Question from a student Question on 2012-2013pp Q5

Dear Kkkkkk,

Apple juice: E.coli  (low acidity, it can tolerant to pH4)

A: Correct

Steak: Staphylococcus aureus (have extracellular enzymes to digest the protein, so high protein content is ok )

A: No. E. coli, grow faster.

Beef: pseudomonas (it can grow at low temp and low sugar content food)

A: No. Listeria....Low temperature and high salt

White wine: acetobacter species (low pH)

A: Correct. But the reason is white wine has ~15% alcohol

bagel:  Saccharomyces cerevisiae (low aw, which many bacteria cannot grow) 

A: No. Aspergillus........low Aw and moderate sugar. Yeast can grow but limited in space and may have growth advantage if high sugar.

Best,

HSK

On Wed, May 6, 2015 at 7:25 PM,

Dear Prof. Kwan,

     Good evening. I want to ask whether my answers are correct because my answers are different from my classmates. 

My answer are:

Apple juice: E.coli  (low acidity, it can tolerant to pH4)

Steak: Staphylococcus aureus (have extracellular enzymes to digest the protein, so high protein content is ok )

Beeif: pseudomonas (it can grow at low temp and low sugar content food)

White wine: acetobacter species (low pH)

bagel:  Saccharomyces cerevisiae (low aw, which many bacteria cannot grow) 

                Thank you for answering my questions.