Risk Assessment Studies
Report No. 3
Microbiological Hazards Evaluation
Moon cakes in Hong Kong
August 2000
Food and Environmental Hygiene Department HKSAR
Table of Contents
- Abstract
- Introduction
- ProductionProcesses and Microbiological Hazards
- Surveillanceon Moon Cakes from 1997 to 1999
- Interpretation
- Recommendation
- Figures1 - 2
- Tables1 - 4
- References
- Appendix1: Guidelines on the Production of Snowy Moon Cakes
Abstract
Moon cakes are commonly taken by Chinese to celebrate Mid-Autumn Festival, which refers to the 15th day of the eighth lunar month. While the conventional Guangdong Moon Cake (CGMC) had been commonly used in Hong Kong, Snowy Moon Cake (SMC) is a variant introduced to the local market in the past years. The microbiological surveillance findings on 70 samples of CGMC and 107 samples of SMC collected from 1997 through 1999 were reviewed in the present study. All CGMC had achieved satisfactory hygienic quality, as reflected in the APC count and/or E. coli (total) measurement, and none was found containing specific pathogens. On the other hand, 11% (12) of all SMC samples, had unsatisfactory hygienic quality. A decreasing trend, from 18.6% in 1997, 7.4% in 1998, and 5.4% in 1999, was observed. In addition, Salmonella spp. was detected in 2 samples in 1997 and one sample in 1999, and S. aureus in one sample in 1998. The final baking step in the production of CGMC had effectively virtually eliminated the microbiological hazards. In SMC, the design of production flow, training for the food handlers, as well as the storage conditions are extremely important in maintaining satisfactory microbiological quality. Both the trade and consumers are advised to take necessary precautions to enhance food safety of consuming moon cakes.
Risk Assessment Studies -
Microbiological Hazards Evaluation
Moon Cakes in Hong Kong
- An Evaluation of Moon Cakes Microbiological Surveillance 1997 - 1999
Introduction
Moon cake is a type of traditional Chinese festive food taken for the celebration of the Mid-Autumn Festival (which refers to the 15th day of the eighth lunar month). It is available on market in August and September of the year.
Moon cakes are categorized as flour confectionery. The production requires a food factory or a bakery licence under the Hong Kong Law. On the other hand, however, sale of moon cakes does not require any special licence or permit. Retail outlets can be found in many places like cakes shops, supermarkets and food stores.
In Hong Kong, the most popular type of moon cakes is the conventional Guangdong moon cakes (CGMC). In the early 1990s, a new type of moon cakes known as snowy moon cakes (SMC) was introduced into the local market and has gained increasing popularity.
Production Process and Microbiological Hazards
Microbiological hazards refer to the presence of pathogens that can cause food poisoning to those who have consumed the food. In moon cakes, pathogens identified are mainly Staphylococcus aureus and Salmonella species which are usually the results of cross contamination during processing or storage.
The pathogens may grow and reach infective dose if the moon cakes especially SMC, are kept within the Temperature Danger Zone (i.e. between 4oC and 63oC) for a prolonged period of time.
For S. aureus, a toxin dose of about 1.0 microgram in contaminated food will produce symptoms of intoxication. This toxin level is reached when S. aureus populations exceed 105 per gram (1). While all people are susceptible to staphylococcal intoxication, intensity of symptoms may vary. Death from staphylococcal food poisoning is, however, very rare (1).
The infective dose of Salmonella spp. may be as few as 15-20 cells, depending upon age and health status of host, and strain differences among the members of the genus (2). Symptoms of (salmonellosis) are most severe among the elderly, infants, and immuno-compromised people (2).
In Hong Kong, no food poisoning cases have been reported due to consumption of moon cakes during the last three years.
Conventional Guangdong moon cakes
The production process of CGMC can be divided into purchasing, storage, preparation, baking, cooling, packaging, storage and delivery (Figure 1). Raw lotus seeds are cooked, ground and wrapped, sometime with a salted egg yolk, by a flour pastry. The wrapped product is then molded and baked at about 200oC-300oC for 15-25 minutes. After cooling, the moon cakes are packaged and ready for delivery.
Handling (e.g. manipulating ground lotus seeds and pastry with bare hands) of raw lotus seeds and flour may introduce some bacteria into the intermediate products. However, baking the intermediate products at high temperature virtually eliminates all bacteria present, thus removing potential microbiological hazards
Snowy moon cakes
The production process of SMC consists of purchasing, storage, preparation, cooling, packaging, storage and delivery (Figure 2). Ingredients for the production of SMC include ground green bean, egg yolk and flour. All these ingredients have already been cooked before molding and further baking is not required.
Handling (e.g. molding and packaging) of SMC ingredients inevitably introduced some bacteria into the final products. Unlike CGMC, bacteria are able to survive in the final products because of the absence of final baking step. Pathogens, if present, may grow and exceed infective dose if SMC is handled improperly during transportation and storage such as displaying SMC within the Temperature Danger Zone for a prolonged period of time.
