Problem med röda hamburgare efter tillagning : bakgrund och möjliga lösningar

Abstract: Persistent pink in beef patties and hamburgers is a problem in the meat industry that has been known for a few decades. It is a costly problem as it can give rejections of food by consumers. Studies around the world have tried to solve the problem but it still remains a mystery. There are many different theories of what is causing the red colour. Some of the most likly theories are reducing hemocromes, high microbiological loads, contamination of nitrite or organic/non organic substanses, DFD meat etc. The intention of the experiments preformed in this project was to try to understand why the hamburgers turned pink and thereby help the company that have this problem to change their production of hamburgers so that pink hamburgers can be avoided. Several experiments were preformed where raw material, additives, time and temperature were tested. Hamburgers with spices (the same as the company use), yeast extracts and without any additive were made. These were stored between 0 and 5 days in different temperatures. After storing, the hamburgers were cooked until reaching a core temperature of 80°C. When the samples had cooled they were cut horizontally and the colour was measured by a Minolta instrument. The results of the measurements showed that hamburgers with spices showed higher a'-values, i.e. more reddish color, when stored in 9°C between 3 to 5 days compared with all other samples. There was obvious red spots in those hamburgers and the spectra were similar to that of the real red hamburgers. Non of the spectra measured by the Minolta showed exact the same spectra as the red hamburgers. The hamburgers were examined for microbiological load, which showed that there was a rather great load on the red hamburgers. This could have a negative effect on the colour of the hamburgers, as bacteria are known to be able to reduce myoglobin from metmyoglobin to deoxymyoglobin. Presence of reduced myoglobin is one theory of why red colour develop in the hamburgers. A principalcomponent analysis was preformed on the results of the measurments from the Minolta instrument. This analysis verified some of the previous results that the hamburgers with added spices were close to the red hamburgers. Other visible results was that hamburgers made from DFD meat also were close to the red hamburgers. The conclusion from this experiment is that time, temperature, raw material and additives affect the red colour in the hamburgers. Extactly how these parameters affect the hamburgers to develop persistent pink is not fully understood. It is also possible that there are other factors needed for this phenomenon to develop.