Yeast Pitch Rate: Single Vial vs. Yeast

[Beer-lord]

http://brulosophy.com/2015/04/20/yeast- ... t-results/
Interesting yeast experiment worth the read. Not scientific, of course, with some opinion mixed in.

[mashani]

Results would vary depending on many factors.

Some examples:

1) How oxygenated and nutrient dense the wort is. This will ultimately control how many generations of growth occur in the underpitched beer - the longer the lag time, the more generations have actually grown. Once it runs out of nutrients it has to switch metabolic pathways and start to actively ferment. IE a lesser oxygenated wort might start to actively ferment *sooner* then a well oxygenated one in such a case. But it might not ferment out as completely if growth didn't reach optimal cell count. But there is no reason that an underpitched batch with enough nutrients/oxygen would not ferment out as completely as one with a starter. With a large amount of nutrients, it might even ferment out more - because all the daughter cells that grew over the many extra generations can become more highly adapted to the specifics of the wort.

2) If anything else got in there. The normal pitch would easily out compete many things. The underpitched one with longer lag time might let some other bug get a foothold. The other bug might not ruin your beer, and depending on what it is will most likely die during the fermentation process, but if it grows enough generations, it could leave some slight flavors behind that could be noticed.

3) If you did this with a wheat beer yeast or a Belgian yeast or some other yeast that has a strong ester/phenol profile. The fully pitched beer and the vial pitched beer using a wheat beer yeast would have turned out *a lot more* noticeably different. As in the vial pitched one would have stronger banana. The Mr. Malty pitched one might have no banana at all. (Mr. Malty pitch rates are *wrong* for wheat beers if you want banana). If you were using say Chimay yeast it might become really phenolic or a banana bomb depending on fermentation temps if you underpitch it too much.

4) Age of that vial. The older, the less cells. The less cells the more of all 3 things above comes into play. Starter "brings it all back into balance" as such. So the starter will always give you more consistent results, even with vials of varying age. Commercial breweries pitch rates are all about getting consistent results.

[John Sand]

I like the Brulosopher experiments, they challenge standard practice.
It's only anecdotal in my case, but the three beers on which I've used liquid yeast were all direct pitched, seemingly no adverse affects. Two were fairly high gravity,a Dubbel and a Golden Strong. I think that pitch rate is not nearly as important as temperature, though some yeasts are tolerant of wide swings.

[mashani]

I think that pitch rate is not nearly as important as temperature, though some yeasts are tolerant of wide swings.

Again, in a wheat beer where you want banana pitch rate is very important, and temperature can't make up fully for a huge pitch, you can still get no banana if you pitch too much. However/because of this - in that case the pitch rate of a vial vs. a starter could very well be what you want. In some Belgians, a vial vs. a starter can also be a good thing. IE 3787 can make some wonderful fruit flavors when underpitched a bit. And 3787 is a beast of a yeast, it will ferment out anything easily even if you abuse it. But Chimay yeast isn't such a good one to underpitch, it makes intense enough flavors on its own that temperature will coax out.

I intentionally under pitch beers sometimes. But other times I pitch at commercial pitch rates. In my case commercial pitch rates are sometimes about out competing my house brett. If I pitch a vial vs. a starter in the summer, and I get some brett, I'm almost guaranteed to get a more strongly brett influenced beer, because it lets the brett get a bigger foothold up front, vs. just letting it eat the left over scraps.

[Beer-lord]

I try to overpitch a bit because of all the differences in the different yeast calculators. I am pretty sure my pitching is spot on and now with better temperature control, I hope to see less differences between the same beers I brew.

[philm00x]

There are few times I will make a starter, mostly due to the fact that my batches are so small. When I brew my big Belgian ales is pretty much the only time I will make a starter because they are 1.080+ gravity and I want to make sure the yeast has a fighting chance.

[ScrewyBrewer]

I brewed an IPA two weeks ago and pitched US-05 dry yeast directly on the 65F wort and oxygenated it after 20 minutes or so. It's a 1.060 beer and later today I'll be taking an FG sample before cold crashing the fermentors. The beer fermented mostly at 66F until the airlocks slowed down to just a few bubbles an hour then I increased the temperature to 68F about four days ago. I've never brewed this recipe before so I'll only be able to safely say how it tastes on it's own and what it finishes at today.

Although I have a 5L flask and a stirplate I don't always have enough advanced notice of when I'll be able to brew to make a starter. Having confidence that a quick pitch of dry yeast can get the job done has allowed me to brew on short notice. I do oxygenate the cooled wort and add nutrients to the kettle to help promote good cell growth but this batch took over 24 hours before I saw any activity in the airlocks. I'll know more in a few hours on how it came out.

[John Sand]

I'm not trying to debate anyone's practice, or their results. But I accept the pitch rate suggested by the yeast producers, with good results. I don't worry that yeast calculators may regard that as an under-pitch, I just think of it as using a 5.5 gallon starter.

[mashani]

I don't worry that yeast calculators may regard that as an under-pitch, I just think of it as using a 5.5 gallon starter.

It effectively is as long as you have enough oxygen and nutrients in the wort. But if you don't have enough dissolved oxygen, the cell count may not reach the same critical mass before fermentation begins, because the yeast are forced to eat their fatty acid reserves and when they run out, they have to switch metabolic pathways (active fermentation begins, regardless of cell count). That's why continuous aerated starters grow more yeast, the yeast don't run out of reserves. But it's hard to get that much oxygen into a 5 gallon batch of beer.

Also the number of growth phase generations (lag time in our minds) necessary to achieve the same cell count once pitched goes from 2-3 generations with a good sized starter to many more possibly 12+ or more even, which does allow other things to compete for the resources more effectively if other things happen to get into the wort. As a general rule of thumb with generic yeast at generic ale temps, figure ~2 hours per generation (temperature has a big effect on this, which is why yeast folks tell you to pitch warmer then fermentation temps quite often, it gets them moving along quicker, and some yeast strains of course act different). This assumes a well oxygenated wort. Without enough oxygen the lag time may seem the short/fast like a starter pitch, but active fermentation will begin with a lower cell count. Because the yeast have no other choice, switch metabolism or go hungry. If you underpitch and you DON'T have a long lag time, then you didn't oxygenate the wort enough for it to be a "starter" as such.

Dry yeast has a big advantage over liquid here, in that dry yeast has additional nutrient reserves "baked in" as such as part of the manufacturing process. So dry yeast will more effectively grow and ferment out a beer even if tossed into an under oxygenated wort and under pitched.

[Kealia]

Unless I'm deliberately under-pitching, I'll follow the yeast starter numbers every time. With so many variables to consider I want to be able to replicate the same beer each time. With yeast vials of varying ages, you may pitch X amount one time, and Y amount the next time because of the viability of the yeast.

Since I pay so much attention to recipe details, temp, etc. I don't want the yeast to be a variable. Since I can control that factor, I like to.