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Microbiological Quality Analysis of Yoghurt in Some Selected Areas of Bangladesh

Abdul Matin
Department of Food processing and Engineering, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Monsur Ahmad
Department of Applied Chemistry and Chemical Technology, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Mohammad Mozibul Haque
Department of Applied Food Science and Nutrition, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Altaf Hossain
Department of Applied Food Science and Nutrition, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Md. Rahim Badsha
Department of Food processing and Engineering, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Tuli Banik
Department of Applied Food Science and Nutrition, Chittagong Veterinary and Animal Sciences University Khulshi, Chittagong-4225, Bangladesh

Abstract/ Executive Summary:

This study was conducted to investigate the microbiological quality of yogurt (Dahi) samples collected from different locations in Bangladesh. A total of 50 yogurt samples were studied from 10 selected areas of Bangladesh. The samples were tested for the Total Viable Bacterial Count (TVBC), Total Coliform Count (TCC), and total yeast and mold count. TVBC and TCC ranged in yogurt samples were from 1.72×10⁷±1.6×10⁵ to 5.04×10⁸±1.5×10⁶ cfu/ml and 1.02×10²±1.58 to 4.51×10²±1.58 cfu/ml; respectively. Total yeast and mold count were ranged from 2.0 ×10²±1.58 to 9.4×10³±158.11 cfu/ml in yogurt samples. This study indicates a need for emphasis on quality control within processing plants. The level of bacteria, coliform, yeast, and mold counts indicated that excessive contamination occurs during the manufacture and packaging of the product. Every small and large-scale yogurt producer is suggested to maintain adequate hygienic conditions to make good quality and healthy yogurt which will reduce the microorganisms load. Overall the hygienic quality of those yogurt samples was lower and must be improved considerably.

Keywords: Yoghurt, TVB & TCC, Total coliform, Total yeast & mold count

Location: Food Science and Technology of Bangladesh Council of Scientific and Industrial Research

Start Date: 00-06-2017

End Date: 00-12-2017

Program Area: Quality and Nutrition

Commodity: Yogurt

Objectives:

To evaluate the microbiological quality of yogurts from different selected areas of Bangladesh, considering the levels of contamination by coliforms, yeast, molds, and total viable bacterial counts.

Methodology:

The study was conducted at the Food Microbiology unit of Food Science and Technology of Bangladesh Council of Scientific and Industrial Research, June 2017 to December 2017. Ten samples of yogurt were collected from each different area of Bangladesh (Dhaka, Bogra, Comilla, Noagoan, Rajshahi, Chittagong, Khulna, Barisal, Pabna, Tangail) under sterilized conditions. Yogurt samples were prepared according to the method recommended by ICMSF 1996. Materials used in the study work were reagent, sample, Petri dish, distilled water, glassware, burner, spreader, conical flask, etc. Serial dilutions of samples were made up to 10⁷ in Rangers Solutions. The bacterial counts were then performed by the standard method recommended by APHA 2001. Plate count agar media was prepared by the standard method recommended by HiMedia Laboratories Pvt. Ltd. MacConkey agar media was prepared by the standard method recommended by HiMedia Laboratories Pvt. Ltd. Sabouraud dextrose agar media was prepared by the standard method recommended by HiMedia Laboratories Pvt. Ltd. Microbiological analysis: Total viable bacterial count is the most common microbiological test that gives a quantitative idea about the presence of microorganisms such as bacteria in a sample. Total Viable Bacterial Count was measured by plate count agar medium by a standard procedure. At first, a series of test tubes (10), each containing 9 ml diluents was taken. Then 0.5 ml yogurt sample was homogenized in 450 ml diluents and made suspension in a beaker. From the original sample, 1 ml is transferred into test tube no.1 and mixed thoroughly. Then transfer 1 ml from the 1st test tube to the 2nd test tube and continue up to the last one and 1 ml is discarded from the last test tube. In the pour plate technique, the homogenizer mixture of the sample was placed in the empty petri dish a sufficient amount (10 ml) of melting agar (melted at 45⁰C) was placed on the sample in the Petri dish. At the same time, the Petri dish was rotated for 5-10 seconds, so those samples were being mixed thoroughly with the media. Then the media can solidify and after solidification of the media containing samples the Petri dish was kept in the incubator at 37⁰C for 2-3 days. The total viable bacterial count was measured in colony-forming unit per gram (cfu/ml). Coliform Counts Total (TCC). The coliform count was measured by using a MacConkey agar medium. According to the pour plate technique, 1 ml of each sample was transferred into a sterile plate, and 15-20 ml of the selected media was added. The medium was mixed immediately and shaken for 5- 10 seconds. Typical pink colonies were counted for the determination of Total Coliform Count after incubation of plates at 37⁰C for 24 hours. Total Yeast & Mold Count Sabauroud dextrose agar media was used for enumeration according to the method of monitoring mycological media. 0.5 ml sample was taken and diluted up to 10 ml by using peptone water. Then 1 ml of that preparation was inoculated on a Sabouraud dextrose agar plate. Finally, it was incubated at 37⁰C for 2-5 days. Then yeast and mold colonies were counted separately from here. Laboratory data were stored in the MS excel-2007 program before exporting to STATA/IC-13 for analysis. Descriptive analysis was performed to determine Total Viable Bacterial Count (TVBC), Total Coliform Count (TCC), Total yeast, and mold count.

Source of Information: International Journal of Natural and Social Sciences, 2018, 5(4): 82-86

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The overall picture of yogurt quality in selected areas of Bangladesh as measured by microbiological evaluation appears to indicate a need for emphasis on quality control within processing plants. The level of bacteria, coliform, yeast, and mold counts indicated that excessive contamination occurs during the manufacture and packaging of the product. Every small and large-scale yogurt producer is suggested to maintain adequate hygienic conditions to make good quality and healthy yogurt which will reduce the microorganisms load.

Knowledge Management: Journal