Imagine biting into a brilliantly colored root vegetable and tasting something closer to radish, mustard or horseradish than potato.
Then roast that same tuber until tender, and much of the sharpness disappears. The flavor becomes mellower, earthier and, in some varieties, noticeably sweet.
That remarkable transformation belongs to mashua, one of the lesser-known food crops of the Andes.
Scientifically known as Tropaeolum tuberosum, mashua is a close botanical relative of the familiar garden nasturtium. The relationship makes sense the moment the tuber is tasted raw: both contain compounds capable of producing a distinctive mustard-like bite.
Mashua has been cultivated for generations in Peru, Bolivia, Ecuador and Colombia, where farmers grow an extraordinary assortment of yellow, cream, orange, red, purple and nearly black varieties. Kew Science identifies Tropaeolum tuberosum as a tuber-forming climbing plant native to western South America.
Yet what makes mashua particularly fascinating is not simply its appearance.
It is a vegetable whose personality changes dramatically between the field and the dinner plate.
A Nasturtium That Grows Underground
Most people recognize nasturtiums for their round leaves and brilliant orange, red and yellow flowers.
Mashua belongs to the same genus, Tropaeolum, but instead of being grown primarily as an ornamental, it produces substantial edible tubers underground.
Above the soil, mashua looks much like a vigorous climbing nasturtium. Long stems scramble through nearby vegetation, carrying lobed leaves and tubular flowers that may be orange, yellow or red.
Below ground is the real surprise.
The plant produces elongated, irregularly shaped tubers that can resemble small pointed potatoes or unusually colorful carrots. Depending on the variety, their skins may be:
Creamy white
Pale yellow
Golden orange
Bright red
Purple
Nearly black
Yellow streaked with purple or red
Slow Food notes that mashua tubers commonly range from approximately 5 to 15 centimeters long and that the crop performs especially well at elevations of roughly 2,400 to 4,300 meters.
That ability to grow at high elevations helped make mashua an important component of Andean agriculture.
The First Bite Can Be a Shock
Raw mashua is not a neutral root vegetable.
Slice into a fresh tuber and the flesh is usually crisp, juicy and dense. Bite into it, however, and a peppery sensation can quickly develop.
Depending on the variety, raw mashua may taste:
Peppery
Radish-like
Mustardy
Bitter
Cabbage-like
Sharp
Pungent
Slightly medicinal
Some varieties are relatively mild. Others can have enough bite to recall horseradish.
This unusual flavor is not accidental.
Mashua contains natural compounds called glucosinolates. When plant tissue is cut, grated or chewed, glucosinolates can interact with an enzyme called myrosinase. That reaction produces several compounds, including isothiocyanates, which contribute the pungent sensation associated with mashua.
The same broad family of chemical reactions helps explain the bite of foods such as mustard, radishes, watercress and horseradish.
Mashua is therefore spicy in a completely different way from a chile pepper.
A chile gets its heat primarily from capsaicin.
Mashua gets its pepperiness from mustard-like plant chemistry.
Then Something Remarkable Happens
Cook mashua, and the vegetable changes.
The raw sharpness can diminish considerably. What seemed peppery and somewhat bitter may become mild, earthy and even sweet.
This is not just culinary folklore.
Research examining mashua found that boiling, microwaving and baking completely inactivated myrosinase, the enzyme involved in converting glucosinolates into the pungent breakdown products associated with mashua’s characteristic bite.
Without the same enzymatic activity occurring in the cooked tissue, the experience becomes dramatically different.
Instead of concentrating on peppery heat, the palate begins noticing other flavors already present in the tuber.
Cooked mashua can develop notes reminiscent of:
Sweet turnip
Cabbage
Roasted radish
Chestnut
Earthy potato
Sweet potato
Mild mustard
Caramelized root vegetables
The exact result depends greatly on the variety.
Some mashua remains distinctly cabbage-like or bitter even after cooking. Other varieties can become surprisingly mild and sweet. Specialty growers familiar with many cultivars describe an enormous range in cooked flavor, from strongly cabbage-like to pleasantly sweet.
This variability is part of what makes mashua so intriguing.
Two tubers that look similar can offer very different eating experiences.
Why Cooking Changes the Flavor
Mashua provides an unusually clear example of how heat can alter not just texture but the chemistry responsible for flavor.
In an intact raw tuber, glucosinolates and myrosinase are stored separately within plant tissues.
