To calculate the remaining microorganisms after heat treatment at 110°C for 18 minutes, we can use the D-value and the concept of microbial reduction.
The D-value represents the time it takes to achieve a 1-log reduction in microbial population at a given temperature. In this case, the D110°C value is given as 2 minutes, meaning it takes 2 minutes at 110°C to reduce the population by 1 log (or by a factor of 10).
A 9-D process indicates a reduction of 9 logs, which means we need to calculate the reduction in microorganisms for each D-value over 9 iterations.
Starting with 10^12 cells per gram of product, we can calculate the remaining microorganisms after each D-value:
1 D-value: 10^12 cells/g * 10^-1 = 10^11 cells/g
2 D-values: 10^11 cells/g * 10^-1 = 10^10 cells/g
3 D-values: 10^10 cells/g * 10^-1 = 10^9 cells/g
4 D-values: 10^9 cells/g * 10^-1 = 10^8 cells/g
5 D-values: 10^8 cells/g * 10^-1 = 10^7 cells/g
6 D-values: 10^7 cells/g * 10^-1 = 10^6 cells/g
7 D-values: 10^6 cells/g * 10^-1 = 10^5 cells/g
8 D-values: 10^5 cells/g * 10^-1 = 10^4 cells/g
9 D-values: 10^4 cells/g * 10^-1 = 10^3 cells/g
After a 9-D process, there would be approximately 10^3 microorganisms remaining per gram of product.
Therefore, after heat treatment at 110°C for 18 minutes (a 9-D process), approximately 10^3 microorganisms would be expected to remain in the sample.