fermentation time with starter

[brewfarmDan]

Background: I just did my 1st starter for liquid yeast. Broke 2 Wyeast smack packs Thursday about noon and pithced the swollen paks into a 70 deg flask (cooled 1200 ML boiled water and 3.5 OZ DME) about 6 hours later. By Sunday AM I had about 1/4" to 3/8" deep yeast covering the bottom of a 2000ML flask. I poured off most of the excess liquid, swirled and pitched into 10 Gallons of Brown Ale at 8PM Sunday. My 1st check at 10 AM Monday I had slow big bubbles thru a 1/2" tube into a half full 1 gallon jug, by 11 AM it was almost constant big bubbles. I checked again last night about 8 PM and it was still blowing almost constant big bubbles. Today at 10 AM (24 hours after fermentation started) I have almost no bubbles. I am new to my SS Fermenter and would be more comfortable if I could have seen the fermentation/yeast settle.

Question: Did it ferment out this fast or do I have a problem? I was going to wait 3 days before taking a gravity check and if it's high I guess I will repitch. If I am at my Final Gravity then my kettle to keg time just got shorter?

 

[WoodlandBrew]

http://www.woodlandbrew.com/2015/02/starter-calculator.html

Try this calculator to see how long it might take. It is reasonable that it is nearly done.

 

[cannman]

What was the og of your 10 gals?

 

[brewfarmDan]

What was the og of your 10 gals?

OG=1.046, TG recipe 1.007-1.010

I was not able to get the Calulator to open

 

[WoodlandBrew]

I was not able to get the Calculator to open

Sorry about that. If you don't have Excel running on a Windows machine I've heard it doesn't work well.

What temperature did you ferment at? I'll plug in the numbers for you.

 

[brewfarmDan]

Thanks WB, that is not as straight forward as it should be. I have a new to me used fridge for a chamber. Pitched at close to 70 deg F and noticed the fridge was not cooling so I added block ice while working on it. My fridge temps stayed close to 70 but the tape thermometer on the SS Fermentor read as high as 77 when it was fermenting at max. Now that I was able to get the fridge running it is cycling at 62 to 68, I have not opened the door to check the tape thermometer but it shoould be down to 74 or lower?

 

[WoodlandBrew]

Let's assume your fermentation temperature was mostly between 70°F and 77°F. (70+77)/2=73.5°F = 23°C
Ale fermentation temperature is normally about 65°F. 65°F = 18°C

Relative growth rate is fairly linear with temperature[1] and fits the following function:
rate = 0.040915 * temperature - 0.23442
rate = 0.040915 *23°C - 0.23442 = 0.706625 h-1
rate = 0.040915 * 18°C - 0.23442 = 0.50205 h-1

0.706625 /0.50205=1.407479 => expect the fermentation to progress about 40% faster at 23°C(73.5°F) than at 18°C (65°F)

Two smack packs would be about 200 billion cells. 3.5oz (100g) of DME will grow about 150 billion cells (75% * 100g * 0.1 g/g = 7.5g of yeast. 7.5g * 20 billion cells per gram = 150 billion cells)[2]

10 gallons of 1.046 wort is 38 liters with 5kg of extract. Assuming 75% fermentable[3], 5000g*75%=3750g

Using a model based on dozens of papers on the subject, that I'm going to put into the next revision of the calculator, it looks like what you are seeing should be expected. The model shows fermentation reaching 90% complete in 23 hours, and high krausen occurring in 14 hours.

However, no model is perfect, and when compared to a laboratory, the brewhouse is a fairly uncontrolled environment. 20% deviation from a model is common, and a factor of two would not be unheard of.

From the activity you described it sounds like you had plenty of healthy yeast, so if it does finish low I wouldn't suspect that the yeast was at fault. You can check this using paper chromatography.

[1] Walsh, R. M., and P. A. Martin. "Growth of Saccharomyces cerevisiae and Saccharomyces uvarum in a temperature gradient incubator." Journal of the Institute of Brewing 83.3 (1977): 169-172.

[2]Van Dijken, J. P., et al. "An interlaboratory comparison of physiological and genetic properties of four Saccharomyces cerevisiae strains." Enzyme and Microbial Technology 26.9 (2000): 706-714.

[3] http://www.brewingwithbriess.com/Assets/PDFs/Briess_PISB_CBWPilsenLightDME.pdf

 

[brewfarmDan]

Thank you WB for the detailed response. It looks like I will be ok but still have a few questions if you have time. 1) How lonng would you wait to check final gravity before cold crash? Would you harvest this yeast or dump it due to the high fermentation temp? Should I harvest yeast before or after cold crash?

Thanks again for the great information.

 

[WoodlandBrew]

Thank you WB for the detailed response. It looks like I will be ok but still have a few questions if you have time. 1) How lonng would you wait to check final gravity before cold crash? Would you harvest this yeast or dump it due to the high fermentation temp? Should I harvest yeast before or after cold crash?

Thanks again for the great information.

I'm glad to help. Personally, I wait about two weeks and keg it. Because it's in the fridge, and there is a pressure regulator if there is any further fermentation, it's not a problem. I don't check gravity in the fermenter to minimize the chance of contamination. However, if you are bottling, or if you want to drink it as soon as possible you could start checking gravity after a few days.

The health of the yeast should be fine. The optimum propagation temperature for s. cerevisiae is about 30°C[1] significant death doesn't occur until about 35°C.[2]

[1] Walsh, R. M., and P. A. Martin. "Growth of Saccharomyces cerevisiae and Saccharomyces uvarum in a temperature gradient incubator." Journal of the Institute of Brewing 83.3 (1977): 169-172.

[2]Parkkinen, Elke, Erkki Oura, and Heikki Suomalainen. "Comparison of methods for the determination of cell viability in stored baker's yeast." Journal of the Institute of Brewing 82.5 (1976): 283-285.

 

[brewfarmDan]

Thanks again WB. I will be kegging and 2 weeks is no problem. I have watched the vent and had no bubbles for 5 minutes plus.

1) Would you harvest yeast now or wait the 2 weeks?

2) Do you Cold Crash before harvesting or after?

 

[cannman]

Thank you WB for the detailed response. It looks like I will be ok but still have a few questions if you have time. 1) How lonng would you wait to check final gravity before cold crash? Would you harvest this yeast or dump it due to the high fermentation temp? Should I harvest yeast before or after cold crash?

Thanks again for the great information.

Here is a brewing life hack: If you create starters, instead of harvesting from the ferm chamber (which may have pathogens, chucks of wort, trub, hops), simply pour some starter into a sterilized 4 oz mason jar or baby food jar and store in the refridgerator before you pitch! Done! And ready for your next starter!

 

[AnOldUR]

Hack v2: Or keep wort, hops and trub to a minimum when harvesting from your primary. Direct pitch the proper amount of fresh slurry into your next batch without making that starter (which also could have the same pathogens, chucks of wort, trub).

Although I've read that pathogens can't grow in beer. :cross:

 

[brewfarmDan]

I went ahead and checked the gravity this morng and it was spot on at 1.010 so I tried my first yeast harvest. Will post some photos of yeast later when finished bottling. After researching I decided to wait and Cold Crash the day before kegging which will likely be 14 days after pitching. Thank you all for your help and comments