The GATE Grind

GATE 2023 AG – Question 26

Dairy and Food Engineering · Preservation of Food · 1 mark · Multiple choice

Microbial death follows $\log_{10}(N_0/N)=1+(t-t_l)/D$,where t is time,$t_l$ lag time and D decimal reduction time. Which statement is correct?

  1. Lag time removes10% of the initial population.
  2. Lag time removes the initial90% of the population.
  3. The first90% kill takes less than D at the same temperature.
  4. Lag approaches D as initial load decreases and temperature decreases.

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Correct answer: (B) Lag time removes the initial90% of the population.

Explanation

Set $t=t_l$ in the supplied relation. Then $\log_{10}(N_0/N)=1$,so $N=N_0/10$:90% of the original population has been removed. Therefore **B** follows directly. The relation is an empirical time-offset model; its term lag should be interpreted through this printed equation rather than assuming zero killing during that interval.

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