Page 22 - FACOT CHEMICALS - LINEA COMFORT

Bacterial proliferations

FAVORABLE
ENVIRONMENTAL FACTORS

Oxygen
Bacteria are divided into two categories: some need oxygen to survive
(aerobic bacteria), and are present in common environments in which we
live, including our homes or workplaces, while for others oxygen is lethal
(anaerobic bacteria). As a result, the latter develop only in the absence of
it, therefore also in vacuum packed products, for example in canned food.
Humidity
Bacteria are composed of 80 -82% water, a natural element essential for
life on our planet. The cells of our body are protected by its natural ar-
mour, so essential, as the skin, a very useful barrier to hinder excessive
evaporation, while bacteria are not organized in so complex structures,
so they are much more fragile and sensitive to dry environments. As a
result, dried foods are not particularly subject to bacterial growth, as op-
posed to fresh and soft foods, which promote development thereof due
to the abundant availability of water.
pH, a strategic factor
pH is a logarithmic parameter ranging from 0 to 14. That is, a small diffe-
rence of only one unit in the pH scale entails values 10 times greater or
smaller. A substance with pH 7 is neutral, a lower pH is called acid, while
a higher value is alkaline (or basic). Most bacteria prefer an environment
with pH between 7.2 and 7.6 or slightly alkaline, except for lactobacilli
and bacteria used for cheese production, which prefer an acidic envi-
ronment.
Light
Light radiation is harmful to bacteria, so exposure to direct light is an un-
favourable environment for their growth. Even our cells can be damaged
by these radiation. Think, for example, of sunburn, but, as for moisture,
our skin represents a protective barrier, which is missing in bacteria.
Temperature
Temperature is a particularly influential parameter on bacterial prolife-
ration. Based on the different growth temperatures we can divide the
bacteria into: Thermophilic bacteria: they grow at high temperatures (47-
70 ° C, optimum temperature: 50-55 ° C) Mesophilic bacteria: they grow
at intermediate temperatures (20-45 ° C, optimum temperature 30-37 °
C). The latter find their natural habitat at medium temperatures, typical
in radiant floor systems. While in the specific of the Legionella bacte-
rium, which proliferates where the water temperature is between 25 and
52 degrees Celsius, critical points favorable to the proliferation of the
bacterium and its diffusion through aerosols are generated in the thermal
systems.
Sizes
• Bacteria: 0.3 – 1.5 µm
• Mold spores: 2.5 – 300 µm
• Yeast spores: 4 – 12 µm
• Viruses: 0.015 - 0.25 µm
(visible only under electron microscope)
Some positive and negative
aspects of bacteria
Although microorganisms are usually associated with diseases, there
are certain species that are extremely useful for humans. Some of them
have been used for centuries in the preparation of foods such as bread,
wine, vinegar and cheese. Some bacteria that live in our gut produce
vitamins and antibiotics, protecting the body and strengthening the im-
mune system; in the same way, lactobacilli protect female body from in-
fections. Only some organisms are, therefore, dangerous to health and
have the ability to cause serious pathologies. Some examples are pla-
gue, cholera, tetanus and tuberculosis. As regards bacteria, candida and
aspergillus for fungal microorganisms, mononucleosis, smallpox, AIDS,
and rubella for viruses.
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