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Fresh concerns over chemicals for ripening fruits, softening foods

By Chukwuma Muanya
02 May 2019   |   3:57 am
In recent times, there have claims and counter claims on health implications of using chemicals such as calcium carbide, ethylene and ethephon for ripening fruits and akanwu (alum/potash) for softening foods. A school of though has associated the rising cases of chronic diseases such as cancer, kidney damage, heart attack, stroke, hypertension, food poisoning, infertility,…


In recent times, there have claims and counter claims on health implications of using chemicals such as calcium carbide, ethylene and ethephon for ripening fruits and akanwu (alum/potash) for softening foods.

A school of though has associated the rising cases of chronic diseases such as cancer, kidney damage, heart attack, stroke, hypertension, food poisoning, infertility, liver failure with intake of artificial fruit ‘ripeners’ and food softeners.

Potash is an ingredient used in preparing some local Nigerian delicacies like nkwobi, abacha, ewedu, ugba, ila asepo, oghwo, masa and the likes. Potash, which is also known as akanwu in Igbo, kanwa in Hausa and kaun by the Yorubas, is a dry lake salt of sodium bicarbonate with water of crystallisation.

Ethylene is the major ripening agent produced naturally within the fruits, which initiates the process of ripening. A very small concentration of ethylene in air is sufficient to promote the fruit ripening process.

Externally applied ethylene is likely to trigger or initiate the natural ripening process of apple, avocado, banana, mango, papaya, pineapple and guava, and therefore, can be marketed before the predicted time.

Calcium carbide is widely used in different parts of the world. Once applied on the fruits Calcium carbide comes into the contact of the moisture and releases acetylene, which has fruit ripening characteristics similar to ethylene.

However, industrial grade calcium carbide contains traces of arsenic and phosphorus hydride, which are hazardous for human health in direct contact.

Ethephon is another agent, which is used to artificially ripen fruits. Ethephon is often considered better than calcium carbide because pineapple, banana and tomato treated with 1000 ppm of ethephon required less time for ripening (48, 32 and 50 hours, respectively) than other treated fruits as well as compared with the non-treated fruits.

The fruits ripened with ethephon have more acceptable colour than naturally ripened fruits and have longer shelf life than fruits ripened with calcium carbide.

Ethephon is decomposed into ethylene, bi-phosphate ion and chloride ion in aqueous solution. The released ethylene further fastens up the ripening process.

Indeed, fruit ripening is a natural process in which the fruit goes through various chemical changes and gradually becomes sweet, coloured, and gets soft and palatable.

With the advancement of science and technology, various artificial methods of fruit ripening has been observed mostly to meet consumers’ demand and other economic factors.

However, in the recent years, artificial fruit ripening has been considered a matter of concern and the effect of artificial ripening has become questionable because of various health related issues.

A study published in Annals of Tropical Medicine and Public has demonstrated possible health hazards of fruit ripeners.

The study titled “A Critical Analysis of Artificial Fruit Ripening: Scientific, Legislative and Socio-Economic Aspects” was conducted by researchers from the Department of Chemical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh and Department of Chemistry, McGill University, Montreal, Canada.

The researchers noted that calcium carbide releases acetylene, which almost works like ethylene in terms of speeding up the ripening process.

Direct consumption of acetylene has been found to be detrimental as it reduces oxygen supply to the brain and can further cause prolonged hypoxia.

Calcium carbide is alkaline in nature and irritates the mucosal tissue in the abdominal region. Cases of stomach upset after eating carbide-ripened mangoes has been reported recently.

Even though eating the carbide-ripened fruit does not lead to any allergic reaction instantly, seizure headache, sleepiness may be faced while applying these chemicals on the fruits.

Impurities like arsenic and phosphorus found in industrial grade calcium carbide may cause serious health hazards when workers are in direct contact with these chemicals while applying the ripening agents.

This may cause dizziness, frequent thirst, irritation in mouth and nose, weakness, permanent skin damage difficulty in swallowing, vomiting, skin ulcer, and so forth. Higher exposure may cause undesired fluid build-up in lungs (pulmonary edema).

Researchers from Bangladesh reported that the nutrition values like the protein content, vitamin-C and beta-carotene decrease in artificially ripened pineapples and bananas; the critical finding was the presence of arsenic (As) and Lead (Pb) within artificially ripened pineapples and bananas.

The researchers noted: “The concentration of As and Pb were within the daily permissible intake limit for an adult, however, regular consumption of such fruits can cause serious health hazards to human beings like cancer, skin irritation, diarrhoea, liver disease, kidney disease, gastrointestinal irritation with nausea, vomiting, diarrhea, cardiac disturbances, central nervous system depression and cardiac abnormalities etc.

Ideally artificial ripening agents release ethylene or acetylene to instigate fruit ripening and should not contain metal or metalloid.

“ But practically industrial grade calcium carbide and ethephon may contain a high percentage of As, Pb and phosphorus compounds, which are toxic for human health and can contaminate artificially ripened fruits. Usage of high grade ripening agents requires low dosing rate and any metal/metalloid contamination must be avoided.”

Another study on Physico-chemical properties and toxic effect of fruit-ripening agent calcium carbide by researchers from the Department of Pharmacy, Guru Ram Das (PG) Institute of Management and Technology, Dehradun, India, concluded that the use of calcium carbide is being discouraged worldwide, due to associated health hazards.

“Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous, and once dissolved in water, it produces acetylene gas. Arsenic, phosphorous and acetylene gas may affect the different body organs and causes various health problems like headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema, seizures and prolonged hypoxia.”

