Certified Cheese Professional Practice Exam

What type of bacteria is affected at 104°F?

1. Thermophilic bacteria

2. Psychotropic bacteria

3. Mesophilic bacteria

4. Lactic acid bacteria

The correct answer is: Psychotropic bacteria

The correct answer indicates psychotropic bacteria, which are typically adapted to thrive at lower temperatures, usually between 32°F and 68°F (0°C to 20°C). At temperatures above this range, especially at 104°F, psychotropic bacteria experience stress, and their growth is significantly inhibited or halted. Understanding the behavior of these bacteria is crucial in food safety and cheese production. Since they are commonly involved in spoilage at refrigeration temperatures, their inability to survive and reproduce at higher temperatures is an important factor in managing cheese quality. In contrast, thermophilic bacteria thrive at high temperatures, generally between 110°F and 158°F, and mesophilic bacteria grow best at moderate temperatures around 70°F to 100°F. Lactic acid bacteria, which are essential in cheese making, typically thrive within the mesophilic range but can also have members that tolerate higher temperatures. However, psychotropic bacteria are specifically impacted negatively at the high temperature of 104°F, making this the appropriate answer in this context.