Gravity of Sweet Potato?

I'm brewing up a sweet potato stout this weekend, and plan on adding 5# of roasted, mashed sweet potato..does anyone have any guess as to how much this will effect my OG? I've tried a few recipe calculators, and searches but have come up with nothing..

exhumedatbirth said:

I'm brewing up a sweet potato stout this weekend, and plan on adding 5# of roasted, mashed sweet potato..does anyone have any guess as to how much this will effect my OG? I've tried a few recipe calculators, and searches but have come up with nothing..

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Check out this post: https://www.homebrewtalk.com/f164/sweet-potato-mash-experiment-211386/#post3354406

You will need to cook the potatoes fully. In my case of using plain white potatoes, I cooked them in a water boil, and then mashed them and liquified them in mash water before adding to the main mash.

MC

The sugar content in sweet potatoes is 4.2 grams for every 3.5 ounces of sweet potatoes. Sweet potatoes average about 22% starch and 5-6% sugar for a total of 27-28% fermentable material. So basically 5 lbs of sweet potato would be the same as adding 1lb of grain to your grain bill.

stillbrewin said:

The sugar content in sweet potatoes is 4.2 grams for every 3.5 ounces of sweet potatoes. Sweet potatoes average about 22% starch and 5-6% sugar for a total of 27-28% fermentable material. So basically 5 lbs of sweet potato would be the same as adding 1lb of grain to your grain bill.

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5x22% would mean the same as may be one pound of 100% fermentable, aka, SUGAR, not grain. Lots of non-fermentables in grain.

MC

Misplaced_Canuck said:

5x22% would mean the same as may be one pound of 100% fermentable, aka, SUGAR, not grain. Lots of non-fermentables in grain.

MC

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Hmm I may have been a bit hasty in my reply. 5 lbs should be about 96 grams of sugar or aprx 1/5th of a lb. Also the starch to sugar to conversion would equal about 2.2 lbs of grain. That is assuming that you get the same efficiency as your grain, and you figure 50% fermentable material in malted barly.