Welcome to the course FNSC5110 Blog

Reminder on Final Examination, 6 December, 2016, Tuesday, 7:00 pm. two hours examination.

Dear students,

Just to remind you to get and study the files on the Blackboard, CUHK Elearning system for Lecture on 6/12/2016:

1. Mind Maps
2. Food Microbiology PPT's shown in class
3. Notes--viruses, parasites, fungi
5. Notes--Spoilage

Also to remind you that you need to study all the materials covered in lectures and also those in the mind maps, ppts, and notes. Only the topics covered in lectures will be included in the final examination. For example, if I do not cover fungal pathogens in the lectures then fungal pathogens will not be inlcuded in the final examination.

The final examination will carry two parts, 50% each. One part from Professor Chung and one part from me.

Go to the FNSC5110 blog to see the questions asked by the students in previous years and also the answers.

http://fnt5110hsk.blogspot.hk/

Final Examination: 6 December 2015, Tuesday, 7:00 pm. two hours examination.

Best,

HS Kwan

FNSC 5110 QUESTION ABOUT REVIEW

Dear AAAAA,

Yes, you are correct. HACCP and hazard analysis are not included in the FNSC5110 final examination.

Best,

HSK

---

From: AAAAAAA
Sent: Thursday, December 01, 2016 1:21 AM
To: hoishankwan@cuhk.edu.hk
Subject: FNSC 5110 QUESTION ABOUT REVIEW

Dear professor,

I am reviewing the old paper about FNSC4180/FNSC3180 and I found that the exam paper covered some questions about HACCP and hazard analysis. Will this part of content also be included in FNSC 5110 final exam? I remember that you did not cover this part of the content in our lecture.

Thank you

Regards,

Question from a student--please note the revised answer

Dear ???,

I think you have look at the old exam paper of FNSC3180/4180. Question B3 has not been covered in FNSC5110 lectures this year and not in past few years so it will not be included in the final examination.

The other question is straightforward:

B3a What are the numbers of D'S targeted in the standard canning process for each of these microorganisms? (3 marks)

Number of D= anti-log10(Starting density/acceptable density)

For example: spoilage bacteria

Number of D = anti-log10(100/0.00000001) = anti-log10 of 10^10 = 10

Answer is 10D

Sorry, my answer is wrong: The targeted number of D's in the standard canning process should be:

25/0.25 = 100D

Because I missed the part of the question of "standard canning process", which means the condition is set as the process. So the achieved number of D's should be the answer.

From: ???????@qq.com]
Sent: Tuesday, 29 November 2016 12:45 PM
To: HS Kwan, Prof. (SLS)
Subject: question of old exam paper

Dear professor

I want to ask two questions of the old exam paper relative to FNSC5110.

Is the answer of a. question of B3 is pizza? Because the attack rate is highest,and if there other reason? And I don't konw how to solve the a.question of B5 

Would it possible for you to help solve these two question？ Thankyou

B3. You are an epidemiologist in the Health Department.

On a hot Saturday in July, 45 students

were reported sick with gastroenteritis and vomiting. You followed this

outbreak and obtained the following information in your study:

1 .   These 45 patients were Food and Nutritional Sciences major students who went to a picnic together with another 115 students and professors. Lunch was served during the picnic:

Menu--Pizza (with topings of ham, olive, pineapples, and green pepper), sushi, and bread. Dinner was served in the evening: Menu--boiled chicken, roasted turkey, fried rice and fried noodles

li.    Lunch in the picnic was served at 12:00 noon on Saturday. Dinner was finished by 7:00pm that evening.

iii.      Patients started to have diarrhea at 1 1 :00pm on Saturday followed by severe vomiting. Some of them went to the hospital immediately after they were sick. The last patient felt sick and went to the hospital at 4:00am on Sunday.

iv.      The hospital laboratory detected low levels of Salmonella enterica serotype Typhimurium from the feces of 5 patients.

v.        The laboratory of the Health Department detected low levels of Salmonella enterica serotype Typhimurium from sushi left over from the picnic and refrigerated after lunch. Also detected are low levels of Staphylococcus aureus from the dough used to make the pizzas and Low levels of Clostridium perfringens endospores in the vegetable stock used to make the turkey stuffing. No bacteria or spores were found from bread, fried noodles, boiled chicken, or fried rice.

vi.      The turkey and bread were prepared in the morning and transported to the picnic area at room temperature. The sushi was also made in the morning, stored in a foam box with ice and transported to the picnic area. The pizzas were baked right before lunch time and transported to the picnic area and they were kept at 65-70 ⁰ C. Boiled chickens were cooked the day before the picnic and kept in refrigerator and sent to the picnic without refrigeration. Fried rice and fried noodles were prepared at noon and transported to the picnic area in containers kept at 65-70 ⁰ C by the supplier.

vii.    Most of the patients recovered after one day of rest.

a.        The foods consumed at breakfast and lunch and the illness records are listed in the following table, calculate the attack rates. Which food would be the most suspected food? Explain briefly.     (8 marks)

                                                                       

Foods served	Ate				Did not Eat
	well	111	Total	Attack rate	Well	111	Total	Attack rate
Pizza	68	40	108		47	5	52
Sushi	66	15	81		49	30	79
Bread	96	40	136		19	5
Boiled Chicken	70	32	102		40	18	58
Roast turkey	64	35	99		51	10	61
Fried rice	50	17	67		63	30	93
Fried noodles	75	25	100		42	18	60

B5. You are the senior technical manager of a well-known ham canning factory.

