Lag Phase/Over Pitching

[junior]

Hi All,
Just did a batch of all grain with o5, it took about 9 hours until I noticed signs of fermentation, that's a bit long of a lag time I usually get. So I did some searches and came across this article, anyone have an opinion about using higher temperature during the lag phase without any negative results? Also what if any opinions on over pitching?
Cheer's

The lag phase can be carried out at a higher temperature than the rest of fermentation because very little flavor compounds are produced. Ethanol production is also very limited, therefore ester formation is not a concern. Some brewers begin the lag phase for ales at 72-75F, and complete the fermentation at 68F. This can be done with success for lagers too, with starting the lag phase at 72-75F and lowering the fermentation temperature to 50-55F.

Brewers will not see any visible activity during the lag phase, hence the way it got its name. But this phase is very important in building new healthy cells that will be able to complete fermentation. If the wort is overpitched, this will decrease the lag phase, and each individual cell will not be as healthy at the end of fermentation. Although it may feel reassuring to a homebrewer to see fermentation activity within one hour of pitching yeast, it is not best for the yeast.

 

[tgmartin000]

Here's the thing - you WANT a lag phase of about 12 hours. During that time the yeast are reproducing and building up their health. Having a short lag time is not necessarily a good thing by any means.

Also, not sure where you got that article, but flavor compounds are produced during the growth phase. I believe ester production is happening.

Also, you want to maintain the temp during fermentation. If you ferment at 64, try to start fermentation at 64, rather than at a higher temp. Sudden reductions in temp during fermentation are detrimental to your yeast. Start low, let it slowly rise after the peak of fermentation activity. At least, that's the way I've always understood things.

 

[BigFloyd]

9 hours isn't too long of a lag time at all, especially if you are pitching (as you should) a few degrees below the low end of the optimal range for the yeast and letting it come up to the target temp.

It's really hard to over-pitch in a detrimental amount unless you are dumping wort atop a whole yeast cake (that will typically have way too many cells for a normal gravity ale) without removing a large portion of it.

What the OP is talking about is a technique that involves using the higher initial temp to encourage more yeast growth to try and compensate for underpitching. I don't see it as a sound home brewing practice and believe there is a real potential for producing off-flavors from stressing the cells during the lag phase. Also, what if the ferment kicks off into exponential growth at the higher temp while you're sleeping or at work?

BTW-- what article are you talking about?

 

[beergolf]

It is difficult to pitch warm and then cool down the wort. It can easily get out of conrol and get too hot, or you can cool it too fast and stall the yeast. It is best to pitch low and slowly raise the temp. Much easier to control.

 

[junior]

9 hours isn't too long of a lag time at all, especially if you are pitching (as you should) a few degrees below the low end of the optimal range for the yeast and letting it come up to the target temp.

It's really hard to over-pitch in a detrimental amount unless you are dumping wort atop a whole yeast cake (that will typically have way too many cells for a normal gravity ale) without removing a large portion of it.

What the OP is talking about is a technique that involves using the higher initial temp to encourage more yeast growth to try and compensate for underpitching. I don't see it as a sound home brewing practice and believe there is a real potential for producing off-flavors from stressing the cells during the lag phase. Also, what if the ferment kicks off into exponential growth at the higher temp while you're sleeping or at work?


Big,
This is the article was referring to. http://www.brewgeeks.com/the-life-cycle-of-yeast.html In particular I was curious who agreed or disagreed with the part that states, during the lag phase higher temperatures can be maintained because little or no flavor compounds are being produced during this phase. If this is true it seems to me that starting at a higher temperature will help the yeast reproduce faster than lower temperatures, also in the article it mentions that over pitching will lessen the lag time but the yeast will not be as healthy at the end, just curious what the knowledgeable people on this site thought about these questions.
Cheer's

 

[jglazer]

I feel I should chime in and say that I have on many occasions pitched between 72f and 75f and then cooled to between 64f and 68f and absolutely none of those beers ever had off flavors. I should note I don't really plan to do this, but the 2 reasons why I would do this is because 1) I couldn't get my wort temp down low enough with the heat where I live and I didn't want to let the wort sit in the fermenter for too many hours before pitching yeast and 2) I knew I was underpitching and wanted to encourage yeast growth.

