11.2: Methods of Physical Control

Sterilization with a dry oven occurs at . . .

150-180°C for 2-4 hours

What are the Average settings of the Autoclave?

15psi, 121 °C, 15 minutes

There are ___ categories of radiation. What are they?

2. 1. Ionizing radiation. 2. Non-ionizing radiation.

There are ___ methods of pasteurization. What are they?

3. 1. Flash Pasteurization 2. Batch pasteurization 3. Ultrahigh-temperature (UHT) Pasteurization.

What is Sonicator?

A water-filled chamber through which the sound waves become vibrations that can disrupt cell structure

Describe cold treatment.

1. Designed to slow microbial growth. 2. Common in food processing and storage. 3. Not considered a viable method of sterilization or disinfection.

Describe Decontamination by Filtration.

1. Effective for removing microbes from air and liquids. 2. Fluid is strained through a filter with openings large enough for fluid but too small for microorganisms. 3.Pore size can be controlled and standardized (Can be small enough to trap viruses.)

Describe the Dry Oven (hot air).

1. Electric coils radiate heat within an enclosed compartment. 2. Used for heat-resistant items that do not sterilize well with moist heat (some glassware, powders, oils, and metallic instruments)

Describe Non-ionizing radiation.

1. Excites electrons causing them to jump orbitals but don't leave the molecule. 2. It leads to abnormal linkages and bonds within molecules. 3. DNA, is again, very susceptible. (*Thymine dimers* are a common result of this process.)

Describe Incineration. "Your Ash is Gas"

1. Ignites and reduces microbes to ashes and gas. 2. This is common practice in microbiology lab - flaming the loop. 3. Hospitals often use incineration to eliminate their infectious waste materials.

Describe Desiccation.

1. Inhibits growth by removing water. 2. Inhibits the spread of most pathogens but not all of them. 3. Not considered a viable method of sterilization or disinfection.

Describe Osmotic Pressure (salt concentration).

1. Involves the use of salt to create a hypertonic environment. 2. Results in water leaving the cell, inhibiting cellular processes

Describe Ionizing radiation.

1. It excites the electrons to the point that they are ejected from the molecule entirely causing the formation of ions. 2. DNA is most sensitive molecule.

Describe Non-pressurized Steam.

1. It is sometimes referred to as intermittent sterilization. 2. Destroys vegetative cells and viruses but *not* spores

Describe Boiling Water.

1. It's used For disinfection and *not* sterilization. 2. Used by many to decontaminate suspect drinking water

What are some Applications of Filtration?

1. Prepare liquids that can't withstand heat. 2. Can decontaminate beverages without altering their flavor. 3. Water purification. 4. Removing airborne contaminants (HEPA filters)

What are some Common Methods of Moist Heat Control? SNPBD

1. Steam Sterilization 2. Non-pressurized Steam 3.Pasteurization 4.Boiling Water. 5. Dry heat.

Describe Steam under pressure (steam sterilization):

1. Steam can only reach 100 °C under normal pressure; increasing the pressure allows for higher temps and better microbe killing. 2. Destroys vegetative cells, spores, and viruses.

Describe Sound Waves.

1. Used high-frequency sound waves to disrupt cell structure. 2. Gram-negative bacteria are most susceptible. 3. Often used to clean debris from instruments before sterilization. 4. Not a reliable form of disinfection or sterilization

Ionizing radiation Is the preferred method for sterilizing what?

Drugs and tissues by hospitals

Describe the process of boiling water.

Expose materials to boiling water for 30 minutes, but 10 minutes will kill all non-spore-forming pathogens & most viruses.

Describe the process of non-pressurized steam.

Expose to free-flowing steam for 30-60 minutes, incubate for 23-24 hours, treat again; repeat for 3 days in a row.

Give examples of Ionizing radiation.

Gamma rays, X rays, and cathode rays

Describe Lyophilization.

It's a mixture of freezing & drying and is used to preserve microbes and other cells for long periods of time.

What is the biggest downside the boiling water method?

Recontamination after removal from water is the biggest downside with disinfection objects with this method.

What are some liquids that can't withstand heat?

Serum and other blood products, vaccines, IV fluids, and enzymes

What are some other methods of Physical control?

Sound waves & Osmotic Pressure.

The Autoclave is effective at what?

Sterilizing heat-resistant materials (glassware, cloth, metallic instruments, liquids, etc) and any material that will be discarded (plastic Petri dishes and pipets)

Non-pressurized steam is *not* effective at what?

Sterilizing objects that don't allow for microbial growth but can disinfect them

The Autoclave is *not* effective in what?

Sterilizing substances that repel or absorb moisture (waxes, oils, powders)

Describe Pasteurization (hot water).

Technique in which heat is applied to liquids to kill potential agents of infection and spoilage while maintaining the flavor and food value.

The Autoclave is . . .

The commercial device used for steam-heat sterilization and is similar in function to a pressure cooker

What is the Goal of pasteurization?

The goal is to prevent the transmission of milk-borne diseases from infected cows and milk handlers.

Disadvantage of UV Rays is that they . . .

Pose a threat to human tissue if overexposure occurs

What are the disadvantages of Ionizing radiation?

Potential danger to machine operators and possible damage to some materials.

what is the primary example of Non-ionizing radiation?

UV rays are the primary example

Describe Ultrahigh-temperature (UHT) pasteurization.

Use 134 °C for 1-2 sec. This allows milk to be stored for long periods at room temp (ex. coffee creamers)

Describe Batch pasteurization.

Use 63-66 °C for 30 min and is the traditional method used in U.S.

Describe Flash pasteurization.

Use 71.6 °C for 15 sec and is common is Europe & Asia

What are some potential problems with using ionizing radiation is the sterilization of commercial food products?

changing flavor and nutritional value, and introducing undesirable chemical reactions.

Ionizing radiation is used in the sterilization of what?

commercial food products

UV Rays are excellent for . . .

disinfecting air.

Desiccation =

drying

What is Radiation?

energy emitted from atomic activities and dispersed at high velocity through matter or space

Heat-Sensitive culture media allow spores to . . .

germinate in-between rounds

What are the two methods of Dry Heat?

incineration and hot air

Pasteurization does not . . .

kill all microbes

UV Rays are commonly seen in . . .

lights found in hospital rooms, operating rooms, schools, food prep areas, and dental offices.

Generally, elevated temperatures are . . .

microbicidal

lower temperatures are usually . . .

microbistatic

Cold Treatment =

refrigeration & freezing

UV Rays does not pass easily through . . .

solids but is used in some applications

Non-pressurized steam is most often used to do what?

sterilize heat-sensitive culture media

UV Rays are sometimes used to . . .

treat drinking water or purify liquids

Ionizing radiation also causes what?

Lethal chemical changes in organelles and the production of toxins.

Radiation can be used as a . . .

Microbial Control Agent

Does Pasteurization sterilize the liquid?

No, because spores, thermoduric and thermophilic organisms still remain.