General food hygiene - the certificate training

* 1 To inhibit the growth of microorganisms.
When you work with foodstuff you take on a big responsibility.
You need to have knowledge of for example the growth conditions of microorganisms. Yes indeed
you need to know how you can inhibit or completely stop the growth and propagation in practice.
The following paragraphs provide an overview of the most important possibilities available in
foodstuff production to kill or inhibit the growth of microorganisms.
• The temperature and oxygen will affect the products from the outside.
• Water activity (salt, sugar, dryness as well as acidity) affects the foodstuff from the inside.
• As methods of preserving preservatives, curing and radiation are mentioned.
*2 Temperature
The microorganisms, especially the bacteria, propagate most quickly between 20 and 40 °C, but
many bacteria can propagate at both higher and lower temperature. The microorganisms can be
killed or their growth can be inhibited by changing the temperature. This take place by:
• Heat treatment.
• Autoclaving (boiling under pressure for a minimum of 15 minutes at 121 °C).
• Cold storing.
• Frost storing.
*3 Heat treatment
Common to all microorganisms is the fact that they will die at high heat. Heat treated foodstuff
must reach 75 °C in the centre (core temperature). To put it in another way, it must be ensured that
the entire foodstuff is heat treated to a temperature of at least 75 °C. At this temperature all the
pathogenic microorganisms are killed. Spores can survive.
***foto
High heat kills microorganisms.
*3 Formation of spores
Some bacteria as Bacillus and Clostridium form spores that can survive ordinary heat treatment,
cooling, drying and exposure to disinfection agents that would normally inhibit or kill bacteria.
Under favourable conditions spores can germinate, that is become a bacteria again and constitute a
treat for the safety of food.
A bacteria spore is only killed by the use of an autoclave that under pressure heats to a minimum of
121 °C for 15 minutes (canned food).
For instance boiling of rice for 10 minutes is not enough to kill B. cereus spores. The spores can
germinate and become ordinary bacteria for example by incorrect storing.
*3 Beware of after contamination.
When all microorganisms in a foodstuff are dead it is important to make sure that contamination
does not arise from i.e. hands, kitchen utensils and packaging. Certain mutual competitions exist
between the different microorganisms and if a recontamination occurs, the new microorganisms
will enjoy enhanced growth conditions because all their “enemies” have died.
***tegning
Certain cold-loving microorganisms can posses a week activity as far down as 0 °and some heatloving
microorganisms can posses an activity as far up as 75 °C. The lower limit for mould
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