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Food Microbiology > Microbial Spoilage + Public Health Concerns (1) > Flashcards

Microbial Spoilage + Public Health Concerns (1) Flashcards

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1
Q

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

A

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

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2
Q

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

A 
muscle
rapid spoilage (nutrient rich, protein rich, moist; supports pathogenic growth)
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3
Q

Where does contamination of meats come from?

A

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

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4
Q

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

A

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

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5
Q

origin of meat contamination can be classified as ___ or ____

A

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

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

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6
Q

What influences the type and numbers of bacteria on meat?

A

animal type, hygiene of facility

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7
Q

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

A

attachment to meat surface

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8
Q

What bacteria is the best at attaching to meat surfaces?

A

Pseudomonas

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9
Q

What is the best way to prevent contamination of meat?

A

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

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10
Q

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

A

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

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11
Q

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

A

25%; 30%

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12
Q

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

A

enterobacteriaceae (Gram neg)

LAB

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13
Q

How does Pseudomonas affect other microbial species?

A 
inhibit Shewanella (uses up glucose and makes iron-binding siderophores)
promote Listeria (hydrolyze proteins and make AA for listeria)
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14
Q

What is spoilage?

A

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

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15
Q

Examples of spoilage characteristics:

A

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

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16
Q

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

A

sour; putrid

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17
Q

the energy source of spoilage bacteria is ____

A

glucose

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18
Q

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

A

pseudomonas

best at metabolizing glucose (outcompetes Brochothrix and Shewanella)

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19
Q

What happens after glucose is depleted in food spoilage?

A

lactate becomes primary substrate; then amino acids (putrid)

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20
Q

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

A

At CFU = 10^7

become slimy, sulfur/ammonia odor, putrid

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21
Q

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

What is an exception to this pattern?

A

glucose, lactate, amino acids

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

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22
Q

Why must crustaceans be kept alive prior to cooking?

A

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

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23
Q

What factors influence the definition of “spoilage?”

A

geography
socioeconomic factors
food type
preservation interventions

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24
Q

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

A

sensory evaluation - requires trained experts, subjective

Microbiological tests - destructive, only give general info

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

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25
Q

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

A

amines, ammonia, trimethylamine, sulfur

26
Q

What characteristics make for a good spoilage indicator?

A
  1. absent or very little in fresh tissue
  2. produced by spoilage bacteria
  3. increase with storage time
  4. correlate well with sensory analysis
27
Q

Are AMR bacteria problematic to food spoilage?

A

Possibly - higher resistance to food processing treatment

28
Q

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

A

traceability - maintain credible custody of identification of animals from production to retail

important for human and animal health (outbreaks, welfare)

29
Q

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

A

ground meat/composite products (many animals)

date, place

30
Q

where did the demand for meat traceability originate from?

A 
BSE outbreak
food fraud (horse meat in IKEA meatballs)
31
Q

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

A

good hygiene

proper storage

32
Q

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

A
  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
33
Q

Characterize the initial microbial load on fresh meat:

A

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

34
Q

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

A

positive

35
Q

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

A

faster

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

36
Q

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

A

faster
more cross-contamination, greater initial load, more surface area

similar to intact meat, but also more LAB (bacteria introduced to anaerobic interior)

37
Q

What microbes cause spoilage in processed meat? Why?

A

Lactobacilli (anaerobic) and Micrococci (aerobic)

less water activity; inhibits growth of gram-neg psychrophiles

38
Q

What are spoilage signs in processed meat?

A

greening, slime, souring

39
Q

What causes slime production in processed meat spoilage?

A

yeast, lactobacillus, enterococcus, B. thermosphacta

40
Q

What causes greening in spoiled processed meat?

A

Lb. viridescens, Streptococcus, Leuconostoc

41
Q

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

A

yeast and mold (surface spoilage)

42
Q

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

A

skin and feathers

43
Q

At the end of poultry processing the bacterial load is:

A

10^1 - 10^4 CFU

Acientobacter, Enterobactericeae, Pseudomonas

44
Q

What are the general steps for processing poultry?

A
  1. stun/kill/bleed
  2. scalding
  3. picking
  4. eviscerate
  5. chill
45
Q

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

A

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

46
Q

How can evisceration increase bacteria load?

A

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

47
Q

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

A

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)

48
Q

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

A

pseudomonas

yeasts

49
Q

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

A

False; crowding and stress increase bacterial/pathogen growth

50
Q

Foodbourne pathogens associated with seafood:

A

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

51
Q

Why is spoilage in seafood particularly of concern?

A

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

52
Q

what microbe is responsible for histamine production in fish flesh?

A

Morganella morganii (symbiotic microbe in fish)

53
Q

True/False: proper cooking can prevent scombroid poisoning

A

False: biogenic amines not destroyed with cooking

54
Q

What are examples of biogenic amines?

A

histamine, cadaverine, putrescine

55
Q

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

A

will react with nitrates -> carcinogenic substances

56
Q

Symptoms of scombroid poisoning:

What can be taken to alleviate this?

A

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

take antihistamines

57
Q

True/False: most shrimp that is produced is exported

A

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

58
Q

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

A

pathogenic vibrios (colonize exoskeleton)

fecal contamination -> coliforms, salmonella

59
Q

What organisms are mainly responsible for spoilage of refrigerated shrimp?

A

pseudomonas, aeromonas

60
Q

Why are oysters common sources of outbreaks?

A

eaten raw; filter feeders (concentrate bacteria)

61
Q

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

A

Vibrio (pathogenic and non-pathogenic)

Food Microbiology (21 decks)

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