microbial spoilage and public health concerns

Question 1

why is it important to understand microbial food spoilage?

Answer 1

to minimize economic losses and provide a high-quality food supply with adequate shelf-life

Question 2

what do meat, poultry, and seafood have in common?

Answer 2

they are muscle foods, rich in nutrients (bacterial substrates), which allows extensive microbial growth and support the growth of bacterial pathogens

Question 3

what are the differences between meat, poultry, and seafood?

Answer 3

They have different “original” microbiota leading to a different succession of microbial spoilage bacteria. they also differ in the handling and storage requirements, which also leads to a different microbial succession. they also differ in handling and storage requirements which also leads to a different microbial succession

Question 4

under what conditions does contamination originate?

Answer 4

1. natural: originating from the animal (GI tract, skin, feathers)
2. originating from the processing environment

Question 5

what is the first event in contamination?

Answer 5

attachment of bacterial cells to the meat surface

Question 6

what bacteria is exceptionally good at attaching to meat surfaces?

Answer 6

pseudomonas

Question 7

what is the best way to preserve meat?

Answer 7

having a very clean processing facility so that minimal numbers of bacteria attach to the surface of the meat

Question 8

what is the significance of biofilms?

Answer 8

they are a major issue in food processing environments. they can form on almost any surface and can persist despite despite extensive cleaning efforts for years. once formed, bacteria can be 10- to 100- fold more resistant to sanitizers in comparison to planktonic cells

Question 9

____ of all meat and __ of all fish are lost due to microbial spoilage

Answer 9

one fourth

30%

Question 10

what conditions affect the microbial succession in meat and fish?

Answer 10

conditions of slaughter, decontamination, and storage

Question 11

In general, _____ bacteria, mostly ______ will dominate the microflora under cold aerobic conditions, and LAB will dominate vacuum-packaged products

Answer 11

gram-negative

enterbacteriaceae

Question 12

Pseudomonas inhibits ____and promotes ______

Answer 12

Shewanella

Listeria

Question 13

Pseudomonas utilizes glucose and produces ____ at higher rates than Shewanella

Answer 13

siderophores

Question 14

Pseudomonas also hydrolyses proteins and provides ____ to _____

Answer 14

amino acids

Listeria

Question 15

what is the definition of spoilage?

Answer 15

consumers rejecting a food based on undesirable sensory characteristics. the definition is based on the consumer and will differ based on socio-economic factors

Question 16

what does proteolytic spoilage result in?

Answer 16

putrid odors due to breakdown of amino acids

Question 17

what does non-proteolytic spoilage result in?

Answer 17

sour odors

Question 18

what is spoilage of canned foods due to?

Answer 18

improper process control, resulting in proliferation on mesophilic spore formers

Question 19

what is the energy source of spoilage bacteria?

Answer 19

glucose

Question 20

glucose is more rapidly metabolized by ____ bacteria than by ____ anaerobes

Answer 20

aerobic

facultative

Question 21

If oxygen is present, ____ predominate in spoilage

Answer 21

Pseudomonas

Question 22

what is the primary energy source of spoilage after glucose?

Answer 22

lactate, in both aerobic and anaerobic bacteria

Question 23

what is the energy source after glucose and lactate?

Answer 23

amino acids

Question 24

why are crustaceans like lobster and crayfish, kept alive until cooking?

Answer 24

their endogenous tissues enzymes in their hepatopancreas cause rapid postmortem muscle breakdown, independent of microbial processes

Question 25

what is the best type of evaluation for quality evaluation?

Answer 25

sensory evaluation

Question 26

the ideal spoilage indicator should...

Answer 26

1. be absent or present in very low levels in fresh tissue 2. be produced by the spoilage microflora 3. increase with storage time 4. correlate well with sensory analysis

Question 27

What is meat traceability?

Answer 27

the ability to maintain credible custody of the identification of animals and their products from production to retail

Question 28

the strategy for microbial control in meats is generally focused on _____ and _____

Answer 28

good hygiene | proper storage

Question 29

methods for microbial control:

Answer 29

1. harvest, or ship animals for slaughter with low contamination 2. reduce the potential for transfer of microorganisms to carcasses, meat, and seafood from water and the environment 3. apply safe and effective decontamination interventions 4. apply processes such as heat, high pressure, irradiation, to reduce or eliminate microorganisms 5. avoid cross-contamination 6. store products at low temperature

Question 30

how is the type and extent of microbial contamination determined on red meats?

Answer 30

determined by the hygiene of the animals before and during slaughter

Question 31

common microbes on fresh red meat are ____ rods and _____

Answer 31

gram-negative rods | micrococci

Question 32

examples of gram-negative rods and micrococci

Answer 32

Pseudomonas, enterobacteriaceae, acinetobacter, staphylococcus, micrococcus, coryneforms, and fecal streptococci

Question 33

what bacteria are present in lower populations on red meat?

Answer 33

LAB, bacillus, and clostridium spores

Question 34

what species of microorganisms are the dominating spoilage microorganisms in red meat?

Answer 34

pseudomonas spp.

Question 35

what happens when meat is immediately vacuum-packed?

Answer 35

gram-positive bacteria will dominate the population

Question 36

Remember, microbes like to use ____ before ____ for energy production, and amino acid degradation leads to more signs of spoilage

Answer 36

glucose | amino acids

Question 37

what pre-slaughter factor leads to faster degradation of amino acids in red meat?

Answer 37

the animal being stressed or exercised before slaughter.

Question 38

____ meats spoil more slowly than _____ meats because of higher initial contamination, larger surface, area, cross-contamination during grinding, and the release of fluids for bacterial growth media due to cells rupturing during grinding.

