sweet potato mash experiment

[bonsai4tim]

This thread https://www.homebrewtalk.com/f164/s...-enzymes-lot-interesting-possibilites-210086/

lead to more reading. Sweet potatoes have amylase (alpha and beta) in them, and a fair amount of starch. In africa, adding ground sweet potatoes to the sorgum mash significantly improved yields in beer making.

So this afternoons experiment:
2.5 pounds grated sweet potato (including skins)
2 gallons water at 150 F

Mashed for 90 minutes, did a single decoction (see note below)

Ended up with 1 1/2 gallons at sg 1.015

1 hour boil with 1/4 oz fuggles. to 3/4 gal and sg at end of boil 1.030

Will pitch s-05 (its what I have) when it cools. Not sure if this will even be drinkable, but the science is fun!

tim

note: one paper, can't find it now, said the starch in sweet potatoes wasn't fully gelatinized until 180F, which is above the temp that the amylase in sweet potatoes is inactivated. Probably should have done several decoctions to increase the avail. starch for conversion

 

[DKershner]

1.030 gives you 30% yield. Normal malted grain gives about 75% for comparison. I would suspect this is because of the gelatinization temps you mentioned...not sure how to get around that exactly. Decoction might help a bit, but would also reduce the amount of enzymes.

The temperature quandary is common among GF grains.

 

[bonsai4tim]

I knew the yield was really low. This was more of a science experiment. Also wondered about cooking 1/2 of the sweet potatoes completely and shredding the other.

A finer shred might help too-

This is fermenting away now, will post an update when its done.

t

 

[AnOldUR]

Interested in hearing your results. My wife loves sweet potatos (not a fan myself.) If nothing else, I think she’d like the novelty, but I’m wondering what it’ll add to the flavor if used as part the grain bill.






edit:
Did a "sweet potato" search. Lots of information. Thanks for idea.

 

[BBBF]

I knew the yield was really low. This was more of a science experiment. Also wondered about cooking 1/2 of the sweet potatoes completely and shredding the other.

A finer shred might help too-

This is fermenting away now, will post an update when its done.

t

Soak the potato grated potatoes in the mash for a while, drain out the liquid (it has the enzymes in it), boil the potatoes, add the liquid mash back in, but make sure the combined temperature is where you want (too hot and you'll lose the enzymes) and then perform a mash and lauter like you would for regular beer... And add a lot of rice hulls.

 

[daxdefranco]

how'd this turn out? i'm thinking of making a sweet potato beer sometime this week.

 

[cuttsjp]

Sweet potatoes and other potatoes are supposed to be gelatinized (read: cooked) before you add them to the mash, so next time just boil or bake them beforehand and then smash them to a pulp and add them to your mash. I love pumpkin beers and I decided to take that whole thing a little further and do a "sweet potato pie" ale next fall. May not even wait that long...

 

[daxdefranco]

After I read a little more about this, I found several different research papers that puts the gelatinization point of starch in sweet potatoes between 58-80C. I've got ~3Kg of sweet potatoes baking in my oven at the moment at 150C for 2 Hours. After that I'll shred/mash them and mash at 67C.

 

[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 )

If sugar is 46 PPG (100% by weight) then sweet potatoes should be 46 * .25 = 11.5 PPG. I know this isn't 100% scientifically correct (so if someone has the real number please chime in) but it should get us in the ballpark.

So in your experiment, 2.5 lbs of sweet potato has a theoretical max of 2.5 * 11.5 = 28.75 points. You got 30 * .75 = 22.5 points. That's an efficiency of 22.5 / 28.75 = 78% which seems about right for a typical all-grain brewer.

cuttsjp is quite correct that potato starches should be gelatinized before mashing to maximize yield. I suspect that a significant fraction of your O.G. is in unconverted dextrins. I know it has been quite some time since the original post. Did you ever take a F.G. reading? If so what was it? How did the resulting beer taste? Starchy? I recently brewed my first sweet potato beer after doing a fair amount of research. It seems strange to me that so little is known about brewing with this vegetable, though it seems to be a great candidate for adding variety to the fermentable list for all-grain brewers. You can follow the progress of my (and others') sweet potato beers here: https://www.homebrewtalk.com/f76/crazy-bettys-sweet-potato-pie-ale-ag-269624/#post3350258

 

[aomagman78]

imrook - I think your math is off. I'm not sure exactly the stoichiometry of it all, but a single starch molecule will break down to form many sugar molecules. I'm not exactly sure how this calculates into PPG, because 26wt% starch would also mean 26wt% sugar once converted. So maybe you don't need a conversion factor. But now I'm curious myself - I may do a sweet potato mash/decoction and include amylase powder.

