This document provides information on sterilization methods used in agricultural sciences. It discusses both physical and chemical sterilization techniques. The physical methods covered are dry heat sterilization using hot air ovens, moist heat sterilization using autoclaves, and radiation sterilization using UV light or gamma rays. The chemical methods discussed are sodium hypochlorite, ethanol, mercuric chloride, formaldehyde, and hydrogen peroxide. Autoclaving at 121°C for 30-60 minutes is described as the most common moist heat sterilization technique. Both physical and chemical sterilization methods aim to kill microorganisms through damaging cellular proteins and structures.

1. UNIVERSITY OF AGRICULTURAL SCIENCES BANGALORE
DEPARTMENT OF PROCESSING AND FOOD ENGINEERING
Submitted to:-
Er. BABU R M ROY
ASSISTANT PROFESSOR
COLLEGE OF AGRICULTURAL
ENGINEERING,GKVK
Presented By:
ABHISHEK J
ID No. : PAMB1374
Snr.M Tech[PFE]
Course title: Basic Concepts In Laboratory
Techniques. PGS 504 (0+1)
1

2. STERILIZATION OF GLASSWARES AND PLANT SAMPLES

3. Sterilization (Latin sterilis meaning barren) is the complete removal or
inhibition of all live forms (living cell, spores, virus, etc.) from any object
INTRODUCTION

4. METHODS OF STERILIZATION
1. PHYSICAL METHOD:
 Involves processes by the use of physical means
 Utilisation of heat, moisture, radiation or membrane filtration methods.
A) DRY HEAT STERILIZATION
 Heat is the most reliable and rapid method of sterilization

5. 1. Sunlight and drying:
Action primarily due to UV rays
2. Heat:
Most reliable method of sterilization and most preferred method.
Eg: Inoculating wire, needles, forceps, etc
3. Flaming:
Passed over flame without allowing utensils and other equipments to
become red hot.
Eg: Culture tube, glass slides, needles, cover slips, etc.

6. 4. HOT AIR OVEN
 Hot air ovens are electrical devices used in
sterilization.
 The oven uses dry heat to sterilize articles.
 Generally, they can be operated from 50 to
300 C (122 to 572 F) .
 There is a thermostat controlling the
temperature.
 This is the most widely used method of
sterilization by dry heat.

7. B) MOIST HEAT STERILIZATION
 Killing of microorganisms with hot water or steam
 Mechanism: Denaturation and coagulation of proteins
Divided into three forms in based of temperature:
1. Temperature below 100°C (Pasteurization method)
2. Temperature at 100°C (Tyndallization method)
3. Temperature above 100°C (Autoclaving method)

8. Autoclaves are used to sterilize equipment and supplies by subjecting them to
pressurized saturated steam at 121 °C (250 °F) for around 30-60 minutes at a pressure
of 15 pa
Uses of Autoclaves:
 Useful for materials which can not withstand high temperature.
 To sterilize culture media, heat stable liquids, saline solutions,
instruments, glasswares, syringes, rubber material, gowns, surgical
dressings, gloves etc.

9. AUTOCLAVE

10. HORIZONTAL AUTOCLAVE

11. C) RADIATION
Two types of radiation: Ionising radiation & Non-ionising radiation
1. Non-ionizing radiation(HOT STERILIZATION)
 Infrared- Used for rapid mass sterilization of pre-packed items such as Syringe.
 UV
 Used for disinfecting enclosed area such as entryways, operation theatres and
labs.
2. Ionising radiation(Cold sterilization)
 Gamma rays: X-rays: Used for sterilising plastics, syringes, swabs, animal feeds,
cardboard, oils, greases, fabric and metal foils.

12. MECHANISM
1. Non-ionizing radiations(UV light) : Induce the production of abnormal
nucleotides such as thymine in the bacterial cell.
2.Ionizing radiation(X-rays, gamma rays ,cathode rays) : causes ionization
resulting in the death of cell.

13. CHEMICAL METHODS OF STERILIZATION
Action of chemical agents Mechanism:
 Protein coagulation
 Disruption of cell membrane resulting in exposure, damage/loss of contents
 Substrate competition.

14. Commonly used chemicals
SODIUM HYPOCHLORITE
Sodium hypochlorite (NaOCl), an oxidizing agent, is used for surface sterilization of plant
parts at a concentration of 0.5%–5%.
NaOCl acts in three ways: saponification, neutralization, and chloramination. It produces
hypochlorous acid (HOCI) and hypochlorite ions (–OCl) that degrade amino acids, suppress
critical enzyme function, damage cell membrane and DNA, and may even hamper
membrane transport
ETHANOL
The ethanol is an amphiphilic compound that affects cell membrane, denatures proteins,
and dissolves lipids in the cell sap. This results in leakage of cell sap and melting of
essential organelles, ultimately leading to cell death. Ethanol acts as lipid solvent. It is
commonly used at a concentration of 60%–85% as a surface sterilant

15. MERCURIC CHLORIDE
Mercuric chloride (HgCl2) is a surface disinfectant and combines with the –SH group
It kills a wide range of microbial targets. The chloride ions generated from HgCl2 are
electronegative that oxidize the peptide linkages and cause protein denaturation . The
HgCl2 at a concentration of 0.01%–0.1% was found effective for surface sterilization of
plant tissues.
FORMALDEHYDE
Formaldehyde is used in both liquid and gaseous states.
It is an alkylating agent that denatures protein and fixes most cellular debris of
microbial flora
Formaldehyde acts on DNA and RNA by alkylating ring nitrogen atoms of purine bases,
and in proteins, it alkylates amino (–NH2) and sulfhydryl (–SH) groups
It is available as 37% (wt/vol) formaldehyde called formalin

16. HYDROGEN PEROXIDE
Hydrogen peroxide is known for broad-spectrum antimicrobial activity against
viruses, yeast, bacteria, and resistant bacterial spores. It is used in various
concentrations ranging from 3% to 90% for surface sterilization. A higher
concentration of hydrogen peroxide (10%–30%) and larger incubation time is
necessary to perform sporicidal function.

17. THANK YOU