Toxic Taters: Practical Lessons From Traditional Potato Processing

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Just like most American kids growing up in the 1970s and 1980s, potatoes were a regu­lar part of my life. One of my favorite ways to eat potatoes was baked with plenty of butter, salt and pepper. I would devour the starchy, salty, buttery flesh and, if I ate fast enough, the hollowed-out skins were still warm enough to melt yet another huge pat of butter that I would fold up like a package and devour with golden melted butter dripping down my smiling face.

Of course, like everyone else my age at the time, I also loved potato skins at TGI Fridays, French fries at Friendly’s and potato chips at parties. Mashed potatoes were one of my fa­vorite parts of the Thanksgiving dinner, and pierogies filled with potatoes were a special treat in my house. One of my fondest potato-related memories as a kid was when my mother entered a tuna fish recipe contest and developed super-cute “tuna boats.” Her creations were made from half of a baked potato; she removed its center and replaced it with a mixture of tuna fish salad, mashed potatoes and cream of mushroom soup finished off with a cheddar cheese “sail” secured with a toothpick “mast.”

Potatoes were even a part of my curricu­lum in high school history class. I learned how early European explorers who arrived in South America encountered indigenous cultures that had between three and five hundred different varieties of potatoes under domestication.

Though I loved eating potatoes, I always felt guilty about the butter I added or the cheese I melted on top. I never would have guessed that the real danger was found in the potato itself.

POTATO TOXINS

Wild potatoes and many ancient heirloom varieties contain high levels of toxins such as glycoalkaloids.¹ Even low doses of glycoalka­loids can result in abdominal pain, diarrhea and bloating, while high doses can result in paralysis and death. Although it is true that selective pressure reduced the glycoalkaloids in the potato over time, they were not eliminated,² and even the modern varieties in our grocery stores continue to contain toxins. That’s why some people have adverse reactions to eating potatoes, and why some diet gurus advocate completely removing potatoes from our diet.

However, this sort of extremism flies in the face of thousands of years of human evolution and food-processing technologies. Instead of removing entire categories of food from our diet—whether potatoes, meat, plants or dairy— we should rethink our approach to foods like this by connecting with the methods still used in traditional societies. We can learn a lot from traditional and ancestral approaches to food preparation—and this is especially the case when it comes to plants, because to optimize the safety and bioavailability of plants, they must first be processed.

THREE TRADITIONAL METHODS

Traditional societies that have coexisted with plants for thousands of years have tre­mendous insights into the best practices for including those plants in the human diet. This is exactly why I flew to South America—traveling through four different countries and enduring a terrible bout of altitude sickness—to live, prepare food and share meals with two indig­enous groups: the Aymara Indians of Bolivia and the Quechua Indians in Peru. I purpose­fully planted myself smack dab in the middle of where archaeologists believe the potato was first domesticated, somewhere between eight and ten thousand years ago, because I figured that the people who had spent the most time with this plant probably had the best chance of understanding the safest and most nourishing ways to include it in their diet.

My primary objective for this research was to learn everything I possibly could about three traditional potato detoxification strate­gies, including the practical aspects of how to process the potatoes and also how the strategies fit within the groups’ larger cultural systems. Initially, the flavors, textures and aromas of the dishes prepared from these potatoes were strong and unfamiliar to me. However, prepar­ing and consuming them alongside the people who relished these foods was simply beautiful and nourishing in so many ways. In addition to learning about potatoes, I learned how to make charque (the original jerky), how to prepare guinea pig using a complete nose-to-tail ap­proach (we ate practically EVERY part!), how to detoxify and prepare amaranth and quinoa and even how to make a traditional regional cheese.

What follow are brief descriptions of the three different potato processing strategies (p’asa, chuño and tocosh) that I observed.

P’asa is the practice of dipping cooked po­tatoes in clay before each bite during consump­tion. This is a form of geophagy, or intentional consumption of earth. The clay binds with the potato toxins into a form that is unrecognizable to the digestive system and passes through the body.³

Chuño is made by leaching potatoes in rivers for months, freezing them overnight and then removing the skins by stomping on them with bare feet, and finally freeze-drying them using the unique climate of the Altiplano⁴—a low atmospheric pressure, the cyclical nature of freezing temperatures at night followed by di­rect sunlight that induces minimal thawing, and wind to support moisture evaporation. These factors all allow the water to move directly from a solid state to a gas state (sublimation). Chuño is very valuable because it is storable and easy to transport.

