I remember reading somewhere that the first 3 -> 15hrs (lag phase) after pitching yeast doesn't result in any nasty flavours coming out of your yeast but after that you open your brew up to some nasty flavours coming though..
So remember pitching high doesn't just kill yeast if you pitch to high and it stays high within the lag phase you could produce some unwelcomed flavour.
full artical http://www.whitelabs.com/beer/Yeast_Life_Cycle.pdf
While this is true, it's not the whole story.Thanks for posting that. I've been trying to tell people that yeast don't make esters in the growth phase, but no one seems to get it. The common idea here is that if you pitch high you'll get esters. It's crap.
The lag phase is most often defined as 0-15hours ('Yeast' book page 66), and as with all things yeast (when dealing with billions of live organisms) there are a wide range of yeast cells doing different things at the same time, hence while some yeast are still in the lag-phase others will be fermenting, even within that 0-15 hours 'lag phase' period. In addition (as indicated above) the brewer should not expect to see any activity during the lag phase, and (if you read some/many of the threads on these and other forums) you'll find that most home-brewers say they see signs of fermentation within hours of pitching (and usually always within 12 hours, or they panic and think something in wrong), indicating the lag phase - for most home-brew situations - is much shorter than 15 hours. What this means is that if pitching warm, the yeast will most likely be fermenting (and producing esters and off-flavours) during the period when the wort is still higher than the desired fermentation temperature.
While it's true that warmer temperatures during the lag phase do not directly create undesired esters or off-flavours ('Yeast' book page 67), it can increase off-flavour precursors, which lead directly to things like diacetyl later in the fermentation. Esters are not produced until yeast start to produce ethanol, however rapid growth during the lag phase (warmer temperatures = higher metabolism = faster growth) will affect flavours later in fermentation.