A powerpoint presentation in Microbiology and Parasitology. BS Education Major in General Science

1. NONHEAT
METHODS

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NONHEAT METHODS
A number of nonheat methods are
also available to control the growth
and presence of microorganisms

3. FILTRATION
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4. FILTRATION
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Removes microbes from air and liquids
• Fluid is strained through a filter with opening large enough for the fluid to pass, too small for microbes.
• Thin membranes of cellulose acetate, polycarbonate and plastics whose pore size is carefully control.
• Charcoal, diatomaceous earth or unglazed porcelain are also used.
• Pore sizes can be controlled to permit true sterilization by trapping viruses or large proteins.

5. FILTRATION
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• Used to prepare liquids that cannot withstand heat.
• Alternative method for decontaminating milk and beer without altering its flavor.
• Can’t remove soluble molecules (toxins) that can cause disease.
• Efficient means of airborne contaminants.
• HEPA (High Efficiency Particulate Air) Filters are used in hospitals and sterile rooms.

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8. RADIATION
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9. • Radiation are very harmful to microorganisms. This is particularly true of ionizing radiation medication, radiation
of very short wavelength or high energy.
• Two forms of ionizing radiation is:
• a.) X-rays which are artificially produced X-rays have considerable energy and penetration ability.
• Gamma rays which are emitted during radioisotope
• Gamma rays are high-energy radiations emitted from certain radioactive isotopes such as 60Co. Gamma rays are
similar to x-rays but are of shorter wavelength and higher energy. These rays have greater penetrating power into
the matter and they are lethal to all form of life.
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RADIATION

10. • Ionizing radiation will produce mutations and may cause death. Destruction of
DNA is the most important cause of death.
• Ultraviolet (UV) radiation can kill all kinds of microorganisms due to short
wavelength (0-400nm) and high energy. The most lethal of UV radiation has a
wavelength of 260 nm, the wavelength most effectively absorbed by the DNA.
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RADIATION

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13. DESSICATION
“drying”
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14. DESICCATION
• Drying-out
• Vegetable cells directly exposed to normal room temperature gradually become
dehydrated
• Streptococcus pneumoniae, the spirochete of syphilis, and Neisseria gonorrhoeae die after
a few hours of air drying
• Endospores of Bacillus and clostridium are viable for thousand of years under extremely
arid conditions
• Staphylococci, streptococci, and the tubercle bacillus surrounded by sputum remain viable
in air and dust.
• Many viruses and fungi can also withstand long periods of desiccation
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15. FREEZE-
DRYING
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16. • Lyophilization, also known as freeze-drying, is a process used for preserving biological
material by removing the water from the sample by sublimation, which involves first
freezing the sample and then drying it, under a vacuum pump, at very low temperature.
• The term “lyophilization” describes a process to produce a product that “loves the dry
state”.
• This process could be considered as a valuable alternative to preserve foods.
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FREEZE DRYING

17. • Freeze drying is mainly used to remove the water from sensitive products, mostly of
biological origin, without damaging them, so they can be preserved easily, in a
permanently storable state and be reconstituted simply by adding water.
• Examples of freeze-dried products are: antibiotics, bacteria, sera, vaccines, diagnostic
medications, protein- containing and biotechnological products, cells and tissues, and
chemicals.
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FREEZE DRYING

18. • Coffee.
• Fruit and juice.
• Vegetables.
• Meat.
• Fish and Seafood.
• Eggs.
• Dairy.
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Food Types Suitable For Freeze Drying

19. To extract water from foods, the process of lyophilization consists of :
1. Freezing the food so that the water in the food become ice.
2. Under a vacuum, sublimating the ice directly into water vapor.
3. Drawing off the water vapor.
4. Once the ice is sublimated, the foods are freeze- dried and can be removed from the
machine.
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Rate of Drying of Water

20. Fundamental Process Steps
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1. Freezing
The product is frozen.
This provides a necessary condition for low temperature drying.
2. Vacuum
After freezing, the product is placed under vacuum. This enables the
frozen solvent in the product to vaporize without passing through the
liquid phase, a process known as sublimation.
Heat
Heat is applied to frozen product to accelerate sublimation.
4. Condensation
Low temperature condenser plates remove the vaporized solvent
from the vacuum chamber by converting it back to a solid. This
completes the separation process. Resulting product has a very
large surface area thus promoting rapid dissolution of dried product.

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22. OSMOTIC
PRESSURE
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23. OSMOTIC PRESSURE
• The pressure build up within the cell as a result of water intake
• If cells are exposed to solutions with higher solute concentration, water will be drawn out
of the cell and the process is called plasmolysis.
• The reverse process, which is the passage of water from a low solute concentration into
the cell is known plasmotysis.
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24. O
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Plasmolysis Plasmotysis
• When bacteria is placed in hypotonic solution
• Turgid state
• When bacteria is placed in hypertonic solution
• Cell shrinking
OSMOTIC PRESSURE
This plasmolysis and plasmotysis kills bacteria because it causes change in
osmotic pressure.

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OSMOTIC PRESSURE
Approximate solute concentration of bacterial
cytoplasm is 0.85 % NaCl, which gives normal
osmotic pressure.

26. OSMOTIC PRESSURE
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• High concentration of salt and sugar
inhibit microbial growth by osmotic
pressure.
• Jam and pickles are classic
examples because of their high
solute loading.

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COLD
TEMPERATURES

29. COLD TEMPERATURES
• Lowering temperature will decrease enzyme activity
• Repeated cycles of freezing and thawing can denature proteins.
Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions
can cause an enzyme to lose its ability to bind to a substrate.
• Psychrophiles grow slowly at freezing temperatures and can secrete toxic products
• Pathogens able to survive several months in the refrigerator
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30. • Lowering temperature will decrease enzyme activity
• Repeated cycles of freezing and thawing can denature proteins.
Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions
can cause an enzyme to lose its ability to bind to a substrate.
• Psychrophiles grow slowly at free
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COLD TEMPERATURES

31. Spoilage bacteria
• Spoilage bacteria cause unsightly growths in a rainbow of colors on refrigerated foods.
• Lactic-acid bacteria may cause foods to taste liver-like or cheesy, and they may cause meat to turn green.
Pathogenic Bacteria
• These are the dangerous bacteria -- disease-causing organisms that can make you sick.
• Listeria species bacteria, which may contaminate fruit and raw milk products
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COLD TEMPERATURES

32. • Pathogens able to survive several months in the refrigerator
 Staphylococcus aureus
 Clostridium species
 Streptococcus species
 Salmonella
 Yeast, molds and viruses
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33. • If your refrigerator is not equipped with a thermometer, use an appliance thermometer to monitor its internal
temperature.
• Maintain the temperature between 34 and 40 degrees F, although colder temperatures prevent food spoilage
better.
• Crowded refrigerators have areas that may be warmer than the thermometer reading because of poor air
circulation, so pack the shelves loosely.
• Inspect the door seal to verify it forms a tight fit with the refrigerator body so there is no heat gain inside
your appliance.
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FOOD SAFETY

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35. april@www.proseware.com
THANK
YOU
Group 3