Exam 1 Flashcards
which kills more bacteria: slow or quick freezing?
slow
HACCP
control over raw materials, process, environment, distribution, and strorage as integrated preventative system
how do bacteria reproduce?
binary fission
generation time
time between divisions
lag stage
bacteria become accustomed to new environment - store nutrients, synthesize enzymes
log stage
active growth and fission; often symptoms
stationary stage
nutrients scarce, waste products accumulating, immuno-response from body
decline stage
further depletion of nutrients leading to cell death
factors affecting growth
food, acidity, time, temp, oxygen, moisture
most bacteria do not grow in pH
less than 4.6
danger temp zone
40-140 degrees F
microbes grow best at water activity
greater than 0.86
which can grow at lower water activity: bac or yeasts?
yeasts
hurdle concept
sub-lethal levels of growth-affecting factors are used in combo to reduce microbes
Q10
temperature coefficient for how fast microbes can metabolize
psychotrophs
microorganisms whose optimum growing range is 10-15 degrees C
blanching
immersion in hot water or steam to inactivate enzymes, reduce microbes, & fix color
fast freezing characteristics
small, intracellular ice crystals
thermal shock
slow freezing characteristics
large, extracellular ice crystals
no shock
better at killing bacteria
cold shock
dying of mesophiles upon sudden chilling
sublimation
moisture evaporates into gas phase without going through the liquid phase
radiation
emission of energy through space
shorter wavelengths are more or less damaging to microorganisms?
more damaging to microorganisms
ionizing radiation
carries enough energy to ionize molecules
compton electron
electron that is ejected from outer shell of a molecule by ionizing radiation
UV rays
have poor penetration, are non-ionizing, cause death due to mutations
gamma rays
radiation emitted from nucleus of 60Co and 137Cs
electron beam
stream of electrons emitted from radioactive substances that have poor penetration & use electricity as source
x-rays
bombardment of heavy metal targets with high velocity targets
radappertization
commercial sterilization (30-40 kGy)
radicidation
pasteurization, reduction of pathogens (2.5-10 kGy)
radurization
pasteurization, reduction of spoilage microbes (0.75-2.5 kGy)
D value
time required to destroy 90% of initial microbial population at specific temp
direct mechanism
targets DNA and RNA, breaks the base pairs, resulting in death of microorganisms
indirect mechanism
result of free radicals’ generation that compromise cellular membrane
free radicals
molecules with unpaired electrons
1st chemical permitted in foods by the FDA
sodium benzoate
effective against molds, yeasts & bacteria
sorbates
specific against molds & fungistatic
propionates
antioxidant in some foods
sulfites
used in meat curing for color stabilization, flavor development & antimicrobial activity
nitrites & nitrates
the perigo factor
heating food with nitrite yields agent 10x more inhibitory than nitrate alone
preservatives that uses concentration of water to inhibit growth
salt & sugars
