Question

Thermal destruction of microorganisms follows kinetics of…….

• A. Zero order
• B. First order
• C. Second order
• D. Fractional order

Hint:

Because it is "First Order," we can never mathematically reach "Zero" survivors—just a very small probability of one surviving. This is why we aim for 12D safety!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks about the mathematical model that best describes the rate of death of microorganisms when exposed to lethal temperatures.
Key Formula or Approach: First-order kinetics formula: $\frac{dN}{dt} = -k \cdot N$ Integrating gives: $\ln\left(\frac{N}{N_0}\right) = -k \cdot t$

Step 2: Detailed Explanation:

• Logarithmic Death: Scientific observation shows that at a constant lethal temperature, the same percentage of the microbial population dies in each successive unit of time. This is characteristic of a first-order reaction.

• Concentration Dependency: In first-order kinetics, the rate of change is proportional to the current amount (number of organisms $N$). As the number of survivors decreases, the absolute number of organisms dying per second also decreases, but the proportion remains constant.

• Semilogarithmic Relationship: This explains why plotting the log of survivors against time results in a straight line. The slope of this line is related to the D-value.

• Significance: This principle allows food scientists to predict the time needed to achieve commercial sterility, ensuring that the probability of a survivor is extremely low (e.g., the 12D concept).

Step 3: Final Answer: Microbial thermal destruction is categorized as a first-order kinetic process.