Study on microbial air contamination of different areas in dairy processing plants

The investigation of microbial flora in dairy factories and the role of environmental factors are very important. This study was to determine the microbial air contamination in various parts of dairy factories in Shahrekord. In this study sampling was done by using sedimentation method. Microbial analysis included counting total aerobic bacteria, staphylococci, bacillus, yeasts, and molds. In each sampling series the plates containing the selective medium, for 1hour, were placed 1meter away from wall and in the height of 1meter from ground in different parts, then the samples were transferred to laboratory and have been kept in 37oC in incubator for 48hours. After counting the colonies, specific biochemical tests were used for determining isolated bacteria identity. For evaluating of fungal the Potato dextrose agar mediums containing choloramphenicol were used. The gender of grown fungal was determined by using routine laboratory methods including the teased mount and slide culture technique.
The results show that the total bacteria number in air ,Among the total isolated colonies, the contamination ratio to gram positive cocci was 44%, gram positive bacilli was 53.1%, gram negative bacilli was 2.7%, and gram negative cocci was 0.57%, Among the total isolated bacteria the most bacterial type was related to Staphylococcus aureus, Bacillus cereus, and Escherichila coli respectively. Also, the results of counting fungi numbers in air showed that ,Among the total 313 various isolated fungal colonies, yeasts 60/3%, Trichosporon14/6%, Paecilomyces7/6 %, Geotrichum5/7%, Madurella5/7%, Cladosporium2/5%, Aspergillus2/2%, Monillia1% and Rhizopus1% were investigate.
According to the suggested air microbial contamination standard amount by America Public Health Association, the results of this study show that the air of different parts of factories have high contamination and the possibility of transfer of contamination to products of these factories is high.