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Food Microbiology > Meat Fermentation > Flashcards

Meat Fermentation Flashcards

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1
Q

What type of fermentation start method is used for meat? Why?

A

Can use any of the 3 (inoculation, spontaneous, backslopping)
BUT: inoculation is best (safety and quality-wise)

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2
Q

Why does meat and fish spoil quickly?

A

moist, nutrient rich environment

pathogens/spoilage bacteria from animal/slaughter

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3
Q

What are the main bacteria in meat starter cultures?

A

LAB

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4
Q

true/false: there are no LAB present naturally on meat.

A

False: LAB present but in small population (need to boost and create favorable environment

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5
Q

Traditionally fermented meats (no starter culture) are at a greater risk of causing ______ infection.

A

Staphylococcus

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6
Q

What are the fermentation conditions for meat products?

A

Anaerobic
Salt 6%
Acidic (from LAB activity)

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7
Q

What are the requirements when choosing a microbe as a starter for meat fermentation?

A
  1. homofermentative (make acid fast!)
  2. survive high salt
  3. no slime production
  4. provide flavor enhancement
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8
Q

What was the first microbe used for commercial meat fermentation culture and what are its advantages? What other organism can it be used with?

A

Pediococcus acidilactici: survive up to 6.5% salt; can be freeze dried, higher optimal growth temp

Can be used with Lb. plantarum

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9
Q

True/False: unfermented fresh meat has a slightly basic pH

A

False: fresh meat about pH 5.6

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10
Q

In about 8 hours, starter culture can lower the pH of meat from 5.6 to ____.

A

4.8

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11
Q

What produces the pink color in fermented meat? Is this absolutely necessary?

A

nitrites/nitrates added
add nitrite/nitrate reducing bacteria to culture
reduced to nitric oxide (pink color)

No; but otherwise will look less appealing (brown)

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12
Q

What microbes can be added to produce nitric oxide?

A

kocuria, staphylococci, some lactobacilli

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13
Q

Aside from nitrates, what else contributes to the reddish hue of fermented meat?

A

Activity of aerobic microbes (near surface):

  • decrease surface oxygen
  • form barrier (prevent oxygen diffusing in)
  • reduce METMYOGLOBIN (brown) -> myoglobin (red)
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14
Q

several species of LAB have an advantage that is important to the prevention of pathogens and spoilage in meat. What is it?

A

Produce bacteriocin: small peptides that kill/inhibit other Gram positive bacteria

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15
Q

Are bacteriocins harmful to humans? What is harmed by them?

A

No

targets gram positive bacteria (of another species)

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16
Q

The largest category of fermented meat products:

Where did they originate from?

A

dry/semidry sausages

came from Mediterranean region (dry warm climate)

17
Q

How are dry/semidry sausages made?

A

stuff meat mixed with salt/seasoning into casings (anaerobic) -> drying + fermentation
(no smoking needed)

18
Q

How is preservation achieved in dry/semidry sausage?

A 
rapid drying (moisture loss)
fermentation -> organic acids, alcohols, lactic acid (inhibitory substances)
19
Q

Sausages made in northern Europe were known as ____ sausages. How did they differ from dry sausages?

A

summer

made in winter
higher water content
smoked
finer texture (finely ground)

20
Q

True/False: semidry sausages do not require tight regulation because they have been cured with nitrate

A

False; need to report MPR, pH, salt, ingredients, etc

unless commercially sterilized

21
Q

True/False: A shelf-stable semidry sausage is NOT permitted to be sold as slices

A

True; but can be sold as slices if vacuum packed (otherwise no)

22
Q

What is “MPR?”

A

moisture to protein ratio

23
Q

List the steps for manufacturing a semidry sausage: (7)

A
  1. grind meat (reduce particle size)
  2. add salt, nitrate, seasonings, culture
  3. blend
  4. vacuum stuff into semipermeable casing
  5. incubate -> pH endpoint
  6. (optional): heat - kill pathogen/starter culture
  7. dry age (remove moisture)
24
Q

Where does bacterial contamination of meat products come from? What microbes are involved and what do they cause?

A

animal, intestines, skin (exposed during slaughter)
GRAM NEGATIVE bacteria
spoilage: proteolysis -> rotten egg smell

25
Q

Before fermentation, LAB CFU/g is about _____. After the process, it is _____.

A

3-4 log, increase to 7-8 log

26
Q

Besides LAB, what other microbes can be present in meat products? How does their population change as fermentation progresses?

A

Staphylococcus
Micrococcaceae

die down when pH declines

27
Q

How does LAB contribute to flavor development in sausage?

A

proteolysis + lipolysis creates smaller flavor compounds

28
Q

What are some undesirable LAB and why?

A

Lb. viridescens: makes H2O2 -> green
Lb. brevis, L. meseneroides -> CO2 -> gas pockets
Brochothrix -> souring

29
Q

True/False: fermented dry/semidry sausages are still considered “raw”

A

True; not enough heat for “cooking” to kill pathogens

30
Q

The primary products of fish fermentations:

A 
fish sauce (liquid)
fish paste
31
Q

The general process for making fish sauce:

A

layer fish/shrimp + salt in 3:1 ratio
seal concrete vat
ferment 9 months - 1 year
remove liquid -> continue for more liquid

32
Q

What contributes to the flavor of fish sauce, and what produces these compounds?

A

Peptides, AA, Ammonia, VFA (enzymes, oxidation)

caramel/sugar/roast corn, etc (added flavor agents)

33
Q

What factors will influence the taste of the final fish sauce? (3)

A

temperature during ferment
fish type
pH

34
Q

Bacteria populations in fish sauce are highest in what period?

A

Early (0-25 days)

35
Q

True/False: it is mostly due to bacteria proteases that the fish tissue will break down

A

False; mostly due to endogenous fish enzymes

36
Q

What type of bacteria are found in fish sauce fermentation?

A

Early: Facultative aerobes (bacilli, staphylococci, kocuria, lactococci)

Near end: mostly bacilli

37
Q

At 80-120 days of the fish ferment, the fish flesh will have been converted to ____. Describe the microbial population.

A

N containing liquid

mostly bacilli

38
Q

In fish sauce/paste production, bacteria are not important for _____, because:
However, they play major roles in: _________

A

proteolysis; fish has enzymes

spoilage, flavor, aroma

39
Q

What egyptian delicacy is notorious for botulinum poisoning, and why?

A 
feseekh (fermented whole fish)
not eviscerated (guts left in); salt cannot reach insides, where there is C. botulinum

Food Microbiology (21 decks)

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