The tocosh method involves fermentation of potatoes in in-ground pits filled with a mas­sive amount of potatoes submerged in water. Whole potatoes are fermented in this anaerobic environment for anywhere from six months to two years. When they are exhumed from the ground, they are peeled and used as the basis of traditional dishes such as mazamorra.⁵ Tocosh is valued for its many medicinal uses, including penicillin, which is produced during fermentation.

BEST PRACTICES

My observations of the three traditional practices, combined with additional academic research and years of experimentation, solidified my current approach to potatoes. I believe that in moderation, potatoes can be part of a nourishing human diet, provided a few basic rules are followed.

First, it is imperative to recognize that all potatoes are toxic. Proper handling, storage and processing are essential for minimizing the toxins in potatoes. Glycoalkaloids continue to increase during the handling and storage of potatoes, but they can be decreased through proper pro­cessing. It should be noted that potatoes create the toxins as protective mechanisms; this means that mishandling actually causes accumulation of higher levels of toxins where the potatoes have been bruised, cut or otherwise damaged. Always remove and discard damaged areas of po­tatoes before using.

Second, understand that storage conditions can have a profound effect on the levels of toxins in potatoes. Potatoes should be stored in the dark at between 41° and 46° Fahrenheit. If potatoes are stored with access to light, two independent reactions occur. One reaction produces chloro­phyll, resulting in a greenish coloring in the skin, and the other reaction increases glycoalkaloids.⁶ Because these reactions occur simultaneously, the greenish color is a clue that the potato is too toxic to consume. Resist the urge to simply cut the green part of the potato away; if any part of the potato is green, discard the whole potato. The green color indicates the presence of the toxin but is not indicative of the entirety of the dangerous area of concern.

One also should resist the urge to store potatoes in the refrigerator. Refrigerator temperatures are too cold and promote the enzymatic conver­sion of sucrose into fructose and glucose. This can create issues during cooking because both fructose and glucose are “reducing sugars”; when heated, they react with amino acids to produce carcinogenic acrylamides during the chemical process known as the Maillard reaction.

Finally, when preparing potatoes, there are several important steps that must always be followed. First and foremost, ALWAYS peel the po­tatoes. For all of the thousands of potatoes that I witnessed being prepared and consumed during my time in South America, there was only one situation where the potato was not peeled. That was when we were eating the potatoes with clay (p’asa), and I believe that speaks to the power of clay’s detoxification properties. ALL other potatoes were peeled—no matter what variety, how toxic or whether they were leached and freeze-dried, fermented, roasted, boiled or fried. I must have sounded like an annoying broken record because I incessantly asked everyone why they peeled the potatoes, and the reply was always the same—because “the skin is where most of the toxins reside and it is, therefore, the most dangerous part.”

They were right. The concentration of glycoalkaloids in the skin of a potato is three to ten times higher than on the inside of the po­tato.⁷ I can hear you all saying, “Stop! I always thought the most nutritious part of a potato was the skin!” It is true that the potato skin contains protein, free amino acids, free organic acids, phenolic compounds and antioxidant com­pounds,8 but any nutrition the skin may provide it is not worth the danger.

After peeling, it is also important to remove all injured or bruised sections of the potato, along with eyes and sprouts, because glycoal­kaloids will concentrate there.^6,9

LEVEL UP SAFETY AND FLAVOR WITH FERMENTATION

Ultimately, the goal of my field research was to identify ways to incorporate one or more traditional techniques into our offerings at my Maryland eatery, the Modern Stone Age Kitchen, and also to identify techniques that people can use at home in modern kitchens. I found the answer in fermentation. I began experimenting with fermenting potatoes after I returned from South America. If you want to add one more level of safety and flavor, ferment your potatoes!

Currently, we ferment all of our potatoes at home and at the Modern Stone Age Kitchen. In addition to helping mitigate the toxins in the potatoes, the bacteria responsible for the fermentation feed on the sugars in the potato, reducing the carbohydrates in the final product; this results in less acrylamide creation when the potatoes are cooked.¹⁰ Even the U.S. Food and Drug Administration (FDA) recommends “using treatments to reduce sugar levels,”¹¹ and the fermentation process does just that. I have included our recipe for fermented potato chips fried in lard to get you started!

