Perfecting potato puree

In the realm of all things spudular, French fries are king, but mashed potatoes are a close second. As with fries, there are certain criteria that can be used to distinguish good examples of the genre from bad. Mashed potatoes, however, come in two acceptable styles, like peanut butter: chunky and smooth. Chunky mashed potatoes (which I call “British mash”) are easy to make: peel potatoes, cut them into large pieces, boil them until tender, then mash with a masher, adding butter, milk and salt to taste.

Smooth mashed potatoes (a.k.a. “potato puree”) are a different story entirely. They need to be handled carefully, lest they turn into a gluey mess. The starch in potatoes is contained in granules; if the potatoes are overcooked or overworked, those granules will break, the starch will leak everywhere, and the puree will get very sticky. (This isn’t as big a problem with chunky mash, since the risk of overworking the potatoes is less when you’re not trying to eliminate every last chunk.)

Fortunately, there is a known fix for this problem: by heating the potatoes precisely to their gelation (or gelatinization) temperature, holding them there, and then chilling them down again, you can retrograde the starch, which stabilizes it and prevents it from leaking out of the granules. This technique is often credited to Jeffrey Steingarten, who described it in his book The Man Who Ate Everything, and is now widely used. (You may recall that I’ve mentioned starch retrogradation before.)

To put this theory into practice, I cobbled together an approach based on notes from eGullet. Because it requires holding the potatoes at a constant temperature over a period of time, it’s a process that is perfectly suited to an immersion circulator, so I started by putting the peeled-and-sliced potatoes into a vacuum bag along with their skins (for added flavour) and some water. I cooked them at 70°C for 45 minutes, then chilled them in ice water and put them in the fridge. Later, I drained them (keeping the starchy water), discarded the peels, and boiled the potatoes until they were softened. I passed them through a food mill fitted with the fine disc, then heated the resulting puree, adding butter and adjusting the texture with the reserved starchy water.

The final product was not the perfect potato puree I was looking for: there was a detectable grittiness to it that could be compared to polenta, which I suspect came from incompletely gelating the starch, or possibly from not chilling it sufficiently. Either way, the fault was in the execution, not the theory. And it was fascinating to be able to work the puree as much as I wanted without it ever getting noticeably sticky.

Which do you prefer: chunky mashed potatoes or smooth potato puree?

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20 Responses to “Perfecting potato puree”

  1. I grew up with boiled whole potatoes, (Norland Red, if you must know,) so for me, I always prefer “smashed” potatoes, as we used to call them.

    I do find boiling them whole, instead of in pieces is preferable.

    In my most peculiar peccadillo, I think the best way to tell when potatoes are done is to pay attention to the smell the water for when it switches from bitter a bitter astringent smell to a sweet smell.

  2. I once had the privilege of making a spud puree along side Jonathan Gushue. He referred to the technique as that of Joel Robuchon. I think it was four medium-sized potatoes into which I beat furiously nearly a pound of butter. It was indeed very tasty.

  3. Matthew Kayahara March 7, 2011 at 5:13 pm

    Erik, I think you’re right that whole potatoes can produce a superior mash than pieces, but I find that they take longer and it’s harder to cook them so that the centres are done without the outsides falling apart. Normally these kinds of challenges wouldn’t stop me, but if I’m going to all the effort, I prefer a good smooth puree. Chunky mash is for when I need dinner on the table in half an hour!

    That tip on how to tell when the potatoes are done is interesting… I’ll “keep a nose out” for it next time!

  4. Matthew Kayahara March 7, 2011 at 5:15 pm

    Andrew, when doing those Robuchon-style potatoes, did you retrograde the starch at all? Was it a cook-chill process with the potatoes, or did they get mashed right after being cooked? I think of Robuchon-style potatoes as being primarily distinguished by the copious amounts of butter; for the mash I did here, I used about one quarter the weight of the potatoes in butter, but I’ve seen recipes that call for as much as equal amounts. Mine were plenty rich enough for me!

  5. Matthew, I admire you going through that long list of steps for your puréed potatoes.

    I want to playfully argue with you here. I believe there are three different dishes. Chunky mashed potatoes, smooth mashed potatoes, and potato purée.

    As I was taught potato purée is a lot looser than smooth mashed potatoes. Smooth mashed potatoes will hold their shape when being piped and when twice-baked, purée is as you say more like polenta.

    For both my smooth mashed potatoes and purée I use a ricer. It makes an airier smooth mashed potato and less gluey purée. Also I cook my potatoes whole in their skins. Peeled and quartered potatoes take on water when they cook and make for a gluier consistency. After ricing, the difference between smooth mashed potatoes and potato purée is the amount of fat and cream (or stock or whatever)

  6. Matthew Kayahara March 8, 2011 at 10:26 am

    Interesting take on things, Skip. I guess I’d say that potato puree and smooth mashed potatoes are two points on a continuum, while chunky mashed potatoes are a different beast altogether. I had a lot of control over the consistency of these retrograded potatoes, so I could easily have made them thick enough to pipe… indeed, I may do just that next time! I’ve never used a ricer for potatoes (I don’t own one), but Steingarten argues that it’s even better than a food mill.

