Hi guys. I have been culturing some Duvel yeast from 6 bottles dregs for 6 days , it is a 200 ml 1030 OG first starter step that sits on a stir plate. It has plenty of new yeast and I know I must make more steps to get the proper qty. for pitching a big beer (1070 OG). My questions are : Is this yeast healthy enough to ferment a new 1070 OG beer?. Is this yeast the Duvel main fermentation yeast or is it just yeast used to carb beer up?. Should I pitch more yeast than needed to compensate stressed yeast?. TIA
Apparently WLP570 Belgian Golden Ale is Duvel strain. I can't find any info on what Duvel uses for their priming yeast, but found an article that states they do re-yeast at bottling with dextrose. Best way forward imo is to do a side-by-side split batch. Perhaps build up 1500 ml starters of each the WLP570 strain and a 1500 ml starter of your Duvel bottle dregs and then pitch each starter to same wort. I think that would be the best way to answer your questions.
Once your yeast starts, yes, it is generally as healthy as when it was in Duvel's brewhaus. I don't know about it being the authentic yeast but would guess it is (my guess and €3.00 will get you a fresh Duvel pour in a bar in Belgium). When re-starting dregs, I estimate 2B cells/ml (of solid-slurry). When you turn your stir plate off you'll see the solid-slurry settle on the bottom. Once this starts growing you know the yeast has recovered. You should also have a pleasant aroma when it re-starts. My experience is that it's easy to miss the initial krausen . . . it will be small, quick, and typically occurs at night. So use your eyeball/nose to measure the growth rate. On the initial step this is tough because of the small quantities involved. Many times I move from step 1 to step 2 based on faith. Once it starts (good krausen, noticeable off-gassing) I keep building the solids until I have what I need (plus some extra for the next brew cycle). If you are not using a yeast calculator, now is the time to start.
