Potatoes

Potatoes © Denzil Green

Potatoes are the enlarged underground stems (aka “tubers”) of the potato plant, in which the plant stores up nutrition for future growth. Consequently, they are classed as a root vegetable.

Potatoes require cooking in some form before eating. Typical cooking methods including boiling, baking, frying and roasting.

Most potatoes sold now have white or yellowish-white flesh inside them, with brown or red skin on the outside. The skin is edible.

In North America, potatoes for the most part are sold by generic classifications rather than variety — classifications such as “table potatoes”, round whites, round reds, long whites, and russets. ^[1]In some American states such as Idaho, vendors are required to list the actual potato variety on the bag. That categorization is very unhelpful to cooks, as hundreds of very differently-behaving varieties can be called “table potatoes.” If the industry wants to market potatoes generically, there is another way to group potatoes which is far more useful: Waxy, Floury, and All-Purpose, plus two special categories, New Potatoes and Salad Potatoes.

When buying potatoes, try to buy according to what you plan to do with them. If there are any “eyes” on the potato, they should be extremely small and not very many of them. Avoid any with black or green spots, and any with skin that is starting to shrivel.

Growing issues

The pathogen that caused the Irish Potato Famine (see history notes) is called Phytophthora infestans (meaning ‘plant destroyer’); it is still with us. It is a significant threat world-wide to growing potatoes. It is a member of the protocista: entities which are not animal, plant or fungus.

Resistant potatoes were developed in 2009, but as of 2020 are grown only in the U.S. and Canada:

“In 2009 scientists from the Sainsbury Laboratory in Norwich, UK, published some groundbreaking research. They placed the R-gene with resistance to Phytophthora infestans into commercially-grown potatoes. These potato plants were successfully modified to resist late potato blight. The R-gene was taken from a wild relative (Solanum venturii) of the commercial potato plant (Solanum tuberosum ‘Desiree’), which was resistant to late potato blight.

The blight-resistant potatoes have been developed by a US-based company under the name ‘Innate Generation 2’ and are available for farmers to grow, harvest and sell. At present they are only available in the US and Canada, where national agencies have approved them.” ^[2]University of Cambridge. Plant biotechnology for pathogen control. Module 1.6, Improving Food Production with Agricultural Technology and Plant Biotechnology. Future Learn. Accessed August 2020 at https://www.futurelearn.com/courses/food-production-agricultural-technology-plant-biotechnology/3/steps/715043

Waxy / Boiling / Low-starch Potatoes

The cells in this type of potato stay together when cooked. This mean that chunks and slices will stay together, making them ideal for salads and layered potato dishes such as scallops. You can slice or cut them after boiling and the slices won’t disintegrate on you. However, waxy potatoes make gluey, heavy, unappealing mashed potato.

13-15% starch

Examples: Cara, Charlotte, New Potatoes, Fingerlings, round white and round red ones.

Floury / Mealy / Baking / High-starch Potatoes

Floury potatoes are the best potatoes for baking and mashing. Their cells separate when cooked, which makes for flaky baked potatoes, good mash and great chips (as in French Fries.) The potatoes will, however, fall apart, when you boil them and attempt to slice them. Floury potatoes make disappointing potato salads for this reason.

20-22% starch.

Examples: Maris Piper, King Edward, Russets

All-Purpose Potatoes

There is yet another type of potato: the general, all-purpose medium-starch potato. The idea is that they’re “acceptable” as either a boiled or mashed potato — though really, it’s luck of the draw as to just exactly how well they will perform in a potato salad or as a mashed potato.

15-17% starch.

Examples: Long Whites, which are long with a pale brown skin. Desiree, Wilja and Estima

Salad Potatoes (Fingerling Potatoes)

These are small, waxy potatoes that are the right size for salads or for steamed, bite-sized morsels on the side of your plate. They won’t grow any bigger than the sizes that you see in the store — that’s their full size. You don’t need to peel them. They are waxy potatoes, so they stay together well when sliced or cut after cooking. These are very popular in the UK, but are now starting to make headway in North America, where they are being called “fingerlings.” They are also good for roasting. These potatoes also taste great when served chilled or room temperature (after cooking first.) New Potatoes can be substituted for Salad Potatoes.

Examples: Anya, Charlotte, Nicola, Ratte, Pink Fir Apple, Belle de Fontenay

How to tell a waxy potato from a floury potato

The way to tell whether the potatoes you have just bought are waxy or flour is to mix 2 tbsps of salt in 350 ml (1 ½ cups / 12 oz) of water in a stout jug or bowl. Then put the potato in, and watch what happens: if it sinks, it is a floury potato, if it floats, it is a waxy potato.

