Indications that yeast are reproducing?

[chawagi]

So I almost shot myself in the foot for my Labor Day brew by nearly throwing out what turned out to be a good batch of stepped-up bottle harvested yeast.

Here's the story:

Planned on brewing a Dunkel Weizen on Labor Day weekend. Wasn't completely sure if my supplier was going to be able to get me a vial of Hefe yeast (he's just getting his official business up and running) and I didn't want to be disloyal and go to another supplier when other means are available, so I decided to try my hand at harvesting and stepping-up bottle-bottom yeast and test out my new DIY stir-plate at the same time. The yeast was being harvested out of my own brewed Hefe so I knew the strain as well as the day it was bottled, so no worries there.

Anyway...took one for the team and reluctantly consumed about 3 bottles of my hefe to gather the yeast, and prepped a very light mixture of about 14g by weight of LME and 200 ml water for an OG of about 1.08 so as not to shock the little fellas. Pitched the yeast and started the stir and saw visible activity in about 2 hours. Stirred for 24 hrs and cold crashed for 24 hrs to settle. All well so far, and saw definite visible growth after settling.

Stepped up volume, but maintained approx. OG by doing 25g by weight LME with 400ml water. Pitched yeast and stirred for another 24 hrs followed by cold crash for 24 hrs. No visible activity in container and visible yeast growth was questionable. Getting a bit worried at this point.

Final step-up in preparation for making a starter. Increased volume and LME to 500ml solution with an OG of about 1.020. Stirred for 24 hrs during which I saw nothing that would indicate the yeast were anything but dead. After 24 hrs I was a bit disappointed and on the verge of tossing what I thought was dead yeast, but decided for some odd reason to RDWHAHB and see the project through to the end. Checked on my cold crashed container this morning, and amazingly have about a 1/2" thick creamy layer of yeast (about 400% increase from step-up 2) settled out and just waiting to do their duty this weekend.

I understand the physiological prcesses for yeast reproduction are different from fermentation (which is very easily recognizable), so my question is...what indications are there that we should look for that indicate the yeast are actually reproducing?

This step-up really threw me off because there weren't even any of the normal things I usually get when doing starters (very distinct beer smell the following morning/ krauzen).

Is there any easy way to tell if the yeast are reproducing, or is this one of those have patience and hope for the best until after the cold crash reveals the results?

 

[william_shakes_beer]

I get a stethoscope and place it about midway down the vessel. If I hear faint strains of Stayin' Alive I know the process is well under way.

 

[chawagi]

I get a stethoscope and place it about midway down the vessel. If I hear faint strains of Stayin' Alive I know the process is well under way.

This is a strain of German Hefeweizen yeast though, so I guess I would be listening for something a bit more techno-ish.

 

[austinb]

Pour off a little and taste it. If it is still relatively sweet like un-fermented wort then they probably didn't do anything. If its relatively dry with little to no sweetness then they probably did something. Sometimes stir plates will reduce the krausen to basically nothing because the stirring motion pops all the tiny little bubbles.

 

[acidrain]

I'm not really understanding the point of gradual gravity increases.
At that low of a gravity, I'm not surprised to hear you're questioning the growth.
I can understand smaller quantities, but not lower gravities.
Have you ever seen a fast action shot of the swirling gas storms of Jupiter? That's what my starters look like. That, and a prominent krousen complete with blow-over.
Low gravity just teases them. Now they hate you.

 

[LovesIPA]

I would step up the gravity to 1.040. Use 100g of DME per liter of water and your yeast will be much happier.

 

[kh54s10]

I have read that the first step should be low gravity and small. This would be more for energizing the yeast and getting them healthy rather than full reproduction. After that use the normal 1.040 gravity in the number of steps to get the proper final cell count.

I have been quite successful doing this with 5 ml of frozen yeast, up to 1.5 years old.

 

[chawagi]

I have read that the first step should be low gravity and small. This would be more for energizing the yeast and getting them healthy rather than full reproduction. After that use the normal 1.040 gravity in the number of steps to get the proper final cell count.

I have been quite successful doing this with 5 ml of frozen yeast, up to 1.5 years old.

Kinda where I was at with this. Remember, this is a step-up for harvesting bottle conditioning yeast, not a starter. I researched this pretty extensively, and most of what I found for harvesting bottle yeast said to start very low OG due to the fact that the yeast are already stressed.

When doing a starter, I indeed do higher gravity wort, but this procedure was to simply step up a very low quantity of bottle-bottom yeast. I was still expecting to see much more activity than I did though.

 

[kh54s10]

Sometimes the only thing is see is a change in the color of the wort as the sugars are consumed, and after chilling an increase in the layer of yeast. I look for bubbles rising in the wort by getting very close and looking at it with a flashlight.

 

[austinb]

Even though you are not getting visible signs of fermentation I bet you actually are. I agree with everyone that you should step it up to a 1.040 gravity starter though. While you want to start with a lower gravity for your first step, 1.008 is really low. I would start with 1.020 for the first step and then step it up to 1.040 for every step after that. At this point I would step it up to a 1 liter 1.040 starter for your final step before pitching. But remember that just because you don't see activity doesn't mean it's not happening. If you are wondering take it off the stir plate for an hour to let the yeast settle and pour off a small little bit to taste. If its sweet it may not be working, if its not sweet then it probably is.

 

[chawagi]

Even though you are not getting visible signs of fermentation I bet you actually are. I agree with everyone that you should step it up to a 1.040 gravity starter though. While you want to start with a lower gravity for your first step, 1.008 is really low. I would start with 1.020 for the first step and then step it up to 1.040 for every step after that. At this point I would step it up to a 1 liter 1.040 starter for your final step before pitching. But remember that just because you don't see activity doesn't mean it's not happening. If you are wondering take it off the stir plate for an hour to let the yeast settle and pour off a small little bit to taste. If its sweet it may not be working, if its not sweet then it probably is.

Thanks, guys.

I did get enough yeast growth that I feel confident I can now pitch to a starter. I successfully went from the little bit of yeast scrim at the bottom of three bottles to a colony thats about 1/2 inch thick at the bottom of a 32oz mason jar. I was just wondering if anybody knew a way to detect an active growth phase while in a stir plate. Until the cold-settling step was complete I had no indications I was doing anything but stirring wort. Based on the replies, I see that it is an exercise in patience, and more sugars.