Cutting or chewing damages the cells.
The compounds come into contact.
Myrosinase begins breaking down the glucosinolates, and pungent products such as isothiocyanates are formed. Researchers identify these compounds as major contributors to mashua’s distinctive sharp flavor.
Heat changes this process because myrosinase is an enzyme, and enzymes can be deactivated by sufficiently high temperatures.
Research comparing cooking methods found myrosinase was inactivated by boiling, microwaving and baking. Boiling also caused some glucosinolates to leach into the cooking water because the compounds are water-soluble.
The practical result is easy to understand:
Raw mashua: sharp, peppery and sometimes bitter.
Cooked mashua: generally softer, milder, earthier and potentially sweeter.
It is almost as though the tuber contains two different vegetables.
The Sun Can Change It Too
Andean cooks discovered another way to modify mashua’s flavor long before scientists analyzed its chemistry.
They exposed harvested tubers to sunlight.
In some communities, mashua is traditionally left in the sun for several days before being eaten. Slow Food reports that this practice concentrates sugars and creates a sweeter taste, helping reduce the bitter and spicy qualities that may be present in freshly harvested tubers.
The sun-dried preparation is sometimes known as chuna.
This means mashua’s flavor can be manipulated at several stages:
Fresh from the soil, it may be strongly peppery.
After resting in sunlight, its sweetness may become more pronounced.
After cooking, its sharpness can diminish further.
Traditional cooks were therefore not simply harvesting a vegetable. They understood that post-harvest treatment could transform how it tasted.
That knowledge is similar to the traditional sunning of oca, another Andean tuber whose sweetness can increase after harvest.
Roasting May Be Mashua’s Best Introduction
For someone tasting mashua for the first time, roasting offers one of the most appealing preparations.
Heat softens the flesh while encouraging browning on the exterior. As the tuber’s sharpness diminishes, roasted flavors become more noticeable.
The result can be surprisingly different from the raw vegetable.
The outside may become lightly caramelized while the interior turns tender and moist. Depending on the cultivar, some cabbage-like or peppery character may remain, but it becomes part of a broader combination of sweetness and earthiness.
Mashua can be roasted:
Whole
Halved lengthwise
Cut into thick slices
Mixed with potatoes and other root vegetables
Cooked beneath roasting meat
Seasoned simply with salt and oil
It pairs naturally with ingredients that complement both sweetness and pungency, including garlic, onions, herbs, chile, butter and roasted meats.
Because mashua varies considerably among cultivars, cooking should be treated as exploration rather than following one universal flavor description.
For the kitchen: A heavy-duty roasting pan can provide plenty of room for roasting potatoes, sweet potatoes and other root vegetables until browned and caramelized.
Boiled Mashua: A Different Experience
Boiling produces a softer and often milder result.
Mashua can be simmered until tender and served much like turnips or small potatoes. Boiling may reduce some of the stronger flavor compounds, in part because water-soluble glucosinolates can move into the cooking water.
Boiled mashua can be:
Mashed
Served with butter
Added to stews
Combined with potatoes
Puréed into soup
Finished with herbs or cheese
Mixing mashua with a milder root such as potato is particularly useful for strongly flavored varieties.
Instead of eliminating mashua’s personality, the potato softens it.
For the kitchen: A sturdy potato masher can make it easier to mash cooked root vegetables such as potatoes, turnips and mashua.
Mashua in Andean Soups and Stews
In the Andes, mashua has long been used as more than a roasted specialty vegetable.
Kew’s plant-use records document the tubers being used in soups in Colombia, and the crop forms part of a much wider tradition of Andean root and tuber cooking.
Mashua works especially well in substantial soups because cooking moderates its pungency while allowing the tuber to absorb broth and seasonings.
It can accompany:
Meat
Corn
Beans
Potatoes
Other Andean tubers
Herbs
Chiles
Cheese
The combination is important.
Mashua does not always need to stand alone. Its stronger flavors can become an advantage when used as one component within a larger dish.
Explore Andean cooking: A Peruvian cookbook can introduce readers to traditional dishes, ingredients and cooking techniques from Peru, where mashua has been cultivated in the Andes for generations.
Not Every Mashua Tastes the Same
One of the biggest mistakes is assuming that mashua represents a single standardized flavor.
It does not.
