Wyeast manufacture date question

[GaryW]

I purchased a couple of Wyeast liquid yeast smak-paks yesterday. The package says "use within 6 months of the manufacture date". However, there is no manufacture date on the package. There is this on the package: "Best by 17 April 2024".

That "best by" date is 5 months from now. Yeast viability can change significantly over that period of time. For purposes of making a proper amount of starter, it would be nice to know the date of manufacture. Does Wyeast have a specific time between the "best by" date and date of manufacture?

 

[GigaFemto]

They use to print the manufacturing date on the package. Sometime in the past year or two they changed to a "Best by" date, and apparently forgot to change the wording that refers to the manufacture date. My guess is that the "Best by" date is 6 months from manufacture. It seems that they decided that a "Best by" date is clearer to the user.

--GF

 

[GaryW]

My guess is that the "Best by" date is 6 months from manufacture. It seems that they decided that a "Best by" date is clearer to the user.
--GF

Thanks. That's my guess also...although it would be nice if they stated something to that effect.

 

[Oginme]

I was at the AHA convention a few years ago and addressed this with several of the yeast manufacturers as they were changing from manufacture date to 'best before' dates on their packaging.

Their answer is that there have been big strides in packaging and preservation of the yeast viability over the years. If you by a package of yeast and use it prior to the date printed as the 'best before' date on the package, you are pretty much assured that the yeast count within the package will be at or very close to the published cell counts for that package.

This did seem to match my counts on yeast packs which I had purchased and one of the reasons I was talking to them. Many of the yeast calculators being used are (a) developed quite a number of years ago when packaging was not so efficient, and (b) conservatively designed to give a 'worst case' calculation of the number of viable cells. It also ensures that the average brewer will achieve close to or more viable cells they desire regardless of their individual techniques.

These days, I rarely do cell counts coming out of the package. If the yeast pack is used prior to the best before date on the package, I consider the number of viable cells as the target count printed on the package and set that date in the yeast calculators.

I save my time and effort doing cell counts when I am repitching yeast.

Edit: Another thing a couple of the people I talked to mentioned is that the viability can be highly dependent upon the strain of yeast.

 

[GaryW]

...Many of the yeast calculators being used are (a) developed quite a number of years ago when packaging was not so efficient, and (b) conservatively designed to give a 'worst case' calculation of the number of viable cells. It also ensures that the average brewer will achieve close to or more viable cells they desire regardless of their individual techniques.

These days, I rarely do cell counts coming out of the package. If the yeast pack is used prior to the best before date on the package, I consider the number of viable cells as the target count printed on the package and set that date in the yeast calculators.

Edit: Another thing a couple of the people I talked to mentioned is that the viability can be highly dependent upon the strain of yeast.

@Oginme Thank you for those comments.
I purchased Wyeast 2007 (Pilsner lager). While building a recipe with BS 3.2.7 software, I note the following viability:
1 month from manufacture: 75.84%
6 months from manufacture: 22.79%

That's a significant reduction in viability. Based on that reduction, it appears that:
- your comment (a) applies to the yeast calculator used in BS 3.2.7 or,
- your comment (b) that a 'worst case' calculation assures an adequate number of yeast cells for the average homebrewer. I would add that this calculation likely helps the yeast manufacturer avoid undesirable customer experiences, and perhaps sells more yeast.
- or both.

 

[McMullan]

Unlike “active” dry yeast, which are in a state suspended animation, liquid/wet yeast are metabolically active cells therefore, under limiting conditions (e.g., diminishing/lack of resources) in a pack, jar in the fridge, bottom of an FV, etc., cell vitality and viability deteriorate at variable rates over time. Cell vitality and viability are inevitably linked in most cases. Cells deficient in resources lose vitality and die. The common assumption among home brewers good yeast pitching practice is just about the number of viable cells is untrue in most cases where freshly prepped/harvested healthy yeast cells are not pitched. An aberrant fermentation is more likely when yeast are under pitched due to poor cell condition as well as cell pitching rate. Viability by itself is not a good measure at all. It’s superstitious nonsense, in reality. That’s assuming sampling for cell counts was representative of the yeast population, which is unlikely in most cases. It isn’t as easy as some believe and generally just a very crude estimate. The long short, when using wet yeast, make a starter regardless of production date. It helps to promote a better fermentation and produces more balanced beers.

