Question from a student 20140423

1)    Am I right with the following answers?

Neurotoxin sensitive to heat: Poliovirus X              botulinim toxin

Protein toxin becoming more toxic after heat-treatment: Staphylococcus aureus Right 

Causing severe food-borne intoxication during famine: Vibrio cholera   Not covered this year

2)    Am I right with the following answers?

Is it just water activity and temperature of survival won’t be affected when the condition is out of the minimum and maximum tolerance, while there will be no growth when it is not within min and max tolerance?

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Temperature higher than maximum will kill the cells. Not so with water activity.

3)    Am I right with the following answers?

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4)    I really don’t understand how should I approach the following questions. But it appears in every year’s past paper, so I have to ask how to do it . Am I correct? Thank you very much.

-Ground beef salted: listeria moncytogene (low temp and salted)

-white wine: saccharomyces cerevisiae

-Bagel: clostridium perfringens

-Steak surface:pseudomonas

Apple juice:norovirus (I am not sure of this , I just think because apple juice has high water activity, so maybe virus can grow in it)

I really don’t understand how should I approach the question, what is special if the food has high redos or low redox? Because all facultative bacteria can grow in -400 to 400mv.

What’s so special does high sugar content and high protein content means?

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 You have to consider all parameters. I have not got the time to do all the questions again. When I have time to-night, I will do it.

  

I am very confused on doing this table.

Am I right with the following answers?

-Ground beef: Listeria monocytogenes(low temp and high salt content)

-Fresh apple juice : norovirus

-Red wine: ?

-Bread: saccharomyces cerevisiae (because it is used in bread)

-Beef steak surface: Clostrdium perfringens

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5)      May I ask what’s the difference between (vi) (Vii). And (viii)?

-Clostridium Botulinum is obligate aerobes and thermophiles

What’s so special if high redox with nitrate or just lower redox? What does it implies? How does it affects growth and survival?

C. botulinum is killed at high redox.

-And also may I ask what’s effect on (ix) and (x)

I have searched for very long but still don’t know the properties of Salmonella Typhimurium and E Coli,

how is pH 4.2 affects their growth and survival?

?

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