A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from 20 to 45 °C (68 to 113 °F. Spore-forming bacteria is known to be able to survive extreme processing conditions.
Spore-forming bacteria of the species Bacillus are common spoilage organisms that can survive pasteurization. Spore forming bacteria are known to have an intrinsically higher resistance to sanitizers.
These procedures listed above enumerate/provide the most probable number (MPN) result to indicate the amount of mesophilic spore former organisms present in a sample.