FST 104 Final F08A Key

8/6/2019 FST 104 Final F08A Key

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Name______________________________Student ID #________________________

FST 104 Fall 2008Final exam (December 10, 2008)

PLEASE RECORD YOUR TEST VERSION LETTER (shown on page 11 of the exam) and the answersto questions 1-67 on a blue Scantron form UCD2000 using a #2 pencil. (If you did not bringthe Scantron form, circle the letter of the correct answer directly on the exam pages. We willcorrect your exam by hand and assess a penalty of twenty points.) [3 points each]

1. Which of the following gases is typically used to replace part of the air in modifiedatmosphere storage of fish or vegetables?A O2 B OzoneC Cl2 (chlorine)D TMAO (trimethylamine oxide)E CO 2 (carbon dioxide)

2. Which of the following is not a result of Bacillus growth during Natto fermentation?A Decrease the amount of pancreatic inhibitor present in the raw materialB Improve nutrient availability and digestibilityC Produce NH 3 and complex flavorsD Produce a sticky polymerE Decrease the pH of the starting material to stabilize the food against microbial attack

3. What is the a w below which no bacterial pathogen will grow?A 0.97B 0.92C 0.90D 0.85

E 0.60

4. When a bacterial cell is shifted from a lower growth temperature to a higher growthtemperature, it must maintain its membrane fluidity. How does it do that?A By more efficiently losing Mg +2 ions from the cellB By more effectively excluding hydrogen ions from the cellC By increasing the proportion of the most temperature-sensitive enzyme in the membraneD By increasing the proportion of saturated fatty acids in the membraneE By increasing the proportion of unsaturated fatty acids in the membrane

5. A food was found to spoil after 12 hours at 30 C. Assuming that the T min for thespoilage organism is 7 C and that the T opt is 40 C, how long would it have taken the

food to spoil at 10 C?A 3 hoursB 6 hoursC 12 hoursD 24 hoursE 48 hours


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6. Which of the following is not a feature that makes E. coli 0157:H7 (EHEC) such adangerous pathogen?A It produces a "Shiga-like" cytotoxinB It is more acid tolerant than most other E. coli strainsC It can cause Hemolytic Uremic Syndrome (HUS)D It has a low infective doseE It survives cooking to 160 F (71 C)

7. Which of the listed microbes would grow over about the same redox range asLactococcus (Streptococcus) lactis?A Pseudomonas fragiB Campylobacter jejuniC Staphylococcus aureusD Aspergillis oryzaeE Clostridium botulinum

8. Compared to cheese made using lactic acid bacteria, cheese made only with rennin isusually:A Found only in SwitzerlandB Less susceptible to microbial spoilageC More of a health threat due to Listeria monocytogenes D Less of a health threat because it contains no Listeria monocytogenes E More acidic

9. Which of the following is not true about antibiotics?A Only nontherapeutic antibiotics can be used in foodsB Nisin is proven to be a clinically useful antibioticC Antibiotics can be used as animal feed supplementsD Penicillin kills pathogens by affecting the cell wall synthesisE One of the concerns with antibiotics is that the bacteria can develop antibiotic resistance

10. CASE STUDY . Nearly a third of the passengers and crew on an airliner developed severegasteroenteritis, and most also had bloody diarrhea. These symptoms appeared between two andthree days after the flight landed. Two elderly passengers died, but the other sufferers recoveredfully in about one week. All of the people who became ill had eaten a minimally processed saladcontaining lettuce, chicken, bread croutons, and a mayonnaise-based dressing. Which of thefollowing organisms is the likely cause of the illness?

A Clostridium perfringensB E coli ETECC Hepatitis AD Staphylococcus aureusE Shigella dysenteriae

11. Leuconostoc cremoris is often used for dairy fermentations because it produces goodquantities of diacetyl in sour cream and related products. Which of the following will

tend to prevent diacetyl formation?A The addition of citrate to the fermentation (pH = 5.5)B Fructose and glucose as sole sources of carbon and energy, in the absence of oxygen (-400 mV)C Fructose and glucose as sole sources of carbon and energy, in the presence of low oxygen (-50 mV)D Glucose as a sole source of carbon and energy, in the absence of oxygen (-400 mV)E Glucose as a sole source of carbon and energy, in the presence of low oxygen (-50 mV)


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12. High fat foods (e.g., unsalted butter) can still be spoiled by bacteria requiring a highaw because:A Fat accelerates bacterial growthB Bacteria survive better at lower a w C Bacteria grow at lower a w in the presence of fatD Such foods may contain micro-environments of high a w E Such foods are often eaten with other highly contaminated foods

13. The serotype of a Gram negative bacterium refers to A The type of toxin they produceB Whether they cause food-borne infections or food intoxicationsC Whether or not they have an outer membraneD Whether or not they have a nuclear membraneE The type of antibody that mammals produce against the bacterial outer membrane and flagellum

O XYGEN PROTECTIVE ENZYMES . For the microbes listed in the next two questions, choosethe correct letter from the list given immediately below. A letter may be used more thanonce.

