Food Safety Certification Practice Test

What water activity level must food have for bacteria that cause foodborne illness to thrive?

1. 0.75

2. 0.85

3. 0.90

4. 0.95

The correct answer is: 0.85

Bacteria that cause foodborne illness require a certain level of moisture in food to grow. The water activity level, measured on a scale from 0 to 1, indicates the availability of water for microbial growth. For most pathogenic bacteria, the critical threshold for growth typically lies at a water activity level of 0.85 or higher. At 0.85, it is generally accepted that this is the minimum water activity needed for bacteria like Salmonella, Listeria, and E. coli to proliferate. Foods with a water activity level below this threshold can inhibit the growth of these harmful bacteria, making them safer for consumption. Therefore, the choice that indicates 0.85 is correct, as it aligns with the established understanding of food safety regarding microbial growth. Food products with water activity levels at or above this mark must be monitored closely to prevent spoilage and foodborne illnesses, which is why understanding these levels is critical when handling and storing food.