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Determination of Microbiological Quality of Packed and Unpacked Bread

Afsana Khanom
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Tahmina Shammi
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Md. Shahidul Kabir*
Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Abstract/ Executive Summary:

Wheat and flour contain essential nutrients such as carbohydrate, minerals, fats and proteins which may aid proliferation of microorganisms in products made from cereal grains and kept under improper storage condition. This study was conducted to determine the microbial load of bread and flour sold in packed and unpacked forms by the local and super markets in Dhaka city. Socioeconomic background, awareness of the microbiological contamination, spoilage of bread and flour and hygiene status of the salespeople were also studied to determine any correlation between the contamination of bread and flour sold by local and super markets. About 20 samples of flour (n=10) and bread (n=10) were included in this study to determine the load of total heterotrophic bacteria (THB), total Staphylococcus aureus (TSA), total Enterobacteriaceae (TE), total coliforms (TC), total yeast and mold (TYM). Equal number of unpacked (local market) and packed (supermarket) bread and flour samples were included in this study. TC, TSA and THB counts were found to be 1.0 log10 cfu/g higher in unpacked (local market) flour samples compared to those of packed (supermarket) samples. TSA counts were significantly higher in unpacked (local market) samples compared to the packed samples (p<0.05). Food handlers of both the groups did not have adequate knowledge and training on food contamination and spoilage. However, salespeople in the supermarkets were found to be more educated, experienced than those in the local markets. This study demonstrates that unpacked (local market) bread and flour are more contaminated than the packed (supermarket) samples and may pose risk of foodborne infection to consumers.

Keywords: Flour; Bread; Coliform; Enerobacteriaceae; Contamination

Location: Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Start Date:

End Date:

Program Area: Pest Management

Commodity: Microbiological aspect, Bread

Objectives:

This study was conducted to determine the bioburden in bread and flours sold in packed (super markets) and unpacked (local market) in Dhaka city. Background information of sales people was also investigated to determine any correlation between their level of knowledge and hygiene practice with the loads of different groups of bacteria in studied samples.

Methodology:

Collection of sample. A total of 20 fresh samples of bread and flour were collected from different local and supermarkets in Dhaka city. Each sample was collected in a sterile sealed polythene bag, appropriately labeled and immediately brought to the microbiology laboratory of Stamford University Bangladesh and stored in the refrigerator (4-8^oC) before processing.

Sample processing. Each sample (10.0 g) was homogenized with 90.0 ml of sterile normal saline to prepare stock solution. Stocks were serially diluted (1:10) to 10-5 by adding 100µl of stock solution to 900µl normal saline in eppendorfs tubes. 100µl of diluted sample was inoculated on Nutrient agar (NA), Mannitol Salt Agar (MSA), membrane Faecal Coliform (mFC), Violet Red Bile Salt Glucose agar (VRBG) and Sabouraud Dextrose agar (SDA) media following spread plate method and incubated at 37^oC for 18-24 hours except for SDA which was incubated at 25^oC for 48-72 hours. All media were procured from Himedia Laboratories Ltd., India.

Determination of total bacterial count. Nutrient agar media was used to determinate the total bacterial count. NA plates were dried and labeled for appropriate dilutions to be used for dilution and spread plate method. Plates were inoculated and incubated at 37^oC for 18-24 hours. Total number of bacteria cfu/g of sample was calculated and recorded for interpretation of the result.

Determination of counts of Staphylococcus aureus. MSA was used to determine the counts of Staphylococcus aureus in bread and flour samples. The suspected colonies of S. aureus showed yellow color for mannitol fermentation and yellow halo for coagulase production around the colony. Suspected colonies were further confirmed by catalase, coagulase tests and Gram staining technique. Typical S. aureus colonies were counted to calculate cfu per gram of sample.

Determination of total Enterobacteriaceae. VRBG agar was used for propagation of Enterobacteriaceae. After incubation at 37^oC for 24 hours characteristic purple and red colonies were counted as members of Enterobacteriaceae. Suspected colonies were counted to determine cfu per gram of sample.

Determination of coliform bacteria. Membrane Faecal Coliform (mFC) media was used to detect the coliform bacteria by using spread plate method. Plates were inoculated and incubated at 37^oC for 24 hours. All blue colored colonies were enumerated to calculate total coliform as cfu/g.

Enumeration of yeast and mold. Diluted samples were inoculated onto SDA medium supplemented with clorampheinicol (40mg/L) by spread plate method as mentioned earlier. The plates were incubated at 25^oC for 48-72 hours. Visible colonies were counted and calculated as the total yeast and mold and recorded as cfu/g.

Source of Information: Stamford Journal of Microbiology, 2016. Vol. 6, Issue 1, 24-29 ISSN: 2074-5346 (Print); 2408-8846 (Online)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Bread and flour are known as safe food commodity due to their low water activity. But microbial isolation and enumeration in this study revealed prevalence of microorganisms including pathogens in higher counts than recommended limits for these food items. As flour and bread are most commonly consumed food products, their microbiological quality is important to consumer’s health. A questionnaire survey among the salespeople indicated many underlying reasons of such poor microbiological standard, like disease history, hygiene practice and educational status. Therefore, stringent regulatory actions on the microbiological quality control on bread and flour together with the training of salespeople on food spoilage are necessary for the better management of public health condition in Bangladesh.

Knowledge Management: Journal