nofima.no
Creating value
2013
13
financed by:
The Foundation for Research
Levy on Agricultural Products
and the Research Council of
Norway
Hamburgers made of ground beef packaged in oxygen-rich atmosphere look thoroughly cooked before they actually are.
photo: Kjell J. Merok © nofima
In order to be safe to eat, raw products made from
ground beef must be cooked until they are at least 71⁰°C
in the centre. However, it can be difficult for consumers
to measure the temperature during cooking.
Meat packaged in oxygen-rich atmosphere is wide-
spread in Sweden, Denmark and other European coun-
tries. But in Norway this method is relatively new. The
advantage of an oxygen-rich atmosphere is that the first
few days after packaging, the meat has a redder colour
than with other packaging methods. A disadvantage is
that the colour in the centre of a hamburger cannot be
used to decide whether it is thoroughly cooked or not.
people use colour as as an indicator for cook-
ing:
In a research project led by Nofima, Norwegian
consumers were asked whether they make hamburg-
ers at home from ground beef or whole muscle meat
and how they judge whether a hamburger is thoroughly
cooked. Laboratory tests were also carried out to study
the connection between killing dangerous E. coli bacteria
and colour change during cooking. The trials showed that
it is difficult to measure temperature during cooking. No
suitable thermometers are on the market.
“Hamburgers should be cooked until they are at least
71 °C in the centre in order to kill bacteria, then they are
cooked through and safe to eat,» says Nofima Research
Scientist Solveig Langsrud.
For ground beef that is vacuum-packaged or pack-
aged in an oxygen-free gas mix, a change in colour from
red or pink to brown is a good indication of whether the
hamburger has been cooked enough to kill bacteria. This
is not the case for oxygen-packaged meat.
“Meat that has been packaged in an oxygen-rich at-
mosphere already looks cooked through when it reaches
60 °C,” says Nofima Research Scientist Oddvin Sørheim.
Meat that has been in contact with oxygen before cooking poses a food
safety risk as the colour may not be used as an indicator for cooking.
Packaging method decides colour
