How can chicken rice be cooked in a way that avoids E. coli growth? Hawkers explain

SINGAPORE: To prevent contamination and bacteria formation, chickens are cooked in batches and their temperatures maintained, hawkers say, in the wake of a viral video claiming E. coli was present in almost half of chicken rice stalls visited by a YouTuber while in Singapore.

But stallholders shared with CNA the measures they take to mitigate the risk of E. coli, ranging from not leaving cooked chickens on display for long periods of time to washing their premises frequently.

E. coli is a type of bacteria found in digestive systems, faecal matter and contaminated soil and water. While most types of E. coli are harmless or cause minor illnesses, a few strains can cause severe stomach cramps, bloody diarrhea and vomiting, according to academic medical centre Mayo Clinic.

E. coli can also be found in contaminated beef, raw milk, vegetables and cheese. 

The video posted by Taiwanese Angel Hsu in early June detailed her visits to 100 chicken rice stalls in Singapore. Apart from assessing each dish's taste and texture, she sent the chicken rice to a laboratory for testing. 

Tests found that 45 samples exceeded Singapore's regulatory limits for E. coli bacteria, which is 100 colony-forming units per gram (cfu/g).

According to Hsu's data - set out in a publicly available Excel sheet - the chicken rice from four stalls returned a reading of more than 490,000 cfu/g, which is the upper limit of the lab's machine.

HOW COOKED CHICKEN IS KEPT FRESH

Mr Daniel Tan, the owner of OK Chicken Rice chain - one of those that tested negative for E. coli in Hsu's Excel sheet - said his chickens are cooked at least three times a day, with only a few cooked each time.

The evidence is in his stall's gas bill, he said.

"When (the chicken is) hanging there for the next one to two hours it's still boiling hot, so if you touch it your hands will be burnt," added Mr Tan.

To maintain a roasted chicken's temperature for the next two hours, the stall avoids slicing it open.

"We open only two chickens (at one time). So a brand new day starts, you order four drumsticks I'll sell it to you, after that I'm not going to open anymore until the (sliced chickens) are more or less sold out. So this is how the chicken is kept fresh."

By Mr Tan's estimate, once a cooked chicken is sliced into, it can only stay hot for about 15 minutes before the temperature drops and bacteria starts to grow. 

Steamed chicken is also cooked in small batches, and each batch kept in clean, sealed ice baths before being served to customers cold. 

Cooked chickens are not kept longer than two hours, Mr Tan said. 

The owner of Ah Lim Chicken Rice stall in Bedok, who only wanted to be known as Mr Lim, also cooks his meat in batches.

The stall was not tested by the YouTuber Hsu.

Mr Lim cooks four roasted chickens ahead of the lunch crowd, and cooks subsequent batches on demand. 

"There are stores that deep fry many and then keep them for the rest of the day," he said. 

"It's a question about hygiene as well as the food quality. Something that is deep fried in the morning, at night when you eat it, it will taste different."

Showing CNA his stall's work space, Mr Lim pointed out potential areas for bacteria growth and described how these were kept clean. 

The chopping board used to cut chickens is scraped, wiped or washed throughout the day to prevent scum from accumulating. 

Cucumbers are cut and served fresh instead of stored in slices, while condiments such as chilli are made available in small amounts and topped up when necessary, as they tend to turn sour the longer they are kept in containers. 

"In a dish like chicken rice, it’s not just the chicken that should command attention," said deputy director of the Nanyang Polytechnic's (NYP) school of applied science Richard Khaw. "But also the accompaniments - cucumbers, tomatoes and parsley. As they're often served raw, they're particularly prone to contamination if washed with unclean water or left exposed."

In Mr Lim's stall, drip trays under displayed chickens are rinsed every hour to prevent oil from collecting.

He said he does not keep chickens displayed throughout the day like other stalls do, in a bid to appeal to customers or show the availability of stock.

Experts CNA spoke to warned that bacteria may grow to high numbers on displayed chickens due to Singapore's high temperature.

Mr Billy Lu, an outlet manager of a chicken rice stall in Hougang, said he cooks more chickens if neighbouring food stalls are closed, as this would mean greater demand for chicken rice. Any spare or leftover chicken parts are used as soup stock. 

HOW SOME PEOPLE HAVE LESS CHANCE OF INFECTION

Despite Hsu's findings, the last reported foodborne illness cases involving chicken rice were in 2020, according to the Singapore Food Agency. 

Food safety experts said the lack of cases could be due to not all strains of E. coli causing severe illnesses. 

"One can consume food with elevated levels of E. coli and remain asymptomatic because they aren’t dangerous strains," said NYP's Mr Khaw.

Out of hundreds of strains, E. coli O157:H7 is the most common type that causes severe intestinal infection in humans, said Republic Polytechnic's (RP) Heng Kiang Soon.

Dr Heng, a lecturer at RP's school of applied science, said an individual's tolerance threshold and health status could also explain a lack of adverse reactions.

"Research has shown that individuals with a better microbiota balance tend to have less chances of being infected with E. coli as the good bacteria in their gut fight against the bad ones," he explained. 

Children and seniors with their weakened immunity, individuals with impaired immunity due to chronic diseases, and those taking medication that suppress the immune system have a higher risk of E. coli infection and complications. 

Nonetheless, a high E. coli count is indicative of poor hygiene practices and increases the chances of pathogens being present, said Assistant Professor Li Dan from the National University of Singapore's (NUS) department of food science and technology.

This is why food safety regulations look at all strains, not just harmful ones, NYP's Mr Khaw added. 

Dr Heng said detecting and quantifying specific strains of E. coli can be complex and time-consuming, and hence impractical for authorities. 

Dr Li said raw chicken was the most possible source of E.coli in chicken rice, with potential cross contamination from water, surfaces and food handlers. Undercooked chicken is also a possible source, said RP's Dr Heng.

The experts advised cooks to cut ingredients closer to serving time and not leave them exposed for more than four hours. 

They suggested that consumers look out for the cleanliness levels, when selecting a stall. 

Dr Heng said consumers should also check if chickens are freshly cooked or have been displayed for some time. 

"It is also important to notice the appearance of the chicken," he added. Chickens should be free of discoloration, off-putting odours and slimy texture."