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Flashcards in Exam 2 Deck (79):
1

measurement based on the resistance in an electric circuit to the flow of alternating current

Impedance

2

DMC

Direct Microscopic Count

3

DMC on filters has been simplified by the use of _________ _______ that bind to bacteria.

fluorescent dyes

4

this method uses dyes and fluorescent microscopy to rapidly enumerate bacteria on a filter

DEFT

5

DEFT

Direct Epifluorescent Filter Technique

6

4 Advantages of DMC (including DEFT)

1. rapid and simple
2. morphology can be determined
3. repeatability is better than SPC
4. solid foods can be examined using the prefiltration step

7

5 disadvantages of DMC (including DEFT)

1. tiring to analyze
2. can’t tell live from dead cells
3. food parts sometimes look like cells
4. cells are usually not distributed evenly
5. different MO don’t stain equally

8

Way to make millions of copies of DNA from a single piece of DNA

PCR

9

Examples of foodborne infections

Salmonellosis
Dysentery
Cholera

10

Difference between exotoxin and endotoxin

h

11

Botulism is also a ________ toxin

neurotoxin

12

causes typhoid fever

Salmonella

13

Different strains of salmonella are classified by ________ and ________ antigens

somatic (O)
flagellar (H)

14

3 epidemiological groups of Salmonella serovars

Those that only infect humans
Host adapted serovars
Unadapted serovars

15

ragdoll syndrome
source?
why is it no longer a risk after 1 year old?

infant botulism
honey
Infant developes intestinal normal flora

16

clostridium perfringens
where is it found?

thermophilic
spore former
needs higher source of AA
found in meats and gravy

17

How to prevent botulism?

pressure can

18

Spoiled Food

Damage or injuries that make food undesirable for human consumption

19

In general what can cause Spoiled Food?

insects
physical injury
enzymatic degredation
microbial activity

20

3 Basic types of Foof Spoilage

Appearance
Texture
Taste and Odor

21

What can make food appear spoiled?

Visible Mycelia and Bacterial Colonies
cloudiness in liquid
Breakdown of heme or chlorophyll

22

What texture changes are seen on spoiled food?

slime
soft rot due to enzymatic degredation

23

What causes changes to taste and color?

Nitrogenous compounds
sulfides
organic acids

24

What can determine what organisms grow on the food and in the number that they do?

Evironment from where the food was taken
intrinsic factors of food
Handling
Packaging and storage conditions

25

Microflora of Whole fresh meat

Pseudomonas
Acinetobacter
Moraxella
Bacillus
Clostridium perfringens

26

What kind of organism is Pseudomonas?

Gram neg aerobic rod

27

Most perishable food?

Fresh meats

28

What can be a source of contamination inside unprocessed meat?

lymph nodes

29

Single most important factor for meat spoilage?

Storage temperature

30

What temp can molds not grow on on meat surface?

5 C and below

31

Under what conditions do Pseudomonas, Acinetobacter and Moraxella spp. usually spoil fresh cut meat?

Refrigerator at high humidity

32

What organisms always spoil ground beef?

Pseudomonas
Acinetobacter
Moraxella

33

What concentration of Bacteria gives meat an odor and slimy look?

10^7 CFU/cm2

34

What is not broken down in all meat spoilage?

Primary protein structure

35

What do bacteria eat on meat?

glucose
free AA
nitrogen

36

What is different microbially between whole and ground beef?

Ground has higher microbial load

37

pH range of ground beef

5-6

38

What can inhibit C. botulinum in vacuum packed meat?

added nitrates

39

Vaccume packed meats are usually safe from pathogens with the exception of what organisms?

S. aureus
Y. enterocolitca

40

What gives away vacuum packed meat spoilage?

Slime
Greening

41

What causes meat greening?

H2O2 or H2S production

42

What organisms produces H2O2 or H2S in V meat packaging?

LAB

43

the H2O2 oxidant reacts with what in V packed meat? to form what?

nitrosohemochrome
porphyrin (green)

44

What organism makes H2S in packed meat? Under O2 permeable packaging? Under O2 impermeable packaging?

O2 permeable
-Shewanella
-Pseudomonas

O2 impermeable
-lactobacilli

45

What conditions cause H2S greening in vaccume packed meat?

above 6 pH
1-5 C

46

In H2S greening what does it react with? what does it form?

myoglobin
sulphmyoglobin

47

Specifically what causes off odors in meat?

Release of short chain fatty acids and volatile compounds like acetoin and H2S

48

Does raw or cooked meat have a higher pH?

cooked meat

49

which pathogen prefers cooked meat?

Yersinia enterocolitica

50

Pathogen that favors uncooked meat? pH of uncooked meat?

LAB
5.6

51

low nitrate levels in meat can favor what organism

B. thermosphacta

52

high nitrite concentration in meat favors what organism?

LAB

53

most common type of organisms to spoil processed meat?

yeast
bacteria

54

Which apparant type of processed meat spoilage means it shouldnt be eaten?

greening

55

why are cured meats like ham and bacon resistant to spoilage?

added nitrite
smoking or brining ham
high fat - low water activity of bacon

56

What organisms do spoil cured meats? What genera?

molds
Aspergillus
Penecillium
Rhizopus

57

How can advanced spoilage be determined in poultry?

the skin will fluoresce under UV because of pseudomonads

58

what occurs before slime buildup on poultry

off odor

59

What can be done to possible salvage poultry?

remove the skin

60

Fish have high _______ content but no carbohydrate

nitrogen

61

What is the microbial activity of fish heavily influenced by?

The quality of water from which the fish was harvested

62

In general, frozen fish products have ______ counts than fresh products.

lower

63

location of bacteria on fresh fish?

outer slime
gills
instestin

64

why can crustacean spoilage occur more rapidly?

CHO and more free AA

65

microflora of vegetables

Gram + bacteria like LAB

66

What organisms get onto vegetables from handlers?

cornyforms
staphylococci

67

organisms that cause soft rot

Erwinia caratovora
Pseudomonas

68

how does polygalacturonase work?

hydrolyzes a 1,4 glycosidic bond in pectin which leads to softening

69

org which causes blue fruit rot

penicillium

70

causes downy mildews in grapes

phytophora mycellium

71

black rot on onions

Aspergillus

72

causes sour rot and comes from harvestors

Geotrichum candidum

73

Raw milk flora can contain almost anything but what is present when it is properly handled?

Gram +

74

what organisms makes temperature stabilizing enzymes im milk?

psyschrotrophic pseudomonads

75

What does pasteurization kill/

G-
yeasts
molds

76

Pasteurized milk used to be spoiled by LAB but now what is it spoiled by? what causes the curdling?

aerobic spore formes like Bacillus
proteolytic enzymes

77

what 3 factors of cheese inhibit growth except for surface molds

low pH
high salt
low water activity

78

molds that produce gas inside of cheese like swiss

C. butyricum
C. sporogenes

79

what can spoil wine and beer?

yeasts and bacteria