I would like to ask below 5 questions. Please kindly advice. Thanks for your
reading & helping.
1.For fresh apple juice, the condition is acidic & high sugar & low salt & keep
at 25C. How could I determine whether it is yeast/ecoli 0157/lactic acid
bacteria (as all seems favour to this condition)?
A: Lactic acid bacteria: more competitive than E. coli and grow faster than yeast
2.For ground beef, the condition is high protein & salt& not acidic, if stored
at 25C, is it resulted as S. aureus? But if stored at 5C, it turns to be L.
monocytogenes?
But if it is high protein & store at 25C,but not salty & acidic,then it became
Ecoli 0157?
A1: Yes, S. aureus, if 5C, L. monocytogenes
A2: Yes, E. coli O157 should grow better.
3. From the pastpaper:
a)pls see attached picture, see if the organism is correctly stated (based on
highlighted reason)
b)the most toxic natural bacterial toxin -> C. botulinum?
c)Culturing does not detected the pathogen in oysters in winter but it appears
in summer to cause liver infection -> hepatitis A rather than V.cholera?
A (a) Go to the end of this post
A (b) Yes
A (c) Yes, hepatitis A.
4. S. aureus make the toxin become stonger if reheat the meat again,
so thats mean we cannot reheat something like sui mei that already cooked & put
in ambient temp (which contain S. aureus)?
A: Yes, the siu mei would still contains toxin
5. One of the controlled method of spore forming bacteria(C. perfringen & B.
cereus) is fully reheated the food before consumption. But it is known that
heating activate endospore to germinate, so why/ how could the food is still
considered to be safe once reheated?
A: The food reheated and then consumed right after reheating would activate endospores to germinate but they would not have enough time to grow and cause problem
Q3 A (a)
From left to right:
Listeria monocytogenes, Salmonella spp./E. coli O157:H7 is ok too, Aspergillus oryzae,
None (pH 4.0 and low temp, high salt), C. perfringens
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