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Street food may look tasty, but beyond the nice aroma, it is a health time bomb ticking.

This is because transformer oil, as well as reused cooking oil, is used to prepare most of the food on the street.

 Experts have warned that many people may be eating their way to the grave unknowingly. In a new study on fried food served along Kampala’s streets, leftover oil has been blamed for food poisoning, cancer and cardiovascular diseases.

The oil in Kampala is recycled or used several times. The report also states that the oil used for frying fish and chips had peroxide values that were about four times above the recommended quality specification.

The peroxide value measures the extent to which an oil has changed. This is also accompanied by changes in colour, with a darker colour showing how much oxygen the oil has absorbed. The study, titled Recycled cooking oils used for street foods in Kampala, Uganda: Quality and recycling frequency, was conducted by three researchers — Emmanuel Okalany, Stellah Byakika and Ivan Muzira Mukisa.

The researchers conducted the study under the department of food technology and nutrition, School of Food Technology, Nutrition and Bioengineering at the College of Agricultural and Environmental Sciences, Makerere University.

This study evaluated the quality of cooking oil used to deep-fry potato chips and fish by street food vendors in Kampala. A safe oil recycling frequency was determined by separately deep-frying several batches of fish and potato chips.

After each frying cycle, the oil’s quality was analysed. The paper was presented in a journal, Science Direct, published by Elsevier. The study noted that street food vendors keep the oil overnight after cooking and keep adding fresh oil. This is done to save money.

HIGH MOISTURE CONTENT

The moisture content of the oil used to deep-fry chips and fish was just above the quality specification. “The slight elevation of values above the specification could be due to traces of water left from the food fried. As earlier mentioned, it was noted that after the potato chips and fish were washed, they, together with their residual wash water, were immediately immersed in the hot oil, significantly hydrating them,” the report stated.

Chips being deep-fried in Ggaba, Makindye Division recently. This is one of the areas where big restaurants and hotels in Kampala get market for recycled cooking oil

PROBLEM'S MAGNITUDE

 In some of the markets our undercover reporters visited, it was established that fish vendors use recycled cooking oil. Vendors confirmed that they rarely use cooking oil from the shop; they prefer to buy used oil. “The new one easily evaporates, and it puts us at a loss, so the old one is better because it lasts longer,” one of the vendors told Weekend Vision.

KAWEMPE, NAMUWONGO

A popular hangout along Kira Road in Kawempe, Kampala is known for selling deep-fried fish. When Weekend Vision visited, it was teeming with customers who attested to the taste of the deepfried fi sh, saying its aroma and brown colour were inviting.

The seller said fresh cooking oil makes the fish look whitish, which does not attract customers.

Along Namuwongo’s railway stretch is a busy place where people queue to feast on food. When Weekend Vision journalists visited, two young men were frying pork. They said they add more oil whenever it is almost finished. The only time they change it is when they are washing the soot-coated frying pan

Jerricans filled with recycled cooking oil ready for sale at the collection centre of a prominent restaurant in Kampala

FRIED FISH SELLER

Every evening, Mama Praise (not her real name) fries fish for a living; it has been her longtime occupation. She also said she hardly uses new cooking oil because of its short shelf life. Mama Praise was busy attending to many customers. We had to leave her since we wanted to observe the nature of her cooking oil, which was dark. A colleague cracked a joke.

“Okimanyi butto omukadde awomesa enva?” (Do you know that recycled cooking oil makes the sauce taste delicious?). “Could you sell me some?” he asked Mama Praise, who quickly responded: “No, I can’t, but we have suppliers who can sell to you, not me.” “Who supplies to you and at how much?” we inquired. A 20ltr jerrycan costs sh60,000–sh70,000, Mama Praise told us.

This is against about sh200,000 for fresh cooking oil of the same quantity. She said they buy the used cooking oil from big hotels that only use it once or twice. Mama Praise added that the suppliers hailed from Ggaba, where most users or customers are. All we wanted was a sample from her, but she declined. “You go to Ggaba and buy the volumes you want; mine is little.”

WHY DOES OIL TURN BLACK?

A chef working with a hotel along Munyonyo Road said when fish is marinated in dark soy sauce and mixed with other spices, the oil turns brown. “It gives the fish more flavour, compared to oil that has not been mixed with other spices,” he said. The chef added that this oil is for fish only, and he uses it for two days and changes it thereafter. He said interested clients buy the used oil, which ends up on the streets.

