28 Oct 2009 @ 11:24 AM 

And by potatoes in your beer, I mean before fermentation. Not after. I like potatoes – they might be the closest thing I have to a cultural food item – but I have my limits.
You say potato, I say potato.
So what brought this on was this wacky idea I had for a rye-potato beer. I’m not sure why or where I got the idea, but once I got it I had to act on it. I have some nice saison yeast that I cultured out of a bottle earlier this year, and plated by a friend of mine at a biology lab this summer, so I had to go for it.

Now the reason that I say that these are new thoughts on potatoes in your beer is because I approached them a little differently than I’ve read about others doing so. Recipes I’ve seen call for enormous amounts of mashed potatoes and instructions note that the potatoes need to be boiled ahead of time. I took a different tack.

I did a little reading and, mind you, these are internet resources. I’m not sure I would use some of them if I were writing a paper on this topic, but this is a blog, and it’s experimentation in my backyard right now, so we’ll have to deal with my less-than-perfect scientific research.

First, I found that potatoes stored under 45°F will being to develop a sweet taste as some of the starches in the potatoes are turned into sugars.

Perfect! Since the end goal is to convert starches into sugars, I figured I’d get a head start. I started keeping my potatoes in the refrigerator at 40°F.

I found that the starches in potatoes gelatinize between 52.5°C and 72.0°C (126°F – 162°F). And at least one article that I found (that I am having a hard time re-finding) cites 150°F specifically. And hey! That’s great! That’s about the same temperature as barley.

Three other items of information that I’m having a hard time re-locating:

1) Most of the protein content in a potato is located in a small layer directly under the skin.
2) Cooling after cooking potatoes increases the amount of complex starches within the potato.
3) MOST of the starches found in potatoes are very, very complex. From a nutritional level, they act – to humans – very much like fiber.

All of this made me think: Why are people boiling their potatoes and then throwing the mashed potatoes into the mash?

You know how vodka is made? You cook the crap out of potatoes, toss the actual potatoes out and work with the leftover water, where all the starches and sugars are. Why are we working with only the potatoes and throwing out all of the good stuff?

Here’s what I did for a process:

The night before I brewed, I peeled my cold potatoes. I wanted to avoid most of the skins, since I’m not sure of the flavor I was going to get from them. I think an earthiness would be nice, but my experience from cooked potato skins, even though I love the flavor, is a certain green bitterness that I didn’t want to translate overpoweringly into the beer. So they went.

Then I sliced and diced them really, really thin and small. I originally wanted to use a food processor, but I felt like the slices were too thick. I figure that, like hops and barley, a lot of surface contact with water is a good thing. Water is the substrate for all of our chemical reactions here. I didn’t want anything to have to fight its way out from the middle of a potato.

I cooked them at a low temperature: 150F. At no time did I ever boil my potatoes. I simmered them at 150F for an hour. In the end, I had a bunch of crunchy, slightly sweet potatoes, in creamy looking water.

Then I threw the whole thing in the refrigerator overnight. Cooling, I was hoping, would help the development of some of those other complex starches.

The next morning, I used the water – with the potatoes in it – as the basis of my infusion water for the first step of my mash. Both the potatoes and the starchy water were in my mash right from the beginning. I did a protein rest. It’s not something I usually do, but since 70% of my grist was either rye or potatoes I wanted to make sure that I had as easy a time as possible with conversion.

After an hour in protein rest, I stepped up to a low mash temperature of 148F, and I let it mash for 2 hours. I wanted to give those enzymes plenty of time to work. From there, normal sparge, boil, etc. There were absolutely no problems with gumminess or a stuck mash or anything.

At the end of the mash, I dug through the grain a bit to find a piece of potato left over. It was still slightly crunchy, maybe a little rubbery, and absolutely lifeless.

As for sugars? My estimated OG with just pilsener malt and rye was 1.041. My OG after the potatoes was 1.052. I felt that was a fairly significant increase in sugar content.

What’s left? Well, I need to find the math I need to use to estimate potential extract from these potatoes so that I can attempt this again with an estimate in place to see if I can repeat it in the future.

Anybody know that?

And finally, I suppose it’ll make a difference if the beer tastes good. I’d love to hear thoughts.

Posted By: erik
Last Edit: 28 Oct 2009 @ 07:12 PM

Tags: ,
Categories: homebrew


Responses to this post » (23 Total)

  1. Jimmy says:

    If you know the weight of each grain and the potatoes, you should be able to figure out the potential extract of the grain (at whatever your extract efficiency is) and subtract from the pre-boil OG to figure out what the potatoes added. Let me know if you want to see some actual numbers, it’s too long to write out in a comment.


