WHat not to do with Sweet Potatoes, or, Maybe the best beer I will never brew again.

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bendavanza

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I wanted to brew a stout with sweet potatoes, they are so tasty when roasted to the point of caramelization without having to add sugar.
I don't particularly like pumpkin beers as they usually have more spice than actual (if at all) pumpkin. So no holiday spice for this brew. Doing some math based on info at this website http://www.nal.usda.gov/fnic/foodcomp/search/
8 lb sweet potatoes, baked in skin, have about 1/2lb sugar and 1/2lb starch. If I'm using this incorrectly, please advise. I'm not a nutritionist. When the potatoes had been in the oven for about an hour and a half, I put them in a pot with 1/2 gallon water to puree them. All the syrup leaked onto the baking sheet looked too good to leave behind, so I poured a bit of hot water in the pan to dissolve it and added that to the puree. It smelled wonderful.
I've read a few places here and on other sites about brewing with potatoes, so I figured some rice hulls would do fine, I used 1/2 lb.
I subbed 4 lbs of 6 row to boost the diastic power of the mash. Here is my recipe:

Batch size 5 gallons
Boil size 6.6 gallons
Boil time 60 minutes
Grain weight 17.5 pounds
Efficiency 70%

Original gravity 1.092
Final gravity 1.021
Alcohol (by volume) 9.4%
Bitterness (IBU) 44
Color (SRM) 51.1°L

MASH
2 Row Base 6 pounds
34.3%
6 Row Base 4 pounds
22.9%
CaraPils 1 pound
5.7%
Crystal 60L 1 pound
5.7%
Chocolate 1 pound
5.7%
Rice (Hulls) 0.5 pounds
2.9%
Barley (Roasted) 0.5 pounds
2.9%
Crystal 120L 0.5 pounds
2.9%
Black Patent 0.25 pounds
1.4%

Additions
Honey 1 pound
5.7%
Dry Sugar - Cane 0.75 pounds
4.3%
Dry Malt - Extra light 1 pound
5.7%

Hops
Nugget hops 12%, Whole 2 ounces
30 minutes (+30)

Fuggles hops 5%, Pellet 1 ounce
10 minutes (+50)
 
Total mash disaster. I've never had a stuck mash like this. The bottom 3" of the tun was like glue. As in it was hard to break up with the mash paddle. I missed my mash temp but figured I'd use my RIMS to ramp it up, but even slow going it kept getting glued up. Eventually I dumped the mash into a spare pot, removed the goop and went back after it. I started out with 1/2 lb of rice hulls but ended up with 1.5 lbs, adding .5lb at a time hoping it would improve flow.
I think my mash ended up around 3 hours total. Since I mashed so low I'm sure it will be dry, but with 1lb crystal 80 and .25lb crystal 120, and the carmelized potato sugars, I hope it will balance out. My efficiency was reasonable, but low considering all the screwing around, since I did not know the actual sugars expected from the potatoes. Maybe 60% rather than the 70-75% I'm used to.
I had some DME so I added about 1lb along with some rock sugar and honey that had crystallized and was destined for the trash can otherwise. 1.090 in the fermenter, regardless, so all in all, I have beer and it may be my best stout yet. Would I ever try mashing in with potatoes again? Maybe if they were shredded and raw rather than baked and mashed, or maybe I would shred and make a syrup on the stovetop separately, strain and add directly to the boil. I dunno. I'll post drinking results in a few weeks. If anyone has more experience with potatoes, please post your results.
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This sounds awesome, dude. I want to drink this so bad. It's going to be amazing.

I'm sure the continual addition of rice hulls also reduced your efficiency - those bastards will suck up all your wort given the chance.

When I made my last pumpkin beer, I was going for something pretty imperial, so I did my runoff really slowly. I actually think I had a partially stuck mash, but it didn't matter because my runoff was still slower than the tiny dripping I heard under my false bottom. I got through it, but it was probably an hour or more of sparging (and drinking).

Oh, and I think you probably didn't need to use the 2row/6row combo. I'm guessing 2row still has plenty of diastatic power. But couldn't hurt.
 
This maybe an oversimplified solution suggestion but what if the cooked sweet potatoes were smashed (but not completely) and then steeped in a fine mesh bag separately from the mash?
 
When I used sweet potatoes, I cubed them before baking. Then I just smushed the cubes with a fork and dumped them in the tun. I didn't have an issue with a stuck sparge doing it this way.
 
If I try this again, I might do a grain bag for the potatoes. And/or cube them. What I did, though, made a compacted goo like nothing I have experienced in brewing.
 
Thinking this over, Using the immersion blender probably made the potatoes too fine and contributed to the stuck mash.
However, the beer is just about ready. It finished very clean and has a nice sweet potato flavor, somewhere in all that roastiness of the dark malts. I'll post an image once the carbonation has settled.
 
In my opinion, I wouldn't use a grain bag for the potatoes, because I wouldn't think a sack of taters would be very water permeable. The only conversion it seems you would get would be on the outside of the sack and nothing inside.

IMHO I would go with the smashed chunks.
 
This beer ended up sweeter than expected, but also has a bit of starch in the middle of the taste. Too much potato, and I would rice or dice them if I used them in the future.
It's very nice but hard to drink more than a glass in one sitting.
 
Argh, nothing like a fiberous (sp?) substance in the mash. Kind of like the time I mashed with canned pumpkin. Never again.
 
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