A Strange Yeast Smell

[katmeefer]

Recently I brewed a Pale Ale and pitched WLP002 English Ale Yeast.
I purchased this yeast from the "expired" rack at my local home-brew store. I didn't create an overnight starter but I did add the yeast to about a cup of wort for a couple of hours prior to pitching.
After about 16 hours after pitching the yeast showed no sign of fermentation. I then added yeast nutrient and yeast energizer. Another 8 hours later and it was fermenting like a mad man.
Here's where my question comes in:
While at high krausen the airlock gave off a very delicious smell, but there was something else there. A slight undertone of what smelled like sulfur.
I am currently on day 7 of fermentation and the krausen has dissipated but the beer is obviously still fermenting. The strange smell has dissipated somewhat as well but is still slightly noticeable.
Is the the product of the over-production of yeast? Is this going to impact the end flavor of my beer? I've had issues in the past with infection, but that's not specifically what this smells like.

 

[Jayslay]

Sulphur smells can be common among different strains of yeast, and often will completely dissipate. I often get them with Belgian yeasts. Now, the real question is, did you calculate how much yeast your beer actually needed? If you did 5 gallons of average strength beer, you need 150-200 billion yeast cells. If you'r "expired" yeast started with 100 billion, and is truly expired, I wouldn't expect anymore then about 50 billion cells. Your addition of the yeast to wort for several hours and then pitching that, probably didnt help much. You may have initiated some yeast growth, but the general rule is the yeast is at its peak in a starter around 24 hours. Its my oppinion that you severely underpitched unhealthy yeast. You may get rid of the sulfur smells but you may be experiencing several off-flavors which may not dissipate. You are correct in that the smells are a product of yeast reproduction, an excess of it if your pitch rate was low.

 

[katmeefer]

thanks for the advice, jayslay!
I'm (relatively) new to this.
Hopefully the beer will turn out okay, i've probably under pitched in worse ways. but in the future i'll definitely be more careful.
cheers!