FOOD PRESERVATION 2 Flashcards
what is pickling
preserves foods through acidification (acidity controls microbial growth)
what is used to pickle
vinegar (acetic acid); other wear organic acids, like lactic and citric
what are the two steps of canning
preparation + heating
what does preparation mean
packing food and liquid into the container
describe headspace
small amount of air left at top after canning preparation; required to ensure vacuum seal
describe heating
boiling water processing; needed for low-acid foods
how does canning destroy and prevent growth of microorganisms
through heating and removal of O, and sometimes addition of acids
what are low-acid foods and what are high-acid foods
low acid foods have a pH higher than 4.6
high acid foods have pH lower than 4.6
what are the two methods of cold preservation
refrigeration + freezing
describe refrigeration
slows down biological, chemical and physical rxns
describe freezing
least damaging preservation method in terms of flavor, nutrient content, and texture
what does freezsing do to microroganisms
makes water unavailable to microorganisms to grow, but still some O present
describe relationship between fat content and shelf life
higher fat content = lower shelf life due to rancidity
what are the four problems with frozen foods
freezer burns, cell-rupturing, fluid loss, recrystallization
describe freezer burn
caused by moisture loss (via sublimation) resulting in altered texture, appearance, and flavor; due to improper packaging or prolonged freezing
describe cell-rupturing
water expands upon freezing; large crytals can rupture food’s cell cells causing inferior texture
should foods with higher water content be frozen
no
describe fluid loss
frozen meat loses water when thawed, which can result in drier texture
describe recrystallization
small ice crystals melt and freeze as larger crystal, which affects texture; occurs with temp. fluctuations; more crystals = worse quality of food
describe boiling
10 min of boiling kills/inactivates most microroganisms
describe ohmic heating
electrical current passed through food to generate heat to destroy microorganisms; used in juice preservation
describe pasteurization
foods heated to specified temp for a certain period of time to destroy microorganisms
describe milk pasteurization
145 F for 30 min
describe high temp short time pasteurization varaiation
161 F for 15 seconds
describe ultra high temp pasteurization variation
temps >280 F for 2 seconds
whats irradiation
cold pasteurization; food exposed to ionizing energy source, like gamma rays, X-rays, or electrons
does irradiation make food radioactive
no
what do free radicals do
damage DNA of microorganisms
what is irradiation used in
wheat flour, potatoes, spices, meat, shellfish, poultry, eggs
what are some concerns with irradiation
possible nutrient loss, environmental hazards, and free-radical production
what are the labeling requirements for irradiation
“treated with radiation”
describe pulsed light
food exposed to intense, brief flashes of light
what does pulsed light do to bacteria
disrupts bacterial cell membrane, but not those of the surrounding foods
damages bacterial DNA
whats high-pressure processing (HPP)
uses high pressure (<50,000 psi for 15 min) to deactivate microorganisms and enzymes responsible for deterioration
when is HPP used
for juices, sauces, ready-to-eat meats
how are macros, fat-soluble vitamins, and minerals effected by processing
relatively unaffected
what vitamins are most susceptible to loss after cooking in liquid
water-soluble vitamins (c and b0
is nutrient data for cooked foods limited
yes
do unprocessed foods undergo nutrient loss
yes
