From the blog April 29, 2013 Scott

Mastering creamy pureed potatoes, no fat required

When made just right, mashed potatoes are the ultimate comfort food: smooth, creamy, warm and filling — not to mention a perfect vehicle for gravy.

But how to get them perfectly smooth and creamy? Too often ridding mashed potatoes of those pesky lumps forces you to overwork the spuds into a gummy, grainy mess. Or you end up adding so much cream and butter that the dairy drowns out the flavor of the potatoes.

If you like your mashed potatoes fluffy, the answer is fairly straightforward. Choose a floury variety of potato, such as Maris Piper or russet, pass the peeled, boiled potatoes through a ricer, then mix in just enough butter and milk or cream to moisten.

But if you’re after a silkier texture — more like what the French call pommes puree — stick with waxy potatoes, such as Yukon gold or fingerlings. You also should try a modernist technique pioneered by food writer Jeffrey Steingarten and refined by the British chef Heston Blumenthal. It adds a step, but it is well worth it.

Steingarten discovered that gently heating the potatoes for a half hour or so in warm water before they are boiled profoundly improves the result. This is because as the potatoes soak in water at about 160 F (70 C), the starch in them gelatinizes, producing a smoother puree on the tongue. The granules that contain the starch also firm up, making it harder to rupture them during mashing.

Recently our research chefs perfected yet another modernist method that yields an amazingly smooth and slightly sweet potato puree, and all without adding any butter, milk or cream. The secret is to deploy a little trick of biochemistry that converts the starch in the potatoes into sugar.

The key to this culinary alchemy is an enzyme known as diastase. Don’t let the fancy name put you off; this ingredient is quite natural (it is derived from malted grain), and you can buy it online or at stores that sell brewing and baking ingredients. The enzyme typically is sold in in a ready-to-use form called diastatic malt powder.

Like other enzymes, diastase is a protein whose complex molecular shape allows it to accelerate chemical transformations with amazing speed and specificity. When you eat a starchy food like bread or potatoes, enzymes in your gut help break down the starch into simpler carbohydrates (such as sugars) that your body can burn or store for energy. By adding diastase to our mashed potatoes, we’re simply getting a jump on the process.

The trickiest part about using diastatic malt powder is measuring the right amount. It’s potent stuff, so you really should measure ingredients by weight. After you have peeled and cubed the potatoes, weigh them. For every 100 grams of potatoes, measure out 1 gram of diastatic malt powder. So 1,100 grams of peeled, cubed potatoes calls for 11 grams of malt powder.

Now fill a pot with water and add 2 grams of sugar and 3 grams of salt for every 100 milliliters of water. Simmer the potato cubes until they are tender, 30 to 40 minutes, then drain. Stir the diastatic malt powder into the potatoes, then pass the mixture through a ricer.

The riced potatoes next get sealed in a zip-close plastic bag, which is set in a pot of hot tap water (about 125 F) for a half hour. The warmth activates the enzyme and starts it gobbling up the potato starch. When the 30 minutes is up, empty the bag into a pot, then heat the puree to at least 167 F (75 C) to halt the enzymatic activity.

That’s it. Even with no butter or cream, the result is sweet and amazingly smooth. If you are avoiding dairy or limiting your intake of fats, this technique may just renew your love affair with the potato.

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Click here for our Dairy-Free Potato Puree recipe made with diastatic malt powder.

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Photo credit: Nathan Myhrvold / Modernist Cuisine, LLC.

Discussion

  1. Josh May 2, 2013 Reply

    Does this work for sweet potatoes as well? They’re especially hard to get smooth. Does the malt and temp measurements change?

    • Larissa Zhou May 6, 2013 Reply

      Josh – We’ve done a lot of tests of Okinawan sweet potatoes, and the results are great. The key lies in being super diligent about the mashing process.

      Research suggests that sweet potatoes are already very high in diastase. Slowly heating the potatoes in water to ~70 °C for 10-20 minutes will increase enzymatic activity enough to digest almost all carbohydrates into sugars. The same scientists measured the diastatic power of sweet potato enzymes to be much higher than that of malt used for brewing. (Here’s a link to a pdf).

      Thus, the step suggested by Heston Blumenthal and Steingarten for gelatinizing starch also works to simultaneously activate diastase naturally found in sweet potatoes to break down the sugars.

      Remember that diastatic malt will only make the puree sweeter. Lumpiness is mostly due to the interactions between starch, liquid, and fat and the method of mashing. For maximum smoothness, we process cooked potatoes in a food mill and then forcefully push them through a tamis (very fine drum sieve).

      • Josh May 7, 2013 Reply

        Thanks for the reply Larissa, not only will I have the technical knowledge to make great food but also the understanding why that works. You’re awesome!

  2. Rich May 6, 2013 Reply

    Does it specifically have to be a ricer? Does it work the same if you pass your taters through a sieve? And while I’m here, which gives superior results? Thanks!

    • Larissa Zhou May 6, 2013 Reply

      Rich – Sieves work too, depending on the mesh size. I mentioned in the above reply to Josh that we’ve achieved our highest smoothness via double processing, first in a food mill and then through a very fine tamis. Use some muscle to force the puree through the tamis, instead of gently scraping the mixture across the screen.

      • Josh May 7, 2013 Reply

        Any food mill you recommend?

        • Larissa Zhou May 8, 2013 Reply

          Definitely go for a heavy-duty stainless steel ricer. Beyond that, price points vary widely. The less expensive models, as long as they are steel and heavy-duty, should still last you through occasional potato mashing on a home cooking scale.

  3. Sarah May 31, 2013 Reply

    We tend to substitute creamed cauliflower for mashed potato. Any chance the same technique would work?

  4. Cathy June 11, 2013 Reply

    When will people realise that fat isn’t your enemy, refined or highly digestible carbohydrates are what cause weight gain!

  5. ph July 7, 2015 Reply

    Really wanted to like these but they are way too sweet! Maybe I have an extra energetic batch of diastatic malt powder.

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