THE SOURCE

Our next stop was Ggaba. Here, the vendors are busy churning out customers’ orders. We counted several jerry cans full of what seemed like cooking oil. We spent about three to four hours in the smoky kitchen, but the cooks are used to it and hardly get bothered. We finally got a sample — about half a litre — which we bought at sh5,000.

UNBS' TAKE

The Uganda National Bureau of Standards (UNBS) has warned consumers of cooking oil and to watch out for fake cooking oil, which has flooded the market. This was after it intercepted young boys selling transformer oil at Wandegeya and Kisekka in Kampala. Deus Mubangizi, the manager of the National Metrology Laboratory at UNBS, said transformer oil is sold to traders who sell chips on the streets.

“Following a tip from someone that some young boys were repackaging transformer oil and selling it, we sent our market surveillance team to investigate. Indeed, we found the boys repackaging it in used cooking oil bottles ready to sell,” Mubangizi said.

He made the remarks on Wednesday during a stakeholder dialogue to mark World Consumer Rights Day 2024 at the Imperial Royale Hotel in Kampala. Mubangizi said the boys informed them that they were selling the cooking oil to those who sell food on the street, especially chips.

“We are calling upon the public to report such criminals because when we arrested those boys, the neighbours knew what they were doing but no one had ever reported. Save millions of Ugandans by calling our toll-free lines,” he said. Asked about the dangers of consuming transformer oil, Mubangizi said you could get diarrhoea or long-term consequences.

“Buy cooking oil from supermarkets, not from the streets. That way, you will avoid eating fake cooking oil, but also criminals who sell these fake things, stop it. You are killing Ugandans,” Mubangizi said.

Some street food vendors mix recycled cooking oil with oil meant for transformers (pictured) to prepare food for clients

TRANSFORMER OIL

On condition of anonymity, a local leader in Kansanga, a Kampala city suburb, said using over-recycled cooking oil and mixing it with transformer oil is common. He said vendors had been dealing in transformer oil for years, mixing it with cooking oil. Dr Max Ojangole Igune, a nutritionist at Hunger Fighters Uganda, a nongovernmental organisation working in refugee settlements, said reused cooking oil, mixed with transformer oil, is slow-killing poison.

The mixture of the two, the nutritionist said, causes abnormalities in newborn babies such as blindness, missing limbs and hearing problems. Igune said the fatal concoction causes an array of respiratory illnesses, which, after prolonged consumption, can escalate into throat cancer.

He noted that some droplets of the reused cooking oil get deposited in the body and become hard to remove. The body forms antibodies to fight them, which become complex. Igune said these droplets turn into boils

Some tend to remain inside the body, and others protrude. He said the increasing cases of fibroids in women, for example, is a related outcome. Igune recommends using cooking oil only twice, beyond that, it will break down into carcinogens. He explained that this happens after it loses its value.

Igune added that charred particles in the recycled cooking oil can cause the same problems. Foods fried with transformer oil, such as cassava, Irish, sweet potato chips, samosa and mandazi; have a harder skin, which is not common with foods fried with uncontaminated cooking oil. They look more crunchy and crispy with a brown colour.

EXPERTS SPEAK OUT

Prof. Charles Muyanja, consultant on food safety, president of the Institute of Packaging Partners Uganda

Kampala Capital City Authority (KCCA) should crack the whip concerning regulation because they need support. KCCA has a role to play, but they cannot do it alone. What should be done is to ensure sensitisation for the processors to understand the implications and also food preparation.

There is also a need to put in place alternatives for the used oil. This can be used for burning furnace oil. Street food vending is important because it employs many people and is also a source of revenue. Above all, food must be safe to sustain a healthy and productive population.

Dr Barnard Bwambale, specialist working with Food Safety Coalition Uganda

Used cooking oil increases the risk of forming low-density lipoproteins linked to cardiovascular diseases. Rancid or overstayed oil creates a risk of food-borne diseases among consumers. Similarly, overused oil when consumed by humans can lead to unnecessary body reactions that lead to allergies.

Reporting by Carol Kasujja Adii, Ibrahim Ruhweza, Stuart Yiga, Sulaiman Mutebi
and Gerald Tenywa