What Thanksgiving Day is complete without potatoes? Boiled, mashed, roasted, and puréed, sweet or savory, rare will be the Thanksgiving feast that lacks one or more of these varieties. Like the turkey, also a New World endemic species, potatoes are certain to have made a vital contribution to the Pilgrims’ diet on their arrival to the New World.
With Irish ancestors of my own who arrived in Canada during the Potato Famine, this terrific tuber holds a special place in my heart, as well as my diet. The potato is more nutritious than it is often given credit. Still, extracting maximum flavor and nutrition from potatoes benefits from science – botanical science, biochemistry and the science of cooking alike.
(Natural) History
The potato was first domesticated about 8,000 years ago in the Andes of what is now Peru and Bolivia. It was unknown to all but the indigenous peoples of the Americas prior to the 1490s. In rather short order, the potato has since found its way into all countries, cuisines and diets. It is remarkable that so many words for potato have been invented in such a short time.
Most words for potato are variants on the Taino ‘batata’ and the Quechua ‘papa’: patata, potato, pataca, and potet. Others are variants of ‘earth-apple’ and ‘ground-pear’: pommes de terre, kartoffel, krompir, and תפוח אדמה (tapuakh adama). Even the Mandarin tǔdòu means ‘earth bean’.
The Hindi ‘aaloo’ is borrowed from an unrelated South Asian tuber, the elephant-foot yam. The Korean word for potato, however, is a case of mistaken identity. ‘Gamja’ originally meant the pork spine that goes into gamjatang soup. Later, potatoes acquired the moniker ‘gamja’ in light of their having long been a staple ingredient of that pork soup.
Evolutionarily speaking, sweet potatoes (Convolvulaceae, like morning glories) are not potatoes (Solanaceae, like tomatoes, eggplant and deadly nightshade) and they are certainly not yams (Dioscoreaceae).
This gets even more complex given that the New Zealand ‘yam’ (Oxalidaceae, like the star fruit) is neither a yam, nor a sweet potato. Where it comes from – again the Andes – the New Zealand ‘yam’ is called ‘uqa’. But ‘uqa is not yucca (Euphorbiaceae, like poinsettias). ‘Yucca’ is the Carib word for what the neigboring Taino called ‘cassava’, and what the Tupi called ‘tipioca’, but which was first called ‘manioc’ by the people who first figured out how to eat this tremendously toxic tuber in Brazil some 10,000 years ago.
Like the Chinese Mountain yam, Japan’s deep purple ‘ube’ is a true yam (Dioscoreaceae) originating in Oceania. On the other hand, the Japanese ‘purple yam’ is a not a yam, but rather a variety of the New World sweet potato – one with purple skin and white flesh that is not to be confused with the Okinawan sweet potato, which has white skin and purple flesh. None of which should be confused with the purple taro (Araceae, like the gigantic corpse flower).
Anatomy
Though obviously considered a starchy Thanksgiving dinner element, potatoes and sweet potatoes both bring much more to the table than empty calories. Potatoes have the edge on vitamin C. Sweet potatoes are a solid source of vitamin A. Both have twice as much fiber as pasta and plenty of vitamin B6.
Because they grow underground, tubers absorb vital minerals from the soil around them, especially iron, potassium, zinc, calcium, magnesium and copper. Those essential nutrients are concentrated in the outermost flesh. Alas, peeling potatoes can significantly reduce their nutritional content. It’s not just loss of the skin, but also loss of the cortex just under the skin that was closest to the dirt they were grown in.
There really isn’t any good reason to peel a potato. The skin is not toxic… unless it’s green. Then it’s got some solanine in it, but usually not enough to worry about. Only 3 people in all of human history are known to have perished from pea-green potatoes.
Even where the skin is not desired, as in mashed potatoes, there are easy ways to remove the skin without carving away and discarding that most nutritious flesh. Potatoes, sweet potatoes, carrots, parsnips or beets, pressured cooked over (not in) a half cup of water for as little as a minute will allow the skin to come off easily with a paper towel (like a par-boiled tomato), and without cooking the root vegetable all of the way through.
