Botany: Neither a Tree nor a Palm

From a botanical standpoint, papaya is not a tree, and certainly not a palm. The plant's trunk contains no wood. It is a hollow, fast-growing herbaceous stem without annual rings, pith, or bark. Papaya belongs to the large herbs.

The plant develops very quickly. Under favorable conditions, a stem about five meters tall, covered with dozens of kilograms of fruit, grows from a seed in 9–12 months. Its lifespan, however, is short. After 4–5 years the plant ages, its roots rot, and the stem breaks under its own weight, even in a strong gust of wind. For this reason, farmers regularly uproot old plantings and replant their fields.

The papaya fruit is a berry, specifically a large multiseeded berry that develops from the superior ovary of the flower. The mass of individual fruits of wild and cultivated varieties reaches 9 kg.

Sexual Polymorphism

Three types of individuals occur in the papaya population:

Farmers on commercial plantations prefer hermaphroditic plants. Male individuals are capable of changing sex. When the top of a male plant is cut off or when there is a sharp drop in temperature, a hormonal disruption occurs in its tissues. The male inflorescences begin to form pistils and set fruit. In this way, the plant changes sex in a stressful situation in order to leave offspring.

History of Distribution

The papaya's homeland is considered to be the tropical forests of Mesoamerica, including the territory of present-day southern Mexico and Central America. The Maya and Aztec civilizations domesticated papaya thousands of years before European caravels arrived in the New World.

The Maya called the plant "chichivaltsapol," which translates as "sweet fruit resembling a woman's breast." The root "ababai" later became the basis of the modern name "papaya," which the conquistadors used. For indigenous peoples, the plant was sacred and served as a pharmacy. The many shiny black seeds were considered a symbol of fertility. Fruits were offered to the harvest gods, and priests used parts of the plant in rituals.

The ancient peoples' observations had practical significance:

• Wound healing. The white milky sap of the unripe fruit, applied to a festering wound, a burn, or the bite of a venomous insect, quickly cleansed the affected area. The tissues healed without visible scars.
• Tenderizing meat. Indigenous hunters were the first to use papaya leaves in cooking. The meat of a wild boar or deer was tightly wrapped in broad leaves and left in the shade for several hours. The tough fibers became soft, like tenderloin after grilling.

In the early 16th century, Spanish conquistadors landed in these territories. The first documented description of papaya was left by the chronicler Gonzalo Fernández de Oviedo in 1526. He described a fruit found on the coast of Panama.

A legend connected with Christopher Columbus is also associated with the plant. According to this version, Spanish sailors exhausted by a long voyage landed on islands in the Caribbean Sea. They suffered from stomach pains, digestive disorders, and the effects of a diet of salt meat and moldy hardtack. The local inhabitants treated them to the soft orange pulp of an unknown fruit. The pains quickly subsided, and their strength returned within a few hours. According to the ship's logs, Columbus called papaya the "fruit of angels."

Papaya seeds retain their viability in dry form for months and germinate immediately after contact with moist soil. By the mid-16th century, Manila galleons had carried the seeds across the Pacific to the Philippines. From there the plant spread to Malaysia, Indonesia, and Indochina. Portuguese caravels brought papaya to the western coast of India, where it was called "papita," and then to the shores of Africa. In less than 100 years, the plant had made a round-the-world journey and became a traditional crop for many peoples on both sides of the equator.

Biochemistry: Papain

The enzyme system of the papaya explains both its history of medicinal use and its culinary properties. The plant's tissues, especially the green skin, the leaves, and the milky latex of unripe fruit, contain the enzyme papain. It belongs to the class of cysteine endopeptidases. Papain is a proteolytic enzyme that breaks complex protein molecules down into simple peptides and amino acids.

In nature, papain serves as a chemical defense against pests. If a caterpillar, a beetle, or another herbivorous insect tries to bite an unripe fruit, a thick white sap spurts onto it. The enzymes begin to break down the tissues of the insect's mouthparts, causing chemical burns and paralysis.

In a series on the hidden life of plants, British naturalist and BBC documentary presenter David Attenborough remarked, in jest, that the papaya is one of the few fruits on the planet that tries to digest a person while that person is eating it.