Answer 38

``` intact meats (steak) comminuted meats (ground beef) ```

Question 39

processed meats have lower ___ due to added salt

Answer 39

water activity

Question 40

spoilage by what kind of bacteria is limited in processed meats?

Answer 40

gram-negative psychotropic bacteria

Question 41

spoilage by what kind of bacteria is prevalent in processed meats?

Answer 41

lactobacilli (anaerobic) or micrococci (aerobic)

Question 42

examples of processed meats:

Answer 42

1. bologna 2. cooked or fermented sausage 3. cold-cuts

Question 43

sliming is the result of what bacteria?

Answer 43

growth of yeasts, lactobacillus, enterococcus, and B. thermosphacta

Question 44

greening is the result of waht bacteria?

Answer 44

production of hydrogen peroxide by lactobacillus viridescens, streptococcus, or leuconostoc

Question 45

how do dry-cured meats spoil?

Answer 45

presence of yeasts or molds that tolerate extremely low water content

Question 46

most of the microbiota associated with poultry is acquired from which regions of the bird?

Answer 46

bird's skin, feathers

Question 47

bacterial populations associated with the carcass at the end of processing are _____ bacteria

Answer 47

predominantly gram-negative

Question 48

gram-negative bacteria in carcasses at the end of processing?

Answer 48

Acientobacter/ morazella, enterobacteriaceae, and pseudomonas

Question 49

during refrigeration storage, ____ spp. group becomes predominant

Answer 49

pseudomonas

Question 50

steps of processing poultry:

Answer 50

1. stunning/ killing / bleeding 2. Scalding 3. picking 4. evisceration 5. chilling

Question 51

stunning/killing

Answer 51

Birds are placed onto moving shackles and are stunned with electricity or low oxygen

Question 52

scalding

Answer 52

birds are immersed in hot water to ease the removal of feathers

Question 53

picking

Answer 53

the feathers are removed by placing the bird in a picker, containing rubber fingers to grab the feathers and full them out. this process aerosolized bacteria and can spread them to other carcasses

Question 54

evisceration

Answer 54

Intestinal tract is mechanically removed. this could sometimes damage thigh and back muscles resulting in tissue rupture and more nutrients being available for spoilage. intestines could also rupture leading to fluid leakage into the carcass which increases bacterial load

Question 55

chilling

Answer 55

carcasses chilled to reduce microbial growth which improves shelf-life and food safety. air chilling is the most common method

Question 56

spoilage bacteria metabolizes _____ first, which leads to a CFU population of _____

Answer 56

glucose | 10^8 CFU/cm^2

Question 57

the most common spoilage organism at refrigeration temperatures is ______ but ____ can also be involved in spoilage

Answer 57

Pseudomonas spp. | yeasts

Question 58

what are foodborne pathogens associated with seafood?

Answer 58

salmonella, Clostridium botulinum, aeromonas, S. aureus, L. monocytogenes, vibrio cholerae, vibrio parahaemolyticus, and vibrio vulnificus

Question 59

aqua-cultured fish tend to have a higher ______ than their wild counterparts

Answer 59

bacterial load

Question 60

What are biogenic diamines?

Answer 60

compounds produced by decarboxylation of specific free amino acids, which are produced by postmortem fish or shellfish tissue

Question 61

how does decarboxylation occur?

Answer 61

via the release of decarboxylase from the various microorganisms growing on the food product

Question 62

fish muscle is naturally rich in free ____, and this increases even more after the fish dies

Answer 62

amino acids

Question 63

What are some biogenic diamines?

Answer 63

histamine, cadaverine, and putrescine

Question 64

_____ is not destroyed by cooking, so even properly cooked spoiled fish can result in poisoning

Answer 64

histamine

Question 65

what is a consequence of nitrite being used in cold-smoked fish products that aren't fresh enough?

Answer 65

putrescine and cadaverine will react with nitrite, producing carcinogens

Question 66

consuming biogenic amines can cause what type of food poisoning?

Answer 66

scomboid food poisonings (a disease due to the ingestion of contaminated food, mainly in fish)

Question 67

symptoms of scombroid food poisoning?

Answer 67

flushed skin, headache, itchiness, blurred vision, abdominal cramps, and diarrhea

Question 68

how long can scombroid food poisoning last?

Answer 68

2 days

Question 69

how fast do scombroid food poisoning symptoms come on?

Answer 69

10-60 minutes after eating

Question 70

what are the causes of scombroid food poisoning?

Answer 70

fish being improperly stored, which results in microbial growth, resulting in the production of biogenic amines, such as histamine

Question 71

_____ is the main natural chemical responsible for true allergic reactions, so the symptoms are almost identical to a food allergy

Answer 71

Histamine

Question 72

what can be taken to alleviate symptoms of scombroid food poisoning?

Answer 72

anti-histamines

Question 73

____ are the most exportable seafood product in the world

Answer 73

Shrimp

Question 74

what are pathogenic vibrios?

Answer 74

gram-negative bacteria that cause illness

Question 75

____ can attach to and colonize the exoskeletons of shrimp

Answer 75

pathogenic vibrios

Question 76

what organisms are responsible for refrigerated shrimp spoilage?

Answer 76

pseudomonas and aeromonas

Question 77

what kind of contamination of growing ponds where shrimp are produced, is most common?

Answer 77

fecal contamination, coliforms, and salmonella are common in shrimp rearing environments

Question 78

____ are filter feeders that can concentrate the native water microbiome

Answer 78

Oysters

Question 79

why is it that consuming oysters raw, is problematic?

Answer 79

eating raw oysters is associated with several outbreaks

Question 80

what other type of shellfish besides oysters, is also problematic to eat raw?

Answer 80

mussels - concentrate bacteria