A. Possesses both catalase and superoxide dismutase

B. Possesses both peroxidase and superoxide dismutaseC. Possesses catalase but no superoxide dismutaseD. Has peroxidase and uses Mn ++ in non-enzymatic reactions to remove the superoxide radicalE. Has no apparent oxygen protective enzymes

14. Lactobacillus plantarum D

15. Staphylococcus aureus A

16. During cheese production casein can be precipitated byA Adding rennin to the milk B Allowing a lactic acid fermentation to lower the pH of the milk to about 4.5C Heating the milk to 40 C

D Both A and BE Both B and C

17. You perform an irradiation experiment and find that 12 kGy reproducibly decreasesthe number of bacteria in a food from 1 x 10 5 per gram to 1 x 10 2 per gram. What isthe D?A 0.4 kGyB 1 kGyC 4 kGyD 6 kGyE 40 kGy

18. According to the information given in your syllabus and in class, which of thefollowing food fermentations does not involve a yeast or a mold to produce thecharacteristic flavor of the product?A Camembert cheeseB Sourdough breadC CocoaD Swiss cheeseE Soy sauce


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19. Usually, proper storage of food below 7 C (45 F) or above 60 C (140 F) is sufficientto prevent the growth of a potential pathogen in the food. Which pathogen listed below is an exception at one or both ends of this range?A Clostridium botulinumB Clostridium perfringensC E coli 0157:H7 (EHEC)D Lactococcus (Streptococcus) thermophilus

E Listeria monocytogenes 20. For instrumental methods for rapid detection of microbial contamination, threshold

concentration and detection time are important concepts. The following is not trueabout detection time.A Can be only a few hours if the initial concentration of microbes is highB Linearly related to the initial concentration of microbesC Two instruments with different methods for detecting microbes but with similar threshold

concentrations will yield similar detection times for a sample.D Not useful for subtyping strainsE For one type of instrument, detection time is the time at which a change in temperature caused by

the heat generated by microbial growth can first be detected

21. Which of the following does not need to grow on the food to cause illness?A Claviceps purpuraeB Staphylococcus aureusC Clostridium botulinumD Campylobacter jejuniE Aspergillus flavus

22. Which of the following is true of intestinal salmonellosis?A It is a viral diseaseB It can lead to enteric feverC Its symptoms are similar to those caused by prions (the BSE/vCJD agent)D It can best be controlled by proper sanitationE It can best be controlled by proper cooking

23. Which of the following organisms is often used to produce yoghurt and Swiss cheese?A Lactobacillus plantarumB Lactobcaillus sanfranciscoC Lactobacillus thermophilisD Penicillium roquefortiiE Saccharomyces (Zygosaccharomyces) rouxii

24. CASE STUDY . A family made homemade sauerkraut to serve at a fund raiser at which 200people were hosted. Within 8 hours 90% of the guests experienced diarrhea and vomiting, whichlasted about a day. 80% of the guests asked for their donations back. There was no secondary

transmission of the illness, and all of the victims recovered with no obvious ill effects. Because of thesize of the outbreak, health officials looked into the cause of the problem but could isolate no obviouspathogen from the sauerkraut. However, when the health officials boiled the sauerkraut for 1 hourand fed it to mice, all of the mice became ill, with similar symptoms as the human victims. Whichorganism from the list below is the most likely agent of this disease?

A BSE (Bovine Spongiform Encephalopathy) agentB Giardia lambliaC Clostridium botulinumD Staphylococcus aureusE Shigella dysenteriae


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25. Which of these statements is false regarding lactic acid bacteria?A Lactic acid is a waste product made during the growth of lactic acid bacteriaB Heterofermentative bacteria strictly produce ethanol, CO 2, and acetateC Lactic acid bacteria belong in the same Division of bacteria as Listeria and Clostridium speciesD Heterofermentative lactic acid bacteria contain the phosphoketolase fermentation pathwayE Vitamins are produced by some lactic acid bacteria

26. Under normal circumstances, which of the following microbes usually begins theclassic sauerkraut fermentation we discussed in class? A MoldsB Erwinia speciesC Homofermentative lactic acid bacteriaD Heterofermentative lactic acid bacteriaE Propionibacteria species

Q UESTIONS REGARDING RENNIN PRODUCED BY GENETIC ENGINEERING TECHNOLOGY . For thenext two questions, choose the correct letter from the list given immediately below. Aletter may be used more than once.

