Microbial Spoilage Part 1

Question 1

Why are Meat, Poultry and Seafood similar ?

Answer 1

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

Question 2

In what aspect do Meat, Poultry and Seafood differ?

Answer 2

They have different originial microbiotas, leading to a different succession of microbial spoilage bacteria and also differ in the handling and storage requirements used

Question 3

Difference between natural and external contamination?

Answer 3

Natural: originating from the animal (gastronintesinal tract, skin, feathers) External: Originating from the processing environments (air, soil, water…)

Question 4

What is the best bacteria for attaching onto surface meat ?

Answer 4

Pseudomonas

Question 5

What are the best way to preserve meat?

Answer 5

Have a very clean processing facility + animal carcasses must be washed with water right after slaughter

Question 6

Biofilms are a major issue in food processing environments, why?

Answer 6

• They can form on almost any surface and can persist for years
• Mono-or-multispecies bacteria can be formed by spoilage or pathogenic bacteria
• Bacteria in biofilms can be 10-to 100-fold more resistant to sanitizers in comparison to planktonic cells

Question 7

What bacteria dominate in aerobic conditions vs in vacuum-packaged products?

Answer 7

Cold Aerobic = gram - (Enterobacteriacae)

Anaerobic = LAB

Question 8

Pseudomonas inhibits __________ and promotes _________

Answer 8

Shewanella, Listeria

Question 9

Pseudomonas utilizes glucose and produces _________ at higher rates than Shewanella

Answer 9

siderophores

Question 10

Pseudomonas hydrolyzes proteins and provides amino acids to ________

Answer 10

Listeria

Question 11

What is the energy source of spoilage bacteria?

Answer 11

Glucose

Question 12

Glucose is more rapidly metabolized by which type of bacteria?

Answer 12

Aerobic bacteria like Pseudomonas, if oxygen is present Pseudomonas predominate in spoilage

Question 13

After glucose, _________ is used as the primary energy source in aerobic and anaerobic conditions

Answer 13

lactate

Question 14

After lactate, _______ become the most important source fo energy

Answer 14

amino acids

Question 15

What is the best way to evaluate the freshness of spoiled meat?

Answer 15

Sensory evaluation by trained experts

Question 16

what are the 4 ideal spoilage indicator?

Answer 16

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 17

Meat traceability

Answer 17

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

Question 18

Name some common microbes present on fresh red meat

Answer 18

• Gram - rods and micrococci
• Pseudomonas and Enterobacteriacae
• Present in lower populations are LAB, Bacillus, and Clostridium spores

Question 19

_____________ are the dominating spoilage microorganisms in red meat at cold temperatures, on aerobically stored meat

Answer 19

Pseudomonas spp.

Question 20

If the meat is immediately vacuum packed _________ bacteria will dominate the population

Answer 20

Gram +

Question 21

In ground meat the dominant microflora on the exterior are _______ but ______ dominate the interior due to oxygen limitation

Answer 21

Pseudomonas, LAB

Question 22

Greening of processed meats is associated with ____________

Answer 22

hydrogen peroxide

Question 23

Dry-cured meats are mostly spoiled by _________ or ________ that tolerate low water activity

Answer 23

yeasts or molds

Question 24

Processing of poultry, what are the steps?

Answer 24

1) Stunning, killing, bleeding
2) Scalding (immersed in hot water)
3) Picking (feathers are removed)
4) Evisceration (intestinal tract mechanically removed)
5) Chilling (carcasses are chilled to reduce microbial growth)

Question 25

In poultry, the most common spoilage organism at refrigeration temperatures is ____________ but yeasts can also be involved in spoilage

Answer 25

Pseudomonas spp.

Question 26

Fish : foodborne pathogens associated with seafood include :

Answer 26

salmonella. clostridium botulinum, aeromonas, s.aureus

Question 27

Biogenic amines: ________________ can be produced postmortem by fish or shellfish tissue

Answer 27

histamine, cadaverine, and putrescine

Question 28

How are biogenic amines produced

Answer 28

By the decarboxylation of specific free amino acids

Question 29

At temperature above 16C, histidine is converted to histamine via which enzyme ?

Answer 29

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

Question 30

Consuming biogenic amines can cause

Answer 30

scombroid food poisoning

Question 31

What is scombroid food poisoning?

Answer 31

Foodborne intoxication that results from eating spoiled fish

Question 32

Name a few symptoms of scombroid food poisoning?

Answer 32

• Flushed skin
• Headache
• Itchiness
• Blurred vision
• Abdominal cramps, diarrhea

Question 33

The organisms responsible for refrigerated shrimp spoilage are mainly _________ and _________

Answer 33

Pseudomonas and Aeromonas