  2. erik says:

    I’d love to see some actual numbers, but I didn’t take the pre-boil OG.

    Shucks darn, I’ll have to brew again.

  3. ingrate says:

    I am of the opinion that you have discovered something. When you do this again, take even more data. Then right it up for one of the brewing magazines out there.

    Also, I was about to ask what a protein rest was (extract brewer here), but I did my own research for once: http://www.picobrewery.com/askarchive/proteinrest.html

    Congrats on a successful experiment.

  4. Jimmy says:

    Dust off those 8th grade algrebra skills. Promash/Beersmith normally do this part for you.

    What this is really doing is calculating the potential based on the actual. Which could be a problem if you #fail at mashing and end up with a bunch of unconverted adjunct starches in your wort. I think as long as an iodine test came up ok, then you should be fine. Maltsters do basically the same thing to determine potential extract of grain (look up Congress Mash), so it should be sound.

    Potential Extract is measured in Points per Pound per Gallon (PPG). The malster will give you the yield for a malt at 100% extract. Your pilsner malt might be 1.036 (36 points) and rye 1.029 (29 points)(had to look that one up!). So 1 pound of pilsner malt mashed in 1 gallon of water would give you a 1.036 wort.

    For 6 gallons of pre-boil wort if you used 6 pounds of pilsner and 3 pounds of rye that would work out to:
    6×36 = 216 potential points from pilsner
    3×29 = 87 potential points from rye
    303 potential points divided by 6 gallons = 50.5 or roughly 1.050 SG

    That’s at 100% extract though. Everyone’s system is different based on mash tun design, sparge setup, etc. You just have to do a mash and measure the pre-boil gravity to calculate the efficiency of your system. For this let’s pick 85%. 50*.85 = 1.042

    So if you know that much, you basically just have to take a pre-boil gravity, subtract the potential of the grain and do the math backwards to figure out the potential of the adjunct.

    If you wanted to be a super spaz about it, you do a mini congress mash with an amount of grain to provide some enzymes so that you will get as close to 100% extract efficiency as possible. But it’s probably overkill for what we’re doing.

    Hope that helps.


  5. erik says:

    This, Jimmy, is why you win medals. (Because you’re *smart*.) Thank you.

    I’m gonna go home and do some math and post back here.

  6. shficke says:

    R.E. the gumminess (or lack thereof) in your mash: you also put in rice hulls, yes?

  7. erik says:

    Oh, certainly. But if I didn’t have rye in the beer, I wouldn’t use them again on a potato beer. They simply were not gummy.

  8. Kevin says:

    If what you are going for is a lot of surface area for the potato, did you consider shredding them with the food processor (think hash brown consistency).

  9. erik says:

    I did, yeah. In fact, that was my original plan. I cut them roughly that small.

    I will confess that I got lazy and didn’t want to clean the food processor, so I did it by hand… which was probably more work.

  10. christopher says:

    You bring up a great point about the potato cooking liquid. When making potato dextrose agar (for your home yeast lab) you use the cooking water and toss the potatoes.

    I consulted my old wine making book for potato wine. He makes no mention of peeling the potatoes. The instructions say to scrub. grate and gently simmer for 1 minute before straining into the fermentation vessel. That’s pretty much the drill with the other root vegetable wines as well. I like your process and the research certainly supports the steps you took. I’m looking forward to hearing what else you learn.

    Also related to potatoes but more because its awesome – here’s the jungle juice recipe from the same book:
    3lb very old potatoes, 6 oranges, 1lb raisins, 1lb wheat, 4lb non-inverted sugar, 1oz yeast, 5qt water
    cut up and boil oranges, peel on, for 3 minutes. Let stand aside to cool. Scrub, grate potatoes (do not peel), bring to boil in 6pts water, gently simmer for <10min removing scum (go over 10min mark if scum still arising). Strain potato water into fermenter with 1/2 the sugar until dissolved. Add wheat and cut up raisins, and orange mixture. Allow to cool before pitching yeast. Ferment 10days, rack, add remaining sugar dissolved in 1pt water. Bottle when fermentation completes.

