Add another starter for lactose?

[guinnessface]

Folks-

I'm at the end of the fermentation process for a 6 gal batch of breakfast porter. The OG before adding a pound of lactose at 5 min was 1.064, and 1.072 after the addition. II added a dormant starter of Cal V (made starter a week prior then had to postpone brew day) and 8 days later the gravity was 1.032. I re-agitated it in the conical and finally on Jan 3rd it's still 1.032.

Last year I made a similar batch and it went from 1.056 to 1.022. I'm thinking despite the higher OG of this batch and the lactose, I still think I have a stuck fermentation. I was thinking of drawing off some yeast, making another starter and re-adding it. My main concern there is contaminating the batch. I plan to keg the beer, so there won't be any additional ferm in the bottle.

Am I where I should be or am I off like I suspect? Is there anything else I can do besides adding another starter? Any advice would be most appreciated. I couldn't find a similar thread with my situation involving the lactose.

Cheers,

guinnessface

 

[Beernik]

Your w/o lactose numbers indicate ~64% attenuation (1.068 to 1.024). That's consistant with the ~ 66% I get with mine. But I mash at 154F so I get a low attenuating beer.

What is your yeast and mash temp?

 

[guinnessface]

Beernik,

Thanks for your reply. I mashed at around 156 and fermented in the high 60's. I guess it just seemed awfully high for a FG. I was planning for a 7-ish percent beer, but if I'm taking the reading from FG with lactose away from the OG with lactose, I'm coming in at the low 5's. Thoughts?

 

[Beernik]

I always look at the numbers without the lactose because it's unfermentable. If you include the lactose in your calculations, you risk getting the false impression that you will get more ABV.

A generic assumed 75% attenuation from 1.068 would have got you 6.75% (1.017). 1.068 to 1.024 is 5.9%.

1.033 is a high FG. But you added a full pound of lactose and mashed at 156F. At 156F, you are getting mostly alpha enzymes converting your mash and almost no beta enzymes working on it.

If you have the time and are worried about it, pitch a starter and see if you can get it down a few more points. But I suspect it might be done.

 

[guinnessface]

Thanks Beernik. I can't imagine it'll drop too much more if I re-pitch it. That was a good explanation...much appreciated.