[hopfenundmalz]

I'm not a big user/fan of Chico, but I've heard it throws off peach-like character when fermented cooler than 62F. If ambient is 55F, you might expect exothermic heat to raise the temp of the fermenting beer to just about 62F... maybe pitch warm, around 70F, then place it out there?

Edit for clarification: I'd pitch at 70, let it ride in the cool garage for 2-3 days, then bring it indoors until it's finished.

I've had that happen with US05, but never with 1056.

I have always read the peach thing with US-05. Not with the others.

[brulosopher]

I'm not a big user/fan of Chico, but I've heard it throws off peach-like character when fermented cooler than 62F. If ambient is 55F, you might expect exothermic heat to raise the temp of the fermenting beer to just about 62F... maybe pitch warm, around 70F, then place it out there?

Edit for clarification: I'd pitch at 70, let it ride in the cool garage for 2-3 days, then bring it indoors until it's finished.

I've had that happen with US05, but never with 1056.

I have always read the peach thing with US-05. Not with the others.

Interesting! I've always read US-05 was the same strain as the others. Despite my lacking love for that yeast, I'll have to do a comparative xBmt at some point

[hopfenundmalz]

I'm not a big user/fan of Chico, but I've heard it throws off peach-like character when fermented cooler than 62F. If ambient is 55F, you might expect exothermic heat to raise the temp of the fermenting beer to just about 62F... maybe pitch warm, around 70F, then place it out there?

Edit for clarification: I'd pitch at 70, let it ride in the cool garage for 2-3 days, then bring it indoors until it's finished.

I've had that happen with US05, but never with 1056.

I have always read the peach thing with US-05. Not with the others.

Interesting! I've always read US-05 was the same strain as the others. Despite my lacking love for that yeast, I'll have to do a comparative xBmt at some point

The yeast offered by the suppliers all have subtle differences when reputed to be from the same source. Mark has talked of different isolates of the same strain.

Several years back a friend did a split fermentation, same wort and conditions. We tasted it at a club meeting and they were different, by small amounts. What you could contribute would be to do the same and have those evaluated in a blind triangle test, which was not done at the club meeting.

Some have said the SN yeast is a little different from what is on the market. They maintain their own house strain. You might culture some from a bottle and see if it is different.

[gmac]

I bought a hose. It's in the basement at 20C and life is good.

If anyone wants a sample, let me know because I expect it wont last long (and you won't get one because cross border beer shipping is a PITA, maybe Jeff becuase I have an amber lager to deliver to Detroit but that's another story). I am not a big fan of this one either, 007 is my go to yeast but my LHBS was out so I went this way.

[denny]

Interesting! I've always read US-05 was the same strain as the others. Despite my lacking love for that yeast, I'll have to do a comparative xBmt at some point

It may have come from the same source (I have it on very good authority that Safale simply purchased some 1056 and used that for 05) but that doesn't mean they're exactly the same in terms of performance.  That was one of the main reasons I stopped using 05 and went back to 1056.

[brulosopher]

Interesting! I've always read US-05 was the same strain as the others. Despite my lacking love for that yeast, I'll have to do a comparative xBmt at some point

It may have come from the same source (I have it on very good authority that Safale simply purchased some 1056 and used that for 05) but that doesn't mean they're exactly the same in terms of performance.  That was one of the main reasons I stopped using 05 and went back to 1056.

For sure, I'm certain there are multiple variables contributing to making each strain different. I just started collecting data on an xBmt that is VERY similar to this one, results should be published in 3-4 weeks.

[S. cerevisiae]

There's a key difference between US-05 and the other offerings; namely, US-05 is propagated aerobically in a bioreactor using a molasses-based medium.  This type of propagation is known as continuous propagation.  The other offerings are batch propagated.  In continuous propagation, the medium is held at a steady state below the Crabtree threshold (< 0.3% glucose) while O2 is continuously added and yeast is withdrawn.  The result is little to no ethanol production.  During aerobic propagation, yeast effectively consumes C₆H₁₂O₆, and converts it to yeast biomass, CO₂, and H₂O.  In batch propagation, all biomass growth is fermentative, and fermentative growth is nowhere near as efficient at turning carbon into yeast cells because two major outputs are CH₃CH₂OH (ethanol) and CO₂.

Now, with that said, when one pitches US-05 into batch of wort, one is pitching yeast cells that have been propagated from less than the quantity of yeast found in a White Labs vial to literally tons of yeast using a medium that is not wort.  Furthermore, one is pitching yeast cells that have never experienced ethanol stress. 