    • Bianca says:

      Jason,In truth I completely agree w/ you. Thank you for nociting that I wasn’t presenting a scientifically acceptable cause and effect analysis. I’m guessing that you also realize the BHO attackers’ (e.g. Mr. Bomb Iran, Pence, et. al.) assertions that BHO can positively effect the situation in Iran by raising the heat of his jabber is also lacking scientific causality. But, it is fun to look at history and see actions that were coincident w/ the Bush administrations actions related to Iran. You probably remember how Bush strongly took the side of the protesters in 2003, this was after plenty of tough axis of evil talk, and the freeing of Iraq which were supposed to weaken the Iranian government. How did that work out for the protesters? Who became president of Iran after Bush’s jabber and Iraq attack? What has happened w/ the Iranian enrichment program and support for terrorism in Iraq and Israel since the Iraq attack and tough talk? Has the new Iraqi government shown more respect for Iranian leaders than the Bush administration at the exact time when the Iranians were arming terrorist who were killing Americans in Iraq? Likewise it is interesting to look at the things in Iran that have accompanied BHO’s rejection of the bluster of Mr. Bomb Iran, Pence, et. al.. At a minimum things have been less comfortable for the Iranian leadership since BHO took over. It’s not possible to calculate a statistical causality. But, there is a clear historical narrative that justifies mocking Lyle et. al. who claim that the eight years of Iranian activity during the Bush years were not creditable to Bush. But, supposedly the current circumstances in Iran are the result of Bush. According to Lyle the axis of evil speech is ripening and really taking full effect now. Heh.

  11. ingrate says:


    Your response was mind expanding. Thank you.

  12. Seabass says:

    two thoughts on the use of raw ingredients (=basically not malted to be simple) to increase you OG:
    1) many of those like rice and potatoes are inconsistent when it comes to reproducing your recipes batch after batch once you have found the one you like. but mind me that may not be intended as it is also a fund activity and change is fun and challenging.
    2) one approach to using less predictable ingredients is to not only pre-process them as you have done but get them to a final stage where you would add them at the end of boil. this will allow for more control over flavor and gravity while you do not harm your beer base as you could choose not to add the raw ingredient. it helps the math side as you can add it up without second guessing what happened during mash, lauter and boil.

    • Nadia says:

      HankNovember 11, 2012While that is definitely a great thing, don’t be conetnt in it. It is a trap that we fall into when we are down on ourselves. 30 pounds is awesome. It is incredible, but it will not keep you from getting heart disease or diabetes or worse. I know you Dre. I know you are capable of overcoming this disease of obesity and this addiction to unhealthy living. Think about how much better it will be when that above comment is you’ve lost 100 pounds! That is A LOT! sorry to be tough but I know where you are coming from and some truth will set you free! Do this brother. You can do this!

  13. erik says:

    Hey Seabass! Thanks for the input!

    Question, though:

    Why would a raw ingredient – whether it be potatoes, rice, or even unmalted grains (wheat, rye, or even barley?) – be any less consistent or predictable than malted barley if you’re consistent in the manner in which you measure, handle, and prepare it?

    Most of these raw ingredients are used for other forms of alcohol. I would imagine that someone, somewhere, has a means of processing them consistently. Though, truly, me in my backyard is not it. 🙂

    Your #2 sounds like the way to go about it – pre-process and add at the end of the boil. It’s a longer, more involved process, but it’s a sure-fire way of being able to consistently control sugar content because it’s measurable before adding it in.

    Good stuff. Thanks!

  14. Seabass says:

    to #1
    yes, there are plenty who do extremely well and make great consistant product like Budweiser. But they go to great length to make this happen over and over. Malt has the benefit of being preselected by the farmer then the maltster and finally the large bewers. This allows you and me to get high quality and consistent barley malted to make consistent beer. If you would get barley grown by a local farmer in Farmville and malt it in preperation you might get away with a very dark beer but overall you will have a harder time with sugar and protein levels and malt flavor.

    to #2
    in some cases as you use raw ingredients it will be helpful and make it easier to apply some form of American whisky mash where you will add 5 or 10% of 2-row for enzyme activity as you will benefit from not only adding fermentable sugar to you beer but also keep a nice foamy head.

  15. erik says:

    The latter – putting in the 2-row in an earlier mash before adding to my overall mash – is generally how I deal with oats. It would make perfect sense to do it for other things, as well.

    I’ve never thought of that as a whiskey mash, I’ve just thought of it as adding enzymes to help with starch conversion.

    I clearly need to learn more about whiskey. 🙂

  16. How’s this beer coming along. I just brewed an ESB with carrot sugar that I made and it seems to be doing extremely well. I was think of you and your potato beer when I post my article today.

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