Investigation of selective food-borne pathogens and quality evaluation of Dahi Marketed at Chattogram Metropolitan Area of Bangladesh

Abstract

Fermented milk products are part of the diet in many parts of the world and are consumed on a regular basis. Enhancing the nutritional and therapeutic properties of traditional fermented milk can improve the global public health. Dahi quality and safety is an increasingly important public health matter. Dahi might be contaminated with pathogens due to poor packaging, unhygienic handling and inadequate transport system. Presence of these organisms are critical for the safety of fermented products during consumption. Measures should be taken to interrupt the transmission of pathogens to dahi at the household level. So, the aim of this study was to isolate the zoonotic microorganisms (Escherichia coli and Salmonella sp) and evaluate the quality of dahi samples marketed at Chattogram metropolitan area. A total of fifty (50) dahi samples (local and branded) were collected from July to October 2019, in different shops of Chattogram metropolitan area and tested for the presence of E. coli and Salmonella sp as well as for the total viable count of bacteria. Collected samples were also examined for their chemical quality (acidity, fat and protein percentage). All the samples were inoculated on respective selective bacteriological media for primary isolation of the pathogens of interest. Then the positive isolates were subjected to different biochemical tests for further confirmation. At the same time some qualitative tests of the dahi samples were also performed followed standard laboratory procedure. Significant differences were found in microbial (total viable count) and chemical (percentage of acidity, fat, protein) quality of dahi samples. The average percentage of fat, protein and acidity collected dahi samples ranges from 3.43±0.18 to 3.58±0.11, 4.58±0.34 to 5.13±0.17 and 0.87±0.02 to 0.75±0.03, respectively. The total viable count of all samples ranges within the standard level. All the samples were negative for E. coli and Salmonella sp, that indicates proper hygienic handling, preparation, marketing and storage of dahi. Since all the collected dahi samples of this study were negative for E. coli and Salmonella sp, so it can be said that the dahi samples that were collected from different retail shops of Chattogram metropolitan area were safe for human consumption.