Granted, it’s difficult to know how this knowledge is going help after you’ve already bought a bag of “table potatoes” and dinner hour is approaching. It does, though, at least, let you make an informed decision as to whether to serve them as mash, or as boiled potatoes with a little parsley and butter.

Cooking Tips

Scrub potatoes, and remove any eyes or buds. Trim away any light green tinged areas. Discard the potato if more than that of it is green.

Whether to peel or not to peel depends both upon what you are going to be making with your potatoes, and your personal preferences.

Never leave peeled potatoes to sit out exposed to the air. They won’t be bad to eat or anything, but no one will want to — they can go a very off-putting brownish black colour. What is happening is that they are oxidizing owing to exposure to the air. To keep peeled potatoes fresh and white, keep them covered with water. Some recommend as well adding a bit of lemon juice to the water.

Potatoes sometimes go greyish when cooked. This can be owing to the iron content in the potato, and that is dependent on the iron content in the soil they were grown in. It’s the iron interacting with other compounds in the potato. Adding a little lemon juice or vinegar to the cooking water will prevent this — but admittedly it can be hard to know that doing that is necessary until after it has happened. Their going greyish after cooking can also be owing to the potatoes, at some stage, having been stored at too cold a temperature. This converts the starch in them to sugar, which then “carmelizes” when it’s cooked. And there isn’t much you can do about it.

When you boil potatoes, the reason you start them in cold water rather than in already boiling water is that with already boiling water, the outside of the potatoes would get cooked before the insides had started to really even heat up. Starting with cold water gives time for the increasing heat to reach and cook the inside of the potato so that the potato cooks more evenly.

The most sure-fire way to tell if a potato that you are boiling is cooked is to stick a knife in it, and raise the knife out of the water, keeping the knife pointed straight down. If the potato slips off easily while you are doing this, it is done.

If you have a few spoonfuls of mashed potato in the fridge and are making a soup, especially one that has to be puréed in the blender anyway, consider stirring the leftover mashed into the soup before you purée it. If this sounds odd, remember that mashed potato often contains, milk, butter and potato, and consider that puréed potato is used to make “Vicchychoise” or Cream of Potato soup, and that you would often put milk and butter in a creamed soup, anyway. The mashed potato can make a wonderful thickener that cuts down on the amount of fat in the form of cream or milk you have to add to the soup. You can also use instant mashed potato flakes to accomplish the same thing.

Crispy Skins on baked potatoes: After scrubbing the potatoes, dry them well with a cloth. Prick with a fork in several places to prevent the skins splitting. For added flavour, rub olive oil and a little salt onto the skins. If you’re going to use a sea salt, use a flat sea salt such as Maldon; more chunky seal salt will just fall off. Don’t wrap baked potatoes in tin foil. It steams them rather than baking them, they won’t taste quite as good, and why use tin foil when you don’t have to?

Note: if you are baking the potatoes in an oven (as opposed to barbequing), bake them on a cookie sheet so that the oil doesn’t drip on the bottom of the oven.

When cooking salad potatoes, they are done if you stick a knife in them and they slip off the knife easily when you lift it (keeping the knife vertical).

If you have potatoes break apart on you when you are cooking them, chances are they are floury potatoes, and you have overcooked them. Next time you boil some from that bag of potatoes, try minding them more closely and give them a bit less cooking time. You could also not peel them first, which is fine if you are planning to serve them with skins on, but otherwise it’s always really nerve-wracking when the rest of the meal is ready, just waiting on the potatoes, and you are trying to peel potatoes that are so hot they are burning your fingers.

Substitutes

Any other kind of starchy vegetable, depending on whether you are using it as a side dish or in a dish.

Nutrition

Though a potato can be turned into less healthy food such as French Fries or potato chips, on its own, it is not an empty junk food. A potato has the same amount of calories as an apple of the same size does. It’s high in Vitamin C (Spanish explorers used them to fend off scurvy), and has proteins, potassium and thiamin. The vitamin C in potatoes is just below the skin, which is why wartime government nutrition leaflets encouraged people to eat potatoes with their skins on as much as possible.

It’s how we process them (as in deep frying) or what we ladle onto them (mountains of full-fat sour cream onto a baked potato) that can cause them to be perceived as fattening and unhealthy.

The berries produced by a potato plant betray the plant’s membership in the nightshade family: the berries are toxic and must never be consumed by any human or animal.

Green and sprouted potatoes

When exposed to light, a potato springs to life and starts growing, turning green and sprouting spouts, as nature intended it to. In the process, though, the potato produces glycoalkaloid that is not destroyed by cooking and that could make you sick in sufficient quantity.

