Achieving desired attenuation in porter.

[Erik the Anglophile]

Not sure if this belongs in recipes or here, but I feel it is mostly related to fermentation.
I have a porter brew coming up, and I'm gonna use mangrove jacks m42 at about 18-19c fermentation temp, and wanted to keep the attenuation down a bit as I know it can eat some maltriose and is a high attenuator. The specialty malts will probably get it down a bit but still.
It,s a 1.058 OG beer consisting of Maris Otter as base, 8% crisp medium crystal, 8% Brown malt and 3% black malt, mashing at 68c for 90 mins to get a full body but still some fermentability. Beersmith predicts FG at 1.011, 80% attenuation but I believe this will get me more around 70-75%, wich is what I look for. Am I thinking correctly or should I mash lower?

 

[TheMadKing]

What is your goal with the beer?

Do you want it to be dry but high in mouthfeel? Or do you want it to have a little sweetness and a full body?

 

[VikeMan]

I popped your grain bill, mash time, and mash length into BrewCipher. I used WLP039, which I believe is close, if not the same strain, as M42. It predicts an FG of 1.014 (75.3% apparent attenuation).

 

[Erik the Anglophile]

I am after a little sweetnes, full body and mouthfeel, so around 75% attenuation sounds good, seems I was guesstimating right. Beersmith and beers with higher amounts of specialty grains often involves some guess work and making a stronger beer than you actually want, unfortunately.

What is your goal with the beer?

Do you want it to be dry but high in mouthfeel? Or do you want it to have a little sweetness and a full body?

I popped your grain bill, mash time, and mash length into BrewCipher. I used WLP039, which I believe is close, if not the same strain, as M42. It predicts an FG of 1.014 (75.3% apparent attenuation).

 

[VikeMan]

Beersmith and beers with higher amounts of specialty grains often involves some guess work and making a stronger beer than you actually want, unfortunately.

Yeah. That's because BeerSmith gives the same attenuation % answer regardless of what's in the grain bill.

 

[TheMadKing]

Yeah. That's because BeerSmith gives the same attenuation % answer regardless of what's in the grain bill.

Yep that's a feature of BeerSmith I dislike, but I rarely target a specific FG and just target "more dry" or "more full" etc

 

[Erik the Anglophile]

I choose a mash temp and time, and then run the OG through brewersfriend abv calculator and change the FG until I get an attenuation that seems reasonable for the grist and mash I employ. Then I know kinda what to expect. But brewing new recipes always entail trying and taking notes of the result in order to do some changes a few times to land it just where you want it.

 

[Miraculix]

I would cut the mash time in half. What happens with 90 minutes is that after a short time all the starch is already converted and then the remaining beta amylase enzyme chops the sugars even smaller, which you do not want on that scale. At 68c, there will will be denaturing over time but there's still some beta left throughout the mash which will continue to chop down longer sugars into short ones.

 

[Erik the Anglophile]

Wouldn't that give me a very low attenuation though?

 

[Miraculix]

Wouldn't that give me a very low attenuation though?

I don't think so. It depends in your yeast and I suspect M42 to be Nottingham and Nottingham does not care much about this.

 

[madscientist451]

Wouldn't that give me a very low attenuation though?

Some yeast strains have higher (predicted) attenuation than others, and then you have the availability of fermentable sugars that can be converted to alcohol, and then you have other variables like amount of yeast pitched and fermentation temperature.
What you need to do is go ahead and brew it up and then tweak the results; you want a higher FG, increase your mash temperature. Brewing software gets you close to where you want to be, but your equipment, brewing method and individual taste preference will be different, so you are always going to need to make some adjustments on a re-brew.

 

[dmtaylor]

M42 (Notty) is an extremely consistent performer at 77-78% attenuation every time. If you want lower attenuation, you need to do something more drastic like mashing shorter at higher temperature, like 71 C for just 30-40 minutes. Yes I am serious.

 

[Erik the Anglophile]

I have read some about the method to mash hot and short, vs the old school method of just mashing longer if you want to mash high(ish) but not get too low attenuation. I'll brew it at 68c/90 min, and if I don't get the result I was after I'll try hot and short.
Thanks for the pointers, Cheers!

 

[Miraculix]

I have read some about the method to mash hot and short, vs the old school method of just mashing longer if you want to mash high(ish) but not get too low attenuation. I'll brew it at 68c/90 min, and if I don't get the result I was after I'll try hot and short.
Thanks for the pointers, Cheers!

The thing is, there's no logic behind this.

With the longer mash, you basically destroy the result of mashing at a higher temperature. Especially if the temperature is not that high at all (talking about 68c).

So if you really would want to do something for getting the fermentability a bit lower, you would need to increase the temperature and lower the time. The longer the time, the higher the fermentability.

Remember, you can always cut longer sugars shorter, but you cannot glue them back together. So what happens in a longer mash at medium temperature, is that the beta keeps chopping and chopping till there's not much longer sugar left.

 

[Erik the Anglophile]

I'll reduce it to 60 min, and reduce it even further if it attenuates too high.

 

[Miraculix]

I'll reduce it to 60 min, and reduce it even further if it attenuates too high.

Good idea. At the end, it's like dmtaylor said, you need a base point which seems to be logically ok and from there you have to adapt based on results you are getting.