處理冰皮月餅（例如定形和包裝）的配料時，難免會令最終製成品沾染細菌。由於冰皮月餅的製造有別於傳統月餅，無須經過最後的烘焙程序，因此細菌可在最終製成品中生存。如不妥善處理冰皮月餅，例如在運送、貯存或陳列冰皮月餅時，把冰皮月餅存放於危險溫度範圍內一段長時間，則月餅內如有病原體存在，這些病原體便會繁殖並可能達至足以令人受感染的數量。
Surveillance on moon cakes from 1997 to 1999
Microbiological status of moon cakes was assessed based on the surveillance results of the last few years. Samples of moon cakes were purchased from the market and analysed by the Public Health Laboratories, Pathology Service of the Department of Health.
The microbiological analysis consists of two parts. The first part is an assessment of hygienic quality of moon cakes while the second part is an assessment of safety of moon cakes. The current microbiological criteria for moon cakes include hygienic indicators such as Aerobic Plate Count (APC) and coliform/E.coli (total), as well as the presence of pathogens such as Staphylococcus aureus, and Salmonella spp. (Table 1).
Hygienic quality
APC or E. coli (total) reflects the general hygienic status of moon cakes. During the period between 1997 and 1999, 70 samples of CGMC were taken for microbiological examination (Tables 2 and 3). According to the microbiological guidelines, the results of all these samples were satisfactory.
During the same period, a total of 107 samples of SMC were examined. The unsatisfactory rates were 18.6% (8 out of 43) in 1997, 7.4% (2 out of 27) in 1998 and 5.4% (2 out of 37) in 1999 (Table 4).
Specific pathogens
No sample of CGMC was found containing pathogens during the period under study.
As regards SMC, two samples were found containing Salmonella spp. in 1997, one containing S. aureus (i.e. with level exceeding 104 per gm) in 1998 and one containing Salmonella spp. in 1999.
Discussion
High levels of APC and E. coli (total) reflect unsatisfactory hygienic practice during processing of food from source to table. High counts of APC in foods often indicate contaminated raw materials or unsatisfactory processing and indicate unsuitable time/temperature control during storage (3). Although these organisms may not directly cause human illness, the levels of unsatisfactory samples suggested room for improvement in the production process.
This study showed that the CGMC had obviously achieved a more standard in terms of achieving a better hygienic quality and free of specific pathogens. The final baking step is useful in removing any remaining microbiological hazard introduced during the preparation processes of CGMC.
As for SMC, the hygienic status has to be maintained with a careful design of production flow on the side of manufacturer. Equally important is the training of hygienic practice for the handlers along the process to maintain the hygienic status of the food.
Recommendations
The absence of final baking step during the production of SMC imposes some microbiological risks on the consumption of SMC. However, the risks can be minimized if food manufacturers follow the principles of Good Manufacturing Practice (GMP) and Hazard Analysis and Critical Control Point (HACCP) system (4).
In order to assist food manufacturers in producing safe and sound SMC, the Food and Environmental Hygiene Department (FEHD) has produced, based on the principles of HACCP system, a "Guidelines on the Production of Snowy Moon Cakes" (Appendix 1). Key recommendations are summarized below:
Advice for the trade
- Aprogramme must be established to monitor the quality of raw materials.For example:
All materials should be obtained from approved sources.
An inspection system should be in place to ensure that raw materials/ingredients are in compliance with the agreed specifications.
- Snowy Moon Cakes should be produced, stored, transported and displayed in a proper manner and at appropriate temperatures to protect them from contamination and deterioration.
- Food handlers should receive proper training in handling and preparing snowy Moon Cakes as well as personal hygiene to enable them to take precautions that are necessary to prevent contamination of snowy Moon Cakes.
Advice for the consumer
Consumer are advised to pay special attention to the following -
- Buy SMC onlyfrom retail outlets with refrigerators;
- Checkexpiry date. Consume Moon Cakes within recommended period;
- TakeMoon Cakes (specially snowy Moon Cakes) home immediately after purchaseand refrigerate them immediately;
- Sincemost Moon Cakes contain high sugars and/or fat, consumers are advisedto take a balanced diet even during the festive seasons. Those withdiabetes should consult their dietitians regarding intake of these foods.
