The Centre for Food Safety (CFS) and the Consumer Council (CC) have conducted a study on the microbiological quality of Chinese cold dishes in Hong Kong. This study aimed to give an overview of the microbiological quality of some Chinese cold dishes commonly available at various local food premises and to increase awareness of safe preparation and handling of Chinese cold dishes in the food industry.
2. "Chinese cold dishes" refer to Chinese style dishes which are likely to be served cold and in general the ingredients are cooked or marinated before consumption. These dishes can be consumed without further heat-treatment and may involve manual handling. Uncooked and inadequately cooked ingredients may contain bacteria; in addition, improper handling or storage may contaminate the food and allow bacteria to grow. Proper handling of Chinese cold dishes can improve the microbiological quality and prevent food poisoning.
Methods and Results
3. In this study, a total of 114 Chinese cold dishes (58 meat and meat products; 22 seafood and seafood products; 20 vegetables and soyabean products and 14 others) were collected from food premises, including chain and individual stores, located at different districts in Hong Kong. Seven microbiological parameters, namely aerobic colony count (ACC), Escherichia coli (total), Salmonella species, Vibrio parahaemolyticus, Staphylococcus aureus, Clostridium perfringens and Bacillus cereus, were tested by the Public Health Laboratory Services Branch of the Centre for Health Protection, Department of Health. The microbiological quality of the samples was assessed against the criteria stipulated in the Microbiological Guidelines for Ready-to-eat Food (The Guidelines) issued by the CFS.
4. The Guidelines stipulate criteria indicating the microbiological condition of the food concerned so as to reflect its safety and hygienic quality. According to the Guidelines, microbiological quality of food can be classified into one of the four classes*, namely Class A, Class B, Class C and Class D.
5. Among the 114 samples taken in this study, majority (89%) were of Class A or Class B quality. However, 11 (10%) were of Class C quality, indicating a need for improvement in hygienic conditions, in which seven of them were due to excessive ACC, and four of them were due to relatively high level of Escherichia coli (total) and/or specific pathogens (Staphylococcus aureus or Bacillus cereus). In addition, two samples (a bean curd with lime preserved eggs sample and a liquor-saturated chicken sample) were of Class D quality, which were potentially hazardous to the consumer, due to the detection of Salmonella species in 25 g.
6. Insufficient cooking, post-cooking contamination, prolonged storage at room temperature and unhygienic handling might be the causes for the poor microbiological quality in samples as revealed in the study; highlighting the importance of good hygiene practices in the food industry. In order to help food trade implement food safety measures in their operations so as to produce and sell wholesome and safe cold dishes, the CFS has drafted a set of Trade Guidelines on Safe Production of Chinese Cold Dishes. After consulting with the trade, the Guidelines will be distributed and uploaded to the CFS website for trade reference.
Advice to the Public
- Patronise reliable and licensed food premises.
- Consume Chinese cold dishes as soon as possible.
- If products are not consumed immediately, keep them in the fridge at or below 4 oC.
- Vulnerable groups, such as the elderly, children, pregnant women and persons with lower immunity, should choose food especially high risk food, including Chinese cold dishes, carefully.
Advice to Trade
- Purchase food ingredients from reliable sources.
- Estimate the demand of each dish carefully to avoid over-production.
- Plan the production schedule ahead to avoid preparing Chinese cold dishes too far in advance.
- Except food eaten raw, food should be cooked thoroughly, with core temperature reaching at least 75°C for at least 30 seconds.
- If products are not served immediately, keep them in the fridge at or below 4 oC.
- Always follow good personal hygiene practices.
* Class A: the microbiological status of the food sample is satisfactory.
Class B: the microbiological status of the food sample is less than satisfactory but still acceptable for consumption.
Class C: the microbiological status of the food sample is unsatisfactory. Licensees of food premises should be advised to investigate and find out the causes and to adopt measures to improve the hygienic conditions.
Class D: the microbiological status of the food sample is unacceptable. The food sample contains unacceptable levels of specific pathogens that is potentially hazardous to the consumer.
Risk Assessment Section
Centre for Food Safety
Food and Environmental Hygiene Department