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Hamburgers made of ground beef packaged in oxygen-rich atmosphere look thoroughly cooked before they actually are.
Hamburgers made of ground beef packaged in oxygen-rich atmosphere look thoroughly cooked before they actually are. Photo: Kjell Merok/Nofima

Project year 2013

Packaging method decides colour

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.

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 widespread in Sweden, Denmark and other European countries. 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 AN INDICATOR FOR COOKING: In a research project led by Nofima, Norwegian consumers were asked whether they make hamburgers 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 packaged 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 atmosphere already looks cooked through when it reaches 60 °C,” says Nofima Research Scientist Oddvin Sørheim.

Contact person
Portrettbilde av Solveig Langsrud
Solveig Langsrud

Research Scientist
Tlf: +47 64970182
solveig.langsrud@nofima.no

Contact person
Oddvin Sørheim

Senior Research Technologist
Tlf: +47 64970239
oddvin.sorheim@nofima.no

FINANCED BY:
The Foundation for Research Levy on Agricultural Products and the Research Council of Norway

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