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8. Soft cheese and smoked fish should not be vacuum sealed, as this can cause
the development of anaerobic bacteria of the Listeria species, which in turn can
cause food poisoning resp. listeriosis. This also applies to garlic, onions, mush-
rooms and raw milk.
9. Some enzymes in foods can change the colour, texture and flavour of foods,
which depends on storage time, storage temperature and oxygen. To prevent
this enzyme reaction, vegetable should be blanched or steam cooked for a short
time, or cooked in the microwave. Foods with a high acid content such as most
fruits, must not be blanched. In this case, vacuum packing is enough to slow or
inhibit the enzyme reaction.
10. Some dry foods, such as flour and cereals, can contain insect larvae. If the food
isn’t vacuum packed, these can hatch during storage, making the food inedible.
To prevent this these foods should be vacuumed.
11. Generally, foods should be stored at low temperatures since most micro-organ-
isms can also spread without air.
12. If the temperature in your fridge is above 4 °C then this can, most of all during
long-term storage, support the growth of dangerous micro-organisms. Therefore
the temperature setting in your fridge should be max. 4 °C or less.
13. If the temperature in your freezer is −18 °C or less, it is ideal for storing food, but
remember: freezing does not kill micro-organisms, it only slows their growth.
14. The shelf life of vacuum packed dried foods is also longer, the cooler the storage
temperature is: For every 10 °C cooler the storage temperature, the shelf life
extends by 3 – 4 times.
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FURTHER TIPS FOR SUCCESSFUL VACUUMING:
1. Always wash your hands before preparing and vacuuming, equally the materials
and appliance which you use, should be absolutely clean.
2. As soon as the foods have been vacuumed, put them in the fridge or freezer,
do not leave them to sit at room temperature. Make sure that the temperature
in the refrigerator or freezer does not increase.
3. Vacuum packing extends the shelf life of dried foods, foods with high fat con-
tent quickly become rancid in warm temperatures and oxygen. Vacuum packing
extends the shelf life of nuts, coconuts or cereals. Store these in a cool, dark
place.
4. Vacuum packing does not extend the shelf life of fruit and vegetables such as
apples, bananas, potatoes and root vegetables, unless they are peeled first!
5. Cabbage vegetables such as broccoli, cauliflower or cabbage give off gas when
vacuum packed fresh for refrigeration. To preserve them, they must be first
blanched, then frozen before packing.
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WHY DO VACUUM PACKED FOODS
LAST LONGER?
1. Chemical reactions in food with air, ambient temperature and dampness,
enzym-reactions, the formation of micro-organisms or contamination by insects
can spoil food.
2. The main reason why food nutrients lose their firmness and flavour is the oxygen
in the air. The formation of micro-organisms is usually caused by air, because
this removes the moisture of the foods, on the other hand, it also transports
ambient moisture back into the food if they are not hermetically sealed. Frozen
foods get in the freezer air, often the freezer burn.
3. The vacuuming system removes the air from the packaging. As air consists to roughly
21% of oxygen, this means that practically no oxygen remains in a vacuum sealed
bag or container. However in an oxygen content of less than 5%, most micro-
organisms cannot multiply.
4. In general, micro-organisms can be divided into three categories: mould, yeasts
and bacteria, they are present everywhere, but can only cause damage in
certain conditions.
5. In an environment with little air or moisture,
mould
cannot develop.
6. In moisture, sugar and warmth,
yeast
can spread with or without air, cooling
slows the growth of yeast and freezing stops it altogether.
7.
Bacteria
can spread with or without air.
One of the most dangerous bacteriums is Clostridium botulinum which can,
under certain conditions, spread without air – it only needs a temperature of
between 4 °C and 46 °C. It spreads in food without acid, in environments with
little acid and in temperatures that are above 4 °C for long periods of time.
The bacterium Botulinum cannot do any harm to frozen, dried or acid rich foods
or foods with a high salt or sugar content.
The following foods can be lightly infected with Botulinum:
– Acid free foods like meat, seafoods, poultry, fish, eggs and pickled olives
– Foods with little acid like most vegetable
– Medium-acid foods like tomatoes, chilli peppers, figs and cucumbers.
For storage, the above-mentioned, compromised foods (the list is not com-
plete) should be placed in the fridge for short storage periods resp. fro-
zen for longer storage periods and be consumed right after heating. Soft
cheese, smoked fish, garlic, onions, mushrooms and raw milk should not be
vacuum sealed or stored for longer periods of time due to their sensitivity
to anaerobic bacteria even under vacuum.
