Calculations

Question 1

Define D-value and what a high d-value means

Answer 1

Time required to kill 90% of organisms
The higher the D-value, more resistant a bacterium is

Question 2

How do you calculate the D-value

Answer 2

Either plot on semi-log per or calculate the log values and put in on a linear paper
Use the equation
Read of the graph where there is a 1 log reduction e,g form 10 to 1

Question 3

Define Z-value

Answer 3

The temperature increase that will reduce the D-value by 90% (how many degrees do you need to increase the process to make it 10x more efficient

Question 4

What is the Sterility Assurance Level (SAL)?

Answer 4

The probabilities that in an item, batch or unit a microorganism survives

Question 5

What SAL value is usually considered acceptable?

Answer 5

SAL of 10-6

Question 6

Define PNSU

Answer 6

The probability that 1 unit in a batch is contaminated

Question 7

What do the heating and cooling stages contribute to?

Answer 7

Contribute to the sterilisation process
if the contribution is known the holding stage could be reduced saving time, costs and if the product is thermolabile reduce inactivation of the drug

Question 8

What does the F-value stand for?

Answer 8

Expresses lethality of heat treatment at any temperature equivalent to treatment at a reference temperature
It depends on the resistance of reference organism
F-value is expressed in minutes