sometimes it's a crap shoot on which direction the yeast runs.

I got lucky here in that the flow of yeast was a direct shot.

Once captured, I will store in the fridge until I'm ready to pitch in the next batch of beer. Labeling the container of yeast is important and I simply attach a sticker to the cap and write the yeast type and date and I also put the generation, usually discarding after six or eight uses. Another added benefit to using these bags is you don't have to clean the fermenter, just dispose of the bag and you're done.

One note of caution: Initially, leave the cap loose until the yeast has cooled down to fridge temperatures. There may be pressure building in the jar since the yeast is still active at room temperature. Once cool, tighten lid.


Bill F said...

Can you comment about how long you've saved yeast in the fridge like this, Mark? I've brewed some bad beer from 9 month old saved yeast. Maybe my sanitation was less than perfect, but I've also seen numerous warnings on the web against aging reused yeast.

Beer Diary... said...

Hi Bill,
I prefer to re-use the yeast within a couple of weeks simply because the longer it is stored the less viable because of loss of cell life and not because I am concerned about contamination. I have saved yeast like this for up to 2 months in the past, however, when I re-use yeast that I've saved that long, I reactivate it by feeding it a small (4oz.)solution of maltose a couple days before I brew. I do this to increase cell count, confirm that the yeast is active by watching for co2 discharge and I will smell the yeast noting any odd odors due to bacterial contamination. If everything seems in order, I drain off excess liquid and pitch it. I haven't had any problems using this procedure over the past years and would recommend it as pretty fail safe. Personally, I would probably discard yeast that I've had in the fridge that was over several months old but this is not based on any tested data points, though I suspect that there is significant live cell loss. One last note. Sanitation is critical and should be observed with diligence in these process but I would also take a grain of salt with any warnings gotten from the web. Hope this helps.

Anonymous said...

I use sanitized 2L soda bottles for yeast storage. No worries of creating glass bombs if pressure continues to build(which in some yeasts do, even refrigerated)

Brewer Bob

Beer Diary... said...

Good idea Bob and thanks for the input. I normally don't have that much yeast to harvest at one time but I may use a smaller plastic soda water bottle in the future because of your advice.

Anthony said...

Can you comment on what makes the bag "food grade". Will a regular industrial garbage bag work? Do you sanitize the bag before you add your wort, if so how?

Beer Diary... said...

Hi Anthony,
Yes, what make a bag food grade is that it is manufactured to be in contact with food. This means there will be no transfer of chemicals used in the process of making the bags and there will be no aroma transfer to any food (beer in this case)that is in contact with the bag material. This also applies to plastic buckets or transfer tubing used in the brewing process. If it isn't food grade,you may get off flavors associated with the plastic. Thanks for reading Beer Diary...

Beer Diary... said...

sorry I forgot to tell you that you do not need to sanitize the inside of these bags as they are sanitary from the supplier. But, as you can see from the post, I will sanitize the exterior prior to salvaging the yeast.

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