Sweet Potato Amber Ale, with Brett B.

Most of my beer ideas come from what I have available to me, new ingredients I discover, etc. So when our CSA started dropping sweet potatoes on us like nobodies business, I began thinking of how I could use them in a beer.

I’m not much of a spiced fall beer person, so the obvious; put it in a porter and throw some nutmeg and cinnamon after it, wasn’t going to work for me. In a lot of the pumpkin/sweet potato beers I’ve had, you don’t taste those ingredients, you taste pie spices, which is fine, but not really my thing. Instead, I decided to try to focus on the getting some of the taste of the vegetable in the final beer, and using techniques and flavors that might help bring it out.

I haven’t seen many sweet potato amber ales, so I thought that could be a good start. Not a lot in the way of the potato flavor, and some nice carmel notes to bring the best parts of the sweet potato flavor out.

The malt bill is a bit atypical as well. I decided to use a bit more of the malt bill for specialties than is typically done. Since the brett b should dry this out a good deal, I’m still hoping to have some of those carmelly notes come through.

I also wanted the spicy and earthy components to bring some balance, so I left that to hops and yeast. For hops I went for the nobler end of the spectrum, with Sterling (Couldn’t get it tho, wound up with Brewers Gold) and Saaz. Some of that Saaz is for dry hopping. Should be interesting. For yeast, I used WLP002, to give the Brett a place to shine, and create some of that earthy, funky, spicy complexity I thought would match well with the sweet potato flavor.

I’ve brewed a lot of sour beers, but never used straight Brett before. Resisting the temptation to add some dregs for Lacto and Pedio, is taking all of my strength, seriously. But I think the sourness could stomp all over the flavors I’ve been working to develop, so I’m holding out. However, if this beer is a bit on the boring side after 6 months or so, I imagine dregs will soon follow.

The sweets in our CSA have been like candy recently though, so I’m looking forward to actually being able to taste them in this beer.

Brewing Notes

Here’s the recipe. Missing from this sheet is the 3 pounds of sweet potatoes. They don’t have a tab for that. 🙂 (Note, I also switched yeasts at the last minute)

I looked into a bunch of different ways to add sweet potato to a beer. It seems many people cook them completely to a mash, and hope in the name of rice hulls they don’t get a stuck sparge. I guess if I really wanted to convert the starches completely, I’d try that, but I really didn’t need to, and I have the suspicion that the volume you lose in all that potato kind of kills your efficiency anyway. What I wanted was to open up the potatoes enough so that the sweetness and flavor came out, without breaking them down completely. So, I grated them raw, and then microwaved them for 10 minutes, until the aroma was just where I wanted it. After this, they had a very workable texture. They we soft and sticky, but held their shape. Perfect.

Now, how to deal with liquid volume math. Well, if you’re me, you kind of guess and then deal with the fallout. I estimated about half the absorption of grain (daft, I know), and it was way too much. I ended up with a too-thin mash. Of course that, and my forgetting to think of how the potatoes would react to the temperature, lead to a too cool mash as well. Mash target was 154F, actual, 148F. So I took a calculation for how much boiling water to add to rase the temp, and would up at 152F, which will just have to do.

Well, I must have done something right, the first runnings, were wonderful, like some kind of sweet potato candy. The level of potato in the aroma and flavor was just what I was looking for. Hope enough of it survives the ferment. And the wort flowed with no problems, the potatoes held much of their shape, and the rice hulls helped some too. No stuck sparge.

Sparge had some of the same issues as the mash though, so I undershot mash-out at 168F, and would up with slightly too much volume. So, 90min boil then. Did hit my numbers in the end. Maybe a bit on the high side too.

Chilled down to 70F, with my immersion chiller, aerated, and pitched the yeast.

Fermentation Notes

Initial fermentation began the following morning, or somewhere in the night. I don’t think the temp got above 74F. At the end of high krausen, I pitched the Brett B. Since, the temp has dropped to the mid sixties. There’s just not a lot of warm places in the house this time of year. (Perhaps I need to move my Ferm-tank build further…) That said, the airlock is still bubbling regularly, and I’m not so concerned with the temp, given the long aging this beer will undergo, and the primary ferment already over. And so, as ever, we wait.


  1. Attempting to convert this recipe to a 2.5 gallon half-ass partial-mash. It sounds great – will be brewing this weekend. Thanks for posting!

    1. best of luck! mine’s still fermenting, haha.

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