Advise For Reviving This Yeast Cake

I brewed a 1.070 OG porter on 3.3.12 and racked to secondary on 3.21.12. After I racked, I save the yeast cake in a sanitized mason jar pouring ~750mL of cake in first and topping with 750mL of the porter — I did not wash it.

The mason jar has been sitting in my refrigerator for about 9 months and I'm ready to make the porter again. I opened it for the first time and it smells great! Just like the beer did. No off odors.

I was thinking I should wash the yeast from the mason jar first and then use the washed yeast in the starters. Sound about right? Is washing necessary at this point?

Yes, but the viability on your yeast is going to be very low. I would wash your yeast, and then grow up a starter with 1.020 SG wort first- give it a few more days than usual, and then use THAT to inoculate your starter.

My mileage seems to differ from the common brewing wisdom on this one. In my experience washing yeast that is dormant just throws out good yeast cells. The only difference in the layers is the density of cells, but the viability is the same. I would decant and then make a starter for as much of the yeast as you can. It will take a few days to get going, so don't give up unless you don't have anything after a week.

I'll weight both options. Whether I wash the cake or not, there' still going to be a considerable amount of yeast work with. Maybe 250-500mL of thick, thick slurry. Using the 1:100 started ratio, that would require a starter word of ~2,500mL to 5,000mL. Sound about right?

The viability is likely between 10% and 50%. (Given the age, and forget what Mr. Malty says about slurry viability) Cell density in a harvested slurry is typically 1 billion cells per milliliter. If you wash it and have 250ml of thick cake, then wost case you have 25 billion cells. That's enough for 1 gallons of 1.035 wort if you were ready to pitch. For a starter you might want to do half or a quarter of that max because the yeast is old. Your numbers look pretty good, but you might want to start small at perhaps 1.5 liters.

Nine month old yeast from a 1.070 beer stored at refrigerator temperatures? Ugh. I'd toss it if any of those three things were true, much less all of them.

Seems like a great opportunity to do a side by side experiment and lay some myths to rest. Spend a few bucks on some fresh yeast. Split the batch and ferment half with new yeast and the other half with revived 9mth old yeast.

I would be happy to do a cell count on the yeast if you can spare a white labs vial worth. We're both in New England, and it's colder than a refrigerator outside, so it should be fine in the mail. I can have results the same day I get the sample. If you PM me your email I'll email you details and a sample lab report.

Thanks all. WoodlandBrew, I'll PM you. There's plenty to spare. It's actually Long Trail's proprietary yeast strain so I don't want to dump it. I like the idea to do a split batch although, I feel I can just ferment with THIS yeast and know what it should taste like given I've brewed this recipe before. My planis doing a 10 gallon split anyway. 5 will get dosed with coffee at kegging and the other 5 rest with coconut at kegging.