Foto: © Sinnbild - Fotolia.com
Das Fleisch wird hermetisch in eine
Blech-, Glas- oder Plastikverpa-ckung
eingeschlossen und eine ge-nügend
lange Zeit auf eine hinreichend
hohe Temperatur erwärmt. Dies sichert
das Abtöten von Mikroorganismen, d. h.
ihre Reduzierung auf eine Konzentration,
die nicht ansteigen und den Inhalt ver-derben
kann.
Es ist zwischen dem Abtöten der vege-tativen
Formen von Mikroorganismen
und dem Inaktivieren seiner thermoresis-tenten
Sporen zu unterscheiden. Proble-
Cannery Row
The need to protect meat and
other foodstuffs from spoilage
led to the development of
canned food in Napoleon‘s
times. The French cook and
confectioner Nicolas Apert
(1749-1841) is considered their
forefather. What is the principle
of canned meat?
The meat is hermetically sealed in
metal, glass or plastic packaging
and heated to a sufficiently high
temperature for a sufficiently long time.
This ensures the killing of microorgan-isms,
i.e. their reduction to a concentra-tion
that cannot increase and spoil the
contents.
A distinction must be made between
killing the vegetative forms of microor-ganisms
and inactivating their thermore-sistant
spores. The so-called non-acidic
foods are problematic, i.e. those with a
pH value higher than 4.0. When heated
to temperatures below 100°C, the spores
of thermophilic bacteria, such as Clostri-
dium botulinum, producer of the deadly
botulinum toxin, can survive. If the spores
survive, then it is not real sterilization, but
only pasteurization. Non-acidic foods also
include meat with a pH between 5 and 7.
A higher heat dose is required to inacti-vate
the bacterial spores. The tempera-ture
must be well above 100 °C, which
cannot be done in an open boiler with
boiling water. This is done in autoclaves,
i.e. in a gas-tight pressure vessel. The
higher the pressure, the higher the tem-peratures
of the water bath or the air-steam
mixture are attainable.
Which temperature?
The reference temperature is 121.1°C
(250°F), the sterilization effect achieved
at this temperature is the reference value
F0, in which case the pressure is at least
2 bar. It is not necessary to heat the
medium to this temperature. In order to
achieve the sterilisation effect, i.e. the
desired F value, the temperature of the
medium transferring the heat is con-trolled
and thus the temperature profile
in the filling is well controlled.
This can be achieved by very different
combinations of heating temperature
and heating time. The following example
llustrates this: If a heating time of 10
minutes is required at 121.1°C for an
F-value of 10 minutes for certain thermal
Büchsen-Latein
Die Notwendigkeit, Fleisch
und andere Lebensmittel vor
dem Verderb zu bewahren,
führte in Napoleons Zeiten zur
Entwicklung der Konserven.
Als deren Urvater gilt der
französische Koch und
Konditor Nicolas Apert (1749-
1841). Was ist das Prinzip der
Fleischkonserve?
24 3/2018