sweet potato mash experiment - Page 3

BBBF · 01-09-2012, 01:44 PM

Quote:

Originally Posted by Glossolalia

So do the volatile aromatics of sweet potato survive the mash and boil? I'm working on a beer where 50% of the grist is sweet potato. I'm using koji to saccharify steamed sweet potatoes. I'm then going to make a beer from the remaining ingredients and pour it directly on to the saccharified potato-koji mix. My concern is whether the biota in the koji is sufficiently alcohol- and hop-sensitive to die off or whether I'll end up with a product that isn't shelf stable (e.g. namazake).

There was enough sweet potato aromatics that I had to fight the urge to skip the hops and add raisins and maple syrup.

**dubiouschewy** · 01-26-2012, 07:31 PM

Quote:

Originally Posted by Glossolalia

I'm working on a beer where 50% of the grist is sweet potato. I'm using koji to saccharify steamed sweet potatoes. I'm then going to make a beer from the remaining ingredients and pour it directly on to the saccharified potato-koji mix. My concern is whether the biota in the koji is sufficiently alcohol- and hop-sensitive to die off or whether I'll end up with a product that isn't shelf stable (e.g. namazake).

I am super interested in this experiment! Have you had any results yet?

I'm more interested in using sweet potatos as a source of beta-amylase than as a sugar source... with the koji providing the alpha it would be very interesting to see what comes of it!

**dubiouschewy** · 01-27-2012, 12:45 AM

Quote:

Originally Posted by imrook

I have been doing some homework on brewing with sweet potatoes recently and wanted to post some findings here for potential future visitors.

Sweet potatoes are mostly water and around 22 - 25% starch by weight ( http://www.fao.org/ag/aga/agap/frg/AHPP95/95-217.pdf & http://journeytoforever.org/biofuel_library/ethanol_manual/manual8-10.html )

Interesting bit in the first linked paper notes that uncooked sweet potato is especially resistant to amylase, and that after cooked, the easily hydrolysable (converted) starch content increased from 4% to 55%.

Interesting that it's still only 55% after cooking. I have no idea off the top of my head if that's comparable to barley malt, but it'd be interesting to find out.

**Raudhbjorn** · 01-31-2012, 10:51 AM

Interesting. Not a fan of sweet potatoes but very interested in the science of the idea. Now I'm wondering if you could use regular potatoes to "pad" your OG without noticeably increasing SRM or altering flavor.

ChasidicCalvinist · 02-28-2012, 03:20 AM

So...what happened?

**parkerhd36** · 03-14-2012, 01:52 PM

any updates?

BBBF · 03-16-2012, 09:17 PM

It had a strange flavor, which I can only describe as "soapy." So here is where my decision to use T-58 was a bad one. 1. I'm not familar with that yeast. 2. The package was expired. So was the soapy flavor the result of the yeast, sweet potatoe or the process?

I did find this:

Quote:

Soapy
Tastes/Smells Like:
Soap, detergent, oily, fatty
Possible Causes:
Keeping beer in the primary fermenter for a long time after fermentation is complete
can cause soapy flavors. After a while, the fatty acids in the trub start to break down
and soap is essentially created.
How to Avoid:
Transfer beer into a secondary if you plan on aging it in the fermenter for a long
period of time. Very light beers and lagers are more susceptible to absorbing and
exhibiting off flavors than ales and darker beers.

I can't say how much oil and fatty acids are in a sweet potatoe, but there was a lot of trub and it is a very light beer. I'd like to try again and rack of the trub sooner. Also, roasting some gluten free grains and adding them to the mash could help.

Noontime · 03-19-2012, 01:06 PM

I look forward to hearing more about your next batch. Even just adding some brown rice syrup or something might change things for the better. I'm also hoping to hear results from others who have used sweet potatoes.

I've kind of given up on the GF beer, having experimented with a whole lot of different ingredients and processes. Seeing something new is intriguing and might get me making another one.