Starchy Adjuncts and Sweet Potato ESB

Most brewers are aware that corn or rice is used as a starchy adjunct in some beers, especially American-style Pilsners. However, these aren’t the only starchy adjuncts that can be used to brew beer.

The sweet potato (_Ipomoea batatus_) can be used as a starchy adjunct in brewing.

One interesting beer I have brewed a few times is my sweet potato ESB. (See the recipe below the fold.) Sweet potatoes (Ipomoea batatas) are root tubers — as opposed to potatoes (Solanum tuberosum), which are stem tubers — that are roughly 80% water, with most of the rest of the weight being starch. They contain about 4% protein. At 80% water, you can figure that 5 lbs. (2.3 kg) of sweet potato will yield an extract weight roughly equal to 1.0 lb. of malted barley.

The gelatinization temperature of sweet potato starch is lower than typical mash temperatures, so you don’t need to employ a cereal mash when using them. Even so, it is advantageous to boil them and whip them (as when making mashed potatoes) before stirring them into the mash. Boiled sweet potatoes stirred into the mash add extract weight and an orange color, but will not supply any appreciable sweet potato aroma or flavor. (If you want this, you could try slicing the sweet potato into small “chips” and baking them before the mash. I haven’t tried this so I don’t know if it works or has any other consequences.) My sweet potato ESB is an interesting orange color, but you’d never guess it was brewed with an unusual ingredient from the aroma or flavor. I usually mash in my grains first, with a slightly thin mash, and then stir the whipped sweet potatoes into the top half of the grain bed.

For a 5-gallon (19 L) batch of beer, 5 lbs. (2.3 kg) of sweet potatoes is not enough to interfere with lautering. However, higher percentages can be. Because sweet potatoes are low in protein, I usually a small amount of yeast nutrients in the boil, just to ensure the yeast have enough nitrogen to work efficiently.

Because you need to mash the sweet potatoes with some malted grains to degrade their starches, there is no malt extract option for this recipe.

Sweet Potato ESB

All-grain with starchy adjunct (English units)

by Chris Colby

DESCRIPTION

This is an ESB (Extra Special Bitter) with an interesting orange color due to using sweet potatoes as an adjunct. The sweet potatoes do not add any flavor or aroma, just the color (and some fermentable sugars when they are mashed).

INGREDIENTS (for 5 gallons)

Water Profile 

< 50 ppm carbonate (HCO₃^–)

~150 ppm calcium (Ca⁺²) *

* use 4:1 ratio of CaSO₄ to CaCl₂

Malts and Other Fermentables

(for an OG of 1.056 at 70% extract efficiency and an SRM of 12,

plus the contribution of the sweet potatoes, which is variable)

8 lb. 14 oz. 2-row English pale ale malt (Maris Otter)

8.0 oz. crystal malt (40 °L)

2.0 oz. crystal malt (60 °L)

5.0 lbs. sweet potatoes (peeled and cut into small cubes)

Hops (for 47 IBUs total)

Simcoe hops (12 IBUs)

0.25 oz. (at 13% alpha acids) boiled for 60 minutes

Centennial hops (21 IBUs)

0.75 oz. (at 10% alpha acids) boiled for 30 minutes

Cascade hops (10 IBUs)

0.75 oz. (at 7% alpha acids) boiled for 15 minutes

Amarillo hops (3.7 IBUs)

0.25 oz. (at 8% alpha acids) boiled for 15 minutes

Cascade  hops (0 IBUs)

0.75 oz. (at 7% alpha acids) at knockout

Amarillo hops (0 IBUs)

0.50 oz. (at 8% alpha acids) at knockout

Yeast (to attenuate to FG 1.012, for an ABV of 5.7%)

Wyeast 1056 (American Ale), White Labs WLP001 (California Ale)

or Fermentis US-05 yeast

(a 1.5 qt. yeast starter is suggested for liquid yeasts)

Processing Aids and Other 

1 tsp. Irish moss (boiled for 15 mins)

1/2 tsp. yeast nutrients (boiled for 15 minutes)

4.5 oz. corn sugar (to prime bottles for 2.5 volumes of CO₂)

