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An Investigation into the Microbiological Quality of Ready-To-Eat Cream and
Custard Filled Bakery Products Sold in Dublin City Centre
Laura Duffy and Prof. Nissreen Abu-Ghannam
School of Food Science and Environmental Health, College of Sciences and Health,
Dublin Institute of Technology, Cathal Brugha Street, Dublin 1, Republic of Ireland.
Email: [email protected]
Introduction
•
•
Results
contamination can occur during filling and topping bakery products with sensitive ingredients.
Fig.1: Confirmed S.aureus
Fig. 2: Suspected B.cereus
Staphylococcus aureus (S.aureus) and Bacillus cereus (B.cereus) are common pathogens present in
grown on Baird-Parker agar
grown on B.cereus agar
these products. Their presence is an indication of poor hygiene practices (unhygienic handling),
from bakery samples.
base from bakery samples.
inadequate refrigeration, and poor quality raw materials. The growth of bacteria often occurs between
Black/grey colonies with
Yellow/cream colonies
the cream/custard topping of the dessert and the body of the dessert[1].
clear halo around the
turned sections of the agar
colonies.
turquoise.
•
S.aureus and B.cereus have the ability to produce enterotoxins which survive the baking process.
•
Shelf life is not only dictated by microbiological safety but also by spoilage and loss of quality, in
particular appearance and texture. Staling and mould growth are some of the main causes of spoilage
in bakery products[2].
•
1. Identification of S.aureus and B.cereus Using Confirmation Tests
Baking at high temperatures is adequate to kill any vegetative cells present, but post baking
Table 1: Results of Confirmation Tests on
Black Growth on Baird-Parker Agar
Gram Stain:
Gram positive, cocci
Gram Stain:
Gram positive, bacilli
Catalase:
Positive
Catalase:
Positive
Coagulase:
Positive
Coagulase:
Negative
Oxidase:
Negative
API 50 CHB/E & Biolog Negative for B.cereus
It is vital that bakeries follow the correct hygiene practices to maintain the quality and safety of
products, preventing the risk of foodborne illnesses in consumers.
2. Results of Total Counts For S.aureus and Suspected B.cereus in Samples - Low (Satisfactory),
Moderate (Acceptable/Borderline), High (Unsatisfactory/Hazardous). Set out in Regulation (EC)
2073/2005 – Microbiological Criteria for Foodstuffs
Objectives
•
Assessment of the microbiological quality of ready-to-eat cream and custard filled bakery products,
𝟏/𝟏𝟏
Low
𝟒/𝟏𝟏
𝟒/𝟏𝟏
Observe the degradation of microbiological and sensory quality of cream filled bakery products over
Moderate
𝟔/𝟏𝟏
Moderate
𝟓/𝟏𝟏
Observe the practices applied in bakeries in Dublin and investigate the level of knowledge of hygiene
Fig.3. S.aureus Results
and safety by management and employees.
•
High
𝟐/𝟏𝟏
B.cereus
High
time.
•
Low
S.aureus
sold in Dublin City Centre, using S.aureus and B.cereus as indicators of hygiene and safety.
•
Table 2: Results of Confirmation Tests on Yellow
Growth on B.cereus Agar Base
Conclude if these products are a high risk to consumer health, and whether more stringent control
Fig.4. Suspected B.cereus Results
Total of 11 samples tested. The charts represent the number of samples that tested low, moderate or high
for levels of S.aureus and B.cereus.
measures need to be put in place.
3. Mini Shelf life & Temperature Abuse Study
2.50E+06
Materials & Methods
S.aureus & B.cereus In Cream Cake
cfu/g
2.00E+06
1.50E+06
S.aureus
B.cereus
1.00E+06
5.00E+05
0.00E+00
Day 1: Fresh
Microbiological examination
to determine the presence
of S.aureus and B.cereus[3]
Mini sensory trial to assess the
loss of quality over several
days of storage and
refrigeration
Survey of bakeries to
determine their level of
knowledge and observe their
practices
Day 2: Refrigerated
Day 2: Non-Refrigerated
Time of Testing & Storage Conditions
Fig 4. Increase in Levels of S.aureus & B.cereus over 2 Days, Refrigerated & Non-Refrigerated
• These graphs show an example of the large increase in the levels of bacteria over two days in cream
cake. Similar results were obtained for all cake samples tested.
• Samples increase to high (unsatisfactory) levels in day 2, even when stored at refrigerated
temperatures, indicating that these products should be consumed on the day of purchase.
• The huge difference in levels of bacteria between refrigerated and non-refrigerated samples reinforces
Microbiological Examination[3]
the importance of temperature control of these products throughout their entire shelf life.
Discussion & Conclusions
•
The majority of cream and custard filled bakery products tested had moderate levels of S.aureus and
suspect B.cereus. These products were purchased fresh in the morning, and immediately tested. The
levels should be low, which indicates that hygiene practices, and particularly hygienic handling of
10g of sample weighed
into stomacher bag[3]
90ml of MRD added[3]
products in bakeries, need to be improved. The amount of bacteria could easily reach a high level in
Homogenised for 3
minutes
the afternoon, causing a risk to consumers.
•
A small percentage of samples which had high levels of S.aureus and suspect B.cereus were all
purchased from the same premises, confirming poor hygiene in this particular bakery.
•
All ready-to-eat cream filled bakery products should be consumed on the day of purchase.
Consumers must ensure that these products are wrapped and refrigerated until consumed.
•
The shelf life of these products is also dictated by the loss of sensory quality of refrigerated bakery
products as early as 24 hours after purchase.
Diluted from 10-1 to10-4
Vortexed to mix the
samples
Spread onto selective
agar (everything
carried out in duplicate)
•
Bakery staff have high levels of food safety/hygiene knowledge, but it is not always put into practice.
More stringent control measures must be enforced to protect consumer safety.
References
1. New Zealand Food Safety Authority. (2007). Microbiological Quality of Bakery Products. Auckland :
New Zealand Food Safety Authority.
2. Saranraj, P., & Geetha, M. (2012). Microbial spoilage of bakery products and its control by
Incubated at 37°C for 48
hours
Colonies counted and
converted to cfu/g
preservatives. International Journal of Pharmaceutical & Biological Archives ,3(1): 38-48.
3. Siriken, B., Cadirci, O., Inat, G., & Pamuk, S. (2009). Microbiological examination of meatball, cream
cake and Turkish delight (Lokum). Journal of Animal and Veterinary Advance, 8(10): 2049-2054.