13.2 Flashcards
Thermal death point
The lowest temperature at which all microbes are killed in a 10-minute exposure
Thermal death time
The length of time needed to kill all microorganisms in a sample at a given temperature
Dry-heat sterilization
Direct application of high heat. Can be applied for long periods of times.
Moist-heat sterilization
More effective protocol because it penetrates cells better than dry heat does. Raise temperatures above the boiling point of water to sterilize items.
Who designed the modern autoclave
Charles Chamberland while working with Louis Pasteur.
Retorts
Larger autoclaves used for large-scale sterilization out of laboratory and clinical settings.
Heat-sensitive autoclave tape
Turn black when appropriate temperature is achieved. Does not help with length of exposure so cannot indicate sterility.
Biological indicator spore test
Strip of paper or a liquid suspension of the endospores to determine whether the endospores are killed by the process.
Pasteurization
Used in food. Kills pathogens and reduces the number of spoilage-causing microbes while maintaining food quality.
high-temperature short-time pasteurization
exposes milk to a temperature of 72 degrees for 15 seconds which lowers bacterial numbers while preserving the quality of the milk.
ultra-high-temperature pasteurization
milk is exposed to a temperature of 138 degrees for 2 or more seconds. Can be stored for a long time in sealed containers without being refrigerated.
Psychrophiles
prefer cold temperatures
0 degrees to 7 degrees
inhibits microbial metabolism, slowing the growth significantly and helping preserve refrigerated products
below -2 degrees
may stop microbial growth and even kill susceptible organisms
pascalization
high pressure processing in food industry
Desiccation or dehydration
drying to preserve foods such as raisins, prunes, and jerky. Does not kill all microbes or their endospores
freeze-dying or lyophilization
item is rapidly frozen and placed under vacuum so that water is lost by sublimation. Better than desiccation.
water activity
water content of foods and materials
Ionizing radation
strong enough to pass into the cell where it alters molecular structure and damages cell components.
non ionizing radiation
used for disinfection and uses less energy than ionizing radiation. Does not penetrate cells or packaging.
sonication
use of high-frequency ultrasound waves to disrupt cell structures
cavitation
formation of bubbles inside the cell, which can disrupt cell structures and eventually cause the cell to lyse or collapse.
High-efficiency particulate air filter
effective pore sizes small enough to capture bacterial cells, endospores, and many viruses.
hyperbaric oxygen therapy
air pressure three times higher than normal. Inhibits metabolism and growth of anaerobic microbes.
