Distribution of psychrophilic microorganisms in a beef slaughterhouse in Japan after cleaning

The purpose of this study was to investigate the abundance and distribution of psychrophilic microorganisms associated with spoilage in beef slaughterhouse environments after cleaning. The processing lines and equipment used in slaughtering and boning were swabbed, and the microbial count was determined using a TSA and MRS medium and Chromocult® Coliform agar incubated at 15ºC and 37ºC, respectively. As a result, the brisket saw (handle side) and trolley hook were the most heavily contaminated with microorganisms, with each having a microbial adhesion rate of 66.7%. The microbial adhesion rates of the apron and milling cutter (edge side) were 50%, respectively, and those of the foot cutter (edge and handle side), splitting saw (edge side), and knife (handle side) were 33.3%, respectively. Next, four colonies were randomly isolated from the petri dish used for the bacterial count measurement to identify the predominant microbial species of the microorganisms attached to each equipment. As a result of Sanger sequencing analysis, yeasts such as Candida zeylanoides and Rhodotorula sp. and bacteria including Pseudomonas sp. and Rhodococcus sp. were identified from the equipment used in the slaughtering line, and it was assumed that these microorganisms were of environmental origin. In contrast, only Pseudomonas sp. and Candida zeylanoides were isolated from the boning line. Despite the use of cleaning operations, this study identified some equipment was contaminated with microorganisms. Since this equipment frequently comes into direct contact with the carcass, it is critical to thoroughly remove the microorganisms through accurate cleaning to prevent the spread of microbial contamination on the carcasses.