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Microbial Analysis of Raw and Pasteurized Milk from Selected Areas of Dinajpur, Bangladesh

Dr. Md. Amirul Hasan
Scientific Officer
Training, Planing and Technology Testing Division, Bangladesh Livestock Research Institute

Dr. Md. Aminul Islam
MS Student
Department of Microbiology, Hajee Mohammad Danesh Science & Technology University, Dinajpur, Bangladesh

Abstract/ Executive Summary:

A total of 32 milk samples were collected from 8 sources. Among them three were raw (designated as R1 to R3) and five were pasteurized milk (designated as P1 to P5). Each of the collected samples was investigated during the period from May to December, 2012. Microbiological tests such as viable plate count, coliform plate count, Staphylococcus plate count and Gram’s staining were performed to determine the loads of microbes in raw and different brands of pasteurized milk. Total viable counts (TVC) of three raw milk samples, R1, R2 and R3, were 745000 cfu/ml (log 5.87), 1357500 cfu/ml (log 6.13) and 1972500 cfu/ml (log 6.29), respectively. The presence of Escherichia coli in the samples of R1, R2, and R3 were 236 cfu/ml (log 2.37), 268 cfu/ml (log 2.42), 940 cfu/ml (log 2.97), respectively, but the presence of Staphylococcus were 798 cfu/ml (log 2.90), 590 cfu/ml (log 2.77), 615 cfu/ml (log 2.78), respectively. The average values of TVC were 98500 cfu/ml (log 4.99), 68450 cfu/ml (log 4.83), 195000 cfu/ml (log 5.29), 18950 cfu/ml (log 4.27) and 53375 cfu/ml (log 4.72), respectively for the samples of P₁, P₂, P₃, P₄, and P₅ brands of pasteurized milk, where as Staphylococcal count were 869 cfu/ml (log 2.93), 647 cfu/ml (log 2.81), 443 cfu/ml (log 2.64), 858 cfu/ml (log2.93) and 28 cfu/ml (log1.45), respectively. The coliform counts were 166 cfu/ml (log 2.21), 91 cfu/ml (log1.95), 348 cfu/ml (log 2.54) and 101 cfu/ml (log 2.00) for the samples of P₁, P₂, P₃, and P₅, respectively. Coliform were not detected in P₄pasteurized milk sample. Therefore, it was concluded that high counts of bacteria were found in most of the samples. The detection of high counts of Staphylococcus coupled with the presence of E. coli is of public health significance to consumers.

Keywords: Adulteration, Bacterial distribution, Ppasteurized milk, TVC count

Location: Microbiology laboratory of the Department of Microbiology, Faculty of Veterinary and Animal Science, Hajee Mohammad Danesh Science and Technology University,Dinajpur

Start Date: 00-05-2012

End Date: 00-12-2012

Program Area: Food Safety and Security

Commodity: Milk

Objectives:

(i) To investigate occurrence and load of microorganism in raw and pasteurized milk,

(ii) To compare the microbial load among different brand of pasteurized milk.

Methodology:

The present studies were conducted during the period from May to December, 2012 in the Microbiology laboratory of the Department of Microbiology, Faculty of Veterinary and Animal Science, Hajee Mohammad Danesh Science and Technology University, Bangladesh. Sources of the population in this study were raw and pasteurized milk presented for sale at the daily market. A total of 32 milk samples were collected from 8 sources. Three raw milk samples (designated as R₁ to R₃), remaining five (P₁ to P₅) were pasteurized milk each from different brands. All the samples were collected following standard sampling procedure and immediately transported to the laboratory for microbiological examination. To obtain countable plate with individual colonies the samples were diluted using simple 1/10 dilutions. For a 1/10 dilution 1 part sample was added to 9 parts diluents (Distilled water) then mixed thoroughly. A series of dilutions was made as desired, and from one or more of these dilutions, known amounts were inoculated in an agar by pour plate techniques. The forgoing prepared milk samples were examined in order to determine the total viable count (TVC), total coliform count (TCC), and total Staphyloccus count (TSC) on plate count agar (PCA), MacConkey agar (MCA) and Staphylococcus agar no-110 media respectively. Plates exhibiting colonies were counted. The average number of colonies in a particular dilution was multiplied by the dilution factor to obtain the total count. The total count was expressed as the number of organism of colony forming units per ml (CFU/ml) of samples.

Source of Information: BLRI. Annual Research Review Workshop, 2012-13. BLRI, Savar, Dhaka.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

It was concluded from the study that microbial loads of raw milk were not satisfactory. Therefore, it could be assume that the handler of raw milk do not maintain good personal hygiene. All most all brands of pasteurized milk tested in this study were of low quality based on BSTI standard. Presence of E. coli and Staphylococcus spp. were of public health concern. Government therefore should conduct frequent inspection of the marketed milks to check whether they meet the minimum legal standards and should monitor the overall hygienic condition surrounding the production and handling of milk. Realistic standards for the raw milks need to be revised and appropriate training should be given to the raw milk producers in hygienic handling of milk.

Knowledge Management: Report/Proceedings