Plan: 3lbs sweet potato (food processed) in 1.25gallon water @ 80F. Raise temp to 122F, rest 30 min. Pull 3-4qt heavy mash for decoction (all sweet potato). Boil for 10min, return to mash. Bring mash to 152F, add amylase powder. Rest for 60min - check gravity of cooled sample. Pull 3qt for second decoction. Boil, bring mash to 170F, rest 10 min. Sparge with 1 gallon 170F water. Should have 2 gallons of water, check gravity and boil. I'll ferment this with some US-04 and see how far it'll go.

Thoughts on this schedule?

 

[Psych]

Why does no one ever update their threads with results? Maybe it turned out horrible and was a huge failure but at least letting people know that will mean not everyone makes the same mistakes

Or...sweet potato mash = poison and it's killing the posters off before they can type the word 'poison'...

 

[imrook]

Thoughts on this schedule?

That looks good to me. Make sure you process the potatoes very fine. I cubed and boiled mine before mashing and it didn't gelatinize enough of the starches. They were gelatinized during the boil and I ended up adding amylase in the primary to get them broken down into fermentables. It worked and kicked off a second fermentation, but I'm thinking I'm going to end up with a very thin beer this way. Go ahead and try it and let us know how it works out.

 

[SaccharoVices]

I would like to try a sweet potato wine, using no added sugar. The goal is to make 2 gallons of SG 1.100 using approx 20 pounds of sweet potato. Thinking amylase will help to ensure a complete conversion, I don't want a hazy wine but a really clear one.

I will finely shred the potatoes with a kitchenaid attachment, place the shreds in a fine mesh nylon bag, then into the mash tun. Add water and soak at 150, remove the shreds, boil them, then recombine with the liquid and add Amylase. Mash and drain. I will have to work out the liquid volumes because the liquid will have to be reduced to achieve the desired SG.

Does anyone know if there are pectins in sweet potato that would warrant the use of pectic enzyme? I really want to have a presentable, clear wine. I may also have to back sweeten and add a pie spice mixture for taste.

I will photograph and post much of the procedure here (or in the wine forum) for others to see/critique.

 

[BBBF]

I don't think there are pectins in them, but you could always put some in anyways.

 

[aomagman78]

I'm firing this up right now. I'll try to update with OG and eventually a FG and tasting. I have 3big potatoes, I think it's 3lbs. Whatever I end up with, I'm going to boil to an OG of ~1.035-1.040.

 

[aomagman78]

So I did this, but haven't fermented it or anything.

3lbs of sweet potatoes, peeled. Half food processed, half sliced very thin.

Doughed in, BIAB, at 90F and moved temp to 122, rested 1hr.

Removed bag, and put in enough water to cover. Boiled ~30min, mixing and crushing the potatoes

Added decocation back and brought temp to 152, added alpha amylase (Crosby baker) and rested for 2hr

Extracted bag, and tea-d in 1/2gal or so of room temp water, added this back to whole.

Mixed, and pulled sample for gravity. 1.018 with 2 gallons of water.

Then it got late, so I boiled it for 15min to kill anything, put in milk jug and into the fridge for now.

So that's 12PPG if my math is correct. Really not too bad, considering potatoes are .69/lb here. Considering 2-row is 36PPG and runs $1-$1.50, that's only 5.8c/point compared to 4.2c/point. Now I haven't fermented this, so I don't know what the taste/consistency is like. But it seems like a quality replacement for corn sugar that should add a little more body. I think more important will be the FG to see how much unfermentable/body these will provide. The water was definitely sweet so I'm guessing it'll end pretty dry, but mashing higher could definetly change that.

Anyway, hope this helps. I'll let you know when I ferment it, waiting to bottle a batch where I can grab some yeast cake.

 

[kyleobie]

Consider this my subscription to hear about your results. VERY interested in sweet potatoes!

 

[BBBF]

I have been meaning to experiment with sweet potatoes for the longest time and when I saw 3 lbs bags for $0.99, I couldn't resist. I graded two bags in the food processor and ended up with 5.75 lbs. I did a betaglucan rest @ 104F for 25 minutes. Then a protein rest @ 131F for 25 minutes. Then I decanted off .5 gallons of liquid/enzymes and put it in the fridge. I heated the rest to 158F for 20 minutes and then brought it to boil for 8 minutes. After letting it cool back to 158F, I added the .5 gallons of enzyme liquid and some Glucoamylase to the kettle and mashed for 90 minutes @ 149F. The iodine test was negative, but I gave it another half hour. I ended up with 3 gallons w/ a SG of 1.025.

I used .5oz of cascade @ 60 minutes and another .5oz at 5 minutes. I had some S-33 that is over a year old, so I decided to use that up. I have no clue what this will end up like.

 

[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).

 

[starrfish]

I used some sweet potato in the G.a.P. experiment a few years ago... lot of weird things going on there... may want to try again in a more conventional setting. subscribed.

 

[BBBF]

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]

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]

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]

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]

So...what happened?

 

[parkerhd36]

any updates?

 

[BBBF]

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:

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]

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.

 

[NewTexian]

Any updates?

 

[BBBF]

I haven't followed up with any further experiments, but the soapy flavor has slowly faded away.