A Cow

B Mucor miehiC Escherichia coliD Lactococcus cremorisE Kluyveromyces lactis

27. Source of chymosin gene A

28. Approved microbe genetically engineered to secrete correctly folded chymosin E

29. The food industry is looking for effective substitutes for nitrates/nitrites in curedmeats for the following reason.A They are expensive

B They adversely affect the colorC Nitrosamine formationD They cause blue baby syndromeE All of the above

30. Infant botulism is often associated with the following.A Eating mashed, strained home canned green beansB Drinking baby formula instead of nursingC Eating honeyD A turtle in the houseE Eating mashed, strained marine white fish

31. Assuming that the listed treatments have no negative effect on food quality and thatall are legal, which of the following is the least effective treatment if your goal is toprevent Clostridium botulinum from becoming a health hazard in canned ham?A Treat with NO 3 (nitrate)B Irradiate with Cobalt 60C Ensure that the pH is lower than (more acidic than) 4.5D Treat with NatamycinE Treat with Nisin


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32. Which of the following statements about food-borne protozoa is not true? A Transmitted though poor sanitation or undercooked meatB They are all eukaryotic organismsC Ingestion of the resting stage (cysts) causes the illnessD Are sensitive to the same antibiotics that are commonly used to kill bacteriaE Cysts last a long time in the environment

33. Which of the following products is made (or cured) using only lactic acid bacteria?A TempehB SauerkrautC Swiss cheeseD Cocoa/chocolateE Authentic (not American) kefir

PATHOGENIC M ECHANISMS . For the microbes listed in the next four questions, choose thecorrect letter from the list of pathogenic mechanisms given immediately below. A lettermay be used more than once.

A Activates adenylate cyclase which catalyzes the synthesis of cAMPB Catalyzes the removal of adenine from the 28S rRNA of the ribosome

C Inject Sips protein into the host causing the host to take up the bacteria by endocytosisD Endonuclease activity causes double strand breaks in host DNAE Stimulates that vagus nerve which cause humans to vomit

34. Campylobacter jejuni. Poor question

35. E. coli O157:H7 (EHEC) B

36. Vibrio cholera A

37. DNA microarrays are usually used to determine the levels of the following moleculesin a cell?

A ProteinB DNAC RNAD LipidsE Metabolites

38. For which of the following would you need to add the most (in grams from the bottle)to inhibit mold growth in 100 grams of food at pH 4? You do not need to show yourcalculations.A sorbic acidB propionic acidC methyl parabeneD benzoic acid

E acetic acid

39. Which of the following is a correct match between the pathogen and the best strategyfor its control?A Clostridium perfringens -- proper cookingB Norovirus -- immunizationC Salmonella enteriditis -- proper storage of food after cookingD Taenia solium -- filtering or boiling drinking waterE Rotavirus immunization


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40. Which of the following is true regarding a food borne infection?A The pathogen must produce an enterotoxinB You must ingest the pathogen to become illC The pathogen must grow in the food firstD The pathogen is always a bacteriumE The pathogen is always spread by the fecal-oral route

41. Which of the following is not true about Gram positive bacteria (other than Listeria)that cause food-borne illness in adults?A Cause intoxications (or disease without colonization) rather than infectionsB Must proliferate (grow) in the food to cause illnessC Are usually present in the environment, i.e., soil, air, or on human skinD They are transmitted primarily by poor sanitationE Onset of illness is usually fast (less than 12-24 h)

M ICROBIAL SPOILAGE . For the foods and storage conditions described in the next fourquestions, indicate the letter of the most likely group of spoilage microorganisms.

42. Assuming that all were present initially at low numbers, which of the listed microbeswould be the most likely spoilage agent of homemade ranch-style salad dressing stored at 4C [Composition: 50% fat; 15% protein; 2% sugar (all lactose) ; pH = 3.4, a w = 0.95, Redox = +50 mV]

A YeastsB MoldsC Pseudomonas and relativesD Lactic acid bacteriaE Endospore-forming bacteria

43. Assuming that all were present initially at low numbers, which of the listed microbeswould be the most likely spoilage agent of cottage cheese stored at 7 C [Composition: 3% fat;18% protein; 4% sugar (all lactose); pH = 5.8, a W = 0.98, Redox = +200 mV]

A YeastsB Escherichia coliC Pseudomonas and relativesD Lactic acid bacteriaE Clostridium species

44. Most likely spoilage agent of hot dogs stored in a refrigerator (4C) in a vacuumpackage . [pH = 6.2, 0.5% sugar; 11% protein; 25% fat; aw = 0.97, redox = -50 mV].

