Download Control of Microorganisms

Keeping things clean
Outline
Sterilization, Disinfection and the Bar
 Ways Control Agents Work
 Factors that Affect Control Agents
 Physical Control Agents
 Chemical Control Agents
 Sensitivity to Control Agents

How clean is clean?
Sterilization
 Commercial Sterilization
 Disinfection
 Degerming
 Sanitization

Cost-Benefit Analysis
Weigh risk of infection against cost of
process
 Will process alter product to
unacceptable level?
 Are high tolerance organisms a risk in
product?
 Are sensitive populations exposed to
product?

Salmonella vs. Clostridium
difficile
Both are fecal-oral pathogens
 What differences do they possess?

Facultative Anaerobe vs. Obligate
Anaerobe
 Gram-Negative Coliform vs. Gram-Positive
Endospore former


How does this change control strategies?
Death of a Microbe

All general microbial control agents work
by at least one of two mechanisms.

Disruption of the plasma membrane

Denaturation or damage of cellular
macromolecules (i.e. proteins or DNA)
The Mathematics of Death

Death Rates can be calculated and are
defined.
Thermal Death Point
 Thermal Death Time
 Decimal Reduction Time

Cheating the System

The real world is never as neat as the
lab and many things can screw with
microbial control.
Surrounding Matter
 Acid pH works best
 Warm works better

Let’s Get Physical
Heat
 Cold
 Pressure
 Osmotic Shock
 UV
 Ionizing Radiation
 Ethylene Gas

Ugh, Me Make Fire

Heat is a highly effective method of
control.
Flaming
 Moist Heat
 Dry Heat

Of Ham and Admirals

Osmotic Tension

Salt

Sugar
Why is a Blacklight Purple?
UV is highly effective at disrupting
Cellular DNA.
Shadow Effect
Is My Food Radioactive?
Ionizing Radiation, or Hard
Radiation, is much more effective
At sterilization because it
Penetrates through materials.
The Chemicals Between Us

Chemical Microbial Control is diverse in
form, but limited to general functions.

Examples
 Alcohols
 Hydrides
 Heavy Metals
It isn’t who you know, but who
you are.
Different Types of microbes have
different sensitivity to microbial control
agents.
 The sensitivity is based on the
physiology of the organisms.
 Take the list and compare it to the
disinfection capability of cleaners such
as Lysol. How effective are they?