FPHD/FEHD
September 2000
Figure 1
Production of Conventional Guangdong Moon Cakes
Figure 2
Production of Snowy Moon Cakes
Table 1
Microbiological Guidelines for Moon Cakes *
| Test Criteria | Unsatisfactory |
|---|---|
| Aerobic Plate Count (APC) | > 1 x 106 per g |
| Coliform | > 4 organisms per g (before 1998) |
| E. coli | > 104 organisms per g (after 1998) |
| Staphylococcus aureus | > 104 organisms per g |
| Salmonellae | Present in 25 g |
* The "Microbiological Guidelines for Ready-To-Eat Food" has been updated and the above guidelines may no longer be applicable. Please refer to the latest version at Microbiological Guidelines for Ready-to-eat Food
Table 2
Moon cakes microbiological surveillance in Hong Kong:
Number of samples taken 1997-1999
| Food sample | 1997 | 1998 | 1999 | Total |
|---|---|---|---|---|
| CGMC1 | 22 | 18 | 30 | 70 |
| SMC2 | 43 | 27 | 37 | 107 |
| Grand Total | 65 | 45 | 67 | 177 |
Table 3
Moon cakes microbiological surveillance in Hong Kong:
Hygiene quality of conventional moon cakes 1997-1999
| Year | Number of sample | No. of unsatisfactory samples (%) |
|---|---|---|
| 1997 | 22 | 0 (0%) |
| 1998 | 18 | 0 (0%) |
| 1999 | 30 | 0 (0%) |
Table 4
Moon cakes microbiological surveillance in Hong Kong:
Hygiene quality of snowy moon cakes 1997-1999
| Year | Number of sample | No. of unsatisfactory samples (%) |
|---|---|---|
| 1997 | 43 | 8 (18.6%) |
| 1998 | 27 | 2 (7.4%) |
| 1999 | 37 | 2 (5.4%) |
References
- FD/CFSAN, Bad Bug Book - Staphylococcus aureus 2000.
- FD/CFSAN, Bad Bug Book - Salmonella spp. 2000.
- International Commission on Microbiological Specifications for Foods. Microorganisms in foods. (London: Blackie Academic & Professional. 1978.)
- Joint FAO/WHO Food Standards Programme Codex Alimentarius Commission. Codex Alimentarius Food Hygiene Basic Texts. FAO/WHO. (Rome, 1997.)
Appendix 1
Guidelines on the Production of Snowy Moon Cakes
(A guide to food manufacturers)
Food establishment
The design and facilities of food establishments producing snowy mooncakes should be in compliance with the licensing requirements and conditionsset forth by the Food and Environmental Hygiene Department.
Food establishments should have a cleaning and sanitation programmein place to monitor and control all equipment, utensils, refrigerationunits that have potential impact on the safety of snowy moon cakes.
Raw materials/ingredients
Raw materials and ingredients should only be obtained from reputableand approved sources.
Raw materials/ingredients delivered to a food premises should be inspectedbefore acceptance.
Personnel responsible for inspection should as far as practically possiblesatisfy that :
- there are no signs or indications of contamination or damage to the raw materials/ingredients;
- chilled/frozen raw materials/ingredients have arrived at the proper temperatures (e.g. frozen items at -18oC or below; chilled items at 4oC or below) and free from observable evidence of temperature abuse.
Manufacturers should satisfy themselves that their suppliers have developedand fully implemented an appropriate sampling and inspection systemto ensure that the raw materials/ingredients are in compliance withthe agreed specifications.
Storage of raw materials/ingredients
Raw materials and ingredients should be stored and handled under suitableconditions to prevent spoilage, contamination and damage. Stocks ofraw materials and ingredients should be properly rotated to ensure thatthe first-in-firt-out principle is followed.
Raw materials should be stored at proper temperatures:
- frozen items should be stored at -18°C or below;
- chilled items should be stored at 4°C or below.
Packaging materialsshould be non-toxic and appropriate for snowy moon cakes. They shouldbe stored and handled in a clean and sanitary manner.
Preparation and storage of finished products
Food handlers should receive proper training in handling and preparingsnowy moon cakes as well as personal hygiene to enable them to takeprecautions necessary to prevent contamination of snowy moon cakes.
Frozen ingredients should be thawed under refrigeration that maintainsthe temperature at 4oC or below. Thawed ingredients shouldbe used as quickly as possible for the production of snowy moon cakesand under no circumstances be held above 4oC for more than1 hour.
Finished products prepared at room temperature should be cooled to 4°Cor below within 1 hour.
Finished products intended to be stored frozen should be maintainedat a temperature of -18°C or below.
Finished products should be labelled properly and the label should includea statement of storage conditions.
Transportation, distribution and display of finished products
Finished products should be transported, distributed and displayed ina proper manner and at appropriate temperatures to protect them fromcontamination and deterioration.
Where possible, transportation, distribution and display units of finishedproducts should be equipped with accurate and reliable temperature controland monitoring instruments.
Finished products should be rotated to ensure that the distributionand sale of products is carried out in a first-in-first-out basis.
Appropriate and adequate chillers and/or freezers should be availablein authorized retail outlets selling snowy moon cakes.
Clear instructions on the proper methods of storing, handling and displayingsnowy moon cakes should be available and given to retailers.
Management system
A preventive food safety management system (such as the HACCP system)should be established to ensure that effective control measures arein place to minimize the potential chemical, physical or microbiologicalcontamination of the products during the manufacturing process.
This is a publication of the Food and Public Health Branch of the Food and Environmental Hygiene Department of HKSAR Government. Under no circumstances should the research data contained herein be reproduced, reviewed, or abstracted in part or in whole, or in conjunction with other publications or research work unless a written permission is obtained from the Department. Acknowledgement is required if other parts of this publication are used.
Correspondence:
Risk Assessment Section Food and Environmental Hygiene Department 43/F,
Queensway Government Offices,
66 Queensway,
Hong Kong.
Email: enquiries@fehd.gov.hk