 

[Oginme]

@Oginme Thank you for those comments.
I purchased Wyeast 2007 (Pilsner lager). While building a recipe with BS 3.2.7 software, I note the following viability:
1 month from manufacture: 75.84%
6 months from manufacture: 22.79%

That's a significant reduction in viability. Based on that reduction, it appears that:
- your comment (a) applies to the yeast calculator used in BS 3.2.7 or,
- your comment (b) that a 'worst case' calculation assures an adequate number of yeast cells for the average homebrewer. I would add that this calculation likely helps the yeast manufacturer avoid undesirable customer experiences, and perhaps sells more yeast.
- or both.

So if you were to do a viable cell count on the packages, I would bet that the number of viable cells right now would be somewhere between 900,000 and 1 million at the 6 month date based upon my studies. This is prefaced by the package being kept chilled during that time and the yeast not having a temperature shock which could affect their 'hibernation'.

For my brewing where I do watch the cell counts going into my batches, I would consider the number of viable cells pretty much stable up to the six month mark.

Yes, the yeast calculator in BS is based upon the models from more than a decade ago. BS uses models for all of its calculations (mash pH, yeast viability, IBU). These are not unique to BeerSmith.

My comment about the worst case calculations is more likely to help the yeast companies, as homebrewers will be more likely to pitch more packs based upon the supposed lower viability. Their shift to the best before dates reflects their confidence in packaging process, cell stability in storage, and a desire to improve the homebrewer's confidence in the yeast manufacturing process rather than outdated models.

You can listen to some of Brad's more recent conversations with Chris White of WhiteLabs, which may help understand some of the packaging changes which lead to improved shelf life of the yeast.

 

[McMullan]

Packaging is only ever going to have a very limited effect re increasing the longevity of pitchable wet yeast cells. Claims to the contrary are just marketing primarily, to plug the business. It’s a no-brainier. We can’t actually break the laws of physics, which biology/survival of yeast cells rely on just like everything else. It doesn’t matter what marketing ever claims. It can’t be done. Breaking the laws of physics, that is. Do the biology, not just biased maths. White Labs invested in and developed a packaging process that streamlined production infinitely more than the longevity of wet yeast cells. What they did was quite cool from a practical standpoint for their business, but it didn’t change that much in terms of wet yeast shelf life, which is days to (I’m stretching it) weeks. They kind of seized more control over miniaturising Wyeast’s standard format. Not much more, outside all the marketing. It really doesn’t matter if the expectations of a random home brewer have been met, because his expectations are biased (flawed) by marketing and his personal acceptance criteria based on… Which is important, because it explains why there are so many debates and contrasting opinions among home brewers. If we were all doing science, there’d be a lot less conflict and cognitively dissonant nonsense being expressed.

 

[stevebonny]

So if you were to do a viable cell count on the packages, I would bet that the number of viable cells right now would be somewhere between 900,000 and 1 million at the 6 month date based upon my studies. This is prefaced by the package being kept chilled during that time and the yeast not having a temperature shock which could affect their 'hibernation'.

For my brewing where I do watch the cell counts going into my batches, I would consider the number of viable cells pretty much stable up to the six month mark.

Yes, the yeast calculator in BS is based upon the models from more than a decade ago. BS uses models for all of its calculations (mash pH, yeast viability, IBU). These are not unique to BeerSmith.

My comment about the worst case calculations is more likely to help the yeast companies, as homebrewers will be more likely to pitch more packs based upon the supposed lower viability. Their shift to the best before dates reflects their confidence in packaging process, cell stability in storage, and a desire to improve the homebrewer's confidence in the yeast manufacturing process rather than outdated models.

You can listen to some of Brad's more recent conversations with Chris White of WhiteLabs, which may help understand some of the packaging changes which lead to improved shelf life of the yeast.