[denny]

Interesting info, but what's the take away?  Why should we care how it's propagated?  What does that mean to the beer we brew?

[S. cerevisiae]

We have all been told not to use table sugar as a starter medium.  Well, continuous propagation using molasses as the carbon source is like making a starter using table sugar on steroids.  Molasses is a byproduct from refining table sugar.  It's mostly sucrose.  While sucrose and maltose share the same chemical formula, C₁₂H₂₂O₁₁, maltose consists of two glucose molecules bound by a glycosidic bound whereas sucrose has one glucose and one fructose molecule bound by a glycosidic bound. Yeast cells cannot use maltose and sucrose directly; therefore, the glycosidic bonds have to be broken.  Maltase is used to break the glycosidic bound that holds the two glucose molecules together in maltose whereas invertase is used to break the glycosidic bound that holds the glucose and fructose molecules together in sucrose.

Now, stay with me on this one because I have a hypothesis (more like a SWAG) as to why US-05 behaves differently in dry form than it does in liquid form. It has to do with US-05 being a BRY 96 descendent.  As I mentioned earlier, BRY 96 is a diploid. I also mentioned that diploids are relatively rare in brewing because they tend to be more unstable than polyploids from a genetic point of view.  Diploids are more common in vinting and baking strains of S. cerevisiae, and the reason for that difference is more than likely due to the fact that wine and bread yeast strains are usually not sent through the process, collected, and reused.  Repitching puts selective pressure on a culture, often favoring mutations.  Diploids are more mutation prone than polyploids because the only time that there is a duplicate copy of a gene is when a yeast cell is homozygous for a gene, that is, it inherits an identical copy of the gene from both parents.  I believe that a selective mutation to a gene for which BRY 96 is heterozygous (a different copy from each parent) is occurring during aerobic propagation that results in US-05 creating increased levels of benzyl alcohol, which, when combined with acetic acid, forms benzyl acetate; otherwise, known as the peach ester. 

Let's describe this phenomenon in human terms.  Colorblindness is a genetic mutation (specifically, a single-nucleotide polymorphism, or SNP) that occurs on a gene in the X chromosome that is part of the sex chromosome pair; namely, pair number 23.  The reason why colorblindness is more common in men is that men only have one X chromosome in pair number 23.   The other chromosome is a Y.  As colorblindness is passed on the X, a man inherits colorblindness from his mother.  Women, on the other hand, receive an X from both parents.  If both parents pass a defective X, a woman will be colorblind; otherwise, she will be a carrier who will pass the defective gene to 50% of her offspring via an X chromosome.

Red hair is also a genetic mutation.  It is a melanocortin receptor 1 (MC1R) mutation. However, in this case, the mutation occurs on chromosome 16, which means that the mutation affects both sexes the same way.  A person has to inherit this mutation from both parents (i.e., be homozygous) in order to have red hair.  However, this mutation has a heterozygous (inherited from one parent) expression as well.  It's easier to see in men than in women because men have facial hair (okay, some women have facial hair as well). Men who carry one copy of the mutation will have brown hair and a reddish brown to ginger colored beard.  Their body hair will also tend be the same color as their facial hair. The MC1R mutation in both inheritance patterns tends to result in people having fair skin that burns quickly when exposed the strong sunlight. The UK has the largest percentage of MC1R mutation carriers in the world.

Getting back to US-05, I do not believe that the mutation is in the seed culture.  I believe that the mutation is the result of being propagated for a large number of generations in a medium that is not wort while consuming the carbon source almost exclusively through the respirative metabolic pathway.  This practice puts selective pressure on the cells.  My experience with the culture leads me to believe that the peach ester problem is a true mutation and not an initial pitch deviation that is due to aerobic propagation in a bioreactor.

[denny]

Thanks!  Starting to make sense.

[ynotbrusum]

Being an MC1R I appreciate the example.  But maybe with age, the mutation becomes not so pronounced (like the gray hair and gray beard I now sport....)  Just kidding about the analogy, but I have gone away from US-05 as my "go to" yeast because whenever I repitched, I got mixed results and a lack of consistency.  So most recently I used the liquid form of the yeast without experiencing the off flavor issue at cooler temps and on repitch.  This could be anecdotal and caused by something in my brewing and fementing process, but I just don't trust US-05 on a repitch or when fermented cold.