Different cultivars may be more prone to this than others.

While the green colour is not a specific market for glycoalkaloids per se, in potatoes the colour has been associated with areas of the potato of elevated glycoalkaloid levels (in addition to the sprouts). ^[3]Schaffner, Don. Risks posed by potatoes at the end of the shelf life. Safety risk assistance for private company. August 2021. Available upon request from author.

The sprouts and areas directly under them have the highest glycoalkaloid levels, so you definitely do not want to consume them.

When peeling potatoes, trim out and discard any sprouts and buds. You can cut out any very small green patches that might have formed, but if the potato is a lot more green than that, discard it. If you are making a vegetable broth from peelings, don’t use any potato buds, sprouts or green peels in it.

“Old potatoes can be consumed if sprouts, green colored portions, skin, and
peels including the area under the skin are discarded. Old potatoes which have been cooked, but which taste bitter should not be consumed.” ^[4]Schaffner, Don. Risks posed by potatoes at the end of the shelf life. Safety risk assistance for private company. August 2021. Available upon request from author.

Two potato cultivars with naturally high glycoalkaloid levels which were consequently withdrawn from the market were Lenape potatoes and Magnum Bonum potatoes.

When a potato has a greenish hue, it is called “light struck”.

Safety with potatoes in foil

If you’ve baked potatoes in foil, never leave them out wrapped in foil for long afterwards. The reason is that temperatures reached inside potatoes during baking are not high enough to kill any C. botulinum spores that might be present in the potato. After baking, tightly sealed foil wrapping plus the cooling temperature inside the potato create both the temperature range and the anerobic environment that C. botulinum spores need to germinate, releasing their deadly toxin.

Botulism cases have been documented.

Consequently, the recommendation is to remove the foil after baking, even if you plan to refrigerate them.

Equivalents

Weight Watchers® defines potato sizes like this:

large – 299 g / 10.5 oz;
medium – 173 g / 6.1 oz;
small – 138 g / 4.7 oz.

1 medium-sized potato = 150 g / 5 oz ^[5]University of Idaho Extension. CIS 1153.
1 medium-sized potato = ½ cup mashed = ⅓ cup instant potato flakes = 1 cup peeled and sliced = 1 cup shredded potato
3 – 4 medium potatoes = 500 g (1 lb) = 4 cups diced = 3 ½ cups diced cooked = 1 ¾ cups mashed = 2 cups French fries
6 – 7 medium potatoes = 2 ½ pounds (unpeeled)
1 kg (2.2 lb) potatoes, unpeeled = 750 g (1.6 pounds), peeled = 475 g (17 oz) roasted
1 pound new potatoes = 9 – 12 small new potatoes
1 pound (450 g) potato = 3 cups, shredded
1 bushel potatoes = 60 pounds / 27.2 kg
2 pounds potatoes = 6 servings potato salad

Storage Hints

Light and warmth encourage potatoes to go green and to sprout. You need to store them in a dark, cool place. Ideally, the temperature should be between 45 F to 50 F (7 C to 10 C.)

This is a little trickier to do if you don’t have a basement, and even for those who have basements, can be tricky to do if the basement is warm, as most are these days. Don’t think, however, that you’ve had a flash of inspiration in keeping them in the fridge: others have tried that, and it doesn’t work. Refrigeration causes the starch in potatoes to turn into sugar, giving them a weird texture and even weirder taste. New Potatoes, however, because they are meant to be a bit sweeter, can be stored in the fridge.

Some people maintain that potatoes stored in with onions causes the potatoes to go bad more quickly. Some maintain that putting an apple in with your stored potatoes will cause they to last longer and take longer to start to bud.

Don’t leave potatoes in any plastic bag they might have come in; the plastic will trap moisture and cause the potatoes to go mouldy. Some will say a brown paper bag is ideal for storing potatoes.

Freezing: Wash, peel. Chop into ½ inch (1 cm) cubes. Blanch for 5 minutes. Plunge in cold water, drain, package, and freeze. Don’t attempt to freeze completely raw potato. It will just turn black on you. Don’t thaw frozen potatoes — use them straight from freezer in whatever you are making.

In practice, most potato is frozen cooked or as a dish. When freezing mashed potatoes, allow about ½ inch (1 cm) of headspace in your container as they will expand when frozen.

History Notes

White potatoes are native to the Andes mountain range in Peru and Bolivia. The Incas grew them as long ago as 2000 BC, especially in mountainous areas where corn cannot grow. It was a staple food for them. They often preserved potatoes by drying them. They would grind the dried potatoes to make flour, or rehydrate them in soups.