Researchers have measured wide variation in glucosinolate concentrations among mashua accessions. A recent review reported dramatically different levels among cultivated lines, including relatively low concentrations in varieties described as sweet mashua.
That helps explain why descriptions of mashua sometimes seem contradictory.
One person may describe it as sweet and pleasant.
Another may call it bitter and overwhelmingly pungent.
Both may be correct.
Color does not necessarily provide a dependable guide to pungency, either. Yellow, red and purple cultivars can all vary in their chemistry.
Centuries of farmer selection have created mashua types suited to different local preferences, climates and culinary purposes.
The diversity is one of the crop’s greatest strengths.
A Root Vegetable Built for the Andes
Mashua’s value to Andean farmers extends well beyond taste.
It is adapted to high-altitude environments and can grow where many conventional crops struggle. The plant develops vigorously, produces large amounts of foliage and can yield substantial quantities of tubers.
Its pungent chemistry may also contribute to natural resistance against pests.
Those glucosinolates and related compounds that create mashua’s strong flavor are part of the plant’s chemical defense system.
For farmers, that can be advantageous.
A vegetable that insects or soil pests find less appealing can survive with less intervention than a highly vulnerable crop.
Mashua has consequently been valued not only as food but as part of diversified Andean farming systems.
Mashua, Oca and Ulluco
Mashua is often grown alongside two other colorful Andean tubers: oca and ulluco.
Although all three are frequently grouped together, they are botanically unrelated.
Oca is Oxalis tuberosa, a relative of wood sorrel.
Ulluco is Ullucus tuberosus, a member of the Basellaceae family.
Mashua is Tropaeolum tuberosum, a relative of nasturtiums.
Their flavors are also distinctly different.
Oca often offers pleasant acidity and sweetness.
Ulluco tends to be moist, firm and mild.
Mashua is the most assertive of the three, particularly when raw.
This diversity demonstrates the sophistication of Andean agriculture. Farmers did not depend on a single underground crop. They maintained numerous species, each providing different flavors, growing characteristics and culinary possibilities.
What About Mashua’s Famous Anti-Aphrodisiac Story?
Mashua has one particularly unusual historical reputation.
Accounts have long claimed that Inca soldiers were fed mashua because it reduced sexual desire.
The story is repeated frequently, but it should not be presented as established fact about normal human consumption.
A 1982 animal study found hormonal changes in male rats fed mashua but did not demonstrate infertility; the treated animals remained capable of impregnating females. The research does not establish that eating mashua as part of an ordinary human diet produces the same effect.
The legend is interesting as part of the tuber’s cultural history, but mashua should not be marketed as either a proven aphrodisiac or anti-aphrodisiac.
Its culinary qualities are unusual enough without exaggerating medicinal claims.
Why Mashua Never Became Another Potato
Mashua has many characteristics that might seem ideal for international agriculture.
It is productive.
It tolerates cool conditions.
It has impressive genetic diversity.
Almost the entire plant is edible.
And its colorful tubers are visually striking.
Yet mashua remains uncommon outside South America.
Its raw flavor is one obvious obstacle. A vegetable that can taste sharply mustard-like is more challenging to introduce than a neutral potato.
Its growing cycle can also be difficult in some climates. Mashua is sensitive to day length and commonly forms tubers late in the growing season. Where hard frosts arrive early, the plant may not have enough time to develop a substantial crop.
It is therefore most frequently encountered outside the Andes through specialty growers, experimental farms and gardeners interested in unusual edible plants.
From Peppery to Sweet
Mashua’s greatest culinary appeal may lie precisely in the characteristic that once limited its popularity.
It changes.
A raw slice shows the plant’s defensive side—crisp, sharp and loaded with mustard-like pungency.
Heat reveals something different.
Boiling, roasting or baking quiets the enzymatic reaction responsible for much of that pepperiness. As the sharpness retreats, sweetness, earthiness and the tuber’s deeper flavors become easier to notice.
Traditional sun exposure can transform the experience again, concentrating sweetness before the tuber ever reaches the cooking pot.
Few root vegetables offer such a dramatic before-and-after experience.
Mashua is therefore not merely an obscure substitute for a potato.
It is a vegetable with two personalities: fiery and peppery when raw, mellow and potentially sweet when cooked.
That transformation—created by plant chemistry, heat and generations of Andean culinary knowledge—is what makes mashua one of the world’s most fascinating tubers.