The tingling of the tongue or the dryness of the mucous membrane when eating a slightly unripe papaya is not related to allergy or acidity. It is caused by micro-doses of papain, which begins the contact breakdown of the surface proteins of the oral epithelium.

Industrial Production

Purified papain is a raw material with a high market value. On plantations, longitudinal incisions are made in unripe fruit with bamboo or glass rods. Metal knives must not be used, because iron ions oxidize the enzyme and reduce its activity. The white sap that drips out is collected, dried in vacuum cabinets, and processed into a powder of high activity. The price of high-purity crystalline medical papain reaches hundreds of dollars per kilogram.

Areas of Application

• Brewing. Proteins and tannins from malt form a haze known in the industry as "chill haze" when the beer is cooled. Micro-doses of papain, added at the maturation stage, break down the polypeptides. The beer remains clear even at temperatures close to zero. Brewing is one of the largest consumers of the enzyme.
• Textile industry. Papain treats natural silk and wool. The enzyme dissolves the coarse surface microfibrils. Woolen goods stop prickling, do not shrink during washing, and acquire a matte sheen.
• Leather production. Papain is used in the tanning of hides to remove residues of unwanted protein fibers.
• Ophthalmology. For decades, papain tablets were used for the enzymatic cleaning of contact lenses from protein deposits left by tear fluid.

Culinary Limitations

In cooking, papain can ruin the preparation of jelly. Fresh papaya added to gelatin jelly does not set, even after an hour, two hours, or a full day. Gelatin is an animal protein, collagen. Active papain breaks down peptide bonds, turning the protein network into mush and preventing gel formation.

To make a papaya dessert with gelatin, the fruit must be heated for several minutes. At temperatures above 70 °C, the protein structure of the enzyme denatures, and it irreversibly loses its destructive activity. An alternative is agar-agar. This is a polysaccharide from seaweed, which proteolytic enzymes do not act on.

The Hawaiian Catastrophe and Genetic Rescue

In the mid-20th century, Hawaii became the world's center for breeding and producing premium papaya. Hawaiian farmers developed the Solo variety. It is a very sweet fruit of small size, which is convenient to cut in half and eat with a spoon for breakfast. Export revenue from Hawaiian papaya exceeded $40–50 million a year. The industry provided stable employment for thousands of farm families.

Initially, the plantations were located on the island of Oahu. In the 1940s and 1950s, the papaya ringspot virus (PRSV) reached the island. This pathogen acts like a biological weapon with a delayed effect.

Symptoms and Spread

The virus affects all aerial parts of the plant:

• the leaves become covered with a yellow chlorotic mosaic, curl, and drop off;
• water-soaked black streaks appear on the stem;
• concentric rings resembling targets form on the skin of ripening fruit;
• the flesh loses its sweetness, the trees fall behind in growth, stop bearing fruit, and die.

The vector of the virus is the common aphid. It needs only to settle on an infected leaf for 15 seconds for the virus to attach to the tip of its stylet. When it flies to a neighboring tree, the aphid pierces a leaf, and the healthy plant becomes infected. The aphid does not colonize the papaya. The insects only sample the plants in search of other food and fly away, spreading the epidemic.

Pesticides proved useless. The poison killed the aphid only after it had already inserted its stylet and transmitted a lethal dose of the virus.

Migration and a New Threat

When the plantations on Oahu were practically destroyed, Hawaiian farmers in the late 1950s transported the remaining equipment and seeds by ferry to the island of Hawaii (the Big Island). Production was moved to the isolated volcanic district of Puna. The solidified basalt fields and geographic remoteness created a natural sanitary barrier. For three decades, the farmers of Puna prospered. The district produced 95% of all the archipelago's papaya.

In May 1992, inspectors recorded the first infected trees. Agronomists describe the subsequent events with horror. Under conditions of dense, continuous planting and a favorable climate, the virus spread like a forest fire. Within a few months, thousands of hectares were lost. Papaya production in Hawaii fell by more than 50% within 4 years.

Farmers cleared entire fields, doused them with gasoline, and burned hundreds of thousands of flowering trees in an attempt to create buffer zones. The aphids easily flew over the charred areas. Bankruptcies began. People lost their ancestral lands and mortgaged homes. The industry was doomed to disappear within a few years.