One day the technician rushed into your office and informed you that the ham delivered yesterday for canning was slightly contaminated in an accident during transportation. The ham, however, was still suitable for human consumption. The technician wanted to know whether the standard canning process was still sufficient. He provided you with the information from the quality control laboratory as described below. What would be your decision?

	Approximate densities of microbial flora in the ham before canning		Acceptable cell density in canned ham
	Regular lot	Contaminated lot
Spoilage bacteria	IOO/ml	105/ml	0.00000001/ml and fewer
Bacterial spores	10/ml	104/ml	0.00000001/ml and fewer
Fungal spores	l/ml	10/ml	0.000001/ml and fewer

    Standard canning process for the ham:      25 minutes at 105 ⁰ C.

D values and Z values Spoilage bacteria Bacterial spores Fungal spores

of the microbes : D value at 105 0 C 0.25 minute 2.5 minutes 0.5 minute

Z value 7.50C 150C 150C

Answer the following questions. Show your calculations for partial marks:

a.          What are the numbers of D'S targeted in the standard canning process for each of these microorganisms? (3 marks)

Topics to know well for the Final Examination 2016--physico-chemical parameters

• You should understand the physico-chemical parameters that affect microbial growth and survival. 

• Temperature preferences and effects of different micororganisms.

• The heat treatment in particular is an important way of food safety assurance and need to know all aspects on D value, Z value, and F value. You need to know how they are calculated and used in heat treatment scenarios.

• Moisture contents vs water activities. 

• Strong acids and weak acids effects on growth and survival of different kinds of microorganisms. 

• Aerobic vs anaerobic respiration vs fermentation

• Redox potential as a predictor of kinds of microorganism that grow on the food

• How the phsico-chemical parameters are manipulated for prevention of foodborne diseases and food safety

Microorganisms to know well for 2016-17 Examination

Salmonella enterica
Salmonella enterica subspecies enterica serotype Typhi 
Salmonella Typhi
Salmonella Typhimurium
Salmonella Enteritidis
Escherichia coli

• -EAEC, EHEC, EIEC, EPEC, ETEC, DAEC 

• and the German "hybrid" of EAEC/EHEC

Vibrio cholerae
Vibrio parahaemolyticus
Campylobacter jejunii
Shigella species
Listeria monocytogenes
Clostridium perfringenes
Clostridium botulinum
Bacillus cereus
Staphylococcus aureus
lactic acid bacteria


Viruses:
Norovirus
Hepatitis A virus

You should know their biological characteristics, e.g. pH range, temperature range, and so on.

You should also know the foods closely related to these microorganisms

Question from a student on examination question

From: ZZZZZZZ
Sent: Saturday, 26 November 2016 6:51 PM
To: hoishankwan@cuhk.edu.hk
Subject: FNSC5110 Exam Question

Dear Professor,

I re-do the past exam paper as to prepare for the final exam, but not sure on one question (See attachment). Please let me know if I made any mistake or suggest a better a solution. 


Thank you,

●     What are the numbers of D's targeted in the standard canning process for each of these microorganisms? (2 marks)

                        Spoilage bacteria: 25/0.25=100D                                                                                           Bacteria Spores: 25/2.5= 10D                                                                                                          

●     Calculate the cell densities of the microorganisms remaining in the contaminated ham after a standard canning process treatment. (2 marks)

                        Spoilage bacteria: 10⁵ / 10¹⁰⁰ = 10^-95 (per ml)                                        

                        Bacteria Spores: 10⁴ / 10¹⁰ =10^-6 (per ml)                                                                                                          

●     Was the standard canning process sufficient for the canning ofthe contaminated ham? Explain briefly. (2 marks)

                        Insufficient. Bacteria Spores -> 10^-6 /ml, larger than 10^-8                             

                        To make it sufficient : additional 25 mins at 105°C

                      Bacteria spores at 10^-6 for additional 10D reduction ->10^-6 x10^-10 =10^-16       

Thus, sufficient after 10D reduction.

(Actually may only need additional 5 minutes at 105°C,

                         because 10⁴ /10^30/2.5=10^-8 (per ml))                                              

Better if only 5mins? Additional 25mins is too long?     

●     According to Chart I, what are the Z values                                                        ofthe two types of microbes? (4 marks)           

                        Spoilage Bacteria: -(95-85)/ log 5- log 50=10°C       

Bacteria Spores: -(105-90)/ log 5 - log 50 =15°C

                                                                                                           

●     The canning temperature can be raised 15°C without any adverse effect on the quality of the canned hams. Hence, the technician would like to use l20°C in the canning process to treat this lot of contaminated ham. Calculate the treatment time required at120°C to achieve (i) the acceptable cell density for this contaminated lot and (ii) the acceptable cell densities of the microorganisms of the regular lot of ham after canning with this new process. Justify your answer and explain. (10 marks)

            At 120°C:                                                     

            Spoilage bacteria:

            D120°C=D105°C *10^[(105-120)/10]=0.25*10^(-1.5)=7.9*10^(-3)min

           Bacteria Spores:

            D120°C=D105°C *10^[(105-120)/15]=0.25*10^(-1)=0.25min

          

          Treatment time for regular:

          Spoilage bacteria: 10D120°C=7.9*10^(-2)min

           Bacteria Spores: 9D120°C=2.25min

           Treatment time for contaminated:

           Spoilage bacteria: 13D120°C=0.1027min

           Bacteria Spores: 12D120°C=3min

Your answers to the questions are correct except one: Your answer to the last question is incomplete: you can only use one treatment time to treat each lot. You need to use the time for the most heat-resistant microorganism, in this case, bacterial spores. So the times should be: 

Regular--2.25 min

Contaminated--3 min