PROCEDURE

Make yeast starter 2–3 days ahead of time. Peel sweet potatoes, cube and boil until tender. Whip sweet potatoes prior to mashing grains. Heat 13 qts. of brewing liquor to 164 °F and mash in grains. Stir in whipped sweet potatoes once mashed in. Mash at 153 °F for 60 minutes, stirring every 10 minutes. Perform an iodine test to ensure that the starches in the sweet potato have converted. Heat or add boiling water to mash out to 168 °F. Recirculate wort until clear, then run off. Sparge steadily over 75–90 minutes to collect about 7 gallons of wort. Vigorously boil wort for 90 minutes, to yield post-boil volume around 5.5 gallons. Add hops, Irish moss and yeast nutrient at times indicated. Chill wort, then rack to fermenter. Your yield should be about 5.25 gallons. Aerate wort thoroughly and pitch sediment from yeast starter. Ferment at 68 °F. After fermentation stops, let beer settle for 2–3 days, then rack directly to keg or bottling bucket, for a yield of 5 gallons. Carbonate to 2.5 volumes of CO₂.

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Sweet Potato ESB

All-grain with starchy adjunct (metric units)

by Chris Colby

DESCRIPTION

This is an ESB (Extra Special Bitter) with an interesting orange color due to using sweet potatoes as an adjunct. The sweet potatoes do not add any flavor or aroma, just the color (and some fermentable sugars when they are mashed).

INGREDIENTS (for 19 L)

Water Profile 

< 50 ppm carbonate (HCO₃^–)

~150 ppm calcium (Ca⁺²) *

* use 4:1 ratio of CaSO₄ to CaCl₂

Malts and Other Fermentables

(for an OG of 1.056 at 70% extract efficiency and an SRM of 12,

plus the contribution of the sweet potatoes, which is variable)

4.0 kg 2-row English pale ale malt (Maris Otter)

230 g crystal malt (40 °L)

57 g crystal malt (60 °L)

2.3 kg sweet potatoes (peeled and cut into small cubes)

Hops (for 47 IBUs total)

Simcoe hops (12 IBUs)

7.1 g (at 13% alpha acids) boiled for 60 minutes

Centennial hops (21 IBUs)

21 g (at 10% alpha acids) boiled for 30 minutes

Cascade hops (10 IBUs)

21 g (at 7% alpha acids) boiled for 15 minutes

Amarillo hops (3.7 IBUs)

7.1 g (at 8% alpha acids) boiled for 15 minutes

Cascade  hops (0 IBUs)

0.75 oz. (at 7% alpha acids) at knockout

Amarillo hops (0 IBUs)

0.50 oz. (at 8% alpha acids) at knockout

Yeast (to attenuate to FG 1.012, for an ABV of 5.7%)

Wyeast 1056 (American Ale), White Labs WLP001 (California Ale)

or Fermentis US-05 yeast

(a 1.5 qt. yeast starter is suggested for liquid yeasts)

Processing Aids and Other 

1 tsp. Irish moss (boiled for 15 mins)

1/2 tsp. yeast nutrients (boiled for 15 minutes)

130 g corn sugar (to prime bottles for 2.5 volumes of CO₂)

PROCEDURE

Make yeast starter 2–3 days ahead of time. Peel sweet potatoes, cube and boil until tender. Whip sweet potatoes prior to mashing grains. Heat 12 L of brewing liquor to 73 °C and mash in grains. Stir in whipped sweet potatoes once mashed in. Mash at 67 °C for 60 minutes, stirring every 10 minutes. Perform an iodine test to ensure that the starches in the sweet potato have converted. Heat or add boiling water to mash out to 76 °C. Recirculate wort until clear, then run off. Sparge steadily over 75–90 minutes to collect about 26 L of wort. Vigorously boil wort for 90 minutes, to yield post-boil volume around 21 L. Add hops, Irish moss and yeast nutrient at times indicated. Chill wort, then rack to fermenter. Your yield should be about 20 L. Aerate wort thoroughly and pitch sediment from yeast starter. Ferment at 20 °C. After fermentation stops, let beer settle for 2–3 days, then rack directly to keg or bottling bucket, for a yield of 19 L. Carbonate to 2.5 volumes of CO₂.

“English” option:

Replace the Centennial hops with the same weight of Fuggles hops. Replace both the Cascade and Amarillo hops with the same amount (by weight) of East Kent Goldings hops. Substitute either a high-alpha English hop (such as Challenger) or a neutral high-alpha hop (such as German Magnum) for the Simcoe and adjust it’s amount so the overall IBUs are 38.