Oginme, how do you get a viable cell count? Is fancy equipment needed or just a microscope etc?

 

[McMullan]

You need a lot more than a microscope. Just like a racing driver needs a lot more than a fast car. Or just like a tree needs a lot more than CO2. LOL! Sampling yeast is fraught with biases enthusiastic amateurs and mediocre “professionals” don’t even know about. The irony is intense enough to rank entertaining, tbh. Statistically, along the lines of the average adding one cup or two to “succeed” where a savvy brewer could add a few oz and get a much better fermentation and beer. Context is far too complicated for most home brewers, though. Evidently. Such is the attraction of lore and superstition.

 

[Oginme]

Oginme, how do you get a viable cell count? Is fancy equipment needed or just a microscope etc?

You need a good quality microscope, a hemocytometer, and a cell stain solution such as Trypan Blue or Methylene Blue. You will need to make successive dilutions of a yeast slurry, so a decent scale and precision volumetric pipettes, graduated cylinders, and flasks helps greatly in accuracy.

An excellent source and tutorial can be found at https://suigenerisbrewing.com/. I also learned a lot about cell plating from Bryan's site, which leads down another rabbit hole of skills and activities related to brewing.

I started by using Wyeast packs to help with calibrating myself and that is when I figured out that the yeast calculators were giving me way lower actual viable cells than what I was actually measuring and recording. That brought me to talking to the people at Wyeast and White Labs at convention. My counts on actual number of cells in a package were right on with their standards for packaging, so I have to believe that my mini-study was pretty close as far as viability.

 

[McMullan]

No consideration at all re sampling effects in a highly heterogeneous system. Stunning. Some people live in a fake, 1-dimensional world of their own making, shamelessly reinforcing believes over reason.

 

[Oginme]

No consideration at all re sampling effects in a highly heterogeneous system. Stunning. Some people live in a fake, 1-dimensional world of their own making, shamelessly reinforcing believes over reason.

Considering you have no idea of my methods of sampling, sample pool, or determination of reproducibility/reliability in my testing, this is a pretty ignorant statement.

 

[McMullan]

Considering you have no idea of my methods of sampling, sample pool, or determination of reproducibility/reliability in my testing, this is a pretty ignorant statement.

Actually, in reality, it isn’t ignorant at all. More like “gold dust” for free. The most crucial part of any biological assessment is a defined procedure to collect samples that are representative of the population of interest. This is surprisingly challenging for brewer’s yeast. In most cases the error rate is likely comparable to “1 cup or 2?”. I can guarantee that there is significant spatial and temporal heterogeneity re yeast in fermentation environments and yeast slurry. As a biologist who’s just decommissioned a yeast lab and kept a nice microscope, cell densiometer and carousel of Gilson pipettes, I repitch freshly harvested yeast by the cup, not questionable cell counts. Empirically determined bucket (cup) chemistry is a better strategy for brewers. The probability of over pitching as home brewers is vanishingly small. The focus should be on avoiding under pitching. Far too much poor advice to home brewers promotes a high risk of under pitching. To such an extant, aberrant fermentations have been normalised by propagated misinformation.

The recommended crude estimates for pitching rates are based on business decisions by pros repitching very fresh healthy yeast. They are “over pitching” relative to home brewers generally. By a long way. A key reason why they produce better balanced beers. It’s particularly noticeable with English ales. Following the poor advice recommending home brewers pitch unhealthy yeast at low rates does not produce comparable well-balanced ales. It produces “home brew”. Nor does it make much business sense for yeast suppliers to provide sufficient yeast in top condition at prices affordable for home brewers. We can’t buy it. The only choice for most home brewers - who don’t live next door to a generous brewery - is to produce it at home then repitch it. Just like real brewers do. Even at home brew levels, that G2 slurring is worth a lot. Not just its monetary market value, but its priceless fermentation qualities.

