fermented meat products Flashcards
What are fermented meats?
meat products that are incoulated for contamination control and to ensure sufficient control of microbial activity
what starter cultures are most often used in meat fermentation?
LAB
what are the three ways meat fermentation can be started?
- natural fermentation
- back inoculation
- starter culture
what is back inoculation in meat fermentation?
inoculating new meat with a portion of a previous batch
how is starter culture added in meat fermentation?
inoculating meat with frozen or freeze dried
should the starter cultures in meat fermentation be hetero or homofermentative?
Homofermentative- has to produce enough acid to rapidly lower the pH, grow in 6% salt, and have the capacity to enhance the flavor of the meat without producing slimes
what are pediococcus acidilactici characteristics?
- survives lyophilization
- rapidly produces lactic acid
- has a higher optimal growth temperature than lactobacillus sp.
- is salt tolerant up to 6.5%
what is the starter culture that is typically used for dry and semidry sausage?
Lb. plantarum either with or without P. acidilactici
how rapidly can meat starter cultures lower pH in a meat product?
from 5.6 to 4.8 in 8 hours
what bacteria are used to reduce nitrate/nitrite to nitric oxide
staphylococci and kocuria
what enzymes are involved in reducing nitrite-nitrate to nitric oxide?
nitrate/nitrite reductase
what attributes to the red color in meat?
consumption of oxygen by growing facultative aerobes
what protein contributes to browning in meat?
metmyoglobin (oxidized form of myoglobin, a kind of hemeprotein)
What are bacteriocins?
antimicrobial peptides that either kill or inhibit the growth of certain gram-positive bacteria
why are bacteriocins added to processed meats?
if there is no heat treatment, bacteriocins are added and do what heat application would do. ameliorates safety concerns
what are bacteriocins considered in the meat industry?
natural food preservatives
what species of LAB produce bacteriocins?
lactobacillus
advantages of using cultures with bacteriocins?
- antimicrobial activity against pathogens and spoilage bacteria
- increased shelf life
- reduced rate of meat tissue degradation
what are the two largest categories of fermented meat products?
dry and semidry sausages
where do dry and semidry sausages originate from?
the mediterranean
what contributes to taste and sensory characteristics in dry and semidry sausages?
- addition of salt
- fermentation by indigenous LAB
- indigenous yeasts
- rapid drying conditions of the mediterranean
what is the process in meat fermentation to favor optimal growth of LAB
heavily seasoned and stuffed into anaerobic sausage casings
what compounds preserve sausage products?
- lactic acid
- organic acid
- alcohols
when are northern European sausages mad?
in the winter and stored until summer, hence the name summer sausage
what is MPR?
moisture-to-protein ratios
what are the compositional characteristics of dry and semi-dry sausages?
- MPR
- pH limits
- ingredients
what are the regulations for non-commercially sterilized semidry sausages?
- fermented to a pH of 4.5 or lower
- must be intact, or vacuum packed if sliced
- have an internal brine concentration no less than 5%
- cured with nitrite
- be smoked with wood
what are the manufacturing procedures for semidry sausages?
- reduce particle size of high-quality raw meat
- add salt, spices, nitrite
- uniformly blend all ingredients
- vacuum stuff the meat into semipermeable casing to minimize oxygen
- incubate at starter cultures optimal growth temperature until specific pH is reached
- add heat to inactivate starter culture and ensure pathogen destruction
- dry to the required MPR
what are the factors that affect the final product of semidry sausages?
Raw meat tissues
why are raw meat tissues a factor affecting the end product?
they are easily contaminated during the slaughter process because most bacteria come from the hide, skin, or intestinal contents
what bacteria are mainly responsible for contamination of raw meat tissues?
gram-negative proteolytic bacteria
what are the undesired species of LAB in fermented meats?
- lactobacillus viridescens - cause greening due to production of hydrogen peroxide
- lactobacillus brevis and leuconostoc mesenteroides - produce CO2 creating gas pockets
- brochothrix - cause unpleasant souring
what do non-heated products rely on to control pathogens?
reductions in water activity
what are the organisms of greatest concern in fermented meats?
- staphylococcus aureus
- E. coli
- salmonella
- listeria monocytogenes
- campylobacter
- trichinella spiralis
how are fish sauces made?
predominantly derived from the pressing or decanting of fish that have been fermented from 9 months to a year. fish are layered with salt in concrete vats at a 3:1 ratio (fish to salt), sealing the vats, and allowing a supernatant to develop. the liquid is then carefully removed
what does the supernatant that is formed from the fish, contain?
peptides, amino acids, ammonia, and volatile fatty acids
how are fish sauces enhanced?
by adding caramel, caramelized sugar, molasses, roasted corn, or roasted barley to enhance the color
where do the aroma and flavor of fish sauces come from?
enzymatic activity, oxidation during fermentation, the production of volatile fatty acids, pH, fish composition, and fermentation temperature
timeline of fish sauce production?
0-25 days:
- salt penetrates fish tissues by osmosis
- proteases increase soluble protein content of the liquor, but stops once there’s a buildup of amino acids
- bacterial populations increase to a high concentration
80-120 days:
- a protein rich liquid develops through autolysis
140-200 days:
- fish tissue is converted to a nitrogen containing liquid
- bacterial population decreases, most microbes present at this point are Bacillus sp.
what are fish pastes?
pastes that consist of eviscerated whole or ground fish, shrimp, plankton, or squid with a fish to salt ratio of 3:1 which are then placed in vats to ferment.
proteolytic enzymes break down the fish tissue until it has a pasty consistency
what is pickle?
the liquid exudate from the fish paste fermentation, which forms as a result of the osmotic differential of the brine solution. when the pickle stops forming the fish paste is ready for consumption
what kind of aroma does fish paste have?
salty, cheese like aroma
what is Feseekh?
a traditional Egyptian dish prepared by leaving an intact mullet fish to dry out in the sun, followed by 45 days of fermentation in a vat of brine. caused an outbreak due to botulism
why is there such a high risk for botulism in un-eviscerated fermented fish products?
it’s hard for the added salt to reach the viscera where spores of C. botulinum form
