Microbial Spoilage + Public Health Concerns (1)

Question 1

True/False: spoilage means a food is unsafe to eat

Answer 1

False; not always unsafe (but probably unpalatable; and cannot tell if it is unsafe)

Question 2

meat, poultry, and fish are ____ foods. What implications does this have on spoilage?

Answer 2

muscle
rapid spoilage (nutrient rich, protein rich, moist; supports pathogenic growth)

Question 3

Where does contamination of meats come from?

Answer 3

from skin/guts/equipment; contaminated during slaughter/processing/dressing

Question 4

True/False: the internal part of meat is usually very low in microbes

Answer 4

True (if from a healthy animal); since not exposed to outer environment

Question 5

origin of meat contamination can be classified as ___ or ____

Answer 5

natural (from animal: skin, feathers, guts, etc)

external (from equipment, air, soil, humans, etc)

Question 6

What influences the type and numbers of bacteria on meat?

Answer 6

animal type, hygiene of facility

Question 7

What is the first step by bacteria in contamination of meat?

Answer 7

attachment to meat surface

Question 8

What bacteria is the best at attaching to meat surfaces?

Answer 8

Pseudomonas

Question 9

What is the best way to prevent contamination of meat?

Answer 9

cleanliness of processing facility (less bacteria can attach); rinse meat to prevent attachment of bacteria

Question 10

What is a major issue in food processing equipment? Why is it such a big issue?

Answer 10

formation of biofilms (combination of spoilage/pathogenic bacteria) - can form on almost any surface! HIGHLY PERSISTANT

can be 10-100x more resistant to sanitizers than planktonic bacteria

Question 11

____% of meat and ___% of fish are lost due to microbial spoilage

Answer 11

25%; 30%

Question 12

What species is dominant in cold aerobic conditions in meat? What species is dominant in vacuum packed meat?

Answer 12

enterobacteriaceae (Gram neg)

LAB

Question 13

How does Pseudomonas affect other microbial species?

Answer 13

inhibit Shewanella (uses up glucose and makes iron-binding siderophores)
promote Listeria (hydrolyze proteins and make AA for listeria)

Question 14

What is spoilage?

Answer 14

development of undesirable sensory characteristics in food that leads to consumer rejection (will depend on personal preferences and socioeconomic differences)

Question 15

Examples of spoilage characteristics:

Answer 15

off flavors, off colors, off-odors, off-textures, discoloration, slime, putridness (proteolysis), sourness

Question 16

Non proteolytic spoilage is characterized by a ___ taste/smell, while proteolytic spoilage is very ____.

Answer 16

sour; putrid

Question 17

the energy source of spoilage bacteria is ____

Answer 17

glucose

Question 18

In an oxygenated environment, what is the first spoilage bacteria that grows and why?

Answer 18

pseudomonas

best at metabolizing glucose (outcompetes Brochothrix and Shewanella)

Question 19

What happens after glucose is depleted in food spoilage?

Answer 19

lactate becomes primary substrate; then amino acids (putrid)

Question 20

When do amino acids become the main substrate in food spoilage? What is the indication that this is happening?

Answer 20

At CFU = 10^7

become slimy, sulfur/ammonia odor, putrid

Question 21

List the main substrates for spoilage in food in the order they are utilized:

What is an exception to this pattern?

Answer 21

glucose, lactate, amino acids

exception: crustaceans - endogenous enzymes in hepatopancreas will break down tissue upon death

Question 22

Why must crustaceans be kept alive prior to cooking?

Answer 22

after death -> rapid proteolysis (spoilage) by endogenous enzymes

Question 23

What factors influence the definition of “spoilage?”

Answer 23

geography
socioeconomic factors
food type
preservation interventions

Question 24

What are ways to evaluate ‘freshness’ of meat? What are the weaknesses of each method?

Answer 24

sensory evaluation - requires trained experts, subjective

Microbiological tests - destructive, only give general info

develop spoilage indicators (measurable biochemical changes) - still in development

Question 25

What are examples of substances that could be used as spoilage indicators (meat)?

Answer 25

amines, ammonia, trimethylamine, sulfur

Question 26

What characteristics make for a good spoilage indicator?

Answer 26

1. absent or very little in fresh tissue 2. produced by spoilage bacteria 3. increase with storage time 4. correlate well with sensory analysis

Question 27

Are AMR bacteria problematic to food spoilage?

Answer 27

Possibly - higher resistance to food processing treatment

Question 28

What is meat traceability and what is it's importance?

Answer 28

traceability - maintain credible custody of identification of animals from production to retail important for human and animal health (outbreaks, welfare)

Question 29

In products such as _____, traceability is very difficult and may be limited to ______.

Answer 29

ground meat/composite products (many animals) | date, place

Question 30

where did the demand for meat traceability originate from?