This pressure-steaming with quick-release, over (not in) water, is a terrific way to achieve various textures without leaching away precious nutrients into water boiling on a stove. Whole potatoes, pressure-steamed for at least 15 minutes, skin stripped off and allowed to cool, are perfect for mashing. Do them (beets too) for only 10 minutes, let them cool, and they are primed to be cut up for a second-cook by roasting, pan-searing, or French-frying.
Cut the times in half for sweet potatoes. They cook faster given their higher water content (a great heat conductor). Just like a steak, letting potatoes rest outside of the pressure cooker before cutting allows carry-over heat to even out the internal cook. You can also limit this to good effect: carrots pressure cooked for 1 minute and removed immediately to cold water will be succulent and yet will still have some “tooth” to them.
Even if you don’t have a pressure cooker, boiling potatoes whole, without cutting them up or peeling them, limits the loss of nutrients to the surrounding water. As long as spud’s skin is intact, even something as simple as table salt cannot penetrate.
Try it yourself by making Syracuse Salt Potatoes: boil whole skin-on 2” to 3” waxy potatoes in saturated salt water (add all the salt that will dissolve). Set them aside to dry and watch the salt crystals appear like a dusting of frost. The flesh will be unsalted, so the balance is perfect.
Mashed
Unless you are hanging wallpaper, never subject a potato to a blender. Starches are sugar polymers. For fluffy soft mashed potatoes you want those starch polymers to stay randomly associated with each other (like lamb’s wool).
Shearing a potato causes the amylopectin polymer molecules to line up in the same direction as the shear force, bringing them into very close proximity (like a skein of yarn). That closer proximity promotes intermolecular associations between adjacent polymer chains, resulting in a tight gluey gel.
If, like me, you think mashed potatoes should have texture, just use a hand-held potato masher. For something finer, break down your cooked potatoes by pressing them through a potato ricer or a food mill. If you hadn’t already stripped off the skin, this alone will separate the periderm without losing the nutritious layers. Then, fold in as much melted butter, hot cream and salt as you like. Like a roux, getting the butter distributed before hydrating with milk or cream will inhibit the formation of a gummy gel.
For restaurant-level “pommes purée” (which oddly translates to “apple purée,” but isn’t), scrape the riced potatoes through a fine-mesh sieve or tami and make the ratios of potato:butter:heavy-cream about 6:3:1. Fold in the butter and cream in that order. But beware: vigorously whisking sill risks lining up the starch polymers into a glue.
Mashed potatoes don’t need much more seasoning than salt. However, in my opinion, mashed potatoes are what mace was made for. Ground mace put right in or dusted over steaming mashed potatoes is wonderfully redolent. An unusual spice, mace is the dried aril removed from around each nutmeg seed.
Like cloves (Syzygium aromaticum), the nutmeg plant (Myristica fragrans) is native solely to the Moluccas of Indonesia – the Spice Islands. Savor the addition of mace or nutmeg to your mashed potatoes knowing that Magellan’s 1519-1522 circumnavigation of the globe was considered a success because he returned with 50 tons of cloves, nutmeg and mace, despite losing 232 of his 250 sailors!
Roasted
The key to a roasted potato is a crispy outer layer and a moist starchy interior. High heat breaks down the amylopectin starch polymer into its sugar monomers. Like starches made of sugars, proteins are polymers of amino acids. The high heat breaks both down. Free sugars taste sweet and the free amino acid glutamate is umami.
But there’s another wonderful thing that happens when you have starches and proteins co-mingling above 300 F. What makes them distinctively delicious is the Maillard Reaction. The amino acids and sugars rearrange themselves into aromatic ring shapes. Because the ring structures reflect light, food takes on a brown color, and those aromatic compounds impart savory aromas.
But boiling cut-up potatoes before roasting them saturates the outer layers with water and inhibits the Maillard reaction. As long as the outside of a potato is wet, it cannot get above the boiling temperature of water (212 F). In fact, any water evaporating off of the surface actually cools the potato the same way that sweating on a hot day keeps your body cool (and why that doesn’t work when it’s humid out).
To quickly roast potatoes from raw, first cut them into 3/4-inch chunks or smaller. This will make for a fully cooked interior without a scorched exterior if roasting or air-frying at 400 F for 20 minutes. This is also the right strategy for air-fryer French fries.
