How much yeast is too much?

[Grandpasbrewery]

I was wondering if there was such a thing as too big of a starter?

I use beersmith which, like most probably already know, tells me what sort of yeast population I need to pitch for a specific brew. If I need, say 350bil cells for a specific brew, is there any harm to pitching more or less that suggested?
Say I pitch 450-500bil instead of 350 or 200-250, what sort of issues could I run into. I know under pitching can lead to a stuck fermentation but what what sort of numbers/percentages over/under will start to cause off flavors or other problems.

I only ask because I was going to brew this past Saturday, but something came up and no dice. So I have this beautiful 2L starter that is sitting in my fridge and I am trying to figure out what to do with it.

Decant, jar and save?
Decant, wash, jar and save?
Either of above and pitch into a small 0.5L starter for a few hours just to get the yeasties awake and going again?
Repitch to another full 2L starter and double the population again?
Leave as is and just warm to room temp before pitching when I get around to brewing?

It's been sitting in the starter wort, in the flask in the fridge since Saturday...

 

[funnycreature]

My advice is to leave it in the fridge and on brew day take a half liter or so of your wort, chill it, and use that to reactivate your yeast. You'll have to decant your starter and resuspend the yeast slurry in the cooled wort. I did that for my last 3 or 4 batches and it worked well so far.

 

[Magic8Ball]

There are several issues with under and over pitching yeast (namely esters, off flavors and under attenuated wort). There are books written on the subject. The numbers given by brewsmith are the ideal. You should strive to make those numbers as it will give you the best beer possible. FWIW I use Mr.Malty.com for pitch rates, I am not sure how they match up to BSmith.

Your 2L of starter will be fine in fridge. Make a small another DME starter the day (.5L) before brew day to wake up the yeast. You won't really grow a significant amount of yeasties in that time. Just getting them yeasties ready to eat wort. Remember to pull the starter out of the fridge a couple of hours before pitching into the "starter", and decant off any beer from the top of the yeast mass below it.

 

[ACbrewer]

Yeast during reproduction produce esters and other chemicals. In large amounts, these create off flavors and are undesirable. If to much yeast is pitched, the yeast don't reproduce as much, and very little of these esters and other chemicals are produced, but beer without any of these flavor chemicals tends to be boring to taste, or lacking. Rather like a recipe with a needed spice needing (say forgetting vanillia in cookies) not bad, just not right.

Some styles do better with over or under pitching. Cleaner beers do well with over pitching, and Belgian styles do well with under. BTW, under/over here is like 10to 20%, not x2 over or 1/10th under. Typically under pitching is more common as yeast die, and as yeast packages are perhaps not enough for a given 5 gallon batch. I agree it is optimal to hit the 'recomended' of Beersmith or mrmalty, but being a little high or low shouldn't do to much to you.

 

[Grandpasbrewery]

Awesome, that's great to know.

I'm Brewing a variation of a Vanilla Porter recipe I found on Northern Brewer.
Beersmith is calling for 310billion cells and that a 1.5L starter would get me to 311billion with my Yeast date. I messed up and made a 2L starter, by clicking on the wrong tab and opening a different recipe, which puts me at the 377billion.
So I'm actually past that 20% threshold you mentioned, which would be 372billion. hopefully it will work out.
I typically brew 7 gallon batches due to my equipment size.

 

[ACbrewer]

I'd suspect your beer might be a little 'blander' in flavor if anything were wrong. BUT, let me say I use the 20% as benchmarks, not absolutes, the tolerances very by style. You may notice nothing at all, especially since you look like you are not that far above the 20% I mentioned, which is more a guide than a rule.
Speaking of styles, Big Belgian Beers receipes (Triples for example) when including pitch rates have thier pitch rate at 80% to 90% of what you'd expect for a particular gravity beer.

Anyhow, I think you will be ok.

 

[Grandpasbrewery]

Thanks for the info.
I think I'd prefer "blander" over more pronounced off flavors if I was going to pick an error.