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.

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

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