Dennis Gonsalves and Genetic Engineering

At this critical moment in the history of genetics, a Hawaiian named Dennis Gonsalves, a plant pathologist working at Cornell University, appeared. Gonsalves understood the nature of pathogens better than others. Back in the late 1970s, he had predicted that sooner or later the virus would overcome the isolation of Puna.

Classical breeding had reached a dead end. In nature, there were no wild varieties of papaya with immunity to the virus that could be successfully crossed with the sweet Solo variety. Gonsalves, together with a group of colleagues that included Richard Manshardt, Maureen Fitch, and Jerry Slightom, decided to apply a concept that no one had previously used to save commercial fruit trees. This was the concept of coat protein-mediated resistance.

The scientists decided to "vaccinate" the plant at the genetic level. The logic of the experiment was as follows. From a dangerous strain of the Hawaiian virus, they isolated a single gene encoding a harmless protein of the outer protein coat. This protein could not cause disease by itself, since it did not contain the genetic material necessary for the virus to replicate.

The Gene Gun and the First Transgenic Lines

The scientists used a gene gun, a device that accelerates microscopic particles of heavy metals with compressed helium. Microparticles of tungsten and gold were coated with strands of the isolated gene and fired into a culture of embryonic cells of the susceptible Hawaiian variety Sunset. The metal particles penetrated the cell walls. Some papaya cells incorporated the foreign DNA fragment into their own genome.

Plants were regenerated from the Petri dish and grown in a closed greenhouse. Every cell of the new plant independently produced microscopic amounts of messenger RNA for the viral protein. A mechanism was triggered, the discovery of which was later recognized with a Nobel Prize: RNA interference. The plant's internal immune system recognized this RNA and prepared to search for foreign molecules.

When a wild virus in field conditions entered a papaya cell through an aphid bite and attempted to replicate, the plant's internal defenses immediately detected it. They cut the viral RNA into fragments, and the pathogen did not manage to create a single copy. According to the developers, the papaya acquired 100% innate immunity.

The first transgenic line was named SunUp. It was a papaya with red flesh that possessed absolute resistance to infection. The market demanded fruit with yellow flesh and the familiar taste of the classic Kapoho variety. Gonsalves crossed SunUp with the traditional Kapoho variety. The resulting first-generation hybrid was named Rainbow. It inherited the taste of classic Hawaiian papaya and genetic protection against the virus.

Patents, Trials, and the Return of Production

Creating a transgenic plant in the laboratory was only a third of the way. In the mid-1990s, the patents on the gene gun technology and molecular promoters belonged to large transnational agrochemical corporations, including Monsanto and DuPont. If the corporations had demanded standard licensing fees, small farms would have gone bankrupt at the stage of buying the seeds.

Dennis Gonsalves negotiated with corporate lawyers and secured free non-commercial licenses for Hawaiian farmers.

Then came a review by three US federal agencies:

• the Department of Agriculture studied the impact of the plantings on the ecosystem;
• the Environmental Protection Agency assessed the variety's sustainability;
• the Food and Drug Administration (FDA) conducted a biochemical and toxicological analysis of the fruit.

The experts' conclusion was unanimous: the Rainbow papaya is safe, non-toxic, and fully equivalent in nutritional value to traditional varieties.

In May 1998, exactly 6 years after the start of the catastrophe, Rainbow seeds were distributed free of charge among the desperate farmers of Puna. By 2000, yields had recovered to pre-crisis levels. Then the effect of herd immunity, known from epidemiology, became apparent. The resistant Rainbow trees surrounded the remaining plantings of traditional varieties and formed a living barrier. The viral load in the air dropped almost to zero, and the farmers were once again able to grow conventional non-modified varieties.

International Conflicts Surrounding Rainbow

Japan had traditionally been the largest buyer of Hawaiian fruit, accounting for up to 30% of the entire harvest. Japanese regulators categorically refused to admit transgenic fruit to the domestic market. They cited strict biosafety legislation and a requirement for many years of testing.

The dispute grew into a thirteen-year trade standoff between Washington and Tokyo. Senators from Hawaii regularly raised the issue at intergovernmental negotiations. They accused the Japanese side of covert protectionism and of defending local farmers under the guise of concern for public health. Endless court proceedings and toxicological inspections followed.

