This study critically investigated and analysed the growth and numbers of thermophilic and thermoduric spore forming bacteria throughout the milk powder production process in a newly-commissioned commercial processing plant. Various milk samples, including raw milk, pasteurised milk, concentrated milk and milk powder, were collected from a company situated in Northern Ireland, over the course of two full production runs; one completed in early December and the other in late January. All samples were tested for thermophilic and thermoduric spores, and in addition to this, the bulk tanker milk was also tested for total viable count, coliforms, Escherichia coli, yeasts and moulds, to gain an indication of the quality of the raw milk. Results concluded that during both pasteurisation and evaporation, thermoduric spore counts did increase slightly; however, it wasn’t until evaporation that the thermophilic spore count began to consistently increase; again only a small increase was noted. The finished product, produced from trial one, contained much lower thermoduric and thermophilic spore counts, compared to that produced in trial two; and this is believed to have been brought about by the fact that higher quality raw milk, with mean thermoduric spore counts of 4.15x103 CFU/ml and mean thermophilic spore counts of 2.5x102 CFU/ml was used in trial one. Overall, this indicated that although a slight increase in the number of thermophilic and thermoduric spores did take place during processing, the majority of spore contamination took place at farm level.
How to cite this article
Gourley, Jill and Mullan, W.M.A. (2019). [On-line]. Available from: https://www.dairyscience.info/index.php/student-projects/355-thermophilic-thermoduric-spore-forming-bacteria.html . Accessed: 18 October, 2021.