sweet potato mash experiment

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

bonsai4tim

Well-Known Member
Lifetime Supporter
Joined
Dec 7, 2009
Messages
198
Reaction score
21
Location
raleigh
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

Well-Known Member
Joined
Jul 30, 2009
Messages
1,855
Reaction score
33
Location
Bend, OR
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.
 
OP
B

bonsai4tim

Well-Known Member
Lifetime Supporter
Joined
Dec 7, 2009
Messages
198
Reaction score
21
Location
raleigh
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

fer-men-TAY-shuhn
Lifetime Supporter
Joined
Mar 12, 2007
Messages
6,847
Reaction score
856
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

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
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.
 

cuttsjp

Well-Known Member
Joined
Jan 5, 2011
Messages
159
Reaction score
3
Location
Plainsboro
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

Active Member
Joined
Jun 30, 2010
Messages
27
Reaction score
0
Location
seoul, south korea
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

Well-Known Member
Joined
Feb 14, 2011
Messages
139
Reaction score
6
Location
Ann Arbor
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

Well-Known Member
Joined
Feb 22, 2011
Messages
113
Reaction score
2
Location
Columbia
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

Well-Known Member
Joined
Mar 17, 2011
Messages
778
Reaction score
41
Location
Kelowna
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

Well-Known Member
Joined
Feb 14, 2011
Messages
139
Reaction score
6
Location
Ann Arbor
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

Well-Known Member
Joined
Jun 5, 2011
Messages
88
Reaction score
2
Location
Graham
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

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
I don't think there are pectins in them, but you could always put some in anyways.
 

aomagman78

Well-Known Member
Joined
Feb 22, 2011
Messages
113
Reaction score
2
Location
Columbia
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

Well-Known Member
Joined
Feb 22, 2011
Messages
113
Reaction score
2
Location
Columbia
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

Well-Known Member
Joined
Apr 19, 2009
Messages
587
Reaction score
4
Location
Chicago, IL
Consider this my subscription to hear about your results. VERY interested in sweet potatoes!
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
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

Well-Known Member
Joined
Sep 26, 2011
Messages
63
Reaction score
1
Location
Hell
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

Well-Known Member
Joined
Oct 27, 2008
Messages
1,978
Reaction score
35
Location
Florence, SC
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.:mug:
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
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

Active Member
Joined
Jun 1, 2010
Messages
42
Reaction score
3
Location
North Plains
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

Active Member
Joined
Jun 1, 2010
Messages
42
Reaction score
3
Location
North Plains
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

Active Member
Joined
Jul 29, 2011
Messages
39
Reaction score
3
Location
Anchorage
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.
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
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

Well-Known Member
Joined
Feb 12, 2010
Messages
198
Reaction score
4
Location
Delray Beach, FL
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.
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
I haven't followed up with any further experiments, but the soapy flavor has slowly faded away.
 
Joined
Nov 5, 2012
Messages
7
Reaction score
2
I'm Gluten-Free and recently started brewing. I've been mooching off this forum, and now that I've got a few successful sweet-potato brews under my belt (thanks to you), I'd like to chime in. Note - I'm still building up my knowledge and equipment as I go, so the below is eyeballed rather than exact - but it's worked well so far.

I'm combining 2# buckwheat and 6 sweet potatos, a blender and a strainer. Note: the blender creates a really fine mash, so my current brews do require a bit of leg work to separate wert from mash (hence the strainer). I'll finder better ways & equipment with time.

Sweet potato prep: scrub the potatos but leave skin on. Chop small enough for blender to handle. Blend with hot water, set aside for mashing.

Buckwheat prep (two options)-
Option 1: malt, dry, roast, then crack with grinder, then add to sweet potato mash with more hot water.
Option 2: is a huge time saver - malt, (skip drying / roasting), blend with hot water directly, then add to sweet potato mash.

Mashing: let stand on low heat for an hour. Strain and collect liquid wert in a large pot. Add more hot water to sparge and strain (repeat until strained liquid runs more or less clear). As a last round, add water to the mash and boil for 30 minutes. Strain and cool this off before adding to the already collected liquid.

Boil: Then Very slowly rais the temperature of the wert (this probably continues some enzyme action for another 30-40 minutes). When its eventually at a boil, I added about 2 cups of raw sugar and my 1st bag of hops. After 40 minutes, + 2nd bag of hops. After 10 minutes + 3rd bag of hops. After ±3 minutes, remove all the hops bags. Cool the Wert as quick as possible.

Fermentation: 20 days in the bucket, 1 week in the bottle. I have only just aquired a hydrometer and thermometer, so I'll have more details in the future. I'm in the process of making more beer now.