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SIDEBARS

BEST POTATO PRACTICES

1. Store potatoes in a cool (NOT COLD), dry, dark place—ideally between 41-46°F.
2. Handle carefully so as not to damage the potatoes.
3. ALWAYS peel potatoes and discard the peels.
4. Cut and discard minor areas of damage such as cuts and bruises. Discard completely if the potato is severely damaged, rotten and/or there is evidence of any green coloring whatsoever.
5. Ferment potatoes if desired (see Fermented Potato Chips recipe).
6. ALWAYS cook potatoes—never eat a raw potato. Cooking at high temperatures may do more to reduce glycoalkaloids.
7. Keep an eye on your oxalate consumption; while all of these steps will help with some of the toxins in the potato, they do not reduce the potato’s oxalate content.

FERMENTED POTATO CHIPS

Ingredients: Potatoes, salt, water and lard or tallow for frying

1. Peel the potatoes, making sure to cut away and remove any areas that have been damaged. Discard any potatoes that have any green coloring whatsoever.
2. Place a container on a scale and tare to zero.
3. Cut potatoes into thin slices and place in the container on the scale.
4. Fill the container with fresh water until all slices are submerged.
5. Take the combined weight of the contents of the container (water and potatoes) and multiply by 2.5 percent. The result is the amount of salt required.
6. Weigh the salt, add to the potatoes and water and stir gently to dissolve.
7. Cover with a lid or cloth and set in a cool place for three to five days.
8. Pour the animal fat into a deep fryer or large, heavy pot and heat to 300°F.
9. While the fat is heating, drain the potato slices in a colander and rinse thoroughly several times. Discard all brining liquid.
10. Spread the slices in a single layer on a cooling rack or dish towel so that the moisture evaporates from the surface. If necessary, blot the tops with a towel. It is important to remove as much moisture as possible from the surface of the potato slices to prevent splattering when frying.
11. Once the fat is at 300°F and the surfaces of the potato slices are relatively dry, deep-fry in batches for five to seven minutes, until the desired crispiness is achieved. (Do not expect them to brown as much as regular potato chips.)
12. Transfer the chips to a wire rack, crumpled-up brown paper or paper towels, immediately sprinkle with salt and toss to distribute.
13. The chips can be eaten as soon as they cool or stored in an airtight container at room temperature for up to one week.

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REFERENCES

1. Friedman M. Potato glycoalkaloids and metabolites: roles in the plant and in the diet. J Agric Food Chem. 2006 Nov 15;54(23):8655-8681.
2. Johns T, Alonso JG. Glycoalkaloid change during the domestication of the potato, Solanum Section Petota. Euphytica. 1990;50:203–210.
3. Johns T. Detoxification function of geophagy and domestication of the potato. J Chem Ecol. 1986 Mar;12(3):635-646.
4. Yoshikawa K, Apaza F. Unfrozen state by the supercooling of chuno for traditional agricul­ture in altiplano andes. Environmental and Sustainability Indicators. 2020 Dec;8:100063.
5. Velasco-Chong JR, Herrera-Calderón O, Rojas-Armas JP, et al. Tocosh flour (Solanum tuberosum L.): a toxicological assessment of traditional Peruvian fermented potatoes. Foods. 2020 Jun 2;9(6):719.
6. Chu J. Toxic glycoalkaloids in potatoes. Centre for Food Safety, Government of the Hong Kong Special Administrative Region, last revised Oct. 6, 2018. https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_112_01.html
7. Los glicoalcaloides en las patatas. Comunidad de Madrid, n.d. https://www.comunidad.madrid/en/servicios/salud/debes-pelar-patatas
8. Torabian S, Qin R, Sathuvalli S, et al. Glycoalkaloids in potato tubers: how to control tuber greening. Oregon State University Extension Service, EM 9407, October 2023. https://extension.oregonstate.edu/catalog/pub/em-9407-glycoalkaloids-potato-tubers
9. Petre A. Are sprouted potatoes safe to eat? Healthline, Mar. 13, 2020.
10. The Research Council of Norway. Limiting harmful acrylamide: lactic acid bacteria to lower risk of cancer. ScienceDaily, Sep. 10, 2010.
11. Acrylamide. U.S. Food & Drug Administration, content current as of Mar. 5, 2024. https://www.fda.gov/food/process-contaminants-food/acrylamide

This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly journal of the Weston A. Price Foundation, Summer 2024

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