Packaging methods and storage time

Consumers base their purchasing choices on perceived quality and a bright red colour of beef is to many a sign of freshness and good meat quality, making colour the most important quality attribute for retailers. The most common consumer packaging types for beef in Sweden is high-oxygen modified atmosphere packaging (MAP), with the gas composition (80% O₂; 20% CO₂). The high-oxygen content gives the beef a stable bright red oxymyoglobin colour that is desirable to consumers at the moment of purchase and the addition of 20-30% CO₂ prolongs the shelf life by inhibiting bacterial growth. Nonetheless, the high level of oxygen promotes oxidation of both proteins and lipids, giving an inferior product compared with packaging systems that exclude oxygen. Vacuum packaging expands the shelf life of beef even further than high-oxygen MAP and the tenderization continues throughout the storage time. However, the purple deoxymyoglobin colour and the visible purge loss in the vacuum bag are thought to be unattractive to consumers. The aim of this thesis was to study how storage time and packaging methods affects the quality of beef, comparing high-oxygen MAP with vacuum packaged and/or skin packed beef, with emphasis on colour, Warner-Bratzler shear force, sensory quality and oxidation of proteins. In conclusion, high-oxygen MAP systems for beef steaks were found to negatively influence shear force and water-holding capacity as well as the sensory attributes tenderness, meat flavour and juiciness, compared with beef steaks packaged in skin pack or vacuum. High-oxygen MAP might also lead to decreased α-tocopherol values and increased oxidation of proteins. Moreover, no clear differences was found between skin packed and vacuum packed steaks for shear force, sensory quality and total loss, however, skin packed steaks had lower purge loss which might be more appealing to the consumers in retail display. Most research is done on frozen meat due to practical reasons. As the consumers mostly eat meat fresh, the differences in quality that comes with freezing should be taken into consideration when planning research