In December 2011, Japan finally gave in and officially permitted the import and retail sale of the Rainbow variety. Hawaiian papaya became the first GMO product for direct consumption to be admitted to the shelves of Japanese supermarkets.

The European Approach

The European Union erected an insurmountable barrier. To this day, the import and sale of the Rainbow and SunUp varieties in the EU territory are strictly prohibited. Here lies the fundamental difference between the legislative approaches:

• The US applies the principle of substantial equivalence. If a product does not differ from its natural counterpart in terms of its content of proteins, fats, and vitamins, it receives approval.
• The EU follows the precautionary principle. A product is considered potentially dangerous from the outset until the applicant proves otherwise through multimillion-euro clinical studies.

Hawaiian papaya was saved by university scientists using state grants. The association of small farmers did not have tens of millions of euros for the procedures of the European Food Safety Authority (EFSA). As a result, the EU enforces a policy of zero tolerance. Any consignment of fresh fruit, juices, or canned goods from the US or Asia undergoes strict PCR testing at the border. If the laboratory detects even a single trace of the P-35S promoter, the cargo is immediately confiscated and burned at the importer's expense.

Conflicts in Hawaii and Thailand

In the early 2010s, an environmental movement against biotechnology erupted on the Big Island. Activists spoke out against transgenic plantations. Nighttime sabotage began. Groups of people in masks, armed with machetes and chainsaws, secretly infiltrated plantations and under cover of night cut down blooming orchards. Over several years, vandals destroyed more than 10,000 fruit-bearing trees belonging to family farmers. The damage amounted to hundreds of thousands of dollars.

To protect their fields, farmers organized armed night patrols with dogs and installed hidden surveillance cameras in the jungle. When the local council attempted to pass a law banning the cultivation of GMOs on the island, the farmers filed a lawsuit in federal court and won it. They proved that without this papaya, the region's agriculture would cease to exist.

In 2004, a similar scandal engulfed Thailand. Commercial cultivation of transgenic crops was prohibited there by law. Experiments were permitted only behind the closed fence of a state station in Khon Kaen province. However, Greenpeace activists conducted an independent investigation and found that seeds resistant to the papaya virus had illegally left the station's territory and were already being sold to local farmers. A large-scale international crisis erupted. The European Union immediately blocked imports of Thai canned goods. Accusations of corruption arose in parliament. The Thai government was forced to uproot and burn the fields of hundreds of farmers in order to restore the country's reputation as an exporter of clean organic produce.

Political Crisis: Tanzania, 2020

In May 2020, a papaya made headlines around the world amid the COVID-19 pandemic. Tanzanian President John Magufuli, who held a doctorate in chemistry, publicly questioned the reliability of imported PCR tests supplied to the country. To check how the laboratories were performing, Magufuli ordered the security services to carry out a covert operation.

Officers collected biological samples from unusual objects: motor oil, a quail, a domestic goat, and a ripe papaya. The samples were assigned fictitious names, ages, and sexes, as if they were human, and then sent to Tanzania's main national health laboratory.

The results were unexpected. The motor oil sample tested negative. The goat and papaya tests showed a confidently positive result for COVID-19. The president called an emergency press conference. He stated that either the tests were erroneous and amounted to Western sabotage, or the tropical trees were due to go into a two-week quarantine.

Magufuli immediately dismissed the laboratory's management, suspended the reporting of statistics to the WHO, and closed the country off from international quarantine protocols. The scandal, dubbed "Papaya-gate" in the press, sparked heated debate among virologists and fueled a wave of conspiracy theories around the world.

The Cuban Taboo

In Cuba, there is a sociocultural taboo associated with papaya. Even Ernest Hemingway strictly observed it. In the Cuban dialect of Spanish, the word "papaya" evolved into vulgar slang referring to female genitalia. Saying this word in a public place, such as a market or a restaurant, is considered an extreme indecency.

To avoid ambiguity, Cuban authorities officially renamed the fruit "fruta bomba" ("bomb fruit"). Hemingway, who lived at the Finca Vigía villa, liked to eat chilled fruit with lime for breakfast. However, he always warned American guests: do not ask a Cuban waiter to serve papaya if you do not want to cause a scandal or provoke loud laughter from the entire room. On Cuban television and on the price tags in state stores, the forbidden word does not appear. Only "fruta bomba" is used.