A YeastsB Bacillus coagulans C Pseudomonas fragi D Erwinia speciesE Lactic acid bacteria

45. Which could spoil pickled broccoli of aw = 0.99; pH = 3.0; redox = +300 mV; storedopen at room temperature (24 C )? [Composition: cellulose 10%, pectin 10%, protein 3%]A Pseudomonas speciesB Erwinia speciesC Bacillus stearothermophilusD Lactobacillus plantarumE Mold species


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46. How many grams of sorbic acid would you need to add to 200 grams of a soft drink atpH 5 in order to inhibit the growth of yeasts and molds? You do not need to showyour calculations.A 0.400 gB 0.266 gC 0.133 gD 0.067g

E 0.049g

47. pH below which a food is considered acidic for the purposes of determining theheat treatment necessary in canning.A 1.5B 3.0C 3.7D 4.6E 5.5

48. Poor sanitation and poor personal hygiene are the primary causes of transmission of all food-related diseases

A Caused by Vibrio vulnificus and Vibrio parahaemolyticusB Caused by fungiC Caused by prionsD Transmitted from animals to humansE Caused by viruses

49. Which of the following is true regarding Gram-positive and Gram-negative bacteria?A Peptidoglycan cell wall of Gram-positive bacteria is thickerB Gram-negative bacteria do not have a cytoplasmic membraneC Gram-negative bacteria outer membranes contain lipopolysaccharide, a potential enterotoxinD Gram-positive bacteria outer membranes do not contain lipopolysaccharideE All of the above

50. Four of the following diseases are transmitted by eating food containing the agent, butone is a very similar disease that appears to occur spontaneously in a certainpopulation. Which is the spontaneous (or genetic) version of the disease?A KuruB CJD (Cruetzfeldt-Jacob Disease)C BSE (Bovine Spongiform Encephalopathy)D Feline Spongiform EncephalopathyE vCJD (variant Cruetzfeldt-Jacob Disease which appeared in Great Britain in the 1990s)

51. CASE STUDY . After a large family picnic lunch many of the celebrants became ill the followingevening, exhibiting symptoms of severe gastroenteritis. Those who became ill had all consumed largequantities of beer and had eaten large quantities of fresh shrimp. This shrimp had been cookedearlier in the day in another city, loaded back into the wooded boxes in which they had beenpurchased, then trucked to the site of the picnic and stored without refrigeration in the shade (87 F)for about five hours before eating. Which of the following organisms is the likely cause of the illness?

A Entameoba histolyticaB Taena soliumC Vibrio parahaemolyticusD Vibrio vulnificusE Rotavirus


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52. CASE STUDY . A disease outbreak in a day care center first appeared in toddlers one to twoyears of age, all of whom experienced gastroenteritis. Two days later, several older children and oneadult worker at the center experienced the same symptoms, and soon thereafter three of the afflictedtoddlers' parents also developed a similar illness. Which of the following is the most likely cause?

A RotavirusB NorovirusC Shigella dysenteriae

D Shigella sonneiE Clostridium botulinum

53. The D80 C value for a problem pathogen in a given food is 8 minutes. The D for thesame pathogen in the same food is 4 kGy upon irradiation. When treating this food at80 C an F of 32 min is always sufficient for the safety. What would be the equivalentif you were to treat the food by irradiating it rather than by heating it at 80C?A 8 minutesB 32 minutesC 8 kGyD 16 kGyE 32 kGy

54. For the soy sauce fermentation three types of inocula are involved. What is theinoculum/inocula used for completing the moromi.A MoldB Lactic acid bacteriaC YeastD Mold and lactic acid bacteriaE Yeast and lactic acid bacteria

55. CASE STUDY . Four college friends got together for a potluck dinner, which consisted of delicious enchiladas made with chicken cooked to an internal temperature of 54C/130F; fresh saladwith commercial ranch dressing; reheated beans; reheated rice; and beer. Between 48 and 60 hoursafter the dinner three of the friends developed watery diarrhea, abdominal cramps, and nausea. Thefourth friend was profoundly sympathetic, and he demonstrated the depth of his sympathy byheartily eating the leftover enchiladas while remarking that he was certainly glad his appetite wasunaffected by illness. He fell ill two days later and manifested the same symptoms. Assuming thatthis illness was food-borne, which of the following agents is the most likely cause?

