Is Imperial A09 Pub a top-cropper?

[corncob]

I've been repitching the first pack of A09 I've ever used for 6 or more batches now. It was maybe damaged shipping to the South in the summer heat, and I mixed some really sad old dirty WY1469 (a monster top-cropper) into a fermentation with it because it was sluggish.

At first I got some strong krausen, but not much, so I started harvesting from the bottom after racking. Over the last few batches, I get less and less krausen. BUT, the ale ferments strong and fast (visibly fizzing like champagne). I'm making 3.8-6+% ABV ales that are substantially clear and out of primary in 4-8 days. Polished and lovely at 2-3 weeks. Gone in a month or so. Flocculation is still robust. Taste is sublime (malty, sweet, marmalade, pear jelly). In fact, I'm making the best English ales I've ever made. I can't stop repitching, once or twice every 6-8 weeks. At this point, I wouldn't even classify this yeast as top-fermenting.

So....what am I pitching at this point? Do others see this behavior from A09?

 

[rmr9]

The times I’ve used A09 it wasn’t a crazy top cropper. Good krausen but not huge by any means. Not close to the size of a 1469 krausen. My guess is that over time the pub has outcompeted the 1469 so you’re seeing less robust top cropping. If you’re making awesome British ales keep the train rolling!

 

[corncob]

I've been repitching the first pack of A09 I've ever used for 6 or more batches now. It was maybe damaged shipping to the South in the summer heat, and I mixed some really sad old dirty WY1469 (a monster top-cropper) into a fermentation with it because it was sluggish.

At first I got some strong krausen, but not much, so I started harvesting from the bottom after racking. Over the last few batches, I get less and less krausen. BUT, the ale ferments strong and fast (visibly fizzing like champagne). I'm making 3.8-6+% ABV ales that are substantially clear and out of primary in 4-8 days. Polished and lovely at 2-3 weeks. Gone in a month or so. Flocculation is still robust. Taste is sublime (malty, sweet, marmalade, pear jelly). In fact, I'm making the best English ales I've ever made. I can't stop repitching, once or twice every 6-8 weeks. At this point, I wouldn't even classify this yeast as top-fermenting.

So....what am I pitching at this point? Do others see this behavior from A09?

I'm leaving this here just in case anybody else runs across the same question in the future. I just repitched this yeast for the 6th time. Due to continued good results, I want to keep using it, but I was starting to get worried about zinc deficiency. I went down a rabbit hole looking for information about what the yeast really need, beyond good wort. I think I got answers to my question:

just zinc, at about a concentration of 0.7mg elemental zinc per gallon of wort, and twice that concentration is actually quite bad for the yeast

But I decided to just buy some yeast nutrient due to the difficulty of hitting that dosage target with the equipment I have in my kitchen.

But then I forgot to order the yeast nutrient. So I dumped out a regular 50mg zinc gluconate vitamin capsule, chalked a uniform line, measured with a ruler, and stirred a tenth of it into my (7 gallon) wort. The resulting fermentation was quick and vigorous, even though I was keeping the temps about 5deg below normal (for the particular recipe) and the slurry was a month old. Relevant to the above: the krausen was dense and persistent, as it was for the first couple of pitches.

Still not a champion top cropper compared to something like wy1469, but apparently subject to zinc deficiency. AND I can't help but feel like my sanitation practices have been validated by this episode. It's a rare win.

 

[DBhomebrew]

I finally got some more Pub on hand, first new batch just about ready for packaging. Like yours, very little krausen, definitely not enough for top cropping, high flocculation, great aroma/flavor. I don't recall this lack of top fermenting behavior from the the last time I used it a few years ago. Maybe this has something to do with the recent months of no shipments due to "packaging" issues?

Oh, well. The beer seems to be coming out as I hoped.