 

[Oginme]

Actually, in reality, it isn’t ignorant at all. More like “gold dust” for free. The most crucial part of any biological assessment is a defined procedure to collect samples that are representative of the population of interest. This is surprisingly challenging for brewer’s yeast. In most cases the error rate is likely comparable to “1 cup or 2?”. I can guarantee that there is significant spatial and temporal heterogeneity re yeast in fermentation environments and yeast slurry. As a biologist who’s just decommissioned a yeast lab and kept a nice microscope, cell densiometer and carousel of Gilson pipettes, I repitch freshly harvested yeast by the cup, not questionable cell counts. Empirically determined bucket (cup) chemistry is a better strategy for brewers. The probability of over pitching as home brewers is vanishingly small. The focus should be on avoiding under pitching. Far too much poor advice to home brewers promotes a high risk of under pitching. To such an extant, aberrant fermentations have been normalised by propagated misinformation.

The recommended crude estimates for pitching rates are based on business decisions by pros repitching very fresh healthy yeast. They are “over pitching” relative to home brewers generally. By a long way. A key reason why they produce better balanced beers. It’s particularly noticeable with English ales. Following the poor advice recommending home brewers pitch unhealthy yeast at low rates does not produce comparable well-balanced ales. It produces “home brew”. Nor does it make much business sense for yeast suppliers to provide sufficient yeast in top condition at prices affordable for home brewers. We can’t buy it. The only choice for most home brewers - who don’t live next door to a generous brewery - is to produce it at home then repitch it. Just like real brewers do. Even at home brew levels, that G2 slurring is worth a lot. Not just its monetary market value, but its priceless fermentation qualities.

Well, since you are throwing around your credentials like they are the answer to your general disdain for my experiments and testing, I have:

43 years of experience in QA/QC,
38 years of experience in process control and design,
33 years in design of experiments and statistical analysis

Fields range from pulp and paper, design and manufacture of inks, coatings, and paints, printing, medical diagnostic testing, medical device design and manufacture, agricultural genetics, and several others.

I know my statistical error, both in sampling and in analysis, for my experiments. I have been designing quality tests for new products and processes for many years and understand sampling methods and associated introduction of error. Actually having a lab which is regularly used for doing fecal counts and parasite identification, I am equipped with much of the standard equipment as most of the yeast labs I have seen at breweries I have toured.

I agree that cell volume pitched can be more valuable than actual cell counts for commercial brewing, given that different strains of yeast have differing cell volumes. For my batch sizes and the consistency of pitching the same range of yeast from batch to batch when I am doing experimentation, the cell counts work just fine.

 

[McMullan]

Well, since you are throwing around your credentials like they are the answer to your general disdain for my experiments and testing, I have:

43 years of experience in QA/QC,
38 years of experience in process control and design,
33 years in design of experiments and statistical analysis

Fields range from pulp and paper, design and manufacture of inks, coatings, and paints, printing, medical diagnostic testing, medical device design and manufacture, agricultural genetics, and several others.

I know my statistical error, both in sampling and in analysis, for my experiments. I have been designing quality tests for new products and processes for many years and understand sampling methods and associated introduction of error. Actually having a lab which is regularly used for doing fecal counts and parasite identification, I am equipped with much of the standard equipment as most of the yeast labs I have seen at breweries I have toured.

I agree that cell volume pitched can be more valuable than actual cell counts for commercial brewing, given that different strains of yeast have differing cell volumes. For my batch sizes and the consistency of pitching the same range of yeast from batch to batch when I am doing experimentation, the cell counts work just fine.

Then you really should know better, frankly. Nor was I throwing my credentials around. I merely noted I was a biologist and suggested, regardless of technique or equipment, ecology of brewer’s yeast is ecology of brewer’s yeast. Understanding this is much more important than faffing around with guesstimated pitching rates. Not just because it isn’t useful information for other brewers, most of whom don’t own microscope. The only genuine value of a completely optional microscope is a quick assessment of viability. Besides, It’s only beer, we’re not fermenting pharmaceuticals. Pitching by the cup or bucket works just fine for professional brewers. No reason why it doesn’t work as well for the home brewer.