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: LauraADuffy93@gmail.com

Introduction Results

Objectives

References

Discussion & Conclusions

Materials & Methods

• Baking at high temperatures is adequate to kill any vegetative cells present, but post baking

contamination can occur during filling and topping bakery products with sensitive ingredients.

• Staphylococcus aureus (S.aureus) and Bacillus cereus (B.cereus) are common pathogens present in

these products. Their presence is an indication of poor hygiene practices (unhygienic handling),

inadequate refrigeration, and poor quality raw materials. The growth of bacteria often occurs between

the cream/custard topping of the dessert and the body of the dessert[1].

• 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].

• 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.

• Assessment of the microbiological quality of ready-to-eat cream and custard filled bakery products,

sold in Dublin City Centre, using S.aureus and B.cereus as indicators of hygiene and safety.

• Observe the degradation of microbiological and sensory quality of cream filled bakery products over

time.

• Observe the practices applied in bakeries in Dublin and investigate the level of knowledge of hygiene

and safety by management and employees.

• Conclude if these products are a high risk to consumer health, and whether more stringent control

measures need to be put in place.

• 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

products in bakeries, need to be improved. The amount of bacteria could easily reach a high level in

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.

• 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.

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

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.

10g of sample weighed into stomacher bag[3]

90ml of MRD added[3] Homogenised for 3

minutes

Diluted from 10-1 to10-4 Vortexed to mix the samples

Spread onto selective agar (everything

carried out in duplicate)

Incubated at 37°C for 48 hours

Colonies counted and converted to cfu/g

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

Microbiological Examination[3]

Fig.1: Confirmed S.aureus

grown on Baird-Parker agar

from bakery samples.

Black/grey colonies with

clear halo around the

colonies.

Fig. 2: Suspected B.cereus

grown on B.cereus agar

base from bakery samples.

Yellow/cream colonies

turned sections of the agar

turquoise.

Gram Stain: Gram positive, cocci

Catalase: Positive

Coagulase: Positive

Oxidase: Negative

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

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.

1. Identification of S.aureus and B.cereus Using Confirmation Tests

3. Mini Shelf life & Temperature Abuse Study

Fig.3. S.aureus Results Fig.4. Suspected B.cereus Results

Table 1: Results of Confirmation Tests on

Black Growth on Baird-Parker Agar Table 2: Results of Confirmation Tests on Yellow

Growth on B.cereus Agar Base

• 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

the importance of temperature control of these products throughout their entire shelf life.

0.00E+00

5.00E+05

1.00E+06

1.50E+06

2.00E+06

2.50E+06

Day 1: Fresh Day 2: Refrigerated Day 2: Non-Refrigerated

cfu

/g

Time of Testing & Storage Conditions

S.aureus & B.cereus In Cream Cake

S.aureus

B.cereus

Fig 4. Increase in Levels of S.aureus & B.cereus over 2 Days, Refrigerated & Non-Refrigerated

Low

Moderate

High

S.aureus

𝟒/𝟏𝟏

𝟏/𝟏𝟏

𝟔/𝟏𝟏

Low High B.cereus

𝟐/𝟏𝟏 𝟒/𝟏𝟏

𝟓/𝟏𝟏

Moderate

Gram Stain: Gram positive, bacilli

Catalase: Positive

Coagulase: Negative

API 50 CHB/E & Biolog Negative for B.cereus