Thermophilic sporeformers are a group of bacteria that proliferate at high temperatures (mostly above 50°C as optimum growth temperatures) and can form spores as a mean to survive in unfavorable environmental conditions. They are of primary concern for food processing plants that apply high temperatures. Even though they have been reported as not pathogenic, they could pose a threat to the quality of food products when they grow because their growth produces off-flavour and changes the texture of the products. This thesis has produced new insights into the life-cycle of thermophilic sporeformers in dairy-concentrate processing environments. For example, the presence of thermophilic sporeformers was observed in dairy-concentrate processing lines, particularly at locations where high temperatures were applied; for the sporeformers to readily grow in dairy environments, the ability to utilize lactose seems essential etc.