Pasteurization and Sterilization Techniques

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Questions and Answers

What is the primary effect of ultraviolet (UV) radiation on DNA?

It causes adjacent thymine molecules to dimerize. (correct)

It leads to gene amplification.

It initiates the process of DNA replication.

It causes DNA to lose its structure.

What is a limitation of UV irradiation for disinfection purposes?

It can be used effectively in water disinfection without any drawbacks.

It can penetrate through all types of surfaces.

It causes cells to become radioactive.

It has very low penetration and may not inactivate microorganisms on dusty surfaces. (correct)

Which type of radiation is typically used to sterilize food and medical supplies?

X-ray radiation

Gamma radiation from cobalt-60 (correct)

Ultraviolet radiation

Infrared radiation

What effect does gamma irradiation have on the nutritional value of food?

It does not change the nutritional value. Signup and view all the answers

How do ionizing radiations primarily damage cells?

By directly ionizing DNA or through the chemical effects of ionizing water. Signup and view all the answers

What is the purpose of the safety valve in an autoclave?

To allow air to escape from the chamber Signup and view all the answers

Which of the following parameters is NOT essential for successful autoclaving?

Chemical composition of the load Signup and view all the answers

What is the first stage in the autoclaving process?

Air evacuation stage Signup and view all the answers

Why is it important to loosely close autoclave bags?

To allow steam penetration Signup and view all the answers

What happens if air pockets remain in the autoclave during the process?

They hinder steam penetration and lead to incomplete sterilization Signup and view all the answers

What is the minimum holding time required for sterilization at 134˚C?

2 minutes Signup and view all the answers

How should materials be organized in the autoclave for effective sterilization?

Load materials to allow efficient steam penetration Signup and view all the answers

At what pressure must the holding time be maintained for 12 minutes at 121˚C?

15 lb per sq.in. gauge pressure Signup and view all the answers

What should be done after the autoclave has been turned off?

Allow the autoclave to cool until atmospheric pressure is reached. Signup and view all the answers

What is a limitation of steam in the sterilization process?

It cannot penetrate hollow instruments or moisture-resistant packaging. Signup and view all the answers

Which of the following is a direct test for sterilization efficiency?

Testing for sterility of products Signup and view all the answers

What is the most lethal wavelength for ultraviolet radiation used in sterilization?

260 nm Signup and view all the answers

What type of radiation is not considered ionizing?

Ultraviolet light Signup and view all the answers

What is the correct purpose of chemical indicators in sterilization?

To indicate the efficiency of sterilization through color change. Signup and view all the answers

What is a deficiency of the simple autoclave mentioned?

It lacks means for drying the sterilized load. Signup and view all the answers

Which of the following is true about the spores of Bacillus stearothermophilus?

They are used to indicate sterilization efficiency. Signup and view all the answers

What is a primary benefit of using membrane filters compared to Seitz filters?

They have a higher filtration rate. Signup and view all the answers

What is the typical pore size range of membrane filters?

0.22 to 0.45 um Signup and view all the answers

Which method is used to test the efficiency of filters?

Adding Serratia marcescens to the fluid. Signup and view all the answers

At what temperature and pressure is moist heat effective in killing endospores?

121°C at 15 p.s.i. Signup and view all the answers

What is the primary function of HEPA filters in biological safety cabinets?

To remove 99.97% of particles. Signup and view all the answers

What temperature and time are used in High Temperature Short Time Pasteurization (HTST)?

72°C for 15 seconds Signup and view all the answers

What is a benefit of Ultra High Temperature Pasteurization (UHT)?

Milk can be stored at room temperature for 2 months. Signup and view all the answers

What is the primary purpose of Tyndallization?

Sterilization of serum or body fluids containing coagulable proteins. Signup and view all the answers

What is one key limitation of boiling at 100°C?

It does not ensure sterility despite killing non-sporing pathogens. Signup and view all the answers

What is the maximum temperature that should not be exceeded during Tyndallization?

