So we were going to try do 2 partial mash brews tomorrow, this is our first try at using base malts so I'm unsure of how mash temperatures and schedule will change our beer. We're kind of doing boil in a bag, we'll be mashing the grains in a large nylon bag in our brew kettle.
The first beer is an imperial oatmeal stout. I've pasted in the recipe below. Most imperial stout recipes I've come across call for a single step infusion between 64 and 67 degrees. Is this just keeping it simple for simplicities sake? I'd rather do it right with 2 or 3 steps, but I know low mash temperatures will give us a more fermentable wort, so what's the point of doing a higher temperature? And which is more advisable for an imperial stout?
If low temps give less body, surely the oatmeal in our recipe will help counter this? Any advice appreciated!
Oats n Mocha Recipe:
2kg Marris Otter Malt
0.6kg Oatmeal
0.5kg Chocolate Malt
0.5kg Munich Malt
0.25kg Roasted Barley
0.25kg Crystal 40L
3kg Amber Dried Malt Extract
60g Cocoa powder
30g East Kent Goldings @ 60min
20g East Kent Goldings @ 0min
Safale S-04 Irish Ale yeast
Soak coffee beans in whiskey (Jameson?) for 5 days and then add to beer after 1 week of fermentation.
Efficiency: 60% OG: 1.069 FG: 1.017 ABV: 6.8%
Coffee beans soaked in whiskey sounds interesting.
A single infusion is just fine for any English style brew - including imperial stouts and would be perfect if you are using 50%ish Maris Otter.
Temperatures can be a bit hit and miss especially with a stainless steel pot on a stove - if you aim for 67 degrees and make sure you focus on not scorching the malt you can't go too far wrong.
Step mashes have their place - but more for pilsener malt based beers, German wheat beers or beers with lots of adjuncts (say a cereal mash for a wit).
Ah crap I'm really sorry I copied the recipe without realising id tinkered with it. I'm using Pilsner malt raher than mariss otter!!
Plus I do have a fair amount of oats in there! Any idea what kind of efficiency I could expect with a single infusion?
If you're using all those coloured malts and it's your first partial mash I'd definitely skip the step mash, even with pilsner malt. Step mashing is a relatively advanced technique and you're better off having a go at single infusion mashing first.
Your efficiency is going to depend on your process. For a long time I didn't measure mine and when I did it was lowish - around 65%.
Again, you're better of just seeing what happens and taking notes. I think you have the right idea assuming it will be on the low side - you can compensate with some DME, or accept the wort you get.
In terms of conversion: the good news is that pilsner malt (assuming that's what you are using) has nearly as much diastatic power as MO. Your grist needs an average diastatic power of 35 Lintners to convert - 2 kgs of pils malt is 220 Lintners. Your grist is 4.1 kg -> 220/4 is 53 so you're in the clear, and that assuming your Munich is fairly highly coloured.
There's more detail on diastatic power on here: http://beersmith.com/blog/2010/01/04/diastatic-power-and-mashing-your-beer/
Wow, thanks a million for the info, very helpful! It also lead me to this, which was very informative aswel if anyone elso comes across this thread! http://beersmith.com/blog/2012/12/20/mash-temperature-and-beer-body-in-all-grain-brewing/
You don't need to mash the crystal, roasted barley a nd chocolate malt if that helps