Slicing and Dicing Mashed Potatoes

January 2, 2005 2:55 PM

If you were a food scientist, and a chef at a restaurant handed you a bowl of mashed potatoes and challenged you to figure out how many potatoes were in there and what kind of potatoes they were, how would you go about it? (Bonus if you can do it without leaving the restaurant.)
posted by adrober to food & drink (30 comments total)

What's the punchline?
posted by orange clock at 3:03 PM on January 2, 2005

i don't think it's possible ... potatoes come in different sizes when you get them from the store
posted by pyramid termite at 3:05 PM on January 2, 2005

I would measure the calorie content. Basically do what you can to mimic the conditions at a lab, where you burn up all the mashed potatoes at a high temp and figure out how much energy is given off by measuring the temp change in some water. Then do a basic estimate of x calories/potato and there's your total potatoes.

Dunno how you could figure out starch content to determine what variety they are.
posted by mathowie at 3:15 PM on January 2, 2005

Good thought Matt. While measuring calories, measure fat content as well to separate the starch calories of the potatoes from the fat calories of the cream and butter.
posted by caddis at 3:18 PM on January 2, 2005

I'd go into the kitchen to look at the skins.
posted by bodabutton at 3:21 PM on January 2, 2005

I'd accuse the chef of using instant mashed potatoes as a way of challenging my food scientist knowledge, and refuse to discuss it any further.

Otherwise I'd go with pyramid termite's answer, especially considering the vast array of sizes various types of potatoes come in.

As for what kind of potato, I've heard that russets produce light, fluffy results, while waxy potatoes like Yukon Golds become creamy smooth.
posted by furtive at 3:22 PM on January 2, 2005

I'd taste it first, since they're probably using either russets or Yukon Gold and the difference would be obvious. Then I'd weigh the bowl, what I thought was an appropriate quantity of milk and butter, and an average-sized spud of the appropriate variety. Weigh the mashed potatoes, subtract weights of bowl, milk, and butter, divide by weight of a single potato and round up.
posted by cali at 3:25 PM on January 2, 2005

Do you mean how many potatoes' worth of potato is in your serving, or how many different invidual potatoes are represented in your serving?

Furtive's right about the starchy/waxy continuum, but there are many kinds of potatoes all along the line, so just texture's out. (Not to mention the proportion of butter to potato will mess with the texture. Apparently the classic proportions are equal parts potato and butter by weight. Insane.)
posted by kenko at 3:27 PM on January 2, 2005

I am a chef at a restaurant, and if a food scientist handed me a bowl of mashed...

Wait, wait, I have the question around wrong, don't I?


I could do it just by instinct, man. ;)
posted by madman at 3:30 PM on January 2, 2005

Wow, thanks for so many quick, intelligent responses. This is actually for something I'm writing about a food scientist, so if you ever see a movie about a food scientist weighing her mashed potatoes you guys can all take a little credit. But no royalties, sorry.
posted by adrober at 3:39 PM on January 2, 2005

DNA fingerprinting. Tough to do at your table in a restaurant but it would give you a definitive answer to what type(s) of potato.
posted by TimeFactor at 3:48 PM on January 2, 2005

The Sherlock Holmes vein seems to be a bit more compelling. He might deduce information from the potato market (vs. dish price) - a discarded supply box on the front curb or in the hallway on the way to the mens room - the cultural background of the chef/owner and a corresponding varietal tendency.

Cooking style and growth conditions could change the characteristics of the potatoes.

I imagine measuring caloric content is only marginally more accurate than measuring volume. You're still assigning an average caloric content or volume per potato. The water content variable is removed via the caloric method, but added ingredients like butter would throw it off more than a simple volume measurement.
posted by Jack Karaoke at 4:37 PM on January 2, 2005

If one could determine what variety of potatoes were used, by taste, then one could estimate how many were used by eyeballing the volume and correlating it with the average size of that potato.

Frankly, that's the only way I'd do it in a movie--as Jack Karaoke says, the "Sherlock Holmes" vein. "Mmmm...tastes like Peruvian fingerlings--no, wait! It's Ecuadorian vine potatoes. Well, the average weight of an Ecuadorian vine potato is 38 grams, but these taste especially young, so I'm going to say 30 grams per potato, and you've got 900 grams of mashed potatoes here, less 100 grams butter and 45 grams heavy cream...I'd say, 275 potatoes, give/take."
posted by Sidhedevil at 5:03 PM on January 2, 2005

pyramid termite is right. how are you supposed to figure this out without knowing how large or massive each potato is?
posted by rxrfrx at 5:23 PM on January 2, 2005

Any guesswork would be very inexact. Some smaller potatoes are fairly standard size, but russet potatoes (for instance) vary a lot, probably as much as 50%, I'd say. Bodabutton has a good idea, can you work some sort of clever pre-event spying into the plot?

...if you ever see a movie about a food scientist weighing her mashed potatoes...