Black Pepper Adulteration

Papaya seeds have long been used to adulterate one of the world's most expensive spices, black pepper. Dried papaya seeds are small, wrinkled, dark brown or black balls. In appearance they are almost indistinguishable from peppercorns of true black pepper (Piper nigrum). Yet the difference in price is enormous. High-quality black pepper consistently trades on international exchanges at $4,000 to$8,000 per tonne.

For juice and canning enterprises, papaya seeds are a free industrial waste that is hauled to landfills by the tonne. Unscrupulous spice traders in India and Southeast Asia quickly found a way to extract extra profit. They dried the papaya processing waste and added 20–30% of it to sacks of expensive black pepper. In ground form, the adulteration cannot be detected, since papaya seeds contain glycosides that give them a sharp, mustard-pepper taste.

Indian inspectors have developed field tests for authenticity. The simplest is based on physics and density. Genuine black pepper sinks in an alcohol solution or in water of a certain density, while dried hollow papaya seeds always float to the surface.

Fermented Papaya Extract and the Pope

Papaya is also used to produce one of the most expensive dietary supplements in modern gerontology. This is fermented papaya extract, FPP (Fermented Papaya Preparation).

The history of this preparation is linked to Nobel laureate Luc Montagnier, who discovered the HIV virus. In the early 2000s, Montagnier investigated oxidative stress as the main cause of brain neuron death in Parkinson's disease. At that time, Pope John Paul II was seriously ill. The pontiff suffered from severe hand tremors and muscle rigidity and was nearly losing the ability to speak.

Montagnier personally met with the Vatican's private physician, Renato Buzzonetti, and handed over a course of FPP for the pontiff. The preparation is produced in Japan using a complex technology. Immature Hawaiian fruits are fermented with special yeast cultures for 10 months. During this time, the original enzymes and vitamins are destroyed. The result is a granulated powder of oligosaccharides and unique peptides.

According to the developers, upon entering the body, the preparation activates the NRF2 signaling pathway in cells. This prompts the body's own cells to intensively produce antioxidant enzymes: superoxide dismutase and glutathione peroxidase.

In the summer of 2002, news agencies worldwide reported a noticeable improvement in the pontiff's condition. The tremor decreased, and his voice stabilized. Pharmacies in Europe were flooded with customers. The cost of the raw material is just a few cents, while three-gram sachets of the extract are sold at a price equivalent to up to $1,000 per kilogram of finished powder.

Papaya and Fingerprints

On tropical plantations there is an unwritten rule: green papaya pickers must work in thick rubber gloves. It is not only a matter of hygiene. When unripe fruit is harvested bare-handed over many years, constant contact with the milky latex causes papain to systematically dissolve the stratum corneum of the epidermis. As a result, the papillary ridges on the pickers' fingertips are literally worn away. The skin becomes as smooth as polished glass. Such people effectively lose their fingerprints.

Biometric scanners at airports and forensic powders for lifting fingerprints are unable to capture the skin pattern until the epidermis completes a lengthy regeneration cycle.

Contraception

In pharmacology, papaya seeds have long been studied as a possible basis for the world's first non-hormonal male contraceptive pill. In traditional medicine in India and Pakistan, men have for centuries chewed dried seeds to prevent pregnancy.

Modern laboratory experiments have confirmed that carpaine, an alkaloid contained in the seeds, reversibly suppresses sperm motility, reducing it to zero. At the same time, levels of male hormones and libido remain unchanged. After discontinuing use, reproductive function fully recovers within several weeks.

Culinary Use

World gastronomy divides papaya into two different products. In the countries of Southeast Asia, it is perceived not as a dessert but as a dense, refreshing, crunchy vegetable.

