[Randall Miller]

I have been using Wyeast Smack Packs for a number of years.  To calculate starter sizes, I have entered the Wyeast "Mfd Date" into Beersmith.  I understand that the viable cells reduce by approximately 20% each month after the "Mfg Date".   I just received a batch of Wyeast Smack Packs and see that Wyeast has moved to printing a "Best if used by Date" (versus "Mfd Date" on their packages).   I am trying to learn how to calculate the "Mfd Date" based on the new "Best if used by Date".  Can anyone help me?  I don't see an answer in the Q&A's on the Wyeast website....nor a means to contact them directly.     Thank you.

[BrewBama]

From their website: “BEST IF USED BY: This package is best when used within 6 months of the manufacturer’s date when stored between 34-40 °F (1-4 °C). Older yeast or yeast that has been exposed to higher or lower temperatures may take longer to become active or swell. “

So, I would calculate 6 months back from the ‘best if used by date’.

https://wyeastlab.com/smack-pack-activator-system

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[Richard]

Yeah, same thing for White Labs. They have changed from a manufacturing date to a "use by" date. They do have a lot number, and you can go to their Yeastman web site and find the actual packaging date, but you can also just subtract 6 months from the "use by" date and get within a day or two.

[Randall Miller]

I also did see on their website "BEST IF USED BY: This package is best when used within 6 months of the manufacturer’s date.....".  However, I was not sure if one can assume that the new "BEST IF USED BY" date printed on the Smack Pack was actually 6 months after the manufacturing date for both Ales and Lagers.  Thanks.

[Randall Miller]

I picked up 3 packs of Wyeast from my LHBS on 8/22/2020.   They included the "Best if Used By Dates" of:
2/15/2021
2/19/2021
2/28/2021

Counting 6 months back to learn the Mfd date, they would be:
8/15/2020
8/19/2020
8/28/2020

Since 2 of the calculated "MFd" dates are within one week of picking up the yeast and 1 date is after I picked-up the yeast, it is clear that counting back 6 months from the "Best if Used By Date" does not work.

I have an inquiry to my LHBS again who originally also thought that the 6 month count-back was correct.

[Saccharomyces]

Please do me a favor and throw BeerSmith away or at least ignore it for making starters. I have been working with brewing yeast in a home brewery/home lab environment the better part of thirty years. The number of viable cells that the average brewer pitches today dwarfs that of what we used to pitch and our beer can out fine. You need to work with a few knowns. If a yeast culture pitched into a starter makes it to high krausen before exhausting the medium, the starter will contain approximately 200 billion cells. If pitched with medium into 5 gallons of wort, one can assume a pitching rate of 10 million cells per milliliter.  At that pitching rate, it will take a little over four replication periods for the entire combined volume to reach maximum cell density. Yeast cultures are truly like nuclear weapons in that close is good enough.

With that said, nothing, and I do mean nothing will ever take the place of observation when it comes to working with yeast. Yeast cells are living things, not automatons. If you are not journaling your observations with respect to starter and fermentation progress, you need to start ASAP. Anything that was observed and not journaled did not occur. No piece of software will ever replace a human maintained journal when it comes to understanding how different yeast cultures behave.

[BrewBama]

... No piece of software will ever replace a human maintained journal when it comes to understanding how different yeast cultures behave.

Oh I dunno, I think this piece of software (below) does a pretty good job of displaying how yeast behaves. As I’ve seen enough of these graphs a pattern has emerged. As a result, I can make fairly accurate predictions based on that pattern.

These charts tell me such yeast behaviors such as when it starts, how aggressive it ferments, and when it’s completed it’s job. That’s all I really care about performance-wise. After that, it’s sensory driven.

A brewer can simply add a pack of yeast to a food source and we get fermentation. Ancient Egyptians, Medieval Monks, and Alewives brewed beer in very rudimentary breweries without even knowing yeast existed.

It just goes to show, brewing has advanced in the technology used and scientific understanding. ...but it still happens despite us wether we know every nuance of every biological mechanism at work and even when we use basic equipment and have no idea about the science behind it.  Gott sei Dank.




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[Saccharomyces]

That graph only displays fermentation rate.  The fact that the gravity line is not smooth demonstrates the limitations of the technology being used to track fermentation rate. Gravity should not oscillate up and down.  Furthermore, I am talking about a specific yeast culture's behavior as a whole, not just its fermentation rate. How does a yeast culture behave in storage after being cropped?  Some yeast cultures will survive a year or more in refrigerator after being cropped while others are challenged to survive six months.  This kind of data is best tracked through observation and note taking.  You pitch a single strain yeast culture over and over and it does not appear that you use cropped yeast. That is a very limited view of yeast behavior.  You should try plating and transferring isolated colonies to slant.  How long does it take for well isolated colonies to form?  Once transferred to slant, how long does it take for the cells to form a film on the entire surface of the slant?  Is is thick of thin film?  These are questions no piece of brewing software can answer.

Once again, brewing software attempts to inject a level of precision that is not obtainable in home brewery.  Yeast calculators are about as useful as mammary glands on a bull.  The only way to know for certain how many viable cells one is pitching is with a microscope, hemocytometer, and methylene blue. In lieu of doing cell counts, we can work from "knowns" and rules of thumb.  We have people sweating the fact that they are not pitching 20m cells per milliliter when Lallemand's high pitch rate for BRY-97 is 5m cells per milliliter.   That is half the rate of a normal 1L liquid starter at high krausen and an 11g packet in 5-gallons of wort is a little more than a fourth of the rate of a normal 1L liquid starter.  Yet, both Lallemand pitching rates work.

[narvin]

There is some middle ground between writing your recipes on papyrus and trusting beersmith for everything.  I'd argue that the real usefulness of these calculators is the attempt to introduce precision.  Obviously things like yeast calculators and IBU calculations are not going to be accurate across the broad spectrum of circumstances used by homebrewers.  The first attempt may get you in the ballpark, but after that it's about repeatability, and as long as you are using the same tool it helps you to try to repeat things.  I agree that the yeast pack age setting is mostly useless to determine viability.

[Kevin]

Honestly, since I began using the SNS starter method I have not even opened the Beersmith yeast tab and I rarely look at the dates on packages of yeast.

[BrewBama]

... How does a yeast culture behave in storage after being cropped?  ...  You should try plating and transferring isolated colonies to slant.  How long does it take for well isolated colonies to form?  Once transferred to slant, how long does it take for the cells to form a film on the entire surface of the slant?  Is is thick of thin film?

I rarely harvest yeast. I prefer one trip yeast from the mfr because I do not have lab equipment to determine potential contamination or drift.  ...nor do I want it.

Slants...plating...etc? Those processes do not interest me in the slightest.

If others enjoy it that’s great. ...but that’s not me.

My interest is in brewing beer to drink vs all the offshoot hobbies that can be involved such as yeast ranching.

All the yeast performance characteristics I need to know is when it starts, how it’s doing, when it stops, and sensory traits.

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