    And it is a long list of steps, isn’t it? To some extent, I think it reflects a mindset of restaurant preparation, because a lot of the steps can be completed in advance, making it faster and easier to finish the product for “service.” Of course, in a home kitchen, that doesn’t always make a lot of sense.

  7. I can buy your two points on a continuum for the smooth mashed and the puréed, especially coming from French cuisine. I would add a third point, and that would be puréed soups, potages. I’ve seen quite a few chefs argue over “that’s too thick to be a soup, I’d call it a purée, “versus “I really like my potages this thick!”

    You talked about graininess in your initial post. From my experience that can come from your choice of potato. Some varieties are just grainier and starchier than others. I didn’t recognize a couple of the varieties listed up above. Mostly available to me are Yukon Gold and Russets. Yukon Gold has less starch and graininess than the Russet. Different cooks like them for different purposes. And the cooks are at odds with each other.

    I do love my Yukons for baked and roasted potatoes. I love that creamy interior. But I find they are more easily gluey for mashed.

  8. Matthew Kayahara March 9, 2011 at 9:05 pm

    I heartily agree on thick potage-style soups being on the same continuum! I wonder if the starch retrogradation technique could be applied to those?

    And I agree on potato variety playing a role as well, but I had heard of others having success with Yukon Golds in their attempts with this technique, so that’s what I used. I generally try to use Russets for mash and fries, and Yukon Gold for other preparations. One point, though: I believe it’s the ratios of the two main types of starch, amylose and amylopectin, that distinguish different varieties of potatoes (and other starchy plants, such as rice), rather than the amount of starch. I need to read up more on the difference between these types of starch, because my understanding of them is pretty basic at the moment.

  9. What about oven cooked potatoes? You can cook them whole en papillote so they won’t dry up too much. In this way the potatoes absorb the flavor from their own peels and don’t get any excess water.
    Cons: you cannot infuse them with salt (like boiling them in salted water) and you cannot control the temperature with great precision.
    Definitely use a potato ricer instead of a stick blender(which destroys the cells) to mash the potatoes.

  10. Matthew Kayahara March 16, 2011 at 1:10 pm

    Good question, Isaia! I’ve cooked potatoes in the oven for gnocchi before, but never for mashed. And I’ve never cooked them en papillote. Sounds like it might be worth trying in terms of moisture content, but I imagine they’d still get hot enough for the starch granules to rupture. I always adjust the seasoning of my potato puree at the end, anyway, so that doesn’t bother me. And I agree, I’d never use a stick blender for potato puree!

  11. In this May-June Cook’s Illustrated they talk about mashed potatoes. The like the ricer and the food mill. The food mill potatoes will be less fluffy but more elegantly smooth. The riced potatoes will be fluffier but a little bit more grainy. Interesting to me. I don’t own a food mill.

  12. Matthew Kayahara April 16, 2011 at 12:33 pm

    Interesting, Skip. I don’t own a ricer, so I’ve never made mashed potatoes that way. When I did the retrograde mash the second time, I used a food processor, and they came out wicked smooth! I use my food mill for a variety of things, including tomato sauce and several types of jams. I bought it because I thought it would be more versatile than a ricer, but maybe I need a ricer, too…

  13. Matthew, I totally agree with with your experience that the puree where the starch has been retrograded does actually come out a bit coarser, grittier. It’s still “smooth” in the sense that all granules are separated and not clumped together, but it has a feeling of being less smooth on the tounge. I have tried this technique a number of times, and although I like it and can see the use for it – a perfectly cooked “normal” puree seems smoother to me. I imagined the grittiness was due to the swelling of the individual starch granules as opposed to them being split open by internal pressure.
    For now I keep my old technique; peeled, sliced potatoes sousvide, cooked in near boiling water, just to the exact moment of being done (not more!). Let the potatoes steam off for 1 minute before pressing through a fine sieve, working it as little as possible. Add butter.
    But potato quality makes up for 50% of the success – here in Italy it’s very hard to get consistent quality potatoes. Sometimes you get good ones, sometimes they’re crap – from the same farmer or vendor!

  14. Thanks, John, glad to hear I’m not the only one! I’ve definitely had better and worse versions of retrograde-starch mash, just like any other kind of mash. I think the hard part of making a great traditional mash is hitting the point of “perfectly” cooked, and working it enough to remove the lumps while not overworking it. Ingredient quality is also very important, for sure, and potato quality in Canada seems pretty hit-or-miss as well, especially for mash, but even more so for fries!

    When you cook your potatoes sous vide, how do you tell when they’re “just done”? What guidelines do you use?

  15. I actually cook them in a bag, in slices. I do not see where that would degrade quality since they’re alone in there, just wiht their own steam. And for the “doneness” simply crush one slice between my fingers and that way you feel instantly at what point they are.

  16. Agreed, cooking them in a bag in just their own moisture is a great way to make sure they don’t get waterlogged. Do you open the bag to check, or just crush them while still in the bag? I can’t imagine wanting to re-seal them if they weren’t done yet!

  17. 65 degrees for 2 hours
    Only potato in the bag, drain after any excess, don’t chill. Cook straight away. Blend in thermo mix with butter and cream.

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