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9.
You are the senior technical
manager of an apple cider bottling factory. You are responsible
for food safety management system ISO22000 based on
HACCP. The following happened last week:
i. On
Tuesday, your technician rushed into your office and informed you that the
quality control laboratory have made a mistake in measuring the pH of the
apple cider delivered yesterday for bottling. The actual pH of
the food was 4.5 and the laboratory used a malfunctioning pH meter
and reported a pH value of 4.0.
ii. Some of
the apple cider was bottled and pasteurized already, using the pasteurization
process designed for apple cider of pH4.0.
iii. The
technician thought that the pasteurization process was not sufficient and
suggested a corrective action that the bottled apple cider should
be processed one more time for 10 minutes at 105°C.
iv. He
provided you with the information from the quality control laboratory as
described below.
v. You had to
judge whether the technician’s decision was correct or not and answer the
questions below.
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Approximate microbial flora in apple
cider (Number/ml)
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Acceptable cell density in bottled apple cider(Number/ml)
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Spoilage bacteria
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1000
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less than
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0.0000001
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Bacterial spores
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100
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less than
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0.000001
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Fungal spores
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100
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less than
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0.000001
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The problematic pasteurization
process: 10 minutes at 105°C.
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D
values and Z values of the microbes at pH4.0:
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D value at 105°C(minute)
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Z value(°C)
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Spoilage bacteria
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0.001
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2
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Bacterial spores
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0.1
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10
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Fungal spores
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0.002
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5
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D
values and Z values of the microbes at pH4.5:
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D value at 105°C(minute)
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Z value(°C)
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Spoilage bacteria
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0.01
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5
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Bacterial spores
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2
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15
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Fungal spores
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0.02
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10
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Answer the following questions. Show your
calculations :
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a.
Calculate the F values set in the pasteurization for these
target
microorganisms?
(1 marks)
At 105°C
Spoilage bacteria: from
1000/ml to 0.0000001/ml -->10D=0.01min
Bacterial spores:
100/ml to 0.000001/ml -->8D=0.8 min
Fungal spores: 100/ml
to 0.000001/ml -->8D=0.016min
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b.
Calculate the number of D’s that actually occurred in the
problematic pasteurization process for these target microorganisms?
(2 marks)
Spoilage bacteria:
10min/0.01min=1000D
Bacterial spores: 10min/2
min=5D
Fungal spores:
10min/0.02min=500D
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c.
Calculate the cell densities of the microorganisms in the
processed apple cider with actual pH of 4.5 after they were processed
for 10 minutes at 105°C?
(2 marks)
Spoilage bacteria: 1000/101000=10-997
(per ml)
Bacterial spores: 100/105=10-3(per
ml)
Fungal spores: 100/10500=10-498
(per ml)
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d.
Was the proposed additional pasteurization
process needed and if needed, was it sufficient for the processing of
the one-time processed apple cider with wrong pH
measurement? Explain briefly.
(1
mark)
Needed. Reason:
Bacterial spores-->10-3/ml, larger than the acceptable level of
10-6/ml.
sufficient or not: additional 10 minutes at 105°C
Bacterial spores at 10-3/ml
for additional 5D reduction
--> 10-3/ml
x 10-5 =10-8/ml
Sufficient
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e.
Was the technician correct in his suggestion of the
additional remedial processing? If he was wrong, fire him and
suggest alternative pasteurization time to treat the problematic bottled
apple cider at 105°C. Explain briefly.
(1 marks)
According to above
calculation. The remedial processing should be sufficient. The technician was
correct.
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f.
Suggest a new process with a combination of pasteurization
temperature and time for the remaining batches of apple
cider (pH4.5). These data may be useful for your
consideration: heating for 10 minutes at 105°C for ten bottles of apple
cider costs HK$1 and heating for 1 minute at 120°C for ten bottles of
apple cider costs HK$5. Explain briefly your process with
justification.
The current cost: HK$1
per 10 bottles=HK$0.1/bottle if 10 min at 105°C.
Need to do it twice. So
cost for the remaining batches would be HK$0.2/bottle.
If we adjust the
If increased to 120°C,
time for pasteurization will need to be:
D value for bacterial
spores: one log decrease-->2 min to 0.2 min
For 8D reduction
target, the time needed will be 0.2min x 8=1.6min
The cost at
120°C for 1.6 min for 10 bottles would be around HK$8
-->HK$0.8/bottle
The process should be
maintained at 20 min at 105°C for a lower cost.
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