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Keeping Quality of Pasteurized Milk at Different Temperature

Md. Azizul Haq Fakir*
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Mahmuda Islam
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Atawar Rahman
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

The experiment was undertaken to study the keeping quality of pasteurized milk at different temperatures (4°C, 7°C and 15°C. One hundred eight pasteurized milk samples were obtained from three different renowned milk company, out of which thirty six samples were collected from each of the three different renowned milk company as replication. All the samples were subjected to physical and microbiological examination. Total viable count and coliform count were done for the microbiological quality at different holding periods at day 0, 2, 5, 6, 8 and day 10 storage at 4°C, 7°C and 15°C. The results revealed that the average highest total viable count in the pasteurized milk was log 8.8325 at 15°C for 10 day storage and lowest value was log 4.0828 at 4°C for 0 day. Average highest coliform was log 2.8808 at 15°C for day 10 storage and lowest value was 0 at after 2nd days of storage at 4°C. It was concluded that pasteurized milk should be held at 4°C to achieve maximum shelf life. Further quality and shelf life of pasteurized milk depends on the raw milk quality, hygienic production of milk and improvement of storage facilities.

Keywords: Pasteurized milk, Quality, Temperature

Location: (Arong, Milk vita and Aftab) from KR market, Bangladesh Agricultural University, Mymensigh

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Milk

Objectives:

The research work was undertaken with the aim to determine the keeping quality of pasteurized milk at different temperature by observing the pattern of microbial growth in pasteurized milk during different storage period and temperature.

Methodology:

Collection and processing of samples Pasteurized milk from three companies (Arong, Milk vita and Aftab) from KR market, Bangladesh Agricultural University, Mymensigh, were collected. The packaged samples were transferred to a wide mouthed thermo flask, kept cool in ice and brought to the bacteriology Laboratory, Department of Microbiology and Hygiene of the said university. All samples were brought in about 30 minutes to one hour for subsequent studies to determine the hygienic quality of milk before delivery to consumers. All the samples (108) were opened aseptically and processed for physical test (color, flavor, consistency, taste, COB tests) and microbiological tests (Total Viable Count, Coliform Count).

Physical Tests (Sensory Evaluation) The milk samples of three farms were judged by a panel of experts at different holding periods to evaluate organoleptic quality in which color, flavor, taste, consistency characters and COB tests were determined. A legend of taste panel scores was taken as a standard to evaluate the organoleptic quality of samples. For example 5 marks were given for excellent quality of milk, 4 marks were given for good quality, 3 marks were given for moderately good, 2 marks for fair quality and 1 mark for bad quality and 0 for spoiled. The physical change of milk is COB. If milk clotted on boiling it was indicated as (+)ve and if not clotted it was indicated as (-)ve test. The microbiological tests including total viable count and coliform count were performed as per the recommendation of APHA (1960).

Data analysis The data on the total viable counts and coliform count per ml of milk and taste panel scores of different farms for different holding periods were analyzed statistically to find out the level of significant correlations. The analyses of variance were studied by the F test. The mean differences were evaluated at 0.1% level of significance by Duncan's New Multiple Range Test (DMRT). Linear correlation coefficient and regression equation were calculated with the standard statistical method.

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The post-pasteurization contamination level was the most critical factor determining keeping quality at 6 or 10°C. The results also showed that the sample volume and the samples storage container influence the plate count of cold-stored samples. The organoleptical quality and acidity of milk samples gradually changed in proportion to bacterial counts. However, the specific gravity did not significantly change after 30 days. No significant correlation was found in the keeping quality of milk between dark and light exposure at room temperature for 30 days. The compositions of fat, solids not fat, protein, and lactose in milk did not significantly change according to the storage conditions for 30 days. The flavour was affected mainly by acid development and proteolytic activity. The thermal stability test was found to be a possible alternative to organoleptic evaluation for determining the shelf life of pasteurized milk.

Knowledge Management: Journal