CFS announces risk assessment study results on microbiological quality of sushi and sashimi in Hong Kong

The Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department today (July 29) announced the results of a recently completed risk assessment study on the microbiological quality of sushi and sashimi in Hong Kong. Results showed that out of the 197 sushi and sashimi samples tested, four were found to be unsatisfactory in terms of hygienic quality but there was no food safety concern.At the same time, 98 per cent of the sushi samples were found to have adequate vinegar in their rice portion, which may reduce the microbiological risk.

"The study aims to assess the microbiological quality of sushi and sashimi available in the local market with a view to examining the microbiological risks associated with these foods. Separately, acidified rice is commonly used in sushi and proper acidification of rice to a pH value of 4.6 or below is known to inhibit the growth of pathogenic bacteria, particularly Bacillus cereus. This study has also analysed the pH values of acidified rice in sushi," a spokesman for the CFS said.

Between July and October last year, the CFS obtained 98 sushi samples and 99 sashimi samples from licensed restaurants and retail outlets for microbiological tests,covering aerobic colony count (ACC), Escherichia coli (E. coli) count, Salmonella spp., coagulase-positive staphylococci organisms (including Staphylococcus aureus) count and Vibrio parahaemolyticus count. Bacillus cereus count was also tested for sushi samples.

The study found that the microbiological quality of most of the samples (98 per cent) was either satisfactory or borderline, and only four samples were found not complying with the limits for ACC (10,000,000 colony-forming units per gram (cfu/g)) or E. coli count (100 cfu/g) as set out in the Microbiological Guidelines for Food. The four unsatisfactory samples were a sea urchin sashimi, a prawn sashimi and a salmon roe sushi with ACC levels of 30,000,000 cfu/g, 20,000,000 cfu/g and 22,000,000 cfu/g respectively, and a salmon sashimi sample with 200 cfu/g of E.coli.

"On food safety, no samples were found to contain excessive pathogens. Though four samples were considered to be unsatisfactory in terms of hygienic quality, consuming them did not represent a health risk. However, it indicated that there was room for improvement in the food manufacturing and handling process.In this connection, the CFS has already offered health advice to the food premises concerned. In follow-up visits by the CFS, no sea urchin sashimi was found on sale in the premises concerned, and the microbiological quality of other follow-up samples was found to be satisfactory," the spokesman said.

On pH value of acidified rice in sushi, 96 sushi samples (98 per cent) were found to have a pH value of 4.6 or below in their rice portion, and only two samples had a pH value of 4.7. However, none of the sampling vendors conducted regular verification of sushi rice acidification.

"To ensure adequate vinegar in sushi rice, food handlers should check the pH value of acidified rice from time to time, especially when there is new staff or recipe," the spokesman said.

The spokesman urged members of the trade to take note of the results of this study and adopt appropriate measures for the hygienic handling and safe display of sushi and sashimi. Finished sushi should be kept at a temperature of four degrees Celsius or below. If sushi is to be displayed at a temperature above four degrees Celsius for over four hours, it should be discarded. In addition, sashimi should be displayed at four degrees Celsius or below because its preparation normally does not involve acidification.

The spokesman also reminded high-risk consumers, including people with weakened immunity, the elderly, pregnant women and young children, to avoid eating raw or partially cooked food since they are at higher risk for foodborne illnesses.

The full report on the study is available on the CFS webpage at www.cfs.gov.hk .

Ends/Wednesday, July 29, 2015