59˚C Signup and view all the answers

Which method is used for sterilizing solutions that may decompose at higher temperatures?

Steaming at 100°C Signup and view all the answers

What is a key principle of autoclaving?

All parts of the load must be permeated by steam. Signup and view all the answers

What is used to promote sterilization during boiling?

Sodium carbonate Signup and view all the answers

Study Notes

Pasteurization Techniques

HTST (High Temperature Short Time): Milk heated to 72°C for 15 seconds.
UHT (Ultra High Temperature): Milk treated at 140°C for 3 seconds, allowing room temperature storage for up to 2 months with minimal flavor change.
Both methods effectively destroy non-spore forming pathogens like Salmonella and Mycobacterium.

Tyndallization

Used for sterilizing solutions containing heat-sensitive coagulable proteins.
Involves heating at 56°C for 1 hour over several days (up to 8 times).
Must avoid temperatures above 59°C to prevent inspissation.

Boiling

Heating water at 100°C for 5-10 minutes kills all non-sporing pathogens but does not guarantee sterility.
Addition of 2% sodium carbonate enhances sterilization efficacy.

Steaming

Sterilizes sugar and gelatin media; utilizes a Koch steam sterilizer.
Can be achieved through a single exposure for 90 minutes or intermittent exposures over 3 days.

Bactericidal Heating

Dissolve medicaments in 0.2% w/v chlorocresol or 0.002% w/v phenyl mercuric nitrate; heat at 98-100°C for 30 minutes for injection sterilization.

Autoclaving

Sterilization occurring in a closed vessel under increased pressure, raising boiling point above 100°C.
Requires penetration of steam, hot and saturated, for effective sterilization.
Essential components include pressure gauge, safety valve, and suitable packaging.

Autoclaving Packaging Guidelines

Do not include volatile chemicals, sharps, or radioactive materials in autoclave.
Use appropriate containers (clear or orange bags); ensure items do not touch sides of the chamber.
Allow for proper steam penetration; containers should be vented.

Autoclaving Parameters

Consider steam, pressure, temperature, and time for effective sterilization.
Essential processes: air evacuation, steam penetration, holding time, chamber evacuation, and drying.

Holding Time Standards

2 minutes at 134°C (30 psi)
12 minutes at 121°C (15 psi)
30 minutes at 115°C (10 psi)

Testing Sterilizer Efficiency

Direct Tests: Assess sterility post-process.
Indirect Tests: Include instrumental checks and cultural tests using Bacillus stearothermophilus spores.
Chemical indicators change color or melting points, indicating sterilization effectiveness.

Radiation Methods

Ionizing Radiation: Includes X-rays and gamma rays, effective for sterilization of food and medical supplies, does not induce radioactivity.
Non-Ionizing Radiation: Examples include ultraviolet light, primarily for disinfection due to low penetration and potential harm to skin and eyes.

Ultraviolet Radiation

Most lethal at 260 nm, effective for disinfecting limited surfaces but ineffective through materials like dust or glass.

Membrane Filtration

Filters made of cellulose esters; offer high filtration rates and allow detection of retained bacteria.
Utilized in water purification and preparation for parenteral solutions.

HEPA Filters

Remove 99.97% of particles with pore sizes of 0.3 µm; essential for sterile environments in surgical and laboratory settings.

Efficiency Testing for Filters

Small bacteria like Serratia marcescens added to fluid; red colonies in filtrate indicate filter malfunction.

Physical Antimicrobials

Moist Heat (boiling): Denatures proteins; effective on vegetative cells but not endospores.
Specific sterilization requires 121°C at 15 psi.

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Description

This quiz explores various methods of pasteurization and sterilization, including HTST, UHT, and Tyndallization. Participants will learn how these techniques effectively eliminate pathogens and their specific applications in food safety and microbiology. Test your knowledge of the science behind food preservation methods!