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35 Cards in this Set

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  • Back
the removal or destruction of all forms of microbial life
Commercial sterilization
subjects canned food to only enough heat to destroy the endospores of Clostridium botulinum.
is the destruction of vegetative pathogens on a surface, usually with chemicals. Spores and viruses are not necessarily destroyed.
the chemical disinfection of living tissue, such as skin or mucous membrane
the absence of pathogens on an object or area, as in aseptic surgery
the removal of transient microbes from skin by mechanical cleansing or by an antiseptic
the reduction of microbial populations on objects to safe public health levels.
suffix indicates the killer of a specified organism
biocide or germicide
kills microorganisms
kill fungi
kill viruses
indicates only that the substance inhibits for example-bacteriostasis
Bacterial populations killed by heat or chemicals tend to die at a _______ rate
The _____ ______ controls the passage of nutrients and wastes into and out of the cell. Damage to the ______ _____ causes leakage of cellular contents and interferes with cell growth
plasma membrane
Chemicals may denature proteins by reacting, for example, with disulfide bonds (or disulfide bridges), which give proteins their 3 dimensional active shape. Chemicals and radiation may prevent proper replication or functioning of _____ or ______
Thermal death point
the lowest temperature required to kill a liquid culture of a certain species of bacteria in 10 minutes
Thermal death time
the length of time required to kill ALL bacteria in a liquid culture at a given temperature
Decimal reduction time (D value)
the length of time, in minutes required to kill 90% of the population of bacteria at a given temperature
Moist Heat:
Boiling (100 C) kills vegetative forms of bacterial pathogens, many viruses, and fungi within 10 minutes.
Endospores and some viruses survive boiling for longer times.
Steam under pressure
allows temperatures above boiling to be reached
retorts, and pressure cookes are vessels in which high steam pressures can be contained. 121 C for 15 minutes. Moisture must touch all surfaces in order to bring about sterilization. Air must be completely exhausted from the container
mild heating that is sufficient to kill particular spoilate or disease organisms without seriously damaging the taste of the product. Dairies use the phosphatase test to determine if products have been properly pasteurized
High temperature, short-time pasteurization
uses temperatures of at least 72 C for about 15 seconds to pasteurize milk
Equivalent treatments
the heat of 115 C acting on an organism for 70 minutes is equivalent to heat of 125 C acting on an organism for only 7 minutes; that is applying a higher temperature for a shorter time may kill the same number of microbes as a lower temperature for a longer time.
Ultra-high-treatment (UHT)
Milk can be sterilized and stored without refrigeration when given UHT)
Dry sterilization:
Incineration, as in direct flaming, is efficient for limited purposes.

Hot air sterilization: as in an oven, requires higher temperatures (170 C) and longer times (2 hrs) to ensure sterilization
Moist heat is generally more efficient
Liquids sensitive to heat can be passed through a thin ______ ______ that has carefully controlled pore sizes to retain microorganisms
membrane filter
Operating theaters and special clean rooms receive air passed through ________
high-efficiency particulate air filters (HEPA)
Refrigerator temperatures (0C to 7 C) slow the metabolic rate of microbes, however, ________ species still grow slowly.
psychrotrophic. Some organisms grow at temperatures slightly below freezing, but microbes at the usual temperatures of freezer compartments are completely dormant.
________ ______ applied to liquid suspensions such as fruit juices can kill vegetative bacterial cells. Endospores are relatively resistant. An advantage is that flavors, colors, and nutrient values are preserved.
High pressure.
Ionizing radiation
such as X rays, gamma rays, and high-energy electron beams carry high energy and break DNA strands. Ionizing radiation forms reactive hydroxyl radicals. Such radiation is used to sterilized pharmaceuticals.
Ionizing radiation cont
irradiation is a type of cold sterilization.
all ionizing radiation can penetrate liquids and most solid materials including our bodies.

Gamma rays are the most penetrating, followed by X-Ray while cathode rays are the least penetrating.
Irradiated food does show a slight decrease in vitamin B1 levels. Radiation treatment results in the production of free radical oxidants (Which dissapear almost immediately)
No food can be sold to consumers without clear labels that it has been irradiated. Radiation is used to reduce pathogens E. Coli and Salmonella in beef & chicken and the reduction of worms and insects on fruits and vegetables.
Nonionizing radiation (UV rays):
UV does not penetrate as many materials as ionizing radiation because it has much lower energy. UV radiation is used to disinfect rather than sterilize.
UV rays do not penetrate liquid well, but liquids can be treated with UV by spreading the liquid into a thin layer. Water treatment plant.
Choosing a Microbial Chemical
1) Rapid action in low concentrations.
2) Solubility in water of alcohol and long-term staility
3) Boad-spectrum microbicidal action without being toxic to humans or animals.
4) Penetration of inanimate surfaces to sustain a cummulative or persistent action.
5)Resistance to becoming inactivated by organic matter.
6) Noncorrosive or nonstaining properties
7) Sanitizing or deodorizing properties
8) Inexpensive and readily available.