The study published in Annals of Tropical Medicine and Public Health noted:
“People exposed to high levels of arsenic can have nausea and vomiting, diarrhea, anemia, and low blood pressure. These symptoms may be followed by a feeling of ‘pins and needles’ in the hands and feet (neuropathy).

Chronic (long-term) exposure to arsenic can cause stomach ailments, headaches, fatigue, neuropathy, dark splotches on the skin, and small “corns” or “warts” on the palms of the hands, soles of the feet, and torso.

People exposed to inorganic arsenic can have more cancer of the lung, skin, bladder, liver, kidney, and prostate. Studies have not linked arsenic exposure to leukemia in adults or children.

Normal urine levels of arsenic are less than 50 μg/L. A level between 50 and 200 μg/L not necessarily represent a health risk. A level over 200 μg/L is considered abnormal and may require treatment if symptoms of arsenic poisoning are present.

“Intentional or unintentional ingestion of arsenic has been notorious as a means of suicide and homicide. Arsenic is used in rodenticide. Arsenic exposure produced severe edema of the eyelids, gastrointestinal irritation, and both central and peripheral neuropathies. It is the first antidote to heavy metal poisoning, and the basis for chelation therapy today. British Anti-Lewisite (dimercaprol) has sulfhydryl groups that bind arsenic, as well as other metals, to form stable covalent bonds in a process called complexation. The body can then excrete the nonionic complexes. Although a high level of suspicion for arsenic poisoning must be maintained because of its role in poisoning, it is rarely seen clinically.

“Physical findings in arsenic toxicity vary with age and dose. Any combination of Gastrointestinal (GI) complaints, neurologic dysfunction, and anemia should prompt a search for arsenic toxicity. GI complaints predominate in adults. Children are more prone to Central Nervous System (CNS) dysfunction, including encephalopathy. Encephalopathy is rare in adults.

Encephalopathy may present as an acute event with seizures, or it may develop slowly over weeks to months with variable nonspecific complaints. Cholera like diarrhoea can be seen in acute arsenic toxicity. Neurologic complaints ranging from neuropathy to encephalopathy have been reported in cases of acute arsenic toxicity. Arsenic toxicity presenting as ascending flaccid paralysis is often.”

According to a report published on NutrifactsBlog titled “What is The Effect of Potash (Akanwu) Consumption on Human Health?” akanwu is a mixture of different substances in order words, it contains impurities that may be injurious to human health.

The Maryland Department of Health and Mental Hygiene (DHMH), United States, has warned people not consume akanwu because it discovered that it contains significant levels of lead ranging from one to 18 parts per million (ppm).

Experts have warned that it should be taken with caution, as consumption of high amount could be detrimental to human health. Potash is known to contain high amount of sodium and this poses health hazards on human beings.

Also studies have shown potash as a mixture of various salts with other earth impurities, which may be toxic, this raises doubt on its ingestion safety by humans. Potash has been found to have the following negative effect on human’s lives.

Reduces sperm production
Studies have shown that excessive consumption of potash is linked to reduced sperm production and testicular injury.

A research conducted by scientists at Federal Institute of Industrial Research Oshodi (FIIRO), Lagos, in collaboration with Biochemistry Department, Bells University in Ota, Ogun State, shows that consumption of potash injures testicles and thereby causes infertility in men.

Renal failure
The high sodium content of Potash also causes injury to the kidney and liver. The excessive consumption of this earthy material (potash-Kaun) may lead to its accumulation that could cause severe and irreparable damage to the kidney and disrupt normal body functions, which may eventually lead to loss of life.

Increase blood pressure
Studies have shown that potash dilates blood vessels to enhance renal blood flow. When taken in excess, the sodium in akanwu accumulates in the blood causing raised blood pressure.

Induces abortion
Pregnant women are advised to refrain from taking any kind of akanwu concoction. This is because studies has shown that it has the ability to increase uterine contractility which may lead to abortion in the early stages of pregnancy if used in high enough concentration.

Reduce protein content of food
The use of akanwu as a tenderizer should be seriously considered before further use as studies has shown that it has the tendency to reduce the protein content of food.

The results of the study on effect of alkaline treatment (akanwu) and supplementary value of corn or crayfish on the protein quality of ukwa (Treculia Africana) showed that addition of akanwu to TA was detrimental to its protein utilisation.

However, akanwu has some health benefits.

According to Turner, 1989, akanwu is ranked next in importance to the common table salt in Nigeria because of its popularity and usage for various domestic purposes. It has been used for centuries in the treatment of various ailments and diseases.

When Potash is used in little quantity, it has little or no health risk. The United States Food and Drug Administration (FDA) has reviewed the safety of Sodium Carbonate, Sodium Sesquicarbonate and Sodium Bicarbonate and determined that these ingredients were Generally Recognized As Safe (GRAS) for direct addition to food.

Relieves toothache
Potash can be used to relieve pain associated with toothache. Just mix ground potash with water and apply on the affected area.

Acts as preservative
It can be used as preservative because of its great fungicide properties. Ancient Egyptians used natron Kanwa solution as preservative in mummification.

Treat cough
Potash can be used to treat cough where it works as expectorant to induce the secretion of respiratory mucosa.

Relieve constipation
Potash can act as antacid to relieve constipation and flatulence

Increase breast milk
In the Northern part of Nigeria, it is also administered in large doses by the ‘Hausas’ in the form of guinea corn and millet porridges called ‘kunun Potash’ which is administered to women immediately after delivery for the purpose of increasing the quality and quantity of breast milk.

However, experts recommend that potash should be used sparingly if need be because of its negative effects on human health.

Alternatively baking soda and the ashes of roasted, unripe plantain peel or ash of part of the palm nut or fruit can be used.