Meat Fermentation Flashcards
What type of fermentation start method is used for meat? Why?
Can use any of the 3 (inoculation, spontaneous, backslopping)
BUT: inoculation is best (safety and quality-wise)
Why does meat and fish spoil quickly?
moist, nutrient rich environment
pathogens/spoilage bacteria from animal/slaughter
What are the main bacteria in meat starter cultures?
LAB
true/false: there are no LAB present naturally on meat.
False: LAB present but in small population (need to boost and create favorable environment
Traditionally fermented meats (no starter culture) are at a greater risk of causing ______ infection.
Staphylococcus
What are the fermentation conditions for meat products?
Anaerobic
Salt 6%
Acidic (from LAB activity)
What are the requirements when choosing a microbe as a starter for meat fermentation?
- homofermentative (make acid fast!)
- survive high salt
- no slime production
- provide flavor enhancement
What was the first microbe used for commercial meat fermentation culture and what are its advantages? What other organism can it be used with?
Pediococcus acidilactici: survive up to 6.5% salt; can be freeze dried, higher optimal growth temp
Can be used with Lb. plantarum
True/False: unfermented fresh meat has a slightly basic pH
False: fresh meat about pH 5.6
In about 8 hours, starter culture can lower the pH of meat from 5.6 to ____.
4.8
What produces the pink color in fermented meat? Is this absolutely necessary?
nitrites/nitrates added
add nitrite/nitrate reducing bacteria to culture
reduced to nitric oxide (pink color)
No; but otherwise will look less appealing (brown)
What microbes can be added to produce nitric oxide?
kocuria, staphylococci, some lactobacilli
Aside from nitrates, what else contributes to the reddish hue of fermented meat?
Activity of aerobic microbes (near surface):
- decrease surface oxygen
- form barrier (prevent oxygen diffusing in)
- reduce METMYOGLOBIN (brown) -> myoglobin (red)
several species of LAB have an advantage that is important to the prevention of pathogens and spoilage in meat. What is it?
Produce bacteriocin: small peptides that kill/inhibit other Gram positive bacteria
Are bacteriocins harmful to humans? What is harmed by them?
No
targets gram positive bacteria (of another species)
The largest category of fermented meat products:
Where did they originate from?
dry/semidry sausages
came from Mediterranean region (dry warm climate)
How are dry/semidry sausages made?
stuff meat mixed with salt/seasoning into casings (anaerobic) -> drying + fermentation
(no smoking needed)
How is preservation achieved in dry/semidry sausage?
rapid drying (moisture loss) fermentation -> organic acids, alcohols, lactic acid (inhibitory substances)
Sausages made in northern Europe were known as ____ sausages. How did they differ from dry sausages?
summer
made in winter
higher water content
smoked
finer texture (finely ground)
True/False: semidry sausages do not require tight regulation because they have been cured with nitrate
False; need to report MPR, pH, salt, ingredients, etc
unless commercially sterilized
True/False: A shelf-stable semidry sausage is NOT permitted to be sold as slices
True; but can be sold as slices if vacuum packed (otherwise no)
What is “MPR?”
moisture to protein ratio
List the steps for manufacturing a semidry sausage: (7)
- grind meat (reduce particle size)
- add salt, nitrate, seasonings, culture
- blend
- vacuum stuff into semipermeable casing
- incubate -> pH endpoint
- (optional): heat - kill pathogen/starter culture
- dry age (remove moisture)
Where does bacterial contamination of meat products come from? What microbes are involved and what do they cause?
animal, intestines, skin (exposed during slaughter)
GRAM NEGATIVE bacteria
spoilage: proteolysis -> rotten egg smell
Before fermentation, LAB CFU/g is about _____. After the process, it is _____.
3-4 log, increase to 7-8 log
Besides LAB, what other microbes can be present in meat products? How does their population change as fermentation progresses?
Staphylococcus
Micrococcaceae
die down when pH declines
How does LAB contribute to flavor development in sausage?
proteolysis + lipolysis creates smaller flavor compounds
What are some undesirable LAB and why?
Lb. viridescens: makes H2O2 -> green
Lb. brevis, L. meseneroides -> CO2 -> gas pockets
Brochothrix -> souring
True/False: fermented dry/semidry sausages are still considered “raw”
True; not enough heat for “cooking” to kill pathogens
The primary products of fish fermentations:
fish sauce (liquid) fish paste
The general process for making fish sauce:
layer fish/shrimp + salt in 3:1 ratio
seal concrete vat
ferment 9 months - 1 year
remove liquid -> continue for more liquid
What contributes to the flavor of fish sauce, and what produces these compounds?
Peptides, AA, Ammonia, VFA (enzymes, oxidation)
caramel/sugar/roast corn, etc (added flavor agents)
What factors will influence the taste of the final fish sauce? (3)
temperature during ferment
fish type
pH
Bacteria populations in fish sauce are highest in what period?
Early (0-25 days)
True/False: it is mostly due to bacteria proteases that the fish tissue will break down
False; mostly due to endogenous fish enzymes
What type of bacteria are found in fish sauce fermentation?
Early: Facultative aerobes (bacilli, staphylococci, kocuria, lactococci)
Near end: mostly bacilli
At 80-120 days of the fish ferment, the fish flesh will have been converted to ____. Describe the microbial population.
N containing liquid
mostly bacilli
In fish sauce/paste production, bacteria are not important for _____, because:
However, they play major roles in: _________
proteolysis; fish has enzymes
spoilage, flavor, aroma
What egyptian delicacy is notorious for botulinum poisoning, and why?
feseekh (fermented whole fish) not eviscerated (guts left in); salt cannot reach insides, where there is C. botulinum