Now, that's a movie I'd pay $10 to see!
posted by Plutor at 5:27 PM on January 2, 2005

Simple. Slip the prep slave $10.
posted by sacre_bleu at 5:51 PM on January 2, 2005

I'd go to the kitchen and ask the guy who peeled the taters, 'cause sure as shooting no self-respecting chef is going to do that menial task himself, especially in a busy restaurant.
posted by five fresh fish at 6:07 PM on January 2, 2005

figure out how many potatoes were in there and what kind of potatoes they were

The kind of potato could probably be discerned from the taste, providing the chef didn't overwhelm the tastebuds with salt and butter.

The amount, however, would be pure speculation along the lines of "How long is the emperor of China's nose?"

Even if you knew what kind of potato was used, and even if you had an average size for that kind of potato, there's absolutely no way of knowing how much of each potato the chef used. There could be black spots that were cut out. He might have only used the cores of the potato. There's no way to know for certain without some lateral-thinking solution (like sacre_belu's answer).
posted by Civil_Disobedient at 8:08 PM on January 2, 2005

'cause sure as shooting no self-respecting chef is going to do that menial task himself, especially in a busy restaurant.

Absolutely right. :D
posted by madman at 9:00 PM on January 2, 2005

Then I would reply "I am a stranger travelling from the West, and it is I who you seek."

No, but seriously, I'm not a food scientist, but this sounds like a Fermi Problem if there ever was one, and so a practiced cook-physicist might expect to be able to get the order of magnitude correct.

I'd simply state my assumptions to the chef: that you used potatoes of average volume for kind x (say, Russet), that the yield of those potatoes was approximately y(x) (say, 3/4 cup), that the cook added m cups of butter (say, 1/2) and n cups of milk (say, 3/4 cup) and any water added was essentially boiled out and spice added was a negligible addition to the final volume V (say 8 cups). Let's also assume a "fluffiness" factor F (say, an increase of 10%, or 1.1), that increases the volume of the material by a certain amount. So, letting N be the number of potatoes:

V = F * ( (N*y(x) ) + m + n)

Rearranging:

V/F - m - n = N*y(x)

Or:

N = ( (V/F) - m - n ) / y(x)

So:

N = ( (8 cups / 1.1 ) - 1.25 cups) / (3/4 cups / potato)
N ~ 8 potatoes

Then I would sing this song.
posted by weston at 9:22 PM on January 2, 2005

Would DNA survive the heat involved in potato mashing? I tend to think not, especially if the mashing process liberated endonucleases.
posted by ikkyu2 at 9:47 PM on January 2, 2005

Restaurant mashed potatoes use a lot more cream, milk and butter than you tend to use at home. Joël Robuchon's pommes puree has a ratio 2:1 potato to butter.
posted by deaddodo at 10:17 PM on January 2, 2005

Fill a large bowl or sink and place the bowl of mashed potato into the water - measure the displacement of the water. Transfer the mashed potato out of the bowl, place the bowl back in the water and begin filling the bowl with loose potatoes. When the displacement is the same as with the mashed, you know how many taters it was. That is, if no other ingredients have been added yet...
How many types of potato are available at this restaurant? Most only use cheap bulk russets. Some nicer places may use yukon golds or reds, but I'd bet on the russet. This sounds like a Monty Python skit.
posted by Technetium at 11:57 PM on January 2, 2005

the answer is 8.

done. next?
posted by warhol at 12:26 AM on January 3, 2005

I suspect the mashing would still leave more than enough DNA in tact. Boiling might be more of a problem though. I was thinking of using DNA fingerprinting for determining the number potatoes too, but potatoes from the same plant will have the same DNA and I suspect there's insufficient variance in DNA even between non-closely-related plants.
posted by fvw at 4:34 AM on January 3, 2005

Potatoes are vegetatively propagate so each plant (and therefore each potato) of a given variety is essentially a clone of all the others. All Finngold potatoes, for example, are essentially from a single plant. So, fvw is right - DNA can't tell you how many potatoes are in the mash (but it could identify that a recipe includes more than one type of potato).

DNA fingerprinting is used to determine animal(s) of origin in cooked, processed, and/or canned meat products so I'd think the boiling and mashing of potatoes wouldn't have an impact. Remember, fingerprinting is done with restriction fragments so long intact strands are not necessary and small fragments that result from degradation will "fall out" in electrophoresis so that shouldn't be a problem either.

But I'd use five fresh fish's suggestion anyway: ask the food prep person. Faster, cheaper, easier.
posted by TimeFactor at 8:13 AM on January 3, 2005

Is there no way to separate the fat from the potato once it has been blended?
posted by trharlan at 8:25 AM on January 3, 2005

weston: 3 Cheers for the Mexican Potato Dance. ;)
posted by bkdelong at 11:45 AM on January 3, 2005

(actually, if this is for a movie....that would be the perfect song to have soundtracking in the background as said food scientist counted her potatoes.)
posted by bkdelong at 11:46 AM on January 3, 2005

Actually, the best solution for a movie would be this: the food scientist pulls the "Sherlock Holmes" routine I described above, astonishing all. Later, her faithful Watson figure is gushing over how amazing the feat was, and the food scientist says, "You idiot--I just asked the food prep guys in the kitchen."
posted by Sidhedevil at 1:22 PM on January 3, 2005