B5--Questions from student 20150426

FNSC 4180 2013-2014 2^ndterm

B3.

a.         Roasted Turkey is the most suspected food. Pizza is kept at 65-70^oC. Therefore,    both Staphylococcus aureus and its toxin won't appear in food. The toxin is          decomposed at 60 ^oC. Sushi is stored with ice, it is unlikely that Salmonella can    grow. Also, the attack rate for roast turkey is quite high, which is 0.35.

b.   The microorganism inviolved is C. perfringens, which incubation period is usually at typically 8-12 hours. The calculated incubated period is 8 hours as dinner starts at 7:00pm on sat and the last patient went to hospital at 4:00am on Sunday. The food involved is roasted turkey. The bacteria is found on vegetable and used as turkey stuffing. The surface of the turkey is cooked. However, the things inside the turkey may not be cooked sufficiently with temperature higher than 60 degree. The bacteria can form spore, which is activated by heating 40-50 degree. Therefore, the bacteria present inside the chicken after it is cooked. It usually presents in small number. However, the turkey transported to picnic site at room temperature, which allow them to proliferate to infective dose, which is 10⁶ -10⁷ cell per gram.

B5.

a. bacteria: 100logD

  Bacterial spore: 10logD

  Fungal spore: 50logD

b. bacteria: 10³ /ml

  Bacterial spore: 10³/ ml

  Fungal spore: 10^-50 / ml

c. bacteria: No, higher than the acceptable cell density

  Bacterial spore: No, higher than the acceptable cell density

  Fungal spore: Yes, lower than the acceptable cell density

d.

	D value at 120oC	Z value
Spoilage bacteria	0.025 mins	7.5 oC
Bacterial spores	0.25 mins	15 oC
Fungal spore	0.05 mins	15 oC

Acceptable cell density:

  bacteria: 8logD

  Bacterial spore: 8logD

  Fungal spore: 6logD

Treatment time required at 120 to achieve accepted cell density foe contaminated lot:

  bacteria: 8 x 0.025 = 0.2 mins

  Bacterial spore: 8 x 0.25 = 2 mins

  Fungal spore: 6 x 0.05 = 0.3 mins

density of the microorganism of the regular lot of ham after canning with new process:

bacteria: 0.001 /ml

bacterial spore: 0.1 /ml

fungal spore: 1X10^-500 /ml