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.
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
A programme 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 only from retail outlets with refrigerators;
Check expiry date. Consume Moon Cakes within recommended
period;
Take Moon Cakes (specially snowy Moon Cakes) home
immediately after purchase and refrigerate them
immediately;
Since most Moon Cakes contain high sugars and/or
fat, consumers are advised to take a balanced
diet even during the festive seasons. Those with
diabetes should consult their dietitians regarding
intake of these foods.
Guidelines
on the Production of Snowy Moon Cakes
(A guide to food manufacturers)
Food establishment
The design and facilities of food establishments
producing snowy moon cakes should be in compliance
with the licensing requirements and conditions
set forth by the Food and Environmental Hygiene
Department.
Food establishments should have a cleaning and
sanitation programme in place to monitor and control
all equipment, utensils, refrigeration units that
have potential impact on the safety of snowy moon
cakes.
Raw
materials/ingredients
Raw materials and ingredients should only be obtained
from reputable and approved sources.
Raw materials/ingredients delivered to a food
premises should be inspected before acceptance.
Personnel responsible for inspection should as
far as practically possible satisfy 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 developed and fully implemented
an appropriate sampling and inspection system
to ensure that the raw materials/ingredients are
in compliance with the agreed specifications.
Storage
of raw materials/ingredients
Raw materials and ingredients should be stored
and handled under suitable conditions to prevent
spoilage, contamination and damage. Stocks of
raw materials and ingredients should be properly
rotated to ensure that the 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 materials should be non-toxic and appropriate
for snowy moon cakes. They should be stored and
handled in a clean and sanitary manner.
Preparation
and storage of finished products
Food handlers should receive proper training in
handling and preparing snowy moon cakes as well
as personal hygiene to enable them to take precautions
necessary to prevent contamination of snowy moon
cakes.
Frozen ingredients should be thawed under refrigeration
that maintains the temperature at 4oC
or below. Thawed ingredients should be used as
quickly as possible for the production of snowy
moon cakes and under no circumstances be held
above 4oC for more than 1 hour.
Finished products prepared at room temperature
should be cooled to 4°C or below within 1 hour.
Finished products intended to be stored frozen
should be maintained at a temperature of -18°C
or below.
Finished products should be labelled properly
and the label should include a statement of storage
conditions.
Transportation,
distribution and display of finished products
Finished products should be transported, distributed
and displayed in a proper manner and at appropriate
temperatures to protect them from contamination
and deterioration.
Where possible, transportation, distribution and
display units of finished products should be equipped
with accurate and reliable temperature control
and monitoring instruments.
Finished products should be rotated to ensure
that the distribution and sale of products is
carried out in a first-in-first-out basis.
Appropriate and adequate chillers and/or freezers
should be available in authorized retail outlets
selling snowy moon cakes.
Clear instructions on the proper methods of storing,
handling and displaying snowy 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 are in
place to minimize the potential chemical, physical
or microbiological contamination 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.
Last
review date: 19-01-2005