Question from a student 20170502a

Q&A:
 I would like to ask for the answer of B2 and B3a in 14-15 pastpaper. For B2, is the most suspected food Roast Turkey?

No. According to differences in attack rates and incubation period, and other evidences, it is probably Pizza and Staphylococcus aureus.


 For B3a, drying means heat drying that lowers the aw? For the comparison made, that means in this case, we have to point out lowering pH is more effective in preserving food? 

Yes, lowers Aw and water content.

No, lowering pH is not more effective in preserving food.



Lastly, can I answer all the questions in exam? Thanks a lot!

Yes, but if you answer all the questions, I will only count the number of questions required which have higher marks.

Some more Q&A from another email:


Also, as I see from the approach of doing 14-15 B4(e), the last question about justifying the answer and explain, that means we have to first find out the D value at 120°C, then calculate the treatment time required for both bacteria in regular blot ( spoilage bacteria: 10D x 0.0079= 0.079min, spores: 9D x 0.25= 2.25min), both bacteria in contaminated blot (spoilage: 0.1027min, spores: 3mins), then we use 3 mins at 120 degree celsius as the new time, then we follow part a to c to calculate the corr. D values, cell densities for both bacteria, then we come with conclusion to see if new method is ok. Am I correct?

You have to carry out all the calculations and answer both (i) and (ii). Your calculation to reach the two treatment times already shows whether the times you concluded to use are long enough to achieve the goals. "Justify" means you have to indicate why the times you use are good ones, "explain" means you need to give some details on your calculation and justification.