If the pieces are too big, the time it will take to cook the interior may be long enough to push past the Maillard reaction and into bitter scorched carbonization. But the reaction doesn’t need a scorching 400 F. If you have the time for it, 325 F for 50 min is optimal using larger chunks.
For larger roasted potato chunks (> 2” across), first pressure-steam or boil the potatoes skin-on as described above. If you half-cook them this way, and then remove the skin (or not) and cut them up, 45 minutes at 325 F should create the right external crispiness and internal doneness.
Fully pressure-steaming or boiling skin-on potatoes for roasting is fool-proof because there is no risk of a raw interior. This approach will benefit from a trick that accelerates the Maillard reaction at a higher pH. Dissolve a teaspoon of baking soda (not baking powder) in a quart of water to make an alkaline pH.
Not only does the higher pH promote the Maillard reaction, it also causes cellulose in plant matter to break down faster. This will make for extra-delicious crispy edges on your roasted potatoes.
With still-hot skin-on fully-cooked pressure-steamed or boiled potatoes, strip off the skin (or don’t) and cut them into big 2.5-inch chunks, then drop them into the alkaline water for 5 seconds while they are still hot. Immediately remove them to a baking rack and let the carry-over heat drive moisture off the surface. Incidentally, a very high alkaline water dunk (using slaked lime or lye) is how you get a bagel exterior to perfection with a moist interior.
If you trust your fine-dusting abilities, you can skip the alkaline water dunk and just finely dust the cut-up potatoes every-so-slightly with baking soda (from 2 feet above) as they cool on the baking rack. At this point you can safely just roast them at 325 F until they look right to the eye.
What about oil? In a pan, oil helps to conduct the heat of a flat pan to the uneven surfaces of the food in the pan. This is irrelevant in an oven or an air fryer where the food is surrounded by the right temperature. What oil will do is trap moisture in your food. This is a good thing in order to avoid an over-dry interior, but don’t do it right away.
Hit the roasting spuds with cooking spray after 5 minutes in the hot oven. This will give the exposed surfaces time to dry out past the steam point and get up above 300 F for the Maillard reaction to start.
Boiled
Of course, you can cook peeled and cut up potatoes in boiling water as long as you understand that doing so is going to leach out a lot of nutrition. Less will be lost if you steam them above, not in, boiling water. Either way you can take advantage of different pH levels. Add 1/8 to 1/4 tsp of baking soda if you want fluffy outer layers. Or add a splash of vinegar if you want the outsides to remain firm. When you stick a paring knife in them vertically and cannot outcompete the force of gravity when you try to lift them straight up, they are done.
Casseroles and Chowders
The French word ‘casserole’ originally referred to the deeper cooking vessel, distinguishing it from a shallow pan (‘casse’). Post-war mid-20th Century marked the height of popularity for casserole dishes in America. Today the baby-boomers’ nostalgia for these dishes of their childhood has brought casseroles back to the table. And let’s face it, they are perfect for family-style and pot-luck Thanksgiving meals – especially when you want to go back for seconds and thirds.
There’s also a clear nutritional advantage to a potato casserole or a chowder. Even though essential nutrients are leached out of potatoes cooked in liquid, those minerals remain in the wet parts of the final dish: the delicious cream, butter, stock or gravy. One can even improve the nutritional content of a potato in a casserole by adding other things to it (see Bubble and Squeak or Jansson’s Temptation below).
The variations on casseroles and chowders are too many for this post. I will simply name my favorites, all of which include cream and butter, of course, except for the tagine.
- s/mashed potatoes with leeks and cabbage (colcannon, bubble and squeak),
- julienned or paysanne potatoes with anchovies (Jansson’s Temptation)
- scalloped potatoes with oysters
- grated potatoes and grated cheese (Potatoes Romanoff)
- with chickpeas, green olives, preserved lemons, ras el hanout, and saffron (Potato Tagine)
- chowder with clams (New England)
- chowder with fish, cockles, sea snails and saffron (British Seaside)
- chowder with corn kernels stripped off the cob, and a pressure-cooked stock made from the corn cobs
Do not put potatoes in gumbo. In Louisiana, that’s what potato salad is for.
