General food hygiene - the certificate training

By using big amounts of salt or sugar the growth of bacteria can be limited or decreased totally. The
water activity (aw) is said to be lowered (aw). The water activity is an expression of how much of
the water is bound by salt or sugar and how much of the water is accessible.
The combination of sugar/preservative is often used for instance for jam, fruit preserve and juice.
The combination of sugar/vinegar/preservative is often used for instance for cucumbers and
beetroot.
The combination of salt/cooling/preservative is used in many cold cuts as well as in bacon, smoked
saddle of pork, fish and so on.
The combination of salt/drying is used for both fish and meat. Among known examples are ham
imported from Italy.
It is possible to preserve foodstuff solely by the use of salt and sugar, but the products will turn out
to salty or to sweat respectively for most people.
*2 pH
Only a few pathogenic bacteria can grow < pH 4.5. Sour products as pickled beetroot, cucumber,
red cabbage, pickles, mayonnaise, remoulade and many others have a sourness pH < 4.5 and will
often have preservatives added. That’s why they can be stored without cooling as long as they
remain unopened.
***foto
Mayonnaise has a pH < 4.5 and may consequently be stored - unopened - without cooling.
Yeast and mould can however tolerate a lower pH (pH 2-6) and that’s why it is common practice to
add preservatives to the aforementioned products.
Other foodstuff, as for example sour milk products, have a low pH, but the pH is not sufficiently
low for storing without cooling. Sour milk products stored in the fridge have a very long shelf life,
much longer than for instance milk, because of the low pH.
***Skema
Maximum Optimum
The largest group of bacteria 8.0-9.0 7.0-7.6
Particularly acid resistant bacteria 8.0-9.0 7.0
Yeast 8.0 4.0-7.5
Mould 8.0 4.0-7.5
Tekst: Growth limits of microorganisms compared to pH.
*2 Preservatives
Microorganisms are limited or killed by preservatives. A lot of chemical preservatives exist on the
marked. The most widely used are benzoic acid, sorbic acid and propionic acid. These products are
found in almost all preserved fruit and jam products. Packed rye bread can also be surface preserved
with propionic acid.
By lowering the pH in the foodstuff the chemical preservatives have a greater effect.
Sodium benzoate is an aqueous solution of benzoic acid. It is mostly intended for private
households.
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