Almost 50 people fell ill in two Salmonella outbreaks in Hong Kong in May and June.

The two food poisoning outbreaks involved seven and 40 victims, respectively, and were related to consumption of soft-scrambled eggs. Patients suffered abdominal pain, vomiting, diarrhea and fever after eating the undercooked scrambled eggs with either rice and pasta and some required hospitalization.

Cooking or holding temperature issues
Kenneth Yip, scientific officer in the risk communication section at the Centre for Food Safety, said the cases were caused by inadequate cooking or improper holding temperature of scrambled eggs after cooking.

“Field investigation of some cases found that semi-cooked scrambled eggs were kept at room temperature for a prolonged period. No further reheating was conducted before they were being served. These food incidents highlight the food safety risk of consuming scrambled eggs without proper heat treatment and storage conditions,” he said.

Salmonella causes food poisoning with an incubation period between  six to 72 hours, usually within 12 to 36 hours. Because such food poisoning from egg dishes is related to improper cooking and holding temperatures, particular attention should be paid to whether food is fully cooked and kept at correct temperatures, public health officials advise.

Previous incidents
From late February to mid-March 2018, there were 16 people who fell ill after eating at the same restaurant. Epidemiological investigation suggested their illnesses were related to consumption of various dishes with stir-fried eggs on the same day.

Field investigation found unpasteurized eggs were used and cooked for a very short time before serving so inadequate cooking might have contributed to the outbreak.

In late October to early November 2017, 22 people were part of a Salmonella outbreak linked to a restaurant. Epidemiological investigation showed they were related to consumption of scrambled egg in fusilli or noodles.

An investigation revealed scrambled eggs were prepared in a semi-cooked condition in advance and kept at room temperature for a prolonged period. After receiving a customer order, the semi-cooked scrambled egg was placed on top of the fusilli and noodles without further reheating or cooking.

Cooking and heating can destroy bacteria including Salmonella. Foods should be cooked to a core temperature of at least 75 degrees C. Cooked foods served hot should be kept at above 60 degrees C prior to serving, while cold dishes should be kept at 4 degrees C or below.

Cooked foods should be consumed immediately and not left at room temperature for more than two hours. If cooked food is kept at room temperature for more than two hours, it should be discarded.

High risk groups including pregnant women, young children, the elderly and immunocompromised people are advised not to consume raw or undercooked egg dishes.

Meanwhile, the Centre for Food Safety cited media reports that some baby napa cabbages were recently found to contain formaldehyde in mainland China to keep them fresh in transit.

Formaldehyde can be naturally present in fruits, vegetables, meats, marine fish and crustaceans in a small amount but it is not a permitted food additive. In the last year, the Centre for Food Safety has taken 150 samples including vegetables to test for formaldehyde and all results were satisfactory.

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