A RotavirusB Taenia soliumC Shigella dysenteriae D Campylobacter jejuniiE Clostridium perfringens

56. You are given that the D of Salmonella enteritidis is 2 kGy. A culture containing 1 x105 bacteria per ml was irradiated with 6 kGy and 1 ml samples of the survivors wereplated on two different media: one that is selective for Salmonella and a one that is

non-selective. After two days of incubation, no colonies appeared on the selectivemedium but about 90 colonies appeared on the non-selective medium. What is the best explanation of these results?A All the Salmonella were killed by 6 kGy of radiationB Radiation treatment allows Salmonella to grow on the non-selective medium when it couldn't beforeC Radiation treatment injured the Salmonella so that it was unable to grow on the selective mediumD Radiation causes bacterial counts to be falsely high on selective mediaE Radiation actually increases bacterial survival by stopping their metabolism


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57. When harvesting and storage of grains goes as planned, mycotoxins are not aproblem. What change (from the normal values of the parameters listed below) between the time when the grain is ready to harvest and when it is consumed makesmycotoxin formation possible?A Increased pHB Increased temperatureC Increased a w

D Increased redox potentialE Decreased temperature

FOOD FERMENTATIONS . For the next two questions, please choose the correct letter fromthe list given immediately below. A letter may be used more than once

A. Acetic acid bacteriaB. Aspergillus flavusC. Aspergillus oryzaeD Rhizopus speciesE. Propionibacterium species

58. Their metabolism is responsible for the sharp bite of Swiss cheese. E

59. Their metabolic activity, if excessive, is well known to produce inferior chocolate orcocoa. A

60. Which of the following statements about lactic acid bacteria is not true?A They are microaerophilicB They grow throughout the food with a uniform metabolismC They produce a wide variety of extracellular hydrolasesD They are commonly found on the surfaces of plants and animalsE They are Gram positive bacteria and they lack catalase

61. Which of the following is not a part of most Hazard Analysis Critical Control Point(HACCP) schemes implemented the United States? A Identify where agents of food-borne illness might enter a processB Identify where agents of food spoilage might enter the processC Identify Critical Control Points (CCP) in the processD Establish monitoring procedures at each CCPE Establish a comprehensive record-keeping system

62. Which of the following is true concerning microbial food safety and dried-foods? A For foods below aw of 0.85 there is no problem with bacterial pathogensB Pertinent pathogen is SalmonellaC Pertinent pathogen is E. coli O157:H7D Assumption that if a microbes cannot grow in a food there will be no food safety problem is valid

E Pecans have been implicated in outbreaks resulting in infections by food-borne pathogens

63. A food contains microbes A (10 2 cfu/g) and B (10 4 cfu/g). The growth rates on thefood during storage are 2.1 h -1 for A and 0.63 h -1 for B. Assuming no lag, which microbe willreach 105 cfu/g first and how long will it take? (Semi-log graph paper is attached).

A A 3.7 hB B 3.7hC A 3.3 hD B 3.3 hE B 1.7h


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64. Attached is a plot of survival of microorganisms as a function of time at 100C. Whichof the following is correctly calculated from the graph?A Z = 20 CB D 100C = 15 minC D15 = 2000 cfu/mlD td = 15 minE None of the above

65. Which of the following statements regarding probiotics is true?

A All Lactobacillusstrains are probiotic B Probiotics do not need to be alive when consumedC Probiotics are infectious agents available only by prescriptionD Probiotics might benefit our healthE Probiotics are additive intended to improve food flavor

H EAT TREATMENT . Questions 66-67 are a series of related heat treatment questions. You may useeither the formula DT2 = D T1 x 10 ([T1-T2]/Z) or the semi-log graph paper included with theexam, as appropriate, and as you wish. You do not need to show your work.

66. For organism X in milk, D 70 C = 9 seconds and Z = 12 C. What is the value of D 76 C (rounded to the nearest second)?

A 1 secondB 3 secondsC 6 secondsD 24 secondsE 27 seconds

67. If you are certain that milk would never contain more than 1000 cells of organism Xper ml, which of the following is the shortest treatment time at 76 C that would guaranteethe complete destruction of X (rounded up to the nearest second)? (Use D 76 C value for Xfrom #66)

A 1000 secondsB 18 secondsC 12 secondsD 10 secondsE 6 seconds

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FST 104 Final F08A Key

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