all grain wort ferments faster than extract wort?

I just did my first allgrain batch yesterday (Oatmeal Stout), and pitched at about 5:00PM. By 11:00PM there was already some krausen and bubbling and by this morning it was bubbling furiously.

I'm accustomed to a lag time of about 12 hours of late. I use Wyeast Activator packs with 5 gal batches of wort. I aerate the wort for about 3 min after pitching using an aeration stone, aquarium pump and filtered air (not oxygen). These factors haven't changed for the last dozen or so batches. What changed with yesterday's batch is that it's allgrain, and the lag time went from 12 to 6 hours.

Not that I'm complaining, but I wasn't expecting the lag time to go down like that. Going all grain shouldn't have anything to do with it, should it? Has anyone else noticed shorter lag times when you mash your own wort as opposed to using extract?

I also noticed that the prefermented beer (from the OG sample test) tasted better than the samples usually do. In the past I've found the extract-derived prefermented beer really wasn't too tasty. This was almost something I could drink by itself! I think that's a combination of the recipe and also the superior freshness of freshly mashed malt. Maybe the yeast have the same opinion

Your lag time should not really depend on AG vs. extract. There are a lot of factors involved that could have caused what you experienced.

Lower OG will mean less lag time as the yeast doesn't have to grow as much and it's not as stressed.
The more viable yeast you pitch, the less it has to grow before starting fermentation.
Some yeast varieties are more vigorous than others.
Temperature dramatically affects yeast behavior.
And, if the yeast is more active before pitching (ie - just came from a starter or a swelled smack pack), it'll take off faster.

I'm guessing it's some combination of those factors.

AG wort has more nutrients in it and you will see more and faster yeast growth. I'd expect AG to give shorter lag times, but half as long? Maybe you just had a very good pack.

You need to brew more & get more data.

AG wort is a nice uniform gravity due to full boils. if your extract brews were partial boils, I would imagine a stratified wort from not enough mixing might slow down the yeast. High gravity slows their growth cycle, but fermentation fixes an 'uneven' wort.

Don't think it could be unevenly mixed wort, the previous 2 extract brews were both full boils. I didn't notice those behaving any differently in terms of lag time or general yeast activity compared to before when I used to do partial boils.

From what people are saying, it sounds like AG could be one of probably several factors at work. It will be interesting to see if the next AG batch after this one starts and runs as quickly as this one is (now at 29 hrs past pitch and still going strongly, but I won't be suprised at all if it has slowed a bit in the morning)

Update - that had to be a record ferment! Done about 48 hrs after pitching. In the past my ales have taken 3-6 days. "It's gotta be da yeast!"

I just did a second batch of all-grain Oatmeal Stout (LHBS did not have the yeast I wanted to do my first option). The recipe wasn't quite identical - I used Maris Otter instead of the domestic 2-row barley that Midwest included in their Oatmeal Stout kit. Nonetheless, for this second all-grain batch the lag time was short, around 6+ hours rather than 12+ for extract batches, and the fermentation period was also about half that of the extract runs. 2 samples is a little thin statistically but it is looking very much like all-grain ferments faster for me....

much could depend on your mashing as well. A thin mash or one done at a lower temperature, as I recall, creates a more fermentable wort than does a stiff mash or one done at slightly higher tempertatures. A more fermentable wort would give a more "target-rich environment" for your yeast which could have an impact on lag time...

I guess I'll acknowledge that mashing parameters could be a factor. It's hard to evaluate in this case though, since I'm comparing the completely unknown conditions that went on to produce the various forms of malt extract I used up to now (which never had a lag time less than 12 hours) and the 2 all grain batches I've done so far (nearly identical Oatmeal Stout grain bills, same by weight only with different types of base malt and some slight variation in the volume of strike water) both had lag times around 6 hours. I guess I'll know more with further all grain batches with different grain bills.

Have now done a total of 5 all grain batches. Using appropriate wyeast strains, 1 lager, 1 wheat, 3 ale. The ales and wheat all show krausen and/or airlock bubbles by 5-6 hours after pitching (as opposed to 12+ when the malt came from extract). I don't have enough lager batches of either type of malt to represent a good sample but at the least, it's not taking longer for lager yeast to start in on all grain batches.

Temperature is always controlled by a fridge with temp controller regardless of style. The one thing that I could change is that I pitch "warm" - as soon as the wort chiller has gotten the temp below 80F, I pitch, then stick the carboy into the fridge. I think some people cool the wort to ferment temp first and then pitch. I guess for me concern about getting the yeast established outweighs the potential for any adverse flavor issues from having the wort warm until the fridge can bring the temp down.