In thermal processing of food, it is essential to quantify the effectiveness of a heat treatment in destroying microorganisms. The D-value is a standard parameter used in food microbiology and processing for this purpose.
Step 1: Understanding the Question:
The question asks for the correct definition of the 'D-value' in the context of food preservation.
Step 2: Detailed Explanation:
The term 'D-value' stands for 'Decimal Reduction Time'. It is defined as the time required at a specific temperature to destroy 90% of a target microbial population. A 90% reduction corresponds to a one-log cycle reduction (i.e., reducing the population by a factor of 10).
Let's analyze the options:
(A) Time required to destroy all microorganisms: This is practically impossible to achieve and define, as microbial death is logarithmic. The concept of commercial sterility is used instead.
(B) Time required to reduce microbial population by 90%: This is the precise definition of the D-value.
(C) Temperature required to kill microorganisms: This refers to concepts like the thermal death point, not the D-value, which is a measure of time at a constant temperature.
(D) Rate of microbial growth: The D-value measures the rate of microbial death or inactivation, not growth.
Step 3: Final Answer:
The D-value represents the time required to reduce the microbial population by 90%.