Hey
Can anyone help me out with this problem. For part a i understand i plot microbial numbers against time on semi log paper to determine D value for the two temperatures. But i'm unsure how to do part b.
Alicyclobacillus acidoterrestris is a quite hat resistant microorganism that has been causing problems in the fruit juice industry.Data below shows the thermal inactivation data determined experimentally for A. acidoterrestris spores in orange juice at 85.2�‹ and 91�‹C.
85.2 degrees celcius
Time Spore concentration
(min) in the juice N (cfu/ml)
0 min 1.9* 10^7
20 min 1.6* 10^7
40 min 9.1* 10^6
60 min 7.9* 1^0^6
80 min 4.8* 10^6
120 min 6.2* 10^5
160 min 8.9*10^4
180 min 5.5*10^4
91 degrees celcius
time (min) Spore concentration
in the juice N (cfu/ml)
0 min 1.7*10^7
2 min 8.1*10^6
5 min 4.0*10^6
8 min 2.6*10^6
11 min 1.8*10^6
14 min 8.0*10^5
16 min 5.9*10^5
18 min 2.6*10^5
21 min 2.8*10^5
a. Determine thermal resistance parameters of Alicyclobacillus acidoterrestris in the orange juice.
b. Suggest an appropriate P91�‹C�]value for this juice.
Thanks
To determine the thermal resistance parameters of Alicyclobacillus acidoterrestris in the orange juice, we need to use the data provided and plot microbial numbers against time on semi-log paper, as you mentioned for part a.
For each temperature (85.2�‹C and 91�‹C), plot the logarithm (base 10) of the spore concentration (N) on the vertical axis and the time (in minutes) on the horizontal axis. This will give you two separate plots.
Fit a straight line through the data points on each plot. The slope of the line represents the negative D value, which is the time required for a 90% reduction in the microbial population.
To calculate the D value at each temperature, find the difference in time (Δt) corresponding to a one log cycle reduction in microbial concentration.
For example, for the 85.2�‹C plot, the starting concentration is 1.9 * 10^7 cfu/ml, and when the concentration reduces to 1.9 * 10^6 cfu/ml, the time difference is 120 minutes - 20 minutes = 100 minutes. Repeat this calculation for each log cycle reduction in microbial concentration.
Once you have determined the D value for each temperature, you can proceed to part b.
To suggest an appropriate P-value (process value) at 91�‹C for this juice, you can estimate the time required for a specific reduction in microbial population using the D value.
For example, assuming you want to achieve a 10^-6 reduction (equivalent to a 6-log cycle reduction) in microbial population at 91�‹C, you can calculate the time required by multiplying the D value at 91�‹C by 6.
If the D value at 91�‹C is, for example, 10 minutes, then the estimated time required for a 6-log cycle reduction would be 10 minutes * 6 = 60 minutes.
Based on this estimation, you can suggest an appropriate P-value, which in this case would be a 60-minute hold time at 91�‹C to achieve the desired reduction in microbial population.
Remember to use the appropriate D value calculated from the experimental data to estimate the time required for different reductions in microbial population.
I hope this helps! Let me know if you have any further questions.