BeerBorg

Got a question for yinz. I brewed a batch of Cooper's Real Ale,and a Munton's Pilsner on Dec.2nd. After the 1st 24 or so hours the Pilsner had taken off and had a gathering of trub in the bottom and a nice krausen on top,but the Real Ale just had trub in the bottom. I check them evey day and after 5 more days the Real Ale had krausen on top.The temps hadn't changed,the fermenters weren't moved etc. Anyone have an answer or cause to why this happened?Just seems odd to me.TIA

You're good! Could have been older yeast, less oxygenated wort, different gravities could have affected the lag time, different yeasts react differently, some are true top cropping and have a quick and active Krausen, some small, lingering Krausen. RDWHAHB!!

Krausen may have come and gone when you were sleeping. "I have trub at the bottom" is all that matters.

Sounds like long lag time. Trub at bottom forms as yeast grows and stuff drops out of suspension. But krausen won't happen until yeast have grown to a certain critical mass. It sounds like the yeast that came with the real ale was kind of old perhaps. But you should still get good beer out of it as long as you have good sanitation practices.

EDIT: Another thing to consider is Muntons Pilsner kit might have come with an actual lager yeast (some do, some do not, I can't say), where the Coopers kit came with a "real ale" yeast. They like totally different temperatures, with the lager yeast liking it a lot colder. The stuff that comes with the big Coopers cans really likes it more around 66-70 degrees. Less then 64 and it gets pretty sleepy. At least that used to be the case back in the day. (I have not made one of those for a while).

Oxygen, the lack of it I would say

Lack of oxygen actually can shorten lag time (and over oxygenation - IE using pure O2 for too long - can actually increase lag time) because when the yeast run out of oxygen they can't grow anymore (and if they have lots of it they can grow more as long as they have all the other nutrients they need). In either case, once they run out of nutrients needed to grow, they have to switch into active fermentation. It might be a wimpy fermentation, with thin krausen, but something will happen. The long lag to me points more at low initial cell count (more generations need to grow) or too low temps.

The oxygen thing is the main reason why stir starters grow more cells. By continuously aerating the wort, you are keeping the yeast in growth mode (which is lag time) longer before they start to actively ferment your starter. Where a shaken starter or an ignored starter with all other things being equal will start to actively ferment sooner with less cells. Since the whole point is to grow as many cells as you can, adding the oxygen to keep it growing is a good thing.

Dan Gordon once said on The Brewing Network that yeast won't begin fermentation until all oxygen in the wort has been utilized. So I agree, the amount of oxygenation greatly affects lag time.

Sounds like possibly poor yeast health in this situation. A little bit of some kind of nutrient in each fermentation can go a long way towards avoiding issues too.