Answer 30

``` BSE outbreak food fraud (horse meat in IKEA meatballs) ```

Question 31

The general microbial control for meat is focused on _____ and ______.

Answer 31

good hygiene | proper storage

Question 32

What is done to help prevent meat spoilage? (6)

Answer 32

1. harvest/ship animals with low contamination 2. clean water/environment (reduce microbe transfer to carcass) 3. safe decontamination measures 4. processing (heat, high pressure, irradiation) 5. avoid cross contamination 6. store at low temp, proper conditions

Question 33

Characterize the initial microbial load on fresh meat:

Answer 33

10^2 - 10^7 CFU (surface) mostly AEROBIC mesophiles - gram neg rods & cocci (Pseudomonas, Enterobactericeae, Acinetobacter, Staphylococcus, Micrococcus, fecal streptococci) small population of LAB, Bacillus, Clostridium spores

Question 34

In meat that is immediately vacuum packed, the spoilage organisms will be Gram _____.

Answer 34

positive

Question 35

Stressed animals during slaughter will lead to meat that spoils (faster/slower). Why?

Answer 35

faster | stress -> use up glycogen -> less glucose in tissue -> glucose depleted more rapidly -> proceeds to proteolysis (putrid)

Question 36

Ground meat spoils (faster/slower) than intact meat. Why? What is the dominant microbe type?

Answer 36

faster more cross-contamination, greater initial load, more surface area similar to intact meat, but also more LAB (bacteria introduced to anaerobic interior)

Question 37

What microbes cause spoilage in processed meat? Why?

Answer 37

Lactobacilli (anaerobic) and Micrococci (aerobic) less water activity; inhibits growth of gram-neg psychrophiles

Question 38

What are spoilage signs in processed meat?

Answer 38

greening, slime, souring

Question 39

What causes slime production in processed meat spoilage?

Answer 39

yeast, lactobacillus, enterococcus, B. thermosphacta

Question 40

What causes greening in spoiled processed meat?

Answer 40

Lb. viridescens, Streptococcus, Leuconostoc

Question 41

What causes spoilage in dry-cured meat with very low Aw?

Answer 41

yeast and mold (surface spoilage)

Question 42

In poultry, most of the bacterial load is acquired from:

Answer 42

skin and feathers

Question 43

At the end of poultry processing the bacterial load is:

Answer 43

10^1 - 10^4 CFU | Acientobacter, Enterobactericeae, Pseudomonas

Question 44

What are the general steps for processing poultry?

Answer 44

1. stun/kill/bleed 2. scalding 3. picking 4. eviscerate 5. chill

Question 45

How is feather removal achieved? What are potential issues? What is an alternative?

Answer 45

scalding -> picking sprays bacteria, spread to other carcasses and equipment can use "waxing" - lowers aerobic gram-neg counts, but higher Staph aureus

Question 46

How can evisceration increase bacteria load?

Answer 46

equipment contamination rupture tissues -> more nutrients available rupture intestine -> contamination

Question 47

What are the chilling methods for poultry? Which one is advantageous and why?

Answer 47

Air chilled (cold room) or water chilled (immerse in bath) Water chilled -> less psychrotrophic bacteria (spoilage), slight increase in % water (more weight; good for seller but not consumer)

Question 48

Most common spoilage organism in poultry is _____, but can also involve ____.

Answer 48

pseudomonas | yeasts

Question 49

True/False: aquaculture fish will have less bacterial load than wild caught

Answer 49

False; crowding and stress increase bacterial/pathogen growth

Question 50

Foodbourne pathogens associated with seafood:

Answer 50

Salmonella, C. botulinum, Aeromonas, S. aureus, Listeria, Vibrio (cholerae, parahemolyticus, vulnificus)

Question 51

Why is spoilage in seafood particularly of concern?

Answer 51

high in free AA -> converted postmortem by spoilage bacteria (DECARBOXYLATION) -> BIOGENIC DIAMINES (ex: histidine -> histamine) causes SCOMBROID POISONING

Question 52

what microbe is responsible for histamine production in fish flesh?

Answer 52

Morganella morganii (symbiotic microbe in fish)

Question 53

True/False: proper cooking can prevent scombroid poisoning

Answer 53

False: biogenic amines not destroyed with cooking

Question 54

What are examples of biogenic amines?

Answer 54

histamine, cadaverine, putrescine

Question 55

What is a concern of biogenic amines in cured/smoked fish?

Answer 55

will react with nitrates -> carcinogenic substances

Question 56

Symptoms of scombroid poisoning: | What can be taken to alleviate this?

Answer 56

onset 10-60 min after consumption flushed skin, headache, itchy, blurred vision, cramps, diarrhea (similar to allergy rxn) take antihistamines

Question 57

True/False: most shrimp that is produced is exported

Answer 57

True; 75% produced in developing countries, and 75% is consumed in developed countries

Question 58

In shrimp production, colonization of _____ is unavoidable. colonization by ____ may occur with fecal contamination.

Answer 58

pathogenic vibrios (colonize exoskeleton) fecal contamination -> coliforms, salmonella

Question 59

What organisms are mainly responsible for spoilage of refrigerated shrimp?

Answer 59

pseudomonas, aeromonas

Question 60

Why are oysters common sources of outbreaks?

Answer 60

eaten raw; filter feeders (concentrate bacteria)

Question 61

_____ species are often found in the environment for farming shellfish.

Answer 61

Vibrio (pathogenic and non-pathogenic)