Exam 2 Flashcards
thermodurics
survive in relatively high temps but do not necessarily grow
thermophilics
not only survive high temps but require them for their growth
sterilization
destruction of all viable organisms as may be measured by enumerating technique
commercially sterile
no viable microbes can be detected by the usual methods or the number of survivors is so low it is insignificant
heat resistance of microbial cells (increases/decreases) with decreasing humidity, moisture, or Aw
increases
are moist or dried microbial cells more heat resistant?
dried
heat resistance (increases/decreases) with presence of fat
increases
which is better at fat protection: long chain or short chain fatty acids?
long chain fatty acids
how does fat presumably affect resistance?
by directly affecting cell moisture
salts (increase/decrease) resistance
it depends on the type/concentration of salt used; some provide protective effect by decreasing Aw, while some increase Aw and heat sensitivity
sugars/carbs (increase/decrease) resistance
increase
how does pH affect resistance?
most resistant at optimum pH (usually neutral). as pH deviates from optimum value, resistance decreases
the larger the number of organisms, the (higher/lower) the heat resistance
higher
cells are most resistant in which phase?
stationary phase
cells are least resistant in which phase?
log phase
heat resistance is (greater/lesser) when the incubation temp is higher
greater
are spore-formers more or less resistant than non-spore-formers?
more resistant
which is more heat resistant, Gram+ or Gram-?
Gram+
which is more resistant, cocci or rods?
cocci
some factors for why spores are so heat resistant
protoplast dehydration, mineralization, thermal adaption
thermal death time
time necessary to kill a given number of organisms at a specified temp
d-value
time required to destroy 90% of organisms
12-D concept
lethality requirement in effect in the canning industry
z-value
temp increase that causes 1-log change of d-value
important thermophiles
bacilli, clostridia, LAB
minimally processed foods
quality of fresh foods without conventional food preservation, convenient to prepare, serve, and consume
how do microwave and radio-frequency heating work?
by using electromagnetic waves to generate heat in food
2 mechanisms by which mv and rf heat
dielectric and ionic
ohmic heating
alternating current passes through electricity-conducting foods
pulsed electric field
pulses of high electric field to food between 2 electrodes
electroporation
production of pores in membranes by the electric current
manothermosonication
simultaneous heating and ultrasonic waves that reduce spore resistance
high intensity pulsed light
pulses of intense broad spectrum light are used as a surfaces treatment
indicator organisms
used to relate microbiological quality in terms of product shelf-life and safety
food-borne illness
any illness resulting from ingestion of food
infection
infectious bacteria invade and colonize the intestinal tract, disrupting uptake of solutes, causing osmotic pressure imbalance
intoxication
bacteria produce toxins in food, then toxins are rapidly absorbed in the GI tract
endotoxins
composed of LPS in the cell wall of Gram- bacteria, released when the cell dies and induces a fever
exotoxins
proteins, generally associated with Gram+ bacteria, usually synthesized in and secreted by living cells
what did Denys and Barber study in the late 19th/early 20th century?
staphylococcal aureus
how can one test for S. aureus?
catalase (H202) and coagulase tests (clot formation=positive)
which type of strains of C. bot is favored by carbohydrates?
non-proteolytics
which is more heat resistant: proteolytics or non-proteolytics?
proteolytics
most lethal type of botulinal neurotoxin
type A
pasteurization
destruction of all disease-producing organisms
