GATE AG 2013 • Q22 MCQ • 1 Mark

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:

For an initial spore load equal to 25 spores per container inoculated with Clostridium botulinum having D₁₂₁=0.25 min, the spoilage probability of the container subjected to F₁₂₁=1.5 min is

Options:

  • (A) 10⁻⁵
  • (B) 10⁻⁶
  • (C) 10⁻⁸
  • (D) 10⁻⁹

Official Answer Key:

A

Step-by-Step Solution & Explanation

Number of decimal (log) reductions achieved = F/D = 1.5/0.25 = 6 log cycles. Surviving spore count (= spoilage probability per container, for N₀ well below 1 log unit) = N₀/10⁶ = 25/10⁶ = 2.5×10⁻⁵, which is of order 10⁻⁵. Answer: (A).

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