Recipe – Roast Sweet Potato Stout

Gaskelling (verb). To deliberately underate, underplay oneself prior to a competition in order to garner extra sympathy votes or points.

October 2016 in preparation for Macc Homebrews Dark Beer Off, I decided to brew something that was a bit different.
I’ve tried to brew a potato lager before but unfortunately it became infected and tasted awful, and I’m adamant that I’ll brew a pale lager with potato again, but this time I wanted to brew something Autumnal. With every man and his dog dusting off the pumpkin ales I wondered whether sweet roast potato would taste nice in a beer, and with little more thought to it than that, I decided on a Roast Sweet Potato Stout, and despite it tasting overly fruity a week before the comp hence me negging my own beer, it actually came out OK and the verb Gaskelling was created.

Because this is a quite a big beer I’d recommend making a starter before hand which is detailed within the instructions.

unthought out (101)

 Type: All Grain Batch Size: 23.00 l Boil Size: 27.41 l Boil Time: 60 min

End of Boil Vol: 25.52 l

Final Bottling Vol: 23.00 l

Fermentation: Ale, Two Stage

 

Equipment: 

  • 40l Mash tun with false bottom (helps stop grain flowing into kettle)
  • 32l Kettle
  • 10l Pan
  • Sieve
  • Measuring Jug.
  • Digital Thermometer.
  • Coiling Coil
  • Hydrometer (optional).
  • Assorted receptacles for ingredients.
  • Fermenting Bucket and Airlock.

Ingredients

Amt Name Type %/IBU
3.70 kg Lager Malt (Muntons) (3.0 SRM) Grain 42.2 %
2.30 kg Maris Otter Malt (Muntons) (3.0 SRM) Grain 26.2 %
1.00 kg Munich Malt (9.0 SRM) Grain 11.4 %
0.50 kg Caramel/Crystal Malt – 80L (80.0 SRM) Grain 5.7 %
0.44 kg Barley, Flaked (1.7 SRM) Grain 5.0 %
0.42 kg Carafa III (525.0 SRM) Grain 4.8 %
0.28 kg Caramunich Malt (56.0 SRM) Grain 3.2 %
0.08 kg Aromatic Malt (26.0 SRM) Grain 0.9 %
1.50 kg Sweet Potato (Mash 0.0 mins) Spice
66.20 g Comet [9.50 %] – First Wort 60.0 min Hop 57.7 IBUs
0.06 kg Milk Sugar (Lactose) (0.0 SRM) Sugar 0.6 %
1.50 kg Sweet Potato (Mash mins) Spice
1.00 Items Whirlfloc Tablet (Boil 15.0 mins) Fining
1.50 kg Sweet Potato (Boil 60.0 mins) Spice
1.0 pkg Abbey Ale (White Labs #WLP530) yeast

img_6853

 

Prepare for Brewing

Create a yeast starter with 1.00 l of wort – typically this means adding 100gs of DME to 1l of water, bring to boil simmer for 15 mins, cool to pitching temperature, around 21c then pitch yeast. a good vessel for this is a 2l Erlenmeyer flask they come in a variety of sizes but are very handy. Cover the top with sanitised tin foil and aerate over a few days either with a stir plate, or by shaking when you remember to.

 

Brew time.

The first step with any brewing is to make sure your kit (and work area) is clean and free from any cleaning product residue.

Measure out all ingredients, splitting the ingredients into Mash and Boil

This Recipe calls for 1.5kg of Boiled and mashed sweet potato to be added into the Mash, and a further roasted crushed sweet potato to be added to the boil..

For this recipe we need to heat two lots of water at different times.

25.1 l Strike water that we add to the grain to create the mash. heated to 74.7c to create a mash temp of 65.6c

13.4l Sparge water heated to 75.6c to sparge the mash.

Need to boil and Mash 1.5 kg of sweet potato and also roast 1.5kg of sweet potato.

I’ll assume you know how to boil a potato, but in terms of the roast sweet potato, I pre heated the oven 200c and placed potatoes directly on the oven shelf with a tray underneath to catch leakage, after 45 mins or so I turned oven off and left potatoes in the oven until needed.

img_6849    img_6850

Mash or Steep Grains

Mash Ingredients

Amt Name Type %/IBU
3.70 kg Lager Malt (Muntons) (3.0 SRM) Grain 42.2 %
2.30 kg Maris Otter Malt (Muntons) (3.0 SRM) Grain 26.2 %
1.00 kg Munich Malt (9.0 SRM) Grain 11.4 %
0.50 kg Caramel/Crystal Malt – 80L (80.0 SRM) Grain 5.7 %
0.44 kg Barley, Flaked (1.7 SRM) Grain 5.0 %
0.42 kg Carafa III (525.0 SRM) Grain 4.8 %
0.28 kg Caramunich Malt (56.0 SRM) Grain 3.2 %
0.08 kg Aromatic Malt (26.0 SRM) Grain 0.9 %
1.50 kg Sweet Potato (Mash 0.0 mins) Spice

 

 

I have no real idea how much additional fermentables are added when using sweet potato, but the process I used was to boil potatoes until mashable, the water used to boil potatoes was added to my kettle to help bring strike water up to temperature. The potatoes were then mashed with the skin on and allowed to cool then add to mashtun and mash in as normal.

The theory is that the 65c mash will convert anything the potato has to offer into fermentable sugars.

 

Mash Steps

Name Description Step Temperature Step Time
Mash In Add 25.1 l of water to create a mash temp of 65.6 C 75 min

 

This recipe calls for first wort hops so add all the hops to the kettle during sparge, this helps extract aroma from the hops as well as being more frugal with hops and achieving a smooth bitterness.

Fly sparge with 13.41 l water at 75.6 C

Add water to achieve boil volume of 27.41 l

Estimated pre-boil gravity is 1.074 SG

img_6860    img_6859    img_6858

Boil Ingredients

Amt Name Type %/IBU
66.20 g Comet [9.50 %] – First Wort 60.0 min Hop 57.7 IBUs
1.50 kg Sweet Potato (Boil 60.0 mins) Spice
1.00 Items Whirlfloc Tablet (Boil 15.0 mins) Fining

For the last 15mins of the boil add in protofloc and copper coil

Estimated Post Boil Vol: 25.52 l and Est Post Boil Gravity: 1.082 SG

 

Cool and Transfer Wort

Cool wort to fermentation temperature

Transfer wort to fermenter

Add water if needed to achieve final volume of 23.00 l

 

Pitch Yeast and Measure Gravity and Volume

Fermentation Ingredients

Amt Name Type %/IBU
1.0 pkg Abbey Ale (White Labs #WLP530) [35.… Yeast

Once fermentation has completed take reading then add

0.06 kg Milk Sugar (Lactose) (0.0 SRM) Sugar 0.6 %

Target: 1.082 SG)

(Target: 23.00 l)

 

Fermentation

Primary Fermentation (4.00 days at 19.4 C ending at 19.4 C)

Secondary Fermentation (10.00 days at 20 C ending at 20 C)

Cold crash 3c for 20 days

 

Bottling or kegging

Typically I add 1/3 teaspoon of sugar to 330ml bottle or 1/2 teaspoon to 500ml bottles.

Kegging is done at around 14psi and 7c

 

This beer didn’t win the dark beer off.

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