Which of the following treatments is the most effective for controlling microbial growth?

• A. Refrigeration at 4^ext{o}C
• B. Drying in ambient air
• C. Pasteurization at 72^ext{o}C for 15 seconds
• D. Autoclaving at 121^ext{o}C for 15 minutes

Answer: (D)

Verified step by step guidance

1. Understand the goal: controlling microbial growth means reducing or eliminating microorganisms to prevent spoilage or infection.
2. Evaluate refrigeration at 4\^\{\text{o}\}C: this slows down microbial metabolism and reproduction but does not kill most microbes, so it is bacteriostatic rather than bactericidal.
3. Consider drying in ambient air: this removes water necessary for microbial growth, but many microbes can survive in a dormant state and resume growth when moisture returns.
4. Analyze pasteurization at 72\^\{\text{o}\}C for 15 seconds: this heat treatment reduces the number of viable pathogens and spoilage organisms but does not sterilize; some heat-resistant microbes may survive.
5. Examine autoclaving at 121\^\{\text{o}\}C for 15 minutes: this uses pressurized steam to achieve sterilization by killing all forms of microbial life, including spores, making it the most effective method for controlling microbial growth.