A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources & Development

Thesis (M.Sc.) - Asian Institute of Technology, 1984

A survey was conducted to investigate the microbial quality of UHT products in order to find out possible cause of defects and to draw up recommendations for quality improvement. It was carried out in close collaboration with selected milk plants in Thailand and Indonesia using the sampling procedures prescribed by the military standard 105D and the recommendations of Tetra Pak and dairy firms. The results of the laboratory test on the unsterile samples revealed the presence of organisms and flora species which were found through thermoresistance test, pH of PCA test ,gram stain, morphological analyses and catalase test, that some of the organisms are either thermoresistant or non-thermoresistant types. In addition to these, various mixed-flora species were identified. It was found that there is a high probability of contamination during the packaging processes, i.e., changing of strips, changing roll of paper, starting of production, and thus, proper disinfection and control measures should be observed during packaging. In doing so, the presence of non-thermoresistant bacteria due to further contamination during handling operations can also be minimized.