Question Bank • QB_DFE_EXP_086 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Preservation of Food

Subtopic: Kinetics of microbial death – pasteurization and sterilization of milk and other liquid foods

Question Statement:

The thermal destruction of a spore population follows first-order reaction kinetics with a reaction rate constant of $k = 0.921\text{ min}^{-1}$ at $121^\circ\text{C}$. Calculate the decimal reduction time ($D$-value) in $\text{minutes}$.

Answer Key:

2.5

Step-by-Step Solution & Explanation

The relationship between decimal reduction time $D$ and first-order kinetic constant $k$ is: $D = \frac{\ln(10)}{k} = \frac{2.3026}{k}$ $D = \frac{2.3026}{0.921} \approx 2.50\text{ minutes}$
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