Question

An instrument in your lab needs to be shipped out for repair, but it is contaminated with Pseudomonas aeruginosa. You must decrease the microbial population to 10% before shipping this instrument out. If you heat the instrument to 120 °C, it will take 30 hours to achieve this goal, but the shipment must go out today. So, you need to speed up this process by heating the instrument at a higher temperature. If this microbe has a Z value of 50 °C, how long would it take at 170 °C to reduce the microbial population to 10%?

show your work

Answer 1

Solution

The equation required to solve this problem is:

where,

Z-value=This value can be defined as the increase in temperature that decreases the thermal death time (D) by a factor of 10.

T2 (Final temperature) = 170oC

T1 (Initial Temperature) = 120oC

D1 (Initial thermal death time) = 30 hours

D2 (Final thermal death time) = ?

Thus it would take 3 hours to reduce the microbial load of the instrument to 10% when heated at 170oC.