Again I would never plan to do this, usually my goal is to pitch the yeast at the temp I want to ferment at, but if you need to for some reason, I can vouch that in my experience I haven't detected any off flavors from pitching at a higher temp

Oh and a 9 hour lag time is DEF not too long...

 

[junior]

I feel I should chime in and say that I have on many occasions pitched between 72f and 75f and then cooled to between 64f and 68f and absolutely none of those beers ever had off flavors. I should note I don't really plan to do this, but the 2 reasons why I would do this is because 1) I couldn't get my wort temp down low enough with the heat where I live and I didn't want to let the wort sit in the fermenter for too many hours before pitching yeast and 2) I knew I was underpitching and wanted to encourage yeast growth.

Again I would never plan to do this, usually my goal is to pitch the yeast at the temp I want to ferment at, but if you need to for some reason, I can vouch that in my experience I haven't detected any off flavors from pitching at a higher temp

Oh and a 9 hour lag time is DEF not too long...

J,
So can I assume from your post, your opinion is that there were no off flavors in your beer when the lag phase was in the 72-75f range?

 

[jglazer]

Yep from all the beers that I pitched at higher temps, I detected no off flavors.

But of course this is homebrewing and there are a million factors so I don't want to say that I can guarantee there will be no off flavors if you do this. I think one factor that you may want to consider is the type of beer...obviously lighter beers highlight off flavors more and I don't make lighter beers so that's something to consider. I should also mention that when I pitch at those higher temps I am continuing to lower the temp down right away so say I pitch at 72, every 30-45 minutes the temp of the beer is lowered a degree so its not staying at 72 very long...

 

[bierandbikes]

I would say your choice on fermentation temps has everything to do with the yeast strain. Many strains produce flavor compounds during the growth phase. Therefore, higher temps could enhance either desirable or undesirable flavors, or in some cases depending on the yeast strain, produce no additional flavors. Do the research on the characteristics of your yeast first and then decide.

Of course, the only way to really find out is to experiment.

 

[jglazer]

Any idea where can you find info on yeast specific lag phase off flavors?

 

[BigFloyd]

Any idea where can you find info on yeast specific lag phase off flavors?

This is from "Diacetyl Time Line" by Chris White (as in White Labs) (emphasis is mine):

After yeast is pitched into beer, the yeast undergo a lag phase, followed by a phase of very rapid growth called the exponential growth phase. During both the lag and exponential phase, yeast build amino acids, proteins, and other cell components. Most of these components do not make the flavor of the beer, but the various pathways produce individual compounds that leak out of the cell to effect beer flavor. One of the amino acids produced by yeast is valine. An intermediate compound in valine production is acetolactate(Fig. 3). Not all of the acetolactate produced eventually becomes valine, some will leak out of the cell and into the beer. This acetolactate is then chemically (not enzymaticly) converted to diacetyl in the beer. The chemical reaction is an oxidation, and high fermentation temperatures favor this reaction. Other factors that will increase diacetyl production in this phase are insufficient nutrients (i.e. the amino acid valine), which forces yeast to manufacture their own. For example, the more valine yeast produce, the more acetolacate intermediate is required, and hence the more diacetyl made. There is a strain specific phenomena here, because given the same conditions, different strains will produce different levels of diacetyl.

 

[junior]

Yep from all the beers that I pitched at higher temps, I detected no off flavors.

But of course this is homebrewing and there are a million factors so I don't want to say that I can guarantee there will be no off flavors if you do this. I think one factor that you may want to consider is the type of beer...obviously lighter beers highlight off flavors more and I don't make lighter beers so that's something to consider. I should also mention that when I pitch at those higher temps I am continuing to lower the temp down right away so say I pitch at 72, every 30-45 minutes the temp of the beer is lowered a degree so its not staying at 72 very long...

J,
Got it, that's what I do to, in my set up I can monitor the wort and water in my cooler, it is easier for me to pitch around 75 and let it cool down rather then put carboy in cooler at 80 wait one hour(worry about infections) then pitch at 65. As the original question was if I pitch at 75 there would be more yeast reproduction and no off flavors rather than pitching at 65 with longer lag phase