Flavor / color: I have been gluten free for a while, so maybe my standards are low, but I really enjoyed my beers. The rate that my finacé consumes it indicates that they might actually be ok for a normal pallet too. Roasting the buckwheat gives a darker color (see photo with the pour, vs. photo of the 2 clear bottles in the fridge). Roasting also produces a change in the flavor, but I can't say which is better - thats up to personal preference.

:mug:

yield.jpeg


pour.png
 

MattHollingsworth

Well-Known Member
Joined
May 19, 2009
Messages
1,609
Reaction score
53
Location
Samobor, Croatia
Other than saying it tastes okay, what does it taste like? I'd assume with that much sweet potato, you must be getting SOME flavor out of them. What's it like? Buckwheat dominating?

Did you test for starch conversion?
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
Did you get any soapy flavors with your 20 day fermentation?
 
Joined
Nov 5, 2012
Messages
7
Reaction score
2
Soapy flavors - hmmm, no but I don't consider myself a super-taster. So if you mean something subtle, maybe I'm just oblivious to it. I don't get a strong buckwheat or sweet-potato flavor either. To me it just tastes like beer - one was slightly more sour (but nothing compared to how sour Redbridge is), and the other more bitter. The main thing I taste is beer & hopps. For a second opinion, I just consulted with the finacé who concurs: "It just tastes like good beer." Not highly alcoholic, but I wasn't going for that. Sorry, I know that isn't very helpful. If there were effective delivery methods, I'd love to send you a bottle so you could draw your own conclusions and give me some independent, unbiassed feedback.
 
Joined
Nov 5, 2012
Messages
7
Reaction score
2
I didn't test for starch conversion for those first brews- this is something I'll be doing for the first time later today. It will be a slightly different outcome either way because I'm adding in 1# malted Quinoa and 2# Millet in addition to the other ingredients. I'll take pictures and let you know what happens.
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
Soapy flavors - hmmm, no but I don't consider myself a super-taster. So if you mean something subtle, maybe I'm just oblivious to it. I don't get a strong buckwheat or sweet-potato flavor either. To me it just tastes like beer - one was slightly more sour (but nothing compared to how sour Redbridge is), and the other more bitter. The main thing I taste is beer & hopps. For a second opinion, I just consulted with the finacé who concurs: "It just tastes like good beer." Not highly alcoholic, but I wasn't going for that. Sorry, I know that isn't very helpful. If there were effective delivery methods, I'd love to send you a bottle so you could draw your own conclusions and give me some independent, unbiassed feedback.

My batch of sweet potato beer had a very noticeable soapy flavor. It went away over time, but you couldn't miss it at first. I think it was the result of sitting on a large amount of trub for a few weeks, which is why I was curios about your batch. I also didn't get much flavor out of the sweet potato, but it was a good lawn mower beer. If you want to send me a bottle, I'd be more than happy to try it.
 
Joined
Nov 5, 2012
Messages
7
Reaction score
2
I brewed a new batch today with
  • ±1 cup chopped ginger
  • 8 Sweet Potatoes
  • a mix of 2# malted buckwheat / 1# quinoa / 2# millet. 2/3 of the grain was lightly toasted & ground. 1/3 blended with warm water.

I got myself some iodine and confirmed that there was lots of starch early on in the process & none(?) by the time I put it in the fermentation bucket.

It may have been over-kill, but I achieved this by doing a 2 series of rests. First with the mash:

  • 40C / 60C / 70C / 80C-to-Boil.

  • I separated out the wert & replaced with water after each 20 minute rest.

  • All the wert I collected was cooled before being combined (to preserve the enzymes collected at lower temperatures).

Then I went through the same series of 20 minute rests with the wert, while warming up to a final 45 minute boil. For the boil I added:
  • 2/3 cup of chopped ginger & 1 bag of hops for 45 minutes, another bag of hopps and 1/3 cup of ginger for 15 minutes, last bag of hops at 5 minutes.
  • ±2 lbs of sugar (much more than I've ever added - since I have the Hydrometer, I want to get some more alcohol) & a bit more water to reach a total of 5 gallons.
The initial SG is 1042... now its bubbling away. Can't wait to see what happens.

If its good, let me know how to send you a bottle - I don't know of any shippers that will deliver a carbonated alcoholic beverage internationally.
 

BBBF

Well-Known Member
Joined
Aug 16, 2008
Messages
1,687
Reaction score
207
Location
Chicago
I found a bottle of the sweet potato beer this weekend and the off flavor was completely gone, as well as any noticable hops. Much more of the sweet potato flavor was back. It was really light, but good. I definately have to try this again. I'll be looking for sweet potatos after thanksgiving.
 
Joined
Nov 5, 2012
Messages
7
Reaction score
2
Super!

I'll be bottling my latest sweet potato buckwheat brew this weekend, so Ill report back with alcahol content / conversion for the first time- I'm excited.
 
Top