Mash length and attenuation

[McMullan]

I've generally done 60 minutes, sometimes 75 minutes. Recently did a 30 min with no loss of efficiency so done a few more, same efficiency, but higher FGs.

My guess is your mash temperature is favouring beta amylase activity, clibit. Even when conditions are optimised for beta amylase, a little alpha amylase activity can be expected. Most fermentables are produced early in the mash, within 30 minutes, all things being roughly optimal. Then it's starting to look like diminishing returns. The observed lower attenuation for your longer mashes might indicate 20-30 min extra of slow production of unfermentable sugars from less-than-optimal alpha amylase activity?

[BrannigansLove]

I've generally done 60 minutes, sometimes 75 minutes. Recently did a 30 min with no loss of efficiency so done a few more, same efficiency, but higher FGs.

My guess is your mash temperature is favouring beta amylase activity, clibit. Even when conditions are optimised for beta amylase, a little alpha amylase activity can be expected. Most fermentables are produced early in the mash, within 30 minutes, all things being roughly optimal. Then it's starting to look like diminishing returns. The observed lower attenuation for your longer mashes might indicate 20-30 min extra of slow production of unfermentable sugars from less-than-optimal alpha amylase activity?

I think you're misreading Clibit's post. The way I read it, he gets the same efficiency for both a short mash and a long mash, but he gets lower attenuation for the short mash (higher FG). Therefore he's extracting the same amount of various sugars, but the longer mashes are giving the enzymes additional time to break down the longer chain ones into fermentable sugars.

[Clibit]

I've had two high FG beers and may have a third. With the first two, I mashed higher and shorter than usual. 68C and 30-35 mins. Higher temp to achieve a higher FG, cos they are low gravity, and shorter just to save time. One got down to 1015, the other to 1020. With the one still in the FV I mashed at 66C and for 30 mins, and it seems to be struggling to get below 1020 again, with Gervin. May not have finished but its been 6 days.

[McMullan]

I've had two high FG beers and may have a third. With the first two, I mashed higher and shorter than usual. 68C and 30-35 mins. Higher temp to achieve a higher FG, cos they are low gravity, and shorter just to save time. One got down to 1015, the other to 1020. With the one still in the FV I mashed at 66C and for 30 mins, and it seems to be struggling to get below 1020 again, with Gervin. May not have finished but its been 6 days.

In that case, I'd agree it's probably incomplete conversion, Clibit. At 68*C beta amylase is going to have a limited 'wort life' (more limited in thinner mashes). Reducing mash time here leads to less fermentable wort. A 30- vs 60-minute mash might be noted as having a similar efficiency, but likely have different sugar (fermentability) profiles. Unless that's what you want to achieve (nothing wrong with it), a longer mash would produce a more fermentable wort. The effect of reducing mash time when wort temperature is above beta amylase's comfort zone is probably not that different from increasing the mash temperature, in terms of reducing fermentability. It might be a more efficient way of achieving the same result? The one mashed at 66*C should behave differently, though, I would have thought. Did you use the same recipe and yeast strain for these 3 brews?

[Tony1951]

This is a useful discussion.

I'm not that experienced in AG having done about 18 brews in the last ten months. I tend to favour strong pale ales with a big mouth feel these days and have been amateurishly trying to mash at about 68C for about an hour to 65 minutes. Variability has usually been down to sloppy measurement of mash water volume, but I go for about 3L/KG mash thickness. I have never measured alkalinity or altered the water. I seem to have enough trouble hitting the mash temperature exactly. Not quite hitting my strike water aiming point certainly changes the FG. Looking back through my book, the at last few brews, I see that at 69C, I got FG1019, at 68C I got FG1012, and at 67C I got FG1010. None of my beers have ever come in lower than this. I have only been using US05 for APAs and Nottingham/Gervin ale yeast for strong English type pales ales. They seem to attenuate about the same if the strike temperature was the same.

Nice to see that I can also manipulate mash time to get residual sugars. I'll certainly try shorter mash times to try and get what I'm looking for.

[Clibit]

In that case, I'd agree it's probably incomplete conversion, Clibit. At 68*C beta amylase is going to have a limited 'wort life' (more limited in thinner mashes). Reducing mash time here leads to less fermentable wort. A 30- vs 60-minute mash might be noted as having a similar efficiency, but likely have different sugar (fermentability) profiles. Unless that's what you want to achieve (nothing wrong with it), a longer mash would produce a more fermentable wort. The effect of reducing mash time when wort temperature is above beta amylase's comfort zone is probably not that different from increasing the mash temperature, in terms of reducing fermentability. It might be a more efficient way of achieving the same result? The one mashed at 66*C should behave differently, though, I would have thought. Did you use the same recipe and yeast strain for these 3 brews?

Cheers McM. Different recipes and all different yeasts but ended up pitching some Gervin in each to try to reduce the FG! Not understanding what was going on. I'm waiting to see what the 66 mashed beer gets down to. It's only Gervin in that one. I so rarely plan ahead that my yeast preparation is rubbish. I need to get my act together on that front. Make starters in good time for each brew. I have just bought an ITC-308 so looking to step up my fermentation game. Pitch plenty of healthy yeast and control temperature. And hopefully manage the mash to achieve targets more consistently. I'll try 40/45 minute mashes, one of the links earlier describes s mash time experiment that suggests 40 min mashes produce comparable fermentation results to longer mashes.