Question

The lowest water activity ($a_w$) supporting the growth of Staphylococcus aureus in food under aerobic condition is:

• A. 0.98
• B. 0.91
• C. 0.89
• D. 0.86

Hint:

Water activity is a key factor in controlling microbial growth. For Staphylococcus aureus, a water activity value below 0.86 generally inhibits growth, making it an essential consideration for food preservation.

Answer 1

The Correct Option is D

The growth of microorganisms in food is significantly influenced by water activity (\(a_w\)), which is the ratio of the vapor pressure of water in a substance to the vapor pressure of pure water at the same temperature. Water activity plays a crucial role in determining the shelf-life and safety of food products.
Staphylococcus aureus is a Gram-positive bacterium that can be found in various food products, and it is well known for its ability to cause foodborne illness due to the production of toxins. The growth of this bacterium is highly dependent on the water activity of the environment.
Key Points about Water Activity and Staphylococcus aureus: - Water activity range for bacterial growth: Most bacteria, including Staphylococcus aureus, require a water activity above 0.90 for optimal growth. Below this value, microbial growth is either slowed or completely inhibited.
- Minimum water activity for Staphylococcus aureus: Research indicates that Staphylococcus aureus can grow at water activity as low as 0.86 under aerobic conditions. Below this threshold, the growth of this microorganism becomes significantly limited.
- Aerobic growth conditions: Under aerobic conditions, where oxygen is available, Staphylococcus aureus is more likely to grow at slightly lower water activities compared to anaerobic conditions.
Thus, for Staphylococcus aureus, the lowest water activity that supports its growth in food under aerobic conditions is 0.86, which makes option (D) the correct answer.