Module 4.3 Flashcards
Controlling Microbial Growth
Sterilization
Disinfection
Sanitization
antisepsis
Cleaning, degerming, decontamination, preservation
Physical methods of Controlling Microbial Growth - 4
Heat treatment
Irradiation
Filtration
Mechanical removal
a chemical method in controlling microbial growth. (1)
Antimicrobial Chemicals
refers to killing or complete elimination of all viable microorganisms. This uses agents - sterilants or sterilizing agents (e.g ethylene oxide, steam under pressure.
Sterilization
refers to the elimination or reduction of pathogens from inanimate objects or surfaces. It uses agents - disinfectants (e.g alcohol, formaldehyde, chlorine).
Disinfection
refers to the reduction of microbial populations to levels considered safe by public health standards (e.g iodine, chlorine)
sanitization
refers to the prevention of infection in living tissues using chemicals (e.g iodine, alcohol, hydrogen peroxide)
antisepsis
is considered to be one of the most useful methods of microbial control. It is reliable, safe, relatively fast, and inexpensive. It is used to sterilize or decrease microbial numbers. It can be in the form of moist or dry.
heat
refers to the temperature that kills all bacteria in a 24-hour old broth culture at neutral pH in 10 minutes.
Thermal Death Point
refers to the time required to kill all bacteria in a particular culture at a specified temperature
Thermal Death Time
is a form of heat that consists of efficient penetrating properties. It destroys microorganisms by irreversibly coagulating their proteins. It can be through boiling, pasteurization, or pressurized steam.
Moist Heat
requires to be at 100°C. At this temperature, most bacteria are destroyed and some viruses are inactivated. This also kills vegetative cells and eukaryotic spores within 10 minutes.
Boiling
refers to the use of brief heat treatment (moderately high temperature) to reduce the number of spoilage organisms and kill pathogens (e.g Salmonella, Mycobacterium).
This process is also used to make wine, beer, vinegar, milk, juices.
It significantly reduces the number of heat-sensitive microorganisms; does not significantly alter the quality of food.
It increases the shelf-life of food and protects consumers.
Pasteurization
What are the four methods under pasteurization? (4)
- Low-Temperature Holding (LTH) - 62.8°C for 30 minutes
- High-Temperature-Short-Time (HTST) Method - milk: 72°C, 15 seconds (flash method); ice cream: 82°C, 20 seconds
- Ultra-High-Temperature (UHT) Method - 140-150°C (several seconds); involves complex cooling processes; e.g boxed juices, coffee creamers.
- Mechanical Pasteurization (non-food) - e.g hospital anesthesia mask: 80°C, 15 minutes.
____ include using pressure cookers and autoclaves. This can be achieved by heating water in an enclosed vessel that achieves temperatures above 100°C. It can also be in 15 minutes, 15 psi, at 121°C (kills endospores and disrupts viruses’ nucleic acids).
Only items that can be penetrated by steam and withstand heat and moisture can undergo this treatment (e.g surgical instruments, microbiological media, reusable glassware, microbial cultures, and biohazards before disposal).
This also ensures Clostridium botulinum endospores are destroyed.
Pressurized Steam
refers to fractional steam sterilization or intermittent sterilization. This is for materials that can be destroyed at more than 100°C. This puts organisms exposed to 90-100°C for 30 minutes for 3 consecutive days.
This is used for some canned foods and laboratory media.
Tyndallization (Nonpressurized Steam)
is not as efficient as wet heat (lower penetrating properties). It requires longer times and higher temperatures. It is only used for metal objects and glassware. It can be achieved by using an oven or an open flame (incineration).
Dry Heat
uses dry heat; oxidizes cell components to ashes.
Incineration
uses dry heat; oxidizes cell components and irreversibly denatures proteins. It is used to sanitize Petri dishes and glass pipettes. It is by default at 170-180°C for 1 hour. It can be used on powders, oils, or anhydrous materials.
Dry Heat Oven/Hot Air
What are some low-temperature methods? (2)
Refrigeration
Freezing or Deep Freezing
- 4-5°C; limited to a few days because bacteria and molds continue to grow still at low temperatures.
refrigeration
- 0-95°C; used to preserve food in homes and food industries; slows the rate of chemical reactions in bacterial cells.
Freezing or Deep Freezing
What are the two types of filtration methods? (2)
fluid and air filtration
- remove organisms from heat-sensitive fluids.
Fluid Filtration
high-efficiency particulate air (HEPA): remove from air nearly all microorganisms with diameter greater than 0.3 µm.
air filtration
is used to preserve food (in the absence of water that inhibits the action of enzymes). It is also used to minimize the spread of infectious agents (e.g Treponema).
Drying/Desiccation
is also referred to as lyophilization. It is the drying of material from a frozen state. It is for long-term preservation (e.g instant coffee, culture preservation).
Freeze-Drying
causes plasmolysis of bacterial cells. It is said that high salt or sugar conc. creates a hyperosmotic medium, drawing water out of microorganisms.
increased osmotic pressure
Radiation can be categorized into two: (2)
Ionizing
Non-ionizing
- has enough energy to free electrons from the atoms or molecules they are attached to, and therefore ionizing them.
Ionizing Radiation
- lacks the energy to break these same molecular bonds and cannot free electrons from atoms or molecules.
Non-ionizing Radiation
are less reliable than heat; suitable for treating large surfaces and heat-sensitive items; some are non-toxic; can be used as preservatives (bacteriostatic).
Chemical Agents
What are some examples of chemical agent? (8)
Alcohols
Aldehydes
Phenols or Phenolics
Halogens
Heavy Metals
Sterilizing Gases
Surface Active Agents or Surfactants
organic molecule/other (Hydrogen peroxide)
coagulate enzymes and other essentials and damages lipid membranes. They are used as antiseptics for degerming or as disinfectants for treating instruments and surfaces (e.g 60-80% ethyl or isopropyl alcohol.
Alcohols
inactivate proteins and nucleic acids (e.g glutaraldehyde, formaldehyde (formalin (aqueous 37% formaldehyde): kill most forms of microorganisms), orthopthaldehyde (OPA).
Aldehydes
disrupts the cell membrane, denatures proteins, and inactivates enzymes. (e.g phenol, cresol, xylenon, triclosan).
Phenols/Phenolics
oxidizes cell constituents (e.h iodine, chlorine).
Halogens
denatures enzymes and essential proteins (e.g silver nitrate (prevents ophthalmic gonorrhoeae); copper sulfate (algicide); silver sulfadiazine (used on burns); merthiolate (disinfects skin mucous membranes).
Heavy Metals
denatures protein; for heat-sensitive items (catheters, plastic Petri plates); e.g ethylene oxide, ozone, chlorine dioxide.
Sterilizing Gases
include soaps and acid-anionic detergents; mechanical removal of microorganisms. Also included are cationic detergents, they disrupt the cell membrane and denature proteins.
Surface Active Agents or Surfactants
inhibit microbial metabolism (e.g sorbic acid, benzoic acid, calcium propoionate) and are widely used in foods/cosmetics).
Organic Acids
What is another oxidizing agent that can be used to control microbial growth?
Hydrogen Peroxide (oxidation of cell components)