• Thailand. The country's main gastronomic symbol is the salad "som tum." Green unripe papaya is cut into thin strips and placed in a clay mortar. It is lightly pounded with a pestle together with hot chili pepper, garlic, palm sugar, lime juice, fish sauce, dried shrimp, and roasted peanuts. The flesh retains its crunch and absorbs the balance of sweet, sour, salty, and spicy flavors.
• Philippines. The green fruit is pickled with ginger and vinegar to make the appetizer "atchara." In large chunks, it is cooked in the chicken soup "tinola," where the papaya acquires the tender texture of braised zucchini.
• Brazil. Since the 1990s, restaurants of the churrascaria type have served a dessert called "Creme de Papaya." Ripe, sweet flesh is mixed with vanilla ice cream in equal proportions until it reaches an airy, velvety consistency. The dessert is served in a tall glass and generously drizzled with thick blackcurrant liqueur, "crème de cassis." Serving this dessert at the end of hearty meat banquets was no accident. The residual papain in the fresh flesh helped guests quickly digest the kilograms of steak they had eaten.
• Venezuela and Colombia. For Christmas, people prepare "dulce de lechosa." Half-ripe papaya is cut into strips, lightly soaked in carbonated water to preserve its firmness, and simmered for hours in a thick syrup of unrefined panela with cloves and cinnamon. The fruit turns into amber-colored candied pieces with a spicy aroma.

Practical Recommendations

1. Tenderizing Tough Meat

To tenderize cheap beef, sinewy lamb, or dry turkey, do not use vinegar, mayonnaise, or citric acid. These products draw out juices and dry out the fibers.

Procedure:

1. Take one tablespoon of finely mashed papaya flesh. Both ripe and green fruit will work, but green fruit is more potent.
2. Spread the flesh evenly over the piece of meat. Papain will begin to break down collagen and elastin in the connective tissue.
3. Leave the meat for exactly 15–25 minutes. If you leave it in papaya for several hours or overnight in the refrigerator, the enzyme will dissolve the fibers so thoroughly that an expensive steak will turn into a shapeless meat paste when fried.
4. Before frying or grilling, remove excess marinade with a paper towel.

2. Eliminating Unpleasant Odor

Many people dislike papaya because of its slightly musky, earthy, or soapy aftertaste. This smell is linked to volatile organic compounds and enzyme activity.

Professional chefs' advice: do not eat papaya unprocessed. Cut the flesh into cubes, generously drizzle it with fresh lime or lemon juice, and refrigerate for 5 minutes. The acid instantly neutralizes the alkaline enzyme residues on the surface of the flesh. The unpleasant odor disappears completely, and the fruit's natural sweetness becomes noticeably brighter.

3. Making a Spice from the Seeds

Do not throw away papaya seeds. Drain them in a fine sieve. Rinse under cold running water while rubbing them with your fingers to remove the gelatinous coating. Dry on a paper towel, then place in an oven at 60–70 °C (140–160 °F) for 1 hour. Once the seeds are completely dry and brittle, grind them in an ordinary mechanical spice grinder.

Ground papaya seeds have a refined, mild peppery pungency with a slight hint of Dijon mustard. They can be used for fried fish, poultry, and vegetable soups.

4. Homemade Enzyme Peel

Do not discard papaya skin after eating the fruit. A thin layer of flesh with the highest concentration of enzymes remains on its inner surface. Wipe clean, damp skin with the inner side of the peel using circular motions. Leave it on the skin for 3–4 minutes, feeling a light, pleasant tingling, then rinse thoroughly with cool water.

According to the author of the recommendation, this is a natural and gentle enzyme peel for which beauty salons charge significant sums. Papain dissolves dead flakes of the stratum corneum, cleanses pores of oxidized sebum, and evens out skin tone without harsh abrasive scrubs.

5. Insect Bites

If you are bitten by a mosquito at the dacha or on vacation, it is enough to apply a small piece of fresh papaya flesh to the itchy spot for a few minutes. According to the author, the enzymes quickly neutralize the protein toxins in the insect's saliva, and the swelling visibly decreases.

6. Choosing a Ripe Fruit

When buying papaya, use four criteria:

7. Storage Rules

The main rule that most people break: do not put unripe papaya in the refrigerator. Cold instantly and irreversibly destroys the ripening enzymes. The flesh stays hard as wood, and the skin turns gray.

If the fruit is green, place it at room temperature in an ordinary paper bag together with a ripe banana or apple. Bananas release ethylene, a natural gas that triggers ripening. In a day or two, the papaya will become soft, aromatic, and sweet as honey. The fruit should be placed in the refrigerator only when fully ripe. Its storage life in the refrigerator should not exceed 3–4 days.