Spanish explorers recorded mention of potatoes in 1553 in Quito, and brought some back to Spain, where they were planted as curiosities. Sir Walter Raleigh acquired some, probably from a Spanish ship he’d plundered. He planted them on his lands in Ireland at Youghall, near Cork and in Virginia in the late 1500s. During the 1600s, many other settlers in America planted potatoes, but interest in the crop didn’t really take off until Irish Presbyterian immigrants planted potatoes in Londonderry, New Hampshire in 1719. So even though it’s a New World vegetable, potatoes in North America came via Europe, not directly from South America.

Potatoes were introduced into Germany via Belgium in the 1620s. Frederick the Great ordered his people to grow and eat them — but because people thought they were poison, he had to threaten to cut their noses and ears off if they refused. In France, there was similar resistance to the potato. A man named Parmentier had worked out a strategy. He had Louis XVI serve potatoes at court in 1780, and made sure word got around. Then, he had a light guard placed around a potato patch, telling the guard to pretend not to see people stealing from the patch. People figured if the stuff growing there was good enough to guard, it was good enough to steal and eat, and they did. Parmentier also cooked them for Marie Antoinette and Benjamin Franklin.

But an additional reason for potatoes’ lack of earlier popularity was because there were no recipes for them. People had heard that potatoes were a more reliable starch food than wheat — and so tried to use them to make bread with potato flour instead of wheat. Parmentier along with several Italians devised and popularized potato recipes.

The first place in England where potatoes were grown outside an experimental patch was in Lancashire, as a curious delicacy. They were introduced into Scotland in 1725.

The Irish Potato Famine, 1846 – 1850 was so hard hitting because the Irish had become utterly dependent on the potato. Potato crops didn’t just fail in Ireland during those years — they failed all throughout Europe. But no country had become as dependent upon the potato as Ireland. Potatoes provided 80% of people’s daily calories (the Irish peasants ate an average of 10 potatoes a day each!), and provided all the food for their livestock. Three years in a row of heavy rains and potato fungus destroyed the crop out from under them. They had nothing to feed their animals, and nothing to feed themselves. More than a million people died; nearly 2 million emigrated.

Most potato varieties developed in the United States in the 20th century were developed by public institutions, and were considered to be in the public domain. Very few were developed by private companies. In Europe, the trend since the 1970s is for potato variety development to be done by private breeding companies. These receive plant variety protection. American plant variety protection laws excluded potatoes until 1995, so the new European varieties didn’t start making it to America until after then.

Literature & Lore

The name “potato” comes from a Caribbean name for Sweet Potato, which could be pronounced either “batata” or “patata”.

A popular urban food myth is that the colloquial name for potato, “spud”, comes from a group that called themselves Society for the Prevention of Unwholesome Diet (SPUD), who tried to warn people off eating potatoes. Like all urban myths, very easy to swallow, but alas, too easy to be true: the word in the mid 1400s was used for a short knife, and then in the 1500s became used for various digging tools. By the mid 1800s, the word had transferred itself again, from the implement used to dig up potatoes, to potatoes themselves.

The French first applied the name “pomme de terre” to Jerusalem Artichokes, and then later transferred the name to potatoes. Brillat-Savarin, the French food writer, didn’t like potatoes, whatever they were called. He saw them as only of interest to those who had nothing else to eat: “To my mind, the only value of potatoes is as a safeguard against starvation; apart from that, I know of nothing more insipid.”

Sources

British Food Standards Agency. Survey To Investigate The Varietal Labelling of Potatoes – Part 2. December 2003. Retrieved April 2005 from http://www.food.gov.uk/multimedia/pdfs/fsis4503full.pdf.

Scottish Agricultural Science Agency. European Cultivated Potato Database. 2001. Accessed from 2005 onwards at http://www.europotato.org/menu.php

Options for storing potatoes at home. University of Idaho Extension. CIS 1153. March 2009. Page 1.

Related entries

References[+]

References
↑1	In some American states such as Idaho, vendors are required to list the actual potato variety on the bag.
↑2	University of Cambridge. Plant biotechnology for pathogen control. Module 1.6, Improving Food Production with Agricultural Technology and Plant Biotechnology. Future Learn. Accessed August 2020 at https://www.futurelearn.com/courses/food-production-agricultural-technology-plant-biotechnology/3/steps/715043
↑3	Schaffner, Don. Risks posed by potatoes at the end of the shelf life. Safety risk assistance for private company. August 2021. Available upon request from author.
↑4	Schaffner, Don. Risks posed by potatoes at the end of the shelf life. Safety risk assistance for private company. August 2021. Available upon